steam locomotive question
D. Michael McIntyre
Here's a stupid question, and this seems like the best place to ask
it...
I've finally gotten some good steam videos to watch, and have watched
all of them several times through. My first and best love was always
steam power, and no matter how much I've come to appreciate diesels,
they'll never hold the same fascination for me.
Anyway, the stupid question: why do steam locomotives make that
chuff-chuff-chuffing sound, blowing smoke out the stack in time with
the sound? There appears to be no direct relationship at all between
the chuffing sound and the speed of the drive rods... I always just
assumed that it was the sound of steam puffing into the cylinders, but
that doesn't appear to be the case after careful observation.
So where does it come from?
While I'm asking stupid steam questions: why does the smoke puff out
at all? The fire is constant, is it not? So the smoke should be
constant too. Is there some kind of valve in there that backs the
smoke up and only lets it out in puffs?
It seems to me as though it's almost like the sound of a fire being
stoked with a bellows, but I know of no such mechanism in a steam
locomotive. Is there some kind of air injector or something? How do
the fires breathe?
Thanks for having the patience to answer these stupid questions... :)
D. Michael McIntyre
mmci...@swva.net
[insert your favorite cute phrase or ascii drawing here]
hac...@worldnet.att.net
mmci...@swva.net (D. Michael McIntyre) wrote:
<snip>
>I've finally gotten some good steam videos to watch, and have watched
First a question, are your videos modern VCR shot videos or are
they 8mm converted videos? If the later then the sound is badly
out of sync with the rods and "smoke".
>Anyway, the stupid question: why do steam locomotives make that
>chuff-chuff-chuffing sound, blowing smoke out the stack in time with
>the sound? There appears to be no direct relationship at all between
>the chuffing sound and the speed of the drive rods... I always just
>assumed that it was the sound of steam puffing into the cylinders, but
>that doesn't appear to be the case after careful observation.
>
>So where does it come from?
The "Chuff - Chuff" sound is caused by the steam being exhausted
from the cylinders, not entering them. As the speed is increased, and
the hogger starts to notch up, the sound starts to blend into more of
a steady hiss.
>While I'm asking stupid steam questions: why does the smoke puff out
>at all? The fire is constant, is it not? So the smoke should be
>constant too. Is there some kind of valve in there that backs the
>smoke up and only lets it out in puffs?
The "smoke" on a properly fired engine is actualy the steam from
the cylinders. Black smoke is pretty for pictures, but could get a
fireman fined for wasting coal/oil. The valve, is the valve of the
cylinders letting the steam exhaust from the cylinders.
>It seems to me as though it's almost like the sound of a fire being
>stoked with a bellows, but I know of no such mechanism in a steam
>locomotive. Is there some kind of air injector or something? How do
>the fires breathe?
It is being stoked by a bellows. In this instance the steam is
doing the pumping. When the steam is vented from the cylinders it
is sent straightup the stack, the speed of the steam causes a
venturi [sp?] effect. This effect causes the pressure in the smokebox
to drop, air is sucked in from the firebox thru the boiler tubes
creating a draft for the fire and helping to heat the water.
There is an "air injector", it is called a Blower. The blower is
located in the smokebox, and is used to aid in creating a draft
by the method described above. The air it is blowing is actualy
steam.
>Thanks for having the patience to answer these stupid questions... :)
They were not stupid, just "ignorant". Rember "Ignorance" can be
cured by education, "stupid" is to the bone.
>D. Michael McIntyre
>mmci...@swva.net
I hope this helped, this is a very smiple explanation of what goes
on in a steam locomotive. For a better understanding I recommend
that you find a live steam club in your area and spend some time with
them.
Ron Bach
hac...@worldnet.att.net
Arnold Morscher
About steam engine sounds:
>Anyway, the stupid question: why do steam locomotives make that
>chuff-chuff-chuffing sound, blowing smoke out the stack in time with
>the sound? There appears to be no direct relationship at all between
>the chuffing sound and the speed of the drive rods...
There are 4 "chuffs" per revolution of a driver wheel in most
steam locomotives, two from the left cylinder, and two from
the right. These are evenly spaced so as to make a steady
4 chuffs per driver revolution.
Arnie
roger traviss
Arnold Morscher (ax...@po.CWRU.Edu) wrote:
: About steam engine sounds:
That's the theory and where sound systems on model fall down, all beats
are not even. If you listen to a two cylinder simple engige you will hear
"CHUFF, chuff, chuff, chuff, CHUFF, chuff, chuff, chuff, CHUFF, chuff
....." and not an even beat. I have the explaination for this here
somehere but can't lay my hands on it at the moment.
Cheers
Roger Traviss
From sunny Victoria, BC Canada
Karl Andrews
mmci...@swva.net (D. Michael McIntyre) writes:
> Anyway, the stupid question: why do steam locomotives make that
> chuff-chuff-chuffing sound, blowing smoke out the stack in time with
> the sound? There appears to be no direct relationship at all between
> the chuffing sound and the speed of the drive rods... I always just
> assumed that it was the sound of steam puffing into the cylinders, but
> that doesn't appear to be the case after careful observation.
>
As each piston reaches the end of its stroke, the valve gear opens a
port that allows the 'used' steam to escape the cylinder so that it does
not oppose the action of the 'new' steam now coming in on the other side
of the piston to push it the other way. These ports lead to a nozzle in
the smoke-box under the stack that vents the steam up the stack, carrying
out the gases and lowering the pressure in the smoke-box (Venturi
effect). The higher pressure of the gases in the fire-box (sometimes
assisted by a blower) pushes the hot air and gases through the tubes in
the boiler into the smoke-box. The chuff noise comes from the fact that
the 'used' steam still has greater than atmospheric pressure - same
effect as puffing your lips.
You should hear a chuff as each piston reaches its maximum stroke, when
the associated crank pin is at the three-o'clock or nine-o'clock
position. You also get chuffs from the engine on the other side of
the locomotive, whose alignment is rotated 90 degrees compared to the
first side. So you get four chuffs for a complete revolution of the
drive wheels, two from the three- and nine-o'clock positions on this
side, and two from the other side, when this side is at six- or
twelve-o'clock.
- Karl
--
The avalanche has already started. It is too late for the pebbles to vote.
- Kosh Naranek
roger traviss
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: Arnold Morscher writes:
: >> Why do steam locomotives make that chuff-chuff-chuffing sound,
: >> blowing smoke out the stack in time with the sound? There appears
: >> to be no direct relationship between the chuffing sound and the
: >> speed of the drive rods...
: > There are 4 "chuffs" per revolution of a driver wheel in most
: > steam locomotives, two from the left cylinder, and two from
: > the right. These are evenly spaced so as to make a steady
: > 4 chuffs per driver revolution.
This only applies to two cylinder engines.
: The chuffing sound is in exact time with the motion of the rods and
: wheel rotation on a conventional "rod" engine (ones that conspicuously
: "chuff"). And furthermore, the boiler being horizontal would not have
: sufficient draft from the fire, at the cab end, to the smokestack if
: it weren't for the exhaust blast from the cylinders that blow through
: an extractor funnel below the stack and "suck" the smoke and fumes
: from the firebox through the boiler tubes.
The "extractor funnel" is known as the "blast pipe", because it produces a
blast of steam up the stack. This causes the venturi effect and creats
the draft over and through the fire bed in the fire box.
: The four strokes come from two dual acting cylinders, that push and
: pull, and whose cranks are 90 degrees apart on opposite sides of the
: locomotive, unlike those of a bicycle. It is often assumed that the
: cranks of a steam locomotive are opposed like bicycle cranks, but such
: an arrangement would occasionally come to rest with one piston all the
: way forward and one back, so there would be no way of starting, like
: when the pedals of a bicycle stop at the top and bottom. The 90 degree
: arrangement is known as quadrature and can always start.
Cylinders at 90 degrees will still fall on "dead centre" and require the
engineer to reverse slightly on order to over come it. Quartering at 90
vs 180 merely reduces the chances of stopping on dead centre.
: There are locomotives with more cylinders and some with dive shafts
: and gear reduction. Typically the Shay geared locomotive has three
: cylinders located vertically on one side above a crankshaft with shaft
: drive to all wheels through 17:43 ratio bevel gears. With 32 inch
: diameter wheels, the six power pulses per engine cycle come at 6.6
: inch intervals along the track. This gives a steady exhaust roar as
: the locomotive produces an almost uniform drive torque at the wheel
: and can operate continuously at partial slip.
Remember, that three cylinder "rod" engines, while not popular in North
America, are common in the rest of the world as are/were four cyclinder
engines. These give, usually, six and eights "beats" per revolution of
the driving wheels and a softer blast as the cylinders are usually
smaller.
Jobst Brandt
Arnold Morscher writes:
>> Why do steam locomotives make that chuff-chuff-chuffing sound,
>> blowing smoke out the stack in time with the sound? There appears
>> to be no direct relationship between the chuffing sound and the
>> speed of the drive rods...
> There are 4 "chuffs" per revolution of a driver wheel in most
> steam locomotives, two from the left cylinder, and two from
> the right. These are evenly spaced so as to make a steady
> 4 chuffs per driver revolution.
The chuffing sound is in exact time with the motion of the rods and
wheel rotation on a conventional "rod" engine (ones that conspicuously
"chuff"). And furthermore, the boiler being horizontal would not have
sufficient draft from the fire, at the cab end, to the smokestack if
it weren't for the exhaust blast from the cylinders that blow through
an extractor funnel below the stack and "suck" the smoke and fumes
from the firebox through the boiler tubes.
The four strokes come from two dual acting cylinders, that push and
pull, and whose cranks are 90 degrees apart on opposite sides of the
locomotive, unlike those of a bicycle. It is often assumed that the
cranks of a steam locomotive are opposed like bicycle cranks, but such
an arrangement would occasionally come to rest with one piston all the
way forward and one back, so there would be no way of starting, like
when the pedals of a bicycle stop at the top and bottom. The 90 degree
arrangement is known as quadrature and can always start.
There are locomotives with more cylinders and some with dive shafts
and gear reduction. Typically the Shay geared locomotive has three
cylinders located vertically on one side above a crankshaft with shaft
drive to all wheels through 17:43 ratio bevel gears. With 32 inch
diameter wheels, the six power pulses per engine cycle come at 6.6
inch intervals along the track. This gives a steady exhaust roar as
the locomotive produces an almost uniform drive torque at the wheel
and can operate continuously at partial slip.
And much much more...
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
D. Michael McIntyre writes:
> I've finally gotten some good steam videos to watch, and have
> watched all of them several times through. My first and best love
> was always steam power, and no matter how much I've come to
> appreciate diesels, they'll never hold the same fascination for me.
> My question is, why do steam locomotives make that chuff-chuff-
> chuffing sound, blowing smoke out the stack in time with the sound?
> There appears to be no direct relationship at all between the
> chuffing sound and the speed of the drive rods... I always just
> assumed that it was the sound of steam puffing into the cylinders,
> but that doesn't appear to be the case after careful observation.
I missed that you got this impression from videos. The sound track
to many steam videos was added later because the videos are from
amateur and home movies that were without sound. Do not expect steam
videos to have accurate sound. Only few do so.
Jobst Brandt <jbr...@hpl.hp.com>
Richard Alvarez
Roger -
You wrote <<Cylinders at 90 degrees will still fall on "dead
centre", and require the engineer to reverse slightly on order to over
come it. Quartering at 90 vs 180 merely reduces the chances of stopping
on dead centre.>>
Please clarify that.
If one cylinder is on "dead centre", then the other cylinder is
nearly at mid-stroke.
Dick Alvarez
alv...@best.com
roger traviss
Richard Alvarez (alv...@nntp.best.com) wrote:
: Roger -
: Please clarify that.
I'll have to look up the reason in my text books. It's something to do
with the "mid stroke" cylinder leading or following the exhaust beat.
BTW, I know it can happen because it has happened to me, several times.
When I find it I'll repost.
M. Murray
roger traviss (roge...@islandnet.com) wrote:
: Jobst Brandt (jbr...@hpl.hp.com) wrote:
: : > There are 4 "chuffs" per revolution of a driver wheel in most
: : > steam locomotives, two from the left cylinder, and two from
: : > the right. These are evenly spaced so as to make a steady
: : > 4 chuffs per driver revolution.
: This only applies to two cylinder engines.
It also applies to most four-cylinder engines (see below).
: Cylinders at 90 degrees will still fall on "dead centre" and require the
: engineer to reverse slightly on order to over come it. Quartering at 90
: vs 180 merely reduces the chances of stopping on dead centre.
Dick Alvarez has already questioned this. I'm looking forward to your
elaboration.
:
: : There are locomotives with more cylinders and some with dive shafts
: : and gear reduction. Typically the Shay geared locomotive has three
: : cylinders located vertically on one side above a crankshaft with shaft
: : drive to all wheels through 17:43 ratio bevel gears. With 32 inch
: : diameter wheels, the six power pulses per engine cycle come at 6.6
: : inch intervals along the track. This gives a steady exhaust roar as
: : the locomotive produces an almost uniform drive torque at the wheel
: : and can operate continuously at partial slip.
:
: Remember, that three cylinder "rod" engines, while not popular in North
: America, are common in the rest of the world as are/were four cyclinder
: engines. These give, usually, six and eights "beats" per revolution of
: the driving wheels and a softer blast as the cylinders are usually
: smaller.
While three-cylinder engines usually have the cranks set at 120 and 240
degrees, so do give six beats per revolution, four cylinder engines are
usually set at 90, 180 and 270, so the exhaust beats of two cylinders
coincide to give four beats. Although I can't remember the details, there
were some three-cylinder locos with cranks set at 90 and 135 degrees, and
four-cylinder locos with cranks set at 90, 135, and 225 degrees. The
latter would give eight beats (every 45 degrees), while the former would
give six irregular beats (1,3,4,5,7,8).
--
Martin Murray :: School of Chemistry, Bristol University, BS8 1TS, England
Jobst Brandt
Roger Traviss writes:
>>> There are 4 "chuffs" per revolution of a driver wheel in most
>>> steam locomotives, two from the left cylinder, and two from the
>>> right. These are evenly spaced so as to make a steady 4 chuffs
>>> per driver revolution.
> This only applies to two cylinder engines.
No one said ALL locomotives, and besides the use of more cylinders
only complicates the discussion which was about the sound of rod
engines in general. As you see, the concepts of more cylinders was
mentioned in the cited text but conveniently omitted for reasons
unknown. One could also mention that an articulated four cylinder rod
engine usually has a non synchronous exhaust note of two two cylinder
engines while Southern Pacific three cylinder engines had a strongly
syncopated note because the center cylinder was inclined slightly
above the line of the outer cylinders while the crank spacing was 120
degrees causing a 12 3456 12 3465 beat. So let's not get too far
afield on the sound of rod engines.
>> The chuffing sound is in exact time with the motion of the rods and
>> wheel rotation on a conventional "rod" engine (ones that
>> conspicuously "chuff"). And furthermore, the boiler being
>> horizontal would not have sufficient draft from the fire, at the
>> cab end, to the smokestack if it weren't for the exhaust blast from
>> the cylinders that blow through an extractor funnel below the stack
>> and "suck" the smoke and fumes from the firebox through the boiler
>> tubes.
> The "extractor funnel" is known as the "blast pipe", because it
> produces a blast of steam up the stack. This causes the venturi
> effect and creates the draft over and through the fire bed in the
> fire box.
Thanks for the jargon. Had I used that term, I'm sure the writer who
asked the question would not have been enlightened.
>> The four strokes come from two dual acting cylinders, that push and
>> pull, and whose cranks are 90 degrees apart on opposite sides of
>> the locomotive, unlike those of a bicycle. It is often assumed
>> that the cranks of a steam locomotive are opposed like bicycle
>> cranks, but such an arrangement would occasionally come to rest
>> with one piston all the way forward and one back, so there would be
>> no way of starting, like when the pedals of a bicycle stop at the
>> top and bottom. The 90 degree arrangement is known as quadrature
>> and can always start.
> Cylinders at 90 degrees will still fall on "dead centre" and require
> the engineer to reverse slightly on order to over come it.
> Quartering at 90 vs 180 merely reduces the chances of stopping on
> dead centre.
I disagree. There is never a time when quadrature lies on dead
center. That is its purpose. When one cylinder is at the end of its
stroke the other is at mid stroke. When they are at the quarter
points, they are both at the quarter points and have ample torque
because both are acting. However, getting back to your contention,
if it were possible to get on dead center, how could the engineer
reverse to get off dead center? The pistons are bidirectional and
have complete symmetry of operation.
>> There are locomotives with more cylinders and some with dive shafts
>> and gear reduction. Typically the Shay geared locomotive has three
>> cylinders located vertically on one side above a crankshaft with
>> shaft drive to all wheels through 17:43 ratio bevel gears. With 32
>> inch diameter wheels, the six power pulses per engine cycle come at
>> 6.6 inch intervals along the track. This gives a steady exhaust
>> roar as the locomotive produces an almost uniform drive torque at
>> the wheel and can operate continuously at partial slip.
> Remember, that three cylinder "rod" engines, while not popular in
> North America, are common in the rest of the world as are/were four
> cylinder engines. These give, usually, six and eights "beats" per
> revolution of the driving wheels and a softer blast as the cylinders
> are usually smaller.
There were many three cylinder rod engines here in the USA as in other
countries. I don't believe they proved to be what they seemed to
promise. The steam engine evolved over the steam era with many
variations but the two cylinder, quadrature drive remained the
mainstay, whether in single arrangement or in articulated sets.
During that time the gear driven locomotives were widely used in
logging and other industrial uses.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Roger Traviss writes:
>>> Cylinders at 90 degrees will still fall on "dead centre", and
>>> require the engineer to reverse slightly on order to over come it.
>>> Quartering at 90 vs 180 merely reduces the chances of stopping on
>>> dead centre.
>> Please clarify that.
> I'll have to look up the reason in my text books. It's something to
> do with the "mid stroke" cylinder leading or following the exhaust
> beat. I know it can happen because it has happened to me, several
> times.
Citing personal experience does not constitute proof that the well
understood workings of quadrature are not true. I think you need to
present more evidence than stating that it is so. Saying that it
happened to you, only introduces another questionable subject.
> When I find it I'll repost.
Never to be heard from again.
Jobst Brandt <jbr...@hpl.hp.com>
roger traviss
M. Murray (co...@zeus.bris.ac.uk) wrote:
: While three-cylinder engines usually have the cranks set at 120 and 240
: usually set at 90, 180 and 270, so the exhaust beats of two cylinders
: coincide to give four beats. Although I can't remember the details, there
: were some three-cylinder locos with cranks set at 90 and 135 degrees, and
: four-cylinder locos with cranks set at 90, 135, and 225 degrees. The
: latter would give eight beats (every 45 degrees), while the former would
: give six irregular beats (1,3,4,5,7,8).
The Southern's Lord Nelsons were set to give eight exhaust beats per
revolution. I still haven't found the explaination for steam engines
stalling on "dead centre" but it was in one of the UK comics, the one that
features Cliff Groom and his explainations to the workings of steam.
Cheers
Roger Traviss
From rainy Victoria, BC Canada
roger traviss
Distribution:
Jobst Brandt (jbr...@hpl.hp.com) wrote:
I haven't editied the following so that the discussion remains clear. I
hope.
: Roger Traviss writes:
: >> Please clarify that.
: Jobst Brandt <jbr...@hpl.hp.com>
Ooooooooo. Sarcasm. And pray tell what practical steam experience do
you have?
You are correct in that a steam locomotive with cranks set at 90
degrees cannot stall on "dead centre". A poor choice of words on my part
but I didn't want to change what the original poster had written.
However, it is possible for a steam locomotive to stop and not be able to
restart the train because of the position of the valves at the time the
motion came to a stop thus giving the same effect as "dead centre".
As I said, I've not found my text yet as I'm far to busy working 12 hours
per day, seven days per week and newsgroups are a form of relaxation and
education and are not a top priority in my life.
A two cylinder steam locomotive can stop with one set of valves partially
open that will permit steam from that cylinder to escape up the blast
pipe and not provide sufficiant pressure on that cylinder to help in
overcoming the resistance on the train. In this case, the motion is
reversed and the steam is admitted to the other side of the cylinder and
thus into the side where the valve is closed, and the engine can reverse
just a fraction but enough that when put back into forward gear, the valve
is closed and the cyclinder can do its full share of the work.
A simplified version. If you wish, I'll find the detailed explaination.
I was wrong in the use of the term "dead centre" but a steam locomotive
can stall giving the same effect as a "dead centre".
Scott Hiddelston
roger traviss <roge...@islandnet.com> wrote in article
> The Southern's Lord Nelsons were set to give eight exhaust beats per
> revolution. I still haven't found the explaination for steam engines
> stalling on "dead centre" but it was in one of the UK comics, the one
that
> features Cliff Groom and his explainations to the workings of steam.
>
> Cheers
> Roger Traviss
>
> From rainy Victoria, BC Canada
Were Bulleid's pacifics similar to the Lord Nelsons in that they also had
eight beats per cylinder? I remember seeing a video of a Merchant Navy
class loco hauling a long (for Britain) train away from a stop, and all I
heard was this nasal-type chuffing. I never got to count the beats but it
seemed like a lot. I know they had that five-hole blastpipe thingumy, and
that may have contributed. Plenty of power,though
Scotty sco...@whidbey.net
roger traviss
Scott Hiddelston (sco...@whidbey.net) wrote:
: Were Bulleid's pacifics similar to the Lord Nelsons in that they also had
: eight beats per cylinder? I remember seeing a video of a Merchant Navy
: class loco hauling a long (for Britain) train away from a stop, and all I
: heard was this nasal-type chuffing. I never got to count the beats but it
: seemed like a lot. I know they had that five-hole blastpipe thingumy, and
: that may have contributed. Plenty of power,though
All three Bullied pacific classes, Merchant Navy, Battle of Britain and
Westcountry, were three cylinder designs and gace six beats per
revolution. They did have a soft exhaust and when running at any speed
just gave out a loud hissing noise rather than individual exhaust beats.
Jobst Brandt
Roger Traviss writes again:
>>>> Cylinders at 90 degrees will still fall on "dead centre", and
>>>> require the engineer to reverse slightly on order to over come
>>>> it. Quartering at 90 vs 180 merely reduces the chances of
>>>> stopping on dead centre.
>>> Please clarify that.
>> I'll have to look up the reason in my text books. It's something
>> to do with the "mid stroke" cylinder leading or following the
>> exhaust beat. I know it can happen because it has happened to me,
>> several times.
> Citing personal experience does not constitute proof that the well
> understood workings of quadrature are not true. I think you need to
> present more evidence than stating that it is so. Saying that it
> happened to you, only introduces another questionable subject.
>> When I find it I'll repost.
> Never to be heard from again.
> Ooooooooo. Sarcasm. And pray tell what practical steam experience
> do you have?
Alluding to expertise on the internet or claiming to have special
knowledge does not work because the greatest charlatans do this
regularly. What works is to state facts and examples of why one might
believe what is being proposed.
> You are correct in that a steam locomotive with cranks set at 90
> degrees cannot stall on "dead centre". A poor choice of words on my
> part but I didn't want to change what the original poster had
> written.
That's certainly a cryptic excuse for an unambiguously wrong statement.
> However, it is possible for a steam locomotive to stop and not be
> able to restart the train because of the position of the valves at
> the time the motion came to a stop thus giving the same effect as
> "dead centre".
And what may that be. The reversing lever can be put to any position
and the throttle can be opened to apply pressure to the pistons. What
precisely are you talking about? This is dragging on on thin dodges.
> As I said, I've not found my text yet as I'm far to busy working 12
> hours per day, seven days per week and newsgroups are a form of
> relaxation and education and are not a top priority in my life.
Text? You stated you knew how this worked and that it happens. If we
must wait for you to finish school on this, maybe you ought to admit
you don't know and were only guessing. Stop pretending.
> A two cylinder steam locomotive can stop with one set of valves
> partially open that will permit steam from that cylinder to escape
> up the blast pipe and not provide sufficient pressure on that
> cylinder to help in overcoming the resistance on the train.
You are making this up as you go. Please quit while you are only
partly covered with egg on your apron from working in the diner.
Don;t try to operate a locomotive. There is no such position in a
valve gear.
> In this case, the motion is reversed and the steam is admitted to
> the other side of the cylinder and thus into the side where the
> valve is closed, and the engine can reverse just a fraction but
> enough that when put back into forward gear, the valve is closed and
> the cylinder can do its full share of the work.
Go find that text that explains how a steam engine works and come back
when you've got it straight. This is artificial intelligence at its
best.
> A simplified version. If you wish, I'll find the detailed
> explanation. I was wrong in the use of the term "dead centre" but
> a steam locomotive can stall giving the same effect as a "dead
> centre".
Oh, now its virtual dead center. What next?
Jobst Brandt <jbr...@hpl.hp.com>
roger traviss
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: Alluding to expertise on the internet or claiming to have special
: knowledge does not work because the greatest charlatans do this
: regularly. What works is to state facts and examples of why one might
: believe what is being proposed.
have not alluded to any "expertise". I have always couched my
answers so as not to give the impression I am any kind of "expert" as I am
most certainly not. If you remember, I have *always* refered to texts and
do so in this post. I am not pretending to be anything other than someone
who was trying to offer an explaination. You, on the other hand, seem
bent on nothing other than sarcasm. As the balance of this post proves.
: > However, it is possible for a steam locomotive to stop and not be
: > able to restart the train because of the position of the valves at
: > the time the motion came to a stop thus giving the same effect as
: > "dead centre".
: And what may that be. The reversing lever can be put to any position
: and the throttle can be opened to apply pressure to the pistons. What
: precisely are you talking about?
Read on. In fact, read what I wrote before. I'll leave it in the quote
just in case you're memory is failing.
: > As I said, I've not found my text yet as I'm far to busy working 12
: > hours per day, seven days per week and newsgroups are a form of
: > relaxation and education and are not a top priority in my life.
: Text? You stated you knew how this worked and that it happens.
I did *not*. I believe I said something to the effect about not being
sure. I've *always* refered to texts. I am not an expert.
If we
: must wait for you to finish school on this, maybe you ought to admit
: you don't know and were only guessing. Stop pretending.
You seem to be Mr. Know It All, why don't you explain? I'm not the
expert. Get the message? Can you read? How many more times do I have
to repeat myself?
Remember this bit that follows?
: > A two cylinder steam locomotive can stop with one set of valves
: > partially open that will permit steam from that cylinder to escape
: > up the blast pipe and not provide sufficient pressure on that
: > cylinder to help in overcoming the resistance on the train.
: You are making this up as you go. Please quit while you are only
: partly covered with egg on your apron from working in the diner.
: Don;t try to operate a locomotive. There is no such position in a
: valve gear.
Oh? And how does Mr Expert know this? Ever heard of worn motion?
: > In this case, the motion is reversed and the steam is admitted to
: > the other side of the cylinder and thus into the side where the
: > valve is closed, and the engine can reverse just a fraction but
: > enough that when put back into forward gear, the valve is closed and
: > the cylinder can do its full share of the work.
: Go find that text that explains how a steam engine works and come back
: when you've got it straight. This is artificial intelligence at its
: best.
I know how one works, do you?
: > A simplified version. If you wish, I'll find the detailed
: > explanation. I was wrong in the use of the term "dead centre" but
: > a steam locomotive can stall giving the same effect as a "dead
: > centre".
: Oh, now its virtual dead center. What next?
Hardieharhar.
roger traviss
I have now located the article in question. Please refer to the March
1996 issue of "Steam Railway" page 83.
In answer to a question about steam locomotives having to set back because
the drivers say that the locomotive was stopped in "top dead centre", Mr
Clive Groom, an ex driver from Nine Elms shed in London offered, in part,
the following explaination.
"There is no 'dead centre' in a steam locomotive...."
"Dugald Drummond told his enginemen that the least favourable
starting positions were when the right big end was just above the back
quarter and the left big end almost at the bottom bacl angle, or right big
end was just below front quarter and the left big end almost on top front
angle."
"In both cases, on the right side, the piston rod, connecting rod and
crank pin are almost in a straight line, with steam feeding though a
narrowly-opened valve. On the left side the valve is about to claose at
normal 75% cut-off position even in full fore gear. Any push from this
side will be brief. This is as near to a 'dead centre' as you can get -
but a degree of ineptitude by the driver can complete the story."
He goes on to give four explainations of other contributing factors
regarding train brakes not fully released,drivers making 'crash' stops and
having not slack in the train and the following two:-
"The driver might not have bothered to run his reverser to the full
forward gear position before restarting, usually 75%. If he has it at
60%, and the piston on the most beneficial crank angle has stopped at 55%
of its stroke, it will take steam for only a short period before it is cut
off - and none at all if the valve gear has much wear in it. Meanwhile,
the other crank is aound a least effort position".
"The driver may have left the cyclinder cocks closed while waiting for the
signal to start. On modern steam locomotives this results in a steady
flow of atomising steam pouring into the cylinders. On a Bullied
'Pacific' you can see the steam chest gauge rise to 20 or 40lb as you
stand. If this steam enters in front of the piston (big end just above
back quarter), opening the regulator and applying steam to the back of the
piston might not provide enough 'kick' to start a heavy train. If this
steam is building up behind a piston at, say, 51% of its forward stroke,
all the available lack in the system might have been absorbed. Again, the
result is no start, apparently a 'dead centre'".
While my explainations were obviously not as technical and complete, after
all, I am not an expert and was only trying to help, I was on the right
track and had the right idea.
Note the comment above about "a degree of ineptitude by the driver can
complete the story" and you will see why it happened to me.
All I hope is that Mr. Sarcasm reads this and chokes while he eats crow.
roger traviss
Because I don't have an off line mailer I'll post this over three
messages.
Refer to the March 1996 issue of Steam Railway, page 83.
In answer to the question "why do steam locomoives get stuck", Mr Clive
Groom offered the following answers:-
There is no 'dead centre' to a steam locomotive.
"Dugald Drummond told his enginemen that the least favourable starting
positions were when the right big end was just above back quarter and the
left big end almost at bottom back angle, or the right big end was just
below front quarter and the left big end almost on top front angle.
In both cases, on the right side, the piston, connecting rod and the
crankpin are almost in a straight line, with steam feeding through a
narrowly-opened valve. On the left side the valve is about to close at
the normal 75% cut-off position even in full forward gear. Any push from
this side will be brief. This is as near to 'dead centre' as you can get.
roger traviss
Part two.
The explaination also explains how poor braking can leave no slack in the
train and how brakes not fully released will compound the problem.
Two other contributing factors are mentioned, one follows the other will
be in part three.
"The driver may not have bothered to run his reverser to the full gear
position before restarting, usually 75%. If he has it at 60%, and the
piston on the most bebeficial crank angle has stopped at 55% of its
stroke, it will only take steam for a short period before it is cut off -
and none at all if the valve gear has much wear in it. Meanwhile the
other crank is around in a least effort position".
roger traviss
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: Roger Traviss writes again:
: >>>> Cylinders at 90 degrees will still fall on "dead centre", and
: >>>> require the engineer to reverse slightly on order to over come
: >>>> it. Quartering at 90 vs 180 merely reduces the chances of
: >>>> stopping on dead centre.
: >>> Please clarify that.
: >> I'll have to look up the reason in my text books. It's something
: >> to do with the "mid stroke" cylinder leading or following the
: >> exhaust beat. I know it can happen because it has happened to me,
: >> several times.
: > Citing personal experience does not constitute proof that the well
: > understood workings of quadrature are not true. I think you need to
: > present more evidence than stating that it is so. Saying that it
: > happened to you, only introduces another questionable subject.
: >> When I find it I'll repost.
: > Never to be heard from again.
: > Ooooooooo. Sarcasm. And pray tell what practical steam experience
: > do you have?
: Alluding to expertise on the internet or claiming to have special
: knowledge does not work because the greatest charlatans do this
: regularly. What works is to state facts and examples of why one might
: believe what is being proposed.
: > You are correct in that a steam locomotive with cranks set at 90
: > degrees cannot stall on "dead centre". A poor choice of words on my
: > part but I didn't want to change what the original poster had
: > written.
: That's certainly a cryptic excuse for an unambiguously wrong statement.
: > However, it is possible for a steam locomotive to stop and not be
: > able to restart the train because of the position of the valves at
: > the time the motion came to a stop thus giving the same effect as
: > "dead centre".
: And what may that be. The reversing lever can be put to any position
: and the throttle can be opened to apply pressure to the pistons. What
: precisely are you talking about? This is dragging on on thin dodges.
: > As I said, I've not found my text yet as I'm far to busy working 12
: > hours per day, seven days per week and newsgroups are a form of
: > relaxation and education and are not a top priority in my life.
: Text? You stated you knew how this worked and that it happens. If we
: must wait for you to finish school on this, maybe you ought to admit
: you don't know and were only guessing. Stop pretending.
: > A two cylinder steam locomotive can stop with one set of valves
: > partially open that will permit steam from that cylinder to escape
: > up the blast pipe and not provide sufficient pressure on that
: > cylinder to help in overcoming the resistance on the train.
: You are making this up as you go. Please quit while you are only
: partly covered with egg on your apron from working in the diner.
: Don;t try to operate a locomotive. There is no such position in a
: valve gear.
: > In this case, the motion is reversed and the steam is admitted to
: > the other side of the cylinder and thus into the side where the
: > valve is closed, and the engine can reverse just a fraction but
: > enough that when put back into forward gear, the valve is closed and
: > the cylinder can do its full share of the work.
: Go find that text that explains how a steam engine works and come back
: when you've got it straight. This is artificial intelligence at its
: best.
: > A simplified version. If you wish, I'll find the detailed
: > explanation. I was wrong in the use of the term "dead centre" but
: > a steam locomotive can stall giving the same effect as a "dead
: > centre".
: Oh, now its virtual dead center. What next?
: Jobst Brandt <jbr...@hpl.hp.com>
Right, Mr Smart Arse, read my three posts on the reasons for locomotives
stopping on what appears to be 'dead centre' and see just how close I was.
It's obvious that, even though I'm no expert, I know more about the
workings of steam than you do.
Now who should quite while they're "aprtially covered in egg". I think
you should quit before you drown in it.
DO have a nice day. Jerk!
roger traviss
Part three.
"The driver may have left the cyclinder cocks inb the closed position
while waiting for the signal to start. On moder locomotives this results
in a steadt flow of atomising steam pouring into the cyclinders. On a
Bullied 'Pacific' you can see the steam chest gauge rise 20 to 40lb as you
stand. If this steam enters in front of the piston (big end just above
back quarter), opening the regulator and applying steam to the ack piston
might not provide enough 'kick' to start a heavy train. If this steam is
building up behind a piston at, say, 51% of its forward stroke, all the
available slack in the system might have been absorbed. Again, the
result is no start, apparently a 'dead centre'".
Sorry to have to post this over three posts, but I had no choice as my
server kept timeing me out of the newgroup.
This has cost me one hour of my time, I only get one hour per day. I had
to post this to show that while I was not exactly acurate, after all, I'm
not expert, at least I was more correct and on the right track than Mr
Sarcasm was.
It will be worth the loss of one hours time just to see Mr Sarcasm
eat crow. :-)
Cheers
roger traviss
Jim and Dee Woodward (sweet...@xtra.co.nz) wrote:
: While Mr. Brandt was inappropriately heavy handed in his comments to
: you, he was fundamentally right -- there is no "dead center" on a steam
: engine, whether locomotive, marine, or stationery, that has more than
: one cylinder. The article you quote is an example of driver (read
: "engineer" in USA) ineptitude. No one ever said that driving a steam
: locomotive was easy.
I did agree that there is no 'dead centre'.
: I suspect that the beginning of your misunderstanding was in the
: American practice of "taking slack", where a steam locomotive engineer
: would back up to push the slack into the couplers as far back in the
: train as he could. Then when he started the train forward, he didn't
: have to start the whole train at once. I think this did not work in
: British practice, as screw couplers and buffers leave much less slack
: between cars.
That is generally correct. At least when it applies to passenger trains.
There is no slack at all in passenger trains. The screw coupling is
screwed up tight to eleminate any slack at all between passenger coaches
and between the locomotive and the train. However, there is a fair bit of
slack in freight trains which use either the three link coupling or the
instanter coupling. Even when screw coupling cars are in a freight
consist, slack was left between the buffers.
If you read the item carefully, it is, as I stated, possible to stall a
steam locomotive if the valve gear is stopped in the 'wrong' position so
that steam enters both sides of the piston. This gives the same result as
'top dead centre'.
Steam entering both sides of the piston seems to be beyond the
understanding of Mr Brandt. He comments that I should learn more about
the operation of a steam locomotive yey it seems he is the one that needs
the education.
: Taking slack was not a matter of having to back up the locomotive to
: start the locomotive, but to make it easier to start the train.
In North American practice yes. But even North America locomotives could
stall and require the reversal in order to get off so called 'top dead
centre'.
As both you and I point out, engineer ineptitude will also contribute to
the 'top dead centre' effect. Which it undoubtedly did whenever it
happened to me.
E W Wall
I thought he was referring to the same sort of term as "top dead center"
which is used in gasoline powered engines, at least in the USAF. In
pilot training, I was taught that the Lycoming engine in the T-41 was
set to spark at about 3 degrees before "top dead center." This would be
just before the piston reaches its highest point, and the volume of the
cylinder is at its minimum. This allows a little time for propagation
of the flame front so that ignition begins in earnest just as the
cylinder reaches maximum compression. Thus, the majority of the force
of detonation is available for the full stroke of the piston.
Could they mean something like this: full stroke in either direction?
Jim and Dee Woodward
While Mr. Brandt was inappropriately heavy handed in his comments to
you, he was fundamentally right -- there is no "dead center" on a steam
engine, whether locomotive, marine, or stationery, that has more than
one cylinder. The article you quote is an example of driver (read
"engineer" in USA) ineptitude. No one ever said that driving a steam
locomotive was easy.
I suspect that the beginning of your misunderstanding was in the
American practice of "taking slack", where a steam locomotive engineer
would back up to push the slack into the couplers as far back in the
train as he could. Then when he started the train forward, he didn't
have to start the whole train at once. I think this did not work in
British practice, as screw couplers and buffers leave much less slack
between cars.
Taking slack was not a matter of having to back up the locomotive to
roger traviss
E W Wall (ew...@skywire.com) wrote:
: I thought he was referring to the same sort of term as "top dead center"
I think the original poster and Mr Brandt were refering to TDC as it
applies to an internal combustion engine, which of course doesn't happen
in a steam engine, although they can come close. It's this coming close
to TDC, with the valve gear and motion at full extention or stroke on the
side of the engine that is about to recieve steam, that causes problems.
This is made worse by the engineer not having the locomotive in full
forward gear while he waits for the signal to proceed. Steam can build up
behind the piston and cause a counter pressure to the steam entering the
cylinder from the power side when the throttle is opened. Mr Brandt
can't, or won't accept this. The problem is made worse by wear in the
motion which will also cause the valves to be out of time.
: Could they mean something like this: full stroke in either direction?
Yes, see above.
I was unaware that engineers in North America usually set back a little,
to create slack, before they started. This is impossible to do on UK
passenger trains as there is no slack to take up. All the slack is taken
up with the screw coupling as the train is put together in the coach yard.
The slack is also taken up when the train engine 'buffers up' to the
train. In fact, the buffers usually are compressed a little. The
fireman, who is responsible for coupling the engine to the train, as well
conecting the brake hose and steam heat, tights up the screw coupling as
far as it will go.
hac...@worldnet.att.net
roge...@islandnet.com (roger traviss) wrote:
<SNIP>
>If you read the item carefully, it is, as I stated, possible to stall a
>steam locomotive if the valve gear is stopped in the 'wrong' position so
>that steam enters both sides of the piston. This gives the same result as
>'top dead centre'.
>
>Steam entering both sides of the piston seems to be beyond the
>understanding of Mr Brandt. He comments that I should learn more about
>the operation of a steam locomotive yey it seems he is the one that needs
>the education.
>
>: Taking slack was not a matter of having to back up the locomotive to
>: start the locomotive, but to make it easier to start the train.
>
>In North American practice yes. But even North America locomotives could
>stall and require the reversal in order to get off so called 'top dead
>centre'.
>
>As both you and I point out, engineer ineptitude will also contribute to
>the 'top dead centre' effect. Which it undoubtedly did whenever it
>happened to me.
>
>Cheers
>Roger Traviss
>
>From sunny Victoria, BC Canada
I think you are missing a point. IF BOTH INLETS ARE OPEN, as you are
asserting, then putting the engine in reverse will not remove the
problem as the "johnson bar" does not move the slide value. The
purpose of the reverse lever is to change the "stroke" length and the
direction of the stroke. Here in the "states", the side of the piston
containing steam is closed off, on the inlet side, THEN the other
inlet is opened at the same time the exhaust port is opened.
Also there is no TDC possible in later steamers as the center
line of the cylinders is higher than the center line of the drivers,
thus at max extension the main rod is at an angle. In addition the
other side would be at 90 degrees (leading or trailing) and just
starting its power stroke, with max leverage on the drivers.
Ron Bach
hac...@worldnet.att.net
roger traviss
hac...@worldnet.att.net wrote:
: roge...@islandnet.com (roger traviss) wrote:
: I think you are missing a point. IF BOTH INLETS ARE OPEN, as you are
: asserting, then putting the engine in reverse will not remove the
: problem as the "johnson bar" does not move the slide value. The
: purpose of the reverse lever is to change the "stroke" length and the
: direction of the stroke. Here in the "states", the side of the piston
: containing steam is closed off, on the inlet side, THEN the other
: inlet is opened at the same time the exhaust port is opened.
: Also there is no TDC possible in later steamers as the center
: line of the cylinders is higher than the center line of the drivers,
: thus at max extension the main rod is at an angle. In addition the
: other side would be at 90 degrees (leading or trailing) and just
: starting its power stroke, with max leverage on the drivers.
: Ron Bach
We're getting into very technical ground here and my working knowledge is
not that great on the subject.
Many steam locomotives in the UK had their cyclinder centre lines above
the centre line of the drivers and had the cyclinders inclined as well. I
believe this was especially true of the thousands, of inside cylinder
locomotives. The inside cyclide had to be above the centre line of
the leading axle and inclined slighty on 6 coupled locomotives, when the
connecting rod drove on the centre axle even if cranked axles were
used and inclined slighty. Even three cyclinder locomotives
were not immune from stalling on what the drivers called TDC.
Are you sure that there is no possibility of steam being admitted to both
sides of the piston at the same time? What about lead? In UK practice
the valves never fully closed but were designed to leave a 1/4" gap for
"lead" to cushion the piston on the exhaust stroke.
If, on the right side, the piston, connecting rod and the crankpin are in
an almost straight line and with steam feeding through a narrowly open
valve and on the left side, the valve is about to close at 75% cut off
even in full forward gear, then any push from this side will be brief.
When starting a train, this could cause the engine to stall.
Randolph Buchter
Did I miss something, or have you guys forgotten about the drain cocks
on the bottoms of the cylinders? These are what allow those nice
sideways blasts of steam from the cylinders when a locomotive is just
starting out. If your cylinders have cooled and you forget to open these
you could wind up blowing the heads off the cylinders, as condensed
water does not compress very well. This will also allow any pressure
which may have 'leaked' into the cylnder to escape.
Randy Buchter, Fireman, WK&S Steam RR.
Scott Hiddelston
> Jobst Brandt (jbr...@hpl.hp.com) wrote:
>
> : Alluding to expertise on the internet or claiming to have special
> : knowledge does not work because the greatest charlatans do this
> : regularly. What works is to state facts and examples of why one might
> : believe what is being proposed.
would you prefer facts and examples from non experts?
> : The reversing lever can be put to any position
> : and the throttle can be opened to apply pressure to the pistons. What
> : precisely are you talking about? This is dragging on on thin dodges.
Now I understand why you prefer non experts.
Mr Brandt, I fear you would have a much better chance of getting your
newsgroup jollies off at some of the Alt. Flame groups, who would happily
engage you in petty and snide remarks, while offering nothing constructive.
I have been interested in this group for only about 4 months now, and I
have always been impressed with the high levels of knowledge evident among
the posters.
So, dare I say it ?......never to be heard from again
Scotty sco...@whidbey.net
David Forsyth
In article <5d8art$njn$1...@sanjuan.islandnet.com> roge...@islandnet.com (roger traviss) writes:
>From: roge...@islandnet.com (roger traviss)
>Subject: Re: steam locomotive question
>Date: 4 Feb 1997 21:48:45 GMT
if y'all take agander at a valve simulation program and fiddle the values
around a little, you'll probably see this discussed situation arising as you
increase the wear factors.
For such a simulation or two take a gander at my model trains page:
http://www.ru.ac.za/departments/iwr/staff/daf/models/mtrain.html
>Jim and Dee Woodward (sweet...@xtra.co.nz) wrote:
>: While Mr. Brandt was inappropriately heavy handed in his comments to
>: you, he was fundamentally right -- there is no "dead center" on a steam
>: engine, whether locomotive, marine, or stationery, that has more than
>: one cylinder. The article you quote is an example of driver (read
>: "engineer" in USA) ineptitude. No one ever said that driving a steam
>: locomotive was easy.
>I did agree that there is no 'dead centre'.
>: I suspect that the beginning of your misunderstanding was in the
>: American practice of "taking slack", where a steam locomotive engineer
>: would back up to push the slack into the couplers as far back in the
>: train as he could. Then when he started the train forward, he didn't
>: have to start the whole train at once. I think this did not work in
>: British practice, as screw couplers and buffers leave much less slack
>: between cars.
>That is generally correct. At least when it applies to passenger trains.
>There is no slack at all in passenger trains. The screw coupling is
>screwed up tight to eleminate any slack at all between passenger coaches
>and between the locomotive and the train. However, there is a fair bit of
>slack in freight trains which use either the three link coupling or the
>instanter coupling. Even when screw coupling cars are in a freight
>consist, slack was left between the buffers.
>If you read the item carefully, it is, as I stated, possible to stall a
>steam locomotive if the valve gear is stopped in the 'wrong' position so
>that steam enters both sides of the piston. This gives the same result as
>'top dead centre'.
>Steam entering both sides of the piston seems to be beyond the
>understanding of Mr Brandt. He comments that I should learn more about
>the operation of a steam locomotive yey it seems he is the one that needs
>the education.
>: Taking slack was not a matter of having to back up the locomotive to
>: start the locomotive, but to make it easier to start the train.
>In North American practice yes. But even North America locomotives could
>stall and require the reversal in order to get off so called 'top dead
>centre'.
>As both you and I point out, engineer ineptitude will also contribute to
>the 'top dead centre' effect. Which it undoubtedly did whenever it
>happened to me.
>Cheers
>Roger Traviss
>From sunny Victoria, BC Canada
David Forsyth da...@iwr.ru.ac.za
Keeper of the listserver for South African Railways railfans
TRAINS http://www.ru.ac.za/departments/iwr/staff/daf/sartrain.html
GUITAR http://www.ru.ac.za/departments/iwr/staff/daf/guitar/guitar.html
roger traviss
Randolph Buchter (cond...@worldnet.att.net) wrote:
: Did I miss something, or have you guys forgotten about the drain cocks
: on the bottoms of the cylinders? These are what allow those nice
: sideways blasts of steam from the cylinders when a locomotive is just
: starting out. If your cylinders have cooled and you forget to open these
: you could wind up blowing the heads off the cylinders, as condensed
: water does not compress very well. This will also allow any pressure
: which may have 'leaked' into the cylnder to escape.
: Randy Buchter, Fireman, WK&S Steam RR.
Nope, haven't forgotten the drain cocks but they have no effect on what
the post was about, which is stalling a steam engine. Steam engtering
the cylinder on both sides of the piston is only one of the reasons for
it. The main one is the position of the motion when the engine came to a
stop.
This is a very complex subject and I'm getting out of my depth. Sufficed
to say that if someone with the expertise of an ex-Southern Railway and
British Railways driver who still drives steam on the Bluebell railway,
and offers courses to wannabe engineman, say this can happen, then as far
as I'm concerned, it can.
roger traviss
David Forsyth (da...@SPAMLESSiwr.ru.ac.za) wrote:
: In article <5d8art$njn$1...@sanjuan.islandnet.com> roge...@islandnet.com (roger traviss) writes:
: >From: roge...@islandnet.com (roger traviss)
: >Subject: Re: steam locomotive question
: >Date: 4 Feb 1997 21:48:45 GMT
: if y'all take agander at a valve simulation program and fiddle the values
: around a little, you'll probably see this discussed situation arising as you
: increase the wear factors.
Exactly. One of the contributing factors. Probably one of the main ones.
Jobst Brandt
E W Wall writes:
> I thought he was referring to the same sort of term as "top dead
> center" which is used in gasoline powered engines, at least in the
> USAF. In pilot training, I was taught that the Lycoming engine in
> the T-41 was set to spark at about 3 degrees before "top dead
> center." This would be just before the piston reaches its highest
> point, and the volume of the cylinder is at its minimum. This
> allows a little time for propagation of the flame front so that
> ignition begins in earnest just as the cylinder reaches maximum
> compression. Thus, the majority of the force of detonation is
> available for the full stroke of the piston.
There is no combustion in a steam engine and the piston speed is so
low that anticipation will get you nowhere. The valve mechanism is
defined as in the forward or reverse position with respect to the end
of the stroke. It is completely reversible and continuous.
> Could they mean something like this: full stroke in either direction?
No, typically a passenger locomotive uses about 280 wheel rotations
per mile and at 100 miles per hour that is still less than 500 RPM.
Your car idles at about 1000 RPM. If you are trying to come to the
aid of the "expert" who made the TDC claim, forget it, you're wasting
your time, Lycoming and all.
Jobst Brandt <jbr...@hpl.hp.com>
roger traviss
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: No, typically a passenger locomotive uses about 280 wheel rotations
: per mile and at 100 miles per hour that is still less than 500 RPM.
: Your car idles at about 1000 RPM. If you are trying to come to the
: aid of the "expert" who made the TDC claim, forget it, you're wasting
: your time, Lycoming and all.
: Jobst Brandt <jbr...@hpl.hp.com>
I didn't make a TDC claim. Can you get that through your
thick head? I recanted that and explained why. You just responded with
insults. Where did you learn your stuff, from a book? Theory and
practice don't always jive. Only university trained engineers think that.
Your lack of response to the opinion of an expert that I posted here was
very noticable.
You shot your big mouth off and tried to shoot me down with your book
theory, however, you haven't tried to rebut the words of an expert. You
can't, so you still resort to inuendo.
How many times have you driven a steam locomotive? If have several
hundred hours experience. I've had a locomotive, even while running light
engine, "stall" on me several times when trying to move off from a stop,
in both forward and reverse gear. Admittedly it was always the same
locomotive, but it did it.
Your "theory" tell you this can't happen so you resort to insult.
Jobst Brandt
Roger Traviss writes:
> I have now located the article in question. Please refer to the March
> 1996 issue of "Steam Railway" page 83.
> In answer to a question about steam locomotives having to set back
> because the drivers say that the locomotive was stopped in "top dead
> centre", Mr Clive Groom, an ex driver from Nine Elms shed in London
> offered, in part, the following explaination.
> "There is no 'dead centre' in a steam locomotive...."
And goes on to tell in qualitative terms what one side of the engine
and the other are doing. This is an anecdotal report from a driver,
not a technical explanation of how a two cylinder steam engine works.
From the long citation, it seems the upshot is that the torque curve
of quadrature is not flat, and that it has ripple. This is not new
and is one of the reasons steam engines often burn the rails as they
start a heavy load. The characteristic is the two rectified sine
curves shifted by 90 degrees. That is it goes from full torque of one
cylinder (1.0) with the crank at 90 degrees (the top), to both cranks
at 45 degrees (0.707 x 2 =1.4). The weakest position being when one
crank is at maximum torque and the other at zero.
This is not "top dead center" in any sense of the word. You may throw
yourself at the mercy of the readership and defend your hypothesizing
of how steam engines work, but I find it highly presumptuous to
educate others on such matters when you have only read something
anecdotal about it in passing. Besides, at first you claimed to have
experienced this yourself. It doesn't wash.
Jobst Brandt <jbr...@hpl.hp.com>
roger traviss
<5d6uf2$ap6$1...@sanjuan.islandnet.com> <5dj5ff$2...@hplms2.hpl.hp.com>
Distribution:
Jobst Brandt (jbr...@hpl.hp.com) wrote:
: And goes on to tell in qualitative terms what one side of the engine
: and the other are doing. This is an anecdotal report from a driver,
: not a technical explanation of how a two cylinder steam engine works.
: From the long citation, it seems the upshot is that the torque curve
: of quadrature is not flat, and that it has ripple. This is not new
: and is one of the reasons steam engines often burn the rails as they
: start a heavy load. The characteristic is the two rectified sine
: curves shifted by 90 degrees. That is it goes from full torque of one
: cylinder (1.0) with the crank at 90 degrees (the top), to both cranks
: at 45 degrees (0.707 x 2 =1.4). The weakest position being when one
: crank is at maximum torque and the other at zero.
It may be "anecdotal" but it is, AFAIK, true. Are you saying that
practical experience should take second place to book and theory
knowledge?
The rest of what you write I'll take as true. I'm not an engineer and my
practical experience was many moons ago.
I used the term "TDC" for two reasons. 1. That's the term the original
poster used: 2. That was, and is, the term used by ex-British Railway
drivers (Locomotive engineers).
: This is not "top dead center" in any sense of the word. You may throw
: yourself at the mercy of the readership and defend your hypothesizing
: of how steam engines work, but I find it highly presumptuous to
: educate others on such matters when you have only read something
: anecdotal about it in passing. Besides, at first you claimed to have
: experienced this yourself. It doesn't wash.
Why doesn't it wash. Because your theory and book learning says it can't
happen? That's why I quoted another source, which you still don't seem to
want to believe.
I agreed, long ago, that "TDC" was a poor choice or words on my part, but
it was term I was used to. I wasn't trying to educate anyone, but mearly
passing on practical, not book, experience. I have experienced this
stalling of a steam lcomotive, both as a light engine move and while hauling
trains. In one case, we had to get off the engine and move it with pinch
bars as it would not move either forward or reverse. It was stuck!
You seem to dismiss practical experience, both mine and Mr Clive Groome's
who I quoted, and others who I didn't, as unimportant and you seem to
rely mearly on your theory, book learning and isnsults.
I quoted Mr Groome as he is well repected in the UK. It's may interest
you to lknow that if Mr Groome was wrong, then not a single rebutle was
printed in the letters to the editor of Steam Railway. I'm not
sure if I mentioned it, but the question of locomotves stalling or, as
it is generlally known among enginemen in the UK as "getting stuck on
TDC", was raised in the magazine by a signalman working for the Mid Hants
Railway. He regularly notices engines having to "set back" in order to
start their trains.
I give more credance to someone who has been working on steam on a daily
basis for some 40 years (Mr Groome), than I do from someone who seems to
only know the theory from a book. Anyone tradesman or mechnic who works
with any piece equipment knows it takes a mechanical engineer to really screw
things up and complicated the easy and make the easy awkward. The same for
steam engines. The guy on the shop floor and the guy in the cab are the
true experts, just ask any of them who read this news group.
It may interest you to know that I have several hundred hours of actual
steam experience mainly as a fireman. In the UK, being a fireman means
that you occasionaly "have a go" at driving. After all, how else do you
learn? My experience was from the summer of 1962 until January 1965,
working out of Eastleigh shed and Guildford shed on the Southern Reagion of British railways. I
started when I was 16 years old.
I fired everything from expresses on the Waterloo to Bornemouth line to
shunters in the yard. From Merchant Navy, West Country and Battle of
Britian 'pacifics', S-15 4-6-0s, standard class 5 and 4 4-6-0s, Ivatt
2-6-2 tanks, Q1 0-6-0s N, N1, U and U1 2-6-0s, A1X 0-6-0s.
I have experienced "stalling" or as the drivers refered to it "being stuck
on "TDC" on both the the S15 2 cylinder 4-6-0s and the 3 cyclinder
'pacifics' of the MN, WC and BB classes.
What's your practical experience or is it all theory?
Cheers
Roger Traviss
From cloudy Victoria, BC Canada
Bruce H. Jones
Wow! Flame war! I guess I'll jump in and stir the soup. If a steam
locomotive stalls it's usually because of the following:
1) valve gear set wrong.
2) not enough steam
3 guy behind the throttle has HUA
'nuff said
Doc
Jobst Brandt
Roger Traviss writes:
> I didn't make a TDC claim. Can you get that through your thick
> head? I recanted that and explained why.
You can't recant what you didn't do, but I'll take that as an
admission of guilt if you wish.
> You just responded with insults.
"Thick head"? Who's doing what? If you feel insulted by the facts,
maybe you should re-evaluate your claims of understanding how a
railway steam engine works.
> Where did you learn your stuff, from a book? Theory and practice
> don't always jive. Only university trained engineers think that.
I see you have an aversion to learning and feel threatened by engineers
in contrast to locomotive drivers (aka engineers).
> Your lack of response to the opinion of an expert that I posted here
> was very noticeable.
What expert and what did he say about the stalling on top dead center
that you never claimed and fervently defend. I get the notion you
are backpedaling and changing the subject. In your haste to post
endless repetitions maybe you forgot that you started all this by
volunteering that locomotives stall on top dead center, apparently not
being aware of the quadrature arrangement of cranks that I described.
> You shot your big mouth off and tried to shoot me down with your book
> theory, however, you haven't tried to rebut the words of an expert. You
> can't, so you still resort to innuendo.
I think you are trying to rewrite history here. You were the one who
chimed in with the stalling of engines, not I. You were taking a pot
shot at my careful explanation to a reader who asked why there were
four "chuffs" and what relationship they had with respect to the rods'
positions.
> How many times have you driven a steam locomotive? If have several
> hundred hours experience. I've had a locomotive, even while running light
> engine, "stall" on me several times when trying to move off from a stop,
> in both forward and reverse gear. Admittedly it was always the same
> locomotive, but it did it.
Oh that's an old dodge of the sour grapes type. As Mr. Strauss how
many rivets he drove on bridges. He didn't yet he designed the Golden
Gate Bridge. Who knows more about bridge building, the expert steel
worker or the engineer!
> Your "theory" tell you this can't happen so you resort to insult.
Yes, theory is bad stuff, especially if you don't understand it. Just
watch out for them edjumacated kids. They know too much. Stop
exposing yourself.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Scott Hiddelston writes:
>>> Alluding to expertise on the internet or claiming to have special
>>> knowledge does not work because the greatest charlatans do this
>>> regularly. What works is to state facts and examples of why one might
>>> believe what is being proposed.
> would you prefer facts and examples from non experts?
How do YOU detect an expert. Is he one because he claims to be one or
because what he says is supported by evidence and logic. We are
talking about an "expert" who claims that a conventional two cylinder
steam locomotive can get stuck on top dead center and then modified
that claim to be "effectively TDC" but not exactly that.
>>> The reversing lever can be put to any position and the throttle
>>> can be opened to apply pressure to the pistons. What precisely
>>> are you talking about? This is dragging on on thin dodges.
> Now I understand why you prefer non experts.
Nice quip, but what don;t you understand about this? I notice you
offer nothing but tangential commentary. How about explaining how
steam enters both sides of the cylinder at the same time, as was
claimed, or how there is no drive when one of the pistons is at the
end of its stroke.
> Mr Brandt, I fear you would have a much better chance of getting
> your newsgroup jollies off at some of the Alt. Flame groups, who
> would happily engage you in petty and snide remarks, while offering
> nothing constructive.
I have little patience with self appointed and anointed experts who
correct others on the workings of a steam engine when they are dead
wrong. I see you believe everyone has the privilege of offering
conjecture in authoritative style without being called on it. What
sort of newsgroup is it that you prefer.
> I have been interested in this group for only about 4 months now,
> and I have always been impressed with the high levels of knowledge
> evident among the posters. So, dare I say it ?......never to be
> heard from again
If you include the series of incorrect postings from Mr Traviss as
such, I think you are in the wrong group. It was after all he who
corrected others about the workings of steam engines with his
incorrect "facts" while claiming to be an expert. He countered my
explanation of torque during one rotation of the drivers with
conjecture and then backpedaled while claiming persecution. I see you
buy his ploy.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
roger traviss
Distribution:
: Scott Hiddelston writes:
: >>> Alluding to expertise on the internet or claiming to have special
: >>> knowledge does not work because the greatest charlatans do this
: >>> regularly. What works is to state facts and examples of why one might
: >>> believe what is being proposed.
: > would you prefer facts and examples from non experts?
It seems Mr Brandt has this misguided impression that I claim to be an
"expert" on matters of steam, which I'm not. I've repeated this several
times but he doesn't, or will, read what I write. He seems more
interested in insults.
I'm not sure how this all started. Someone mentioned exhaust beats. I
said that if you listen, they sound like "CHUFF, chuff, chuff, chuff, CHUFF,
chuff, chuff, chuff, CHUFF, chuff........" and not just "chuff, chuff,
chuff, chuff".
Someone then asked about TDC and I replied that it was possible for a
locomotive to stall on "TDC" and that it was something to do with lead or
the position of the valve gear or motion "but I wasn't sure and would try
to find my text on the matter" or something to that effect, and went on to
mention that I had experienced this first hand. Hardly the words of an
"expert", would you not agree?
Mr Brandt then launched into his tirade against me all the while refering
to me as a self-proclaimed "expert". He did however, rightly point out
that a steam engine doesn't not have a TDC. My "excuse" is that "TDC" is
what enginemen in the UK call the effect. My steam experience is mainly
in the UK.
I then found and quoted the words of a true expert in steam locomotive
handling and driving who explained the situation far better than I ever
could. I quoted all the relivant items from the magazine to Mr Brandt
who just poopooed the whole thing claiming it was "anecdotal" and should
therefore be ignored. i.e. It couldn't happen because Mr Brandt's book
learning says it can't.
If you notice, Mr Brandt is still being rude and insulting. I will no
longer carry on this discussion with him. Practical experience has shown
that it is possible for a steam locomotive to stop in such a position,
even while light engine, so as to be unable to move. I've quoted a true
"expert" who backs me up and quoted his technical explaination of how this
happens. I've even posed the same question on "uk.railway" and rec'd
several replies backing me up [Mr Brandt will of course say I'm making
this up :-)].
My last thought on this is that perhaps it's just something that only
happen to UK steam? Unlikely though this is.
It's just too bad that there isn't the same interest in steam in North
America as there is in the UK. In the UK there are hundreds of
people with current, day to day hands on experience, unlike in North
America. I was hoping that someone with recent North American steam
experience would write to say they have experienced the same effect.
No such luck. Mr Brandt will no-doubt us this to back up his claim I'm
wrong, but I don't care. I'm right. Been there, done that.
David Forsyth
In article <5dvlpf$f...@hplms2.hpl.hp.com> jbr...@hpl.hp.com (Jobst Brandt) writes:
>From: jbr...@hpl.hp.com (Jobst Brandt)
>Subject: Re: steam locomotive question
[much nocked down for a tenner]
>Jobst Brandt <jbr...@hpl.hp.com>
Jobst, seems the salient 'facts' here are simply this:
Mr Traviss has in fact driven (engineered, whatever) at least one steam loco
that has in fact displayed this 'refusing to go' thing, requiring setting
back a bit to fix it and go forward. He has also cited one other published
driver as having experienced the same thing, likely on a different loco
from the one Mr Traviss drove.
At no point have you claimed to have driven a steam loco, yet you claim that
said steam loco cannot get into a locked state.
I believe that the person with practical experience takes precedence over
the (even highly) qualified theoritician. Theory has it's place, I know a
good deal of it myself in my professional field, however I have found that
here and there the established theories just don't work and you have to go
with what does work.
In this case I tend to believe Mr Travis, not just because he claims to have
been driving and had this happen, but also because he can quote an
independant source for the same info.
I am amazed that other steam drivers here have not made comment on this,
unless of course there are no other steam driver here at all.
I will be foning a friend of mine who drives NG15 Kalahari class 2' gauge
locos near here, and he has other drivers in his organization to enquire
from as well. I will ask them if they have experienced this situation at
all and get back to you.
Jon Rose
Surely the 'getting stuck' is because different positions of the valve
gear offer different amounts of power; the driver has to try stop with
valve gear in the most advantageous position - if he gets it
badly wrong then he's in trouble. Then he has to back up. I've seen this
happen on a 3 cylinder engine (unmodified Bullied West Country
pacific) on an uphill start. I think it's the use of the expression TDC
with its combustion engine connotations that's thrown a spanner in the
works. The engine's not stuck - it just doesn't have enough 'go' to go.
--
Jon Rose,
Crawley, West Sussex, England
John McCoy
In article <5e126m$6go$1...@sanjuan.islandnet.com>, roge...@islandnet.com (roger traviss) writes:
|> NNTP-Posting-Host: island2.islandnet.com
|> X-Newsreader: TIN [version 1.2 PL2]
|>
|> I'm not sure how this all started.
Wish I'd seen the beginning...
|> Someone mentioned exhaust beats. I
|> said that if you listen, they sound like "CHUFF, chuff, chuff, chuff, CHUFF,
|> chuff, chuff, chuff, CHUFF, chuff........" and not just "chuff, chuff,
|> chuff, chuff".
You should get 4 equal "chuffs". If you don't your valve gear is out
of square.
|> Someone then asked about TDC and I replied that it was possible for a
|> locomotive to stall on "TDC" and that it was something to do with lead or
|> the position of the valve gear or motion "but I wasn't sure and would try
|> to find my text on the matter" or something to that effect, and went on to
|> mention that I had experienced this first hand. Hardly the words of an
|> "expert", would you not agree?
TDC was a poor choice of words, from a US perspective. Here we call
it "being stuck on center". Stalling is another poor choice (from the
US perspective), we'd understand that to mean a moving train being
drawn down to a stop (due to lack of tractive effort or steam pressure,
as the case might be).
<snip>
|> My last thought on this is that perhaps it's just something that only
|> happen to UK steam? Unlikely though this is.
Nope, it's happened to me too. I'm of the opinion that it's caused
by wear in the valve gear, since horsing the engine over will get it
moving - if there was no lost motion in the gear, and it was set
square, you should be equally stuck in either direction.
|> It's just too bad that there isn't the same interest in steam in North
|> America as there is in the UK. In the UK there are hundreds of
|> people with current, day to day hands on experience, unlike in North
|> America. I was hoping that someone with recent North American steam
|> experience would write to say they have experienced the same effect.
As you say, it's regretable. I'd guess there are only a few dozen in
the US with steam experience, if you except the live steam modelers.
John
(glad to be one of the "few dozen")
********************************************************************************
John McCoy mc...@plhp002.comm.mot.com
exc...@email.mot.com
Motorola Inc Radio Products Group
8000 W Sunrise Blvd Plantation FL 33322
MDelvec952
Wow, you Euro-railfans are quite animated with your steam discussions.
And the original posting that got you guys started is no longer with the
the posting here, so I don't really know exactly what the original
question was.
But I can say with some certainty that steam locomotives get stuck
more often than tracksiders realize, and there are many reasons for it.
And there are many names for it, too -- all of them profane. "C'mon, you
"%(*&@^%$," are the usual utterings from the hogger who, in spite of a
gauge showing full pressure in the cylinders, got no response from the
wheels for his herculean effort of merely moving a throttle lever.
The best known of these is the Daylight 4-8-4 4449, which has
80-inch drivers and Baker valve gear (Baker gear features all-radial
motion, thus making it more likely to get stuck). No matter how square
the valves are set, or how new the spools are, every once in a while
everything stops on that magic spot and can't get moving again. Several
North American steam engineers have told me, including Smithsonian
Institution's Curator of Transportation William L. Withuhn who is a
licensed engineer and a regular running at Steamtown, that they often
(when they think of it) try to stop a locomotive with the rods all the way
up or down to prevent the phenomenon.
You guys are too critical a crowd for me to take a chance
explaining the physics, but this is a case of once again in practice
something occurrs that's impossible on paper. But I've seen it happen
with the 4449, K4 1361 (Walscharts motion), NKP 2-8-4 765 (Baker),
Steamtown's CPR 4-6-2 2317 (Walscherts), Milwaukee Road 4-8-4 261
(Walschearts) and others. The simple fix is to let the engine roll only
slightly in either direction.
And while I wish that the U.S. was as interested in steam as the
Brits, we do currently have 150 boilers in service, and this June we'll
have four different 4-8-4s and one 4-8-2 on main line rails running at 40
to 70 m.p.h. to keep their place among the freight traffic. And there are
roughly 50 steam locomotives running on almost any warm weather weekend.
The Strasburg Rail Road is actually constructing a replica 4-6-0 and
designing a Belpaire firebox to put on a CPR Ten-Wheeler.
That ain't too shabby for 1997.
....Mike Del Vecchio
Jobst Brandt
Mike Del Vecchio writes:
> I can say with some certainty that steam locomotives get stuck more
> often than tracksiders realize, and there are many reasons for it.
Would you please explain that more carefully. Does this occur because
the drawbar is under load when the engine stops? At what position are
the rods?
> The best known of these is the Daylight 4-8-4 4449, which has
> 80-inch drivers and Baker valve gear (Baker gear features all-radial
> motion, thus making it more likely to get stuck). No matter how
> square the valves are set, or how new the spools are, every once in
> a while everything stops on that magic spot and can't get moving
> again.
I have observed the 44xx locomotives that pulled luxury trains through
this region, including the Lark overnight Pullman between SF and LA
pulling up to 20 car trains. I often watched it start and was always
amazed how smoothly the train started to not wake already sleeping
customers. The exact moment of first motion after hearing the stem
enter the cylinder was difficult to detect. With such a train, the
driver could neither see the position of the rods, nor could he do
much about where they stopped anyway. I never saw an awkward start.
> Several North American steam engineers have told me, including
> Smithsonian Institution's Curator of Transportation William L.
> Withuhn who is a licensed engineer and a regular running at
> Steamtown, that they often (when they think of it) try to stop a
> locomotive with the rods all the way up or down to prevent the
> phenomenon.
Sounds great but please give at least a thin thread of explanation.
From what you say it appears that you believe on can stop a locomotive
with all the rods either up or down. That and that locomotives
operate in quadrature was explained at the outset of this discussion.
The greatest torque being not when the rods are at the top or bottom.
> You guys are too critical a crowd for me to take a chance explaining
> the physics, but this is a case of once again in practice something
> occurrs that's impossible on paper. But I've seen it happen...
What exactly is it that you've seen happen. Can you describe the
circumstances? You allude to knowing th physics behind this
phenomenon but don't mention it further. Could you do more than
use the "I know it when I see it" proof?
> But I've seen it happen with the 4449, K4 1361 (Walscharts motion),
> NKP 2-8-4 765 (Baker), Steamtown's CPR 4-6-2 2317 (Walscherts),
> Milwaukee Road 4-8-4 261 (Walschearts) and others. The simple fix
> is to let the engine roll only slightly in either direction.
How does the engine just "roll" if it is stuck. If you mean take up
slack of the draft gear, as in starting a long freight train, this
has nothing to do with the engine but rather the load to be pulled.
Jobst Brandt <jbr...@hpl.hp.com>
John McCoy
jbr...@hpl.hp.com (Jobst Brandt) wrote:
>Mike Del Vecchio writes:
>> But I've seen it happen with the 4449, K4 1361 (Walscharts motion),
>> NKP 2-8-4 765 (Baker), Steamtown's CPR 4-6-2 2317 (Walscherts),
>> Milwaukee Road 4-8-4 261 (Walschearts) and others. The simple fix
>> is to let the engine roll only slightly in either direction.
>How does the engine just "roll" if it is stuck. If you mean take up
>slack of the draft gear, as in starting a long freight train, this
>has nothing to do with the engine but rather the load to be pulled.
Usually if you're stuck on center you're only stuck one way (there's
probably some cases when you're stuck both ways, but that's never
happened to me). The solution when stuck is to put the reverse
into the opposite corner, and let the engine move just a tad in the
other direction (it doesn't have to be much, sometimes 6 inches
is enough, much less than you'd move to take slack). Then
put the reverse back in the direction you want to go, and the
engine will start to move as it should. You don't mess with the
throttle or brake while doing this, just pull the reverse over,
watch the ground to see yourself start moving, and then
shove the reverse to the other side.
John
Jobst Brandt
John McCoy writes:
>>> But I've seen it happen with the 4449, K4 1361 (Walscharts motion),
>>> NKP 2-8-4 765 (Baker), Steamtown's CPR 4-6-2 2317 (Walscherts),
>>> Milwaukee Road 4-8-4 261 (Walschearts) and others. The simple fix
>>> is to let the engine roll only slightly in either direction.
Walscharts, Walschearts, Walscherts, or wall charts makes not difference.
>> How does the engine just "roll" if it is stuck. If you mean take up
>> slack of the draft gear, as in starting a long freight train, this
>> has nothing to do with the engine but rather the load to be pulled.
> Usually if you're stuck on center you're only stuck one way (there's
> probably some cases when you're stuck both ways, but that's never
> happened to me). The solution when stuck is to put the reverse into
> the opposite corner, and let the engine move just a tad in the other
> direction (it doesn't have to be much, sometimes 6 inches is enough,
> much less than you'd move to take slack). Then put the reverse back
> in the direction you want to go, and the engine will start to move
> as it should. You don't mess with the throttle or brake while doing
> this, just pull the reverse over, watch the ground to see yourself
> start moving, and then shove the reverse to the other side.
Would you please explain what you believe is happening when this
occurs? What "center" do you mean? If the engine can move backward
from its position, then it can move forward, because its torque is
completely symmetrical. If you are at maximum torque forward, you are
also at maximum torque backward by reversing the valving that controls
to which side of the piston steam pressure is applied.
If you understand quadrature, then you must recognize the symmetry
common to these locomotives. They all have air power assisted valve
mechanism, besides which the valves are fully floating, leaving only
piston ring and linkage friction to be overcome. Steam pressure has
practically no effect.
Although the torque is not entirely uniform, there is no dead spot.
Torque is minimum when one rod is at the top (or bottom) and the other
is on wheel center. This give full torque of one cylinder at maximum
leverage. When both drivers have their crank pin at 45 degrees,
torque is 1.414 times as great as when one rod is at its end position.
At no time is torque lower than one cylinder at maximum torque.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
John McCoy writes:
>>> But I've seen it happen with the 4449, K4 1361 (Walscharts motion),
>>> NKP 2-8-4 765 (Baker), Steamtown's CPR 4-6-2 2317 (Walscherts),
>>> Milwaukee Road 4-8-4 261 (Walschearts) and others. The simple fix
>>> is to let the engine roll only slightly in either direction.
Walscharts, Walschearts, Walscherts, or wall charts makes no difference.
John McCoy
jbr...@hpl.hp.com (Jobst Brandt) wrote:
>John McCoy writes:
>> Usually if you're stuck on center you're only stuck one way (there's
>> probably some cases when you're stuck both ways, but that's never
>> happened to me). The solution when stuck is to put the reverse into
>> the opposite corner, and let the engine move just a tad in the other
>> direction (it doesn't have to be much, sometimes 6 inches is enough,
>> much less than you'd move to take slack). Then put the reverse back
>> in the direction you want to go, and the engine will start to move
>> as it should. You don't mess with the throttle or brake while doing
>> this, just pull the reverse over, watch the ground to see yourself
>> start moving, and then shove the reverse to the other side.
>Would you please explain what you believe is happening when this
>occurs? What "center" do you mean?
"Stuck on center" is an engineman's term that goes back eons. I
really don't know exactly what center it's refering to.
>If the engine can move backward
>from its position, then it can move forward, because its torque is
>completely symmetrical.
In theory. In actuallity no steam locomotive is symetrical, and it gets
less so every day it's out of the shop.
> If you are at maximum torque forward, you are
>also at maximum torque backward by reversing the valving that controls
>to which side of the piston steam pressure is applied.
Well, this doesn't happen at maximum torque, obviously. As far as I
can tell it happens when one piston is almost at the end of stroke (and
thus has no leverage on the crank pin, as I hope you recognize) while
the other is shortly past midstroke. Wear in the motion leads to this
piston's valve closing early (actually, what happens is the valve
does not open as the reverse is moved from center to the full position)
and thus no force from this side either. Because it's a wear thing, it
makes sense that it would not necessarily have the same effect in
the other direction.
>If you understand quadrature, then you must recognize the symmetry
>common to these locomotives.
Nothing is perfectly symetrical, least of all steam locomotives.
> They all have air power assisted valve
>mechanism, besides which the valves are fully floating, leaving only
>piston ring and linkage friction to be overcome.
You're joking, right? Go look at all the bearing points in the valve motion,
and tell me friction isn't significant. (BTW, the air assisted reverse is by no
means universal, and it's merely an aid to the engineer anyway, it has no
bearing whatsoever on how the valve motion works)
> Steam pressure has practically no effect.
On what?
>Although the torque is not entirely uniform, there is no dead spot.
>Torque is minimum when one rod is at the top (or bottom) and the other
>is on wheel center. This give full torque of one cylinder at maximum
>leverage. When both drivers have their crank pin at 45 degrees,
>torque is 1.414 times as great as when one rod is at its end position.
>At no time is torque lower than one cylinder at maximum torque.
All this is true, assuming the valve is open. If you got no steam in the
cylinder then you got no torque. Simple enough? Theory says you can't
get stuck because all the valves open & close at precise times. Real
world says the valves don't move precisely when they're intended to,
and sometimes you do get stuck.
John
(just say, someone should call Ross Rowland and see if they got 614T
stuck while it was instrumented...)
MDelvec952
I was reluctant to talk mechanics as a few writers seemed to know much
more than me and weren't afraid to frankly pick apart anything posted.
But y'all are right in that I didn't give enuff info to make any case, so
here goes.
On limited cut-off engines, there is a spot in each direction where
the valves completely cover both ports. When the engineer opens the
throttle, the steam chests fill with full pressure steam, thus registering
on the steam gauge yet, since no steam enters the cylinders, the wheels
don't turn. Simply moving the reverser to the other direction opens the
ports allowing the locomotive to move in the opposite direction, enuff to
allow traveling in the originally desired direction.
Keep in mind that some steam experts disagree with the above
explaination, which was part of my reluctance to get into it. I've never
come across any definative explaination of "limited cut-off," or why some
engines are set up this way. I've been told that some of the
larger-cylinder equipped locos were set up for limited cut-off to limit
the valve from travelling the full distance in its chamber, which, when
running at full stroke, would allow more steam into the cylinder than the
boiler could generate.
On paper this "getting stuck on quarter" can't happen, but it has.
The last time I saw it happen, the locomotive whistled two, and nothing
happened. I was watching the wheels, as I had no way of knowing what
happened in the cab. After about 15 seconds I could see/hear the power
reverse, the locomotive rolled a bit. Then two more toots, and the thing
took off. After the run I asked the engineer what happed, and he said "It
was the damnest thing...."
One of the postings in this or a related thread mentioned a
three-cylinder engine getting stuck this way. That's interesting, and I'd
like to know which loco that way, and whether the 3rd cylinder is
30-degrees off center of the other two, or not. If so, that could make
sense as the eccentric cranks on two-cylinder engines are 30-degrees
either ahead or behind the cylinder travel, and there may be some
relation.
Sorry for being too ambiguous. ....Mike Del Vecchio
roger traviss
John McCoy (*igo...@ix.netcom.com) wrote:
: jbr...@hpl.hp.com (Jobst Brandt) wrote:
John,
Just give up. Mr Brandt says it can't happen, therefore you and me and
all the other engineman that it has happened to are wrong. It didn't
happen, it's theoretically impossible. Don't even bother to quote
detailed descriptions of how it happens, it's a waste on time. Don't
bother to give backup references, he'll just say they don't matter or that
they are wrong. Other people, with real steam experience, have also
posted on this ng that it happens, but all to no avail.
The book says it can't happen, so it can't!!!!!!!!!!!!!!
You've heard the one about the bee being an insect that is aerodynamically
unstable, underpowered and therefore, in theory, unable to fly?
But we all know that a bee can fly.
Why?
Simple, the bee doesn't know squat about aerodynamics. So it flies anyway.
Steam locomotives no nothing about engineering and engineering theory. So
they go ahead and get stuck on what engineman in most english speaking
countries call "Dead centre".
Just be satisfied that we are right and Mr Brandt is wrong. You'll never
get him to admit it. Even, I think, if he is in the cab with you when it
happens. :-)
Cheers
Roger Traviss
From showery Victoria, BC Canada
MDelvec952
I though I responded to this group already.
What is apparently happening when engines get stuck is that they stop is
such a position that the valves actually cover both cylinder ports. When
the throttle opens, no steam is admitted to the cylinders and the wheels
don't move. By simply adjusting or reversing the valve position, the
locomotive can roll for a bit to get itself out of that position. Set the
valves forward again and the locomotive accelerates as if nothing ever
happened. If the hogger knows what he's doing, the tracksider or varnish
rider should never know that it happened.
It's been explained to me that getting stuck on quarter happens
on engines set up for limited cut-off; that's where the valve stroke is
limited from its full travel. I've never seen anything definative written
on limited cut off to fully understand it.
Hope this helps ....Mike Del Vecchio
John McCoy
mdelv...@aol.com (MDelvec952) wrote:
<snip>
> Keep in mind that some steam experts disagree with the above
>explaination, which was part of my reluctance to get into it. I've never
>come across any definative explaination of "limited cut-off," or why some
>engines are set up this way. I've been told that some of the
>larger-cylinder equipped locos were set up for limited cut-off to limit
>the valve from travelling the full distance in its chamber, which, when
>running at full stroke, would allow more steam into the cylinder than the
>boiler could generate.
Limited cutoff was a popular design around the turn of the century, or
somewhat before. It was intended as an economy measure, by
forcing the engineer to run at least partly hooked up. Apparently at
that time there were many lazy engineers who'd run at full stroke
all the time, thereby wasting much steam (and fuel) and wearing out
the boiler faster.
(for those who haven't studied up on this - on a normal steam engine,
the engineer can adjust the length of time the valve is open - from around
65 to 70% of the piston stroke in "full gear" down to always closed when
the reverser is centered. Decreasing the length of time the valve is open
allows the expansion of the steam to move the cylinder, which is more
economical than using full boiler pressure steam; the action of moving
the reverse to decrease the length of time the valve is open is refered
to as "hooking up".
In a limited cutoff engine, the longest the valve could be open would
be around 40% of the stroke - effectively the engine was always run
as if it was hooked up.
Besides being un-economical, on a faster engine running in full gear
will eventually result in the cylinders drawing steam from the boiler
faster than it can be replaced. Depending on the size of the pistons
and drivers, this would occur at a speed around 20 to 45 mph)
As far as I know limited cutoff engines always had a starting valve,
similar to what a compound engine had, which the engineer could
use to admit steam to the cylinders on starting, if the engine happened
to stop with both valves closed, which is fairly likely. This valve would
be small enough not to materially change the steam usage at speed.
John
(just say, this is getting of topic, but hopefully someone is curious...)
S. A. Lee
In <5fimn1$h...@dfw-ixnews8.ix.netcom.com> *igo...@ix.netcom.com (John
McCoy) writes:
>
>mdelv...@aol.com (MDelvec952) wrote:
><snip>
>
>> Keep in mind that some steam experts disagree with the above
>>explaination, which was part of my reluctance to get into it. I've
never
>>come across any definative explaination of "limited cut-off," or why
some
>>engines are set up this way. I've been told that some of the
>>larger-cylinder equipped locos were set up for limited cut-off to
limit
>>the valve from travelling the full distance in its chamber, which,
when
>>running at full stroke, would allow more steam into the cylinder than
the
>>boiler could generate.
>
>Limited cutoff was a popular design around the turn of the century, or
>somewhat before. It was intended as an economy measure, by
>forcing the engineer to run at least partly hooked up. Apparently at
>that time there were many lazy engineers who'd run at full stroke
>all the time, thereby wasting much steam (and fuel) and wearing out
>the boiler faster.
Actually limited cutoff was a fad of the 1920's and first came to
prominence on early "Super Power" designs, but some railroads clung to
it on certain classes of power to the end. Running excessively at full
cutoff does waste steam and thereby, fuel and water, but it's much
harder on the running gear than it is on the boiler.
>
>(for those who haven't studied up on this - on a normal steam engine,
>the engineer can adjust the length of time the valve is open - from
around
>65 to 70% of the piston stroke in "full gear" down to always closed
when
>the reverser is centered.
Non-limited cutoff engines usually worked at 80%-85% cutoff in full
gear. Most limited cutoff engines worked 60%-65% in full gear.
Decreasing the length of time the valve is open
>allows the expansion of the steam to move the cylinder, which is more
>economical than using full boiler pressure steam; the action of moving
>the reverse to decrease the length of time the valve is open is
>refered to as "hooking up".
Well, the cylinder doesn;t move; the piston does. Limited cutoff
engines were conservative of fuel and water, but the trade off for that
economy was reduced starting tractive effort and the aggravating
tendency to get hung up or 'stuck on center' under certain, rarely
occuring conditions.
>
>In a limited cutoff engine, the longest the valve could be open would
>be around 40% of the stroke - effectively the engine was always run
>as if it was hooked up.
See above. They worked 60%-65% in full gear, but the last part of that
stement is absolutely correct.
>
>Besides being un-economical, on a faster engine running in full gear
>will eventually result in the cylinders drawing steam from the boiler
>faster than it can be replaced. Depending on the size of the pistons
>and drivers, this would occur at a speed around 20 to 45 mph)
>
>As far as I know limited cutoff engines always had a starting valve,
>similar to what a compound engine had, which the engineer could
>use to admit steam to the cylinders on starting, if the engine
happened
>to stop with both valves closed, which is fairly likely. This valve
would
>be small enough not to materially change the steam usage at speed.
It wouldn't be used at speed. And it admitted steam to the cylinder
through a separate port arrangment, since the regular ports would be
closed off.
Steve Lee
Jon Rose
MDelvec952 wrote:
>
> I was reluctant to talk mechanics as a few writers seemed to know much
> more than me and weren't afraid to frankly pick apart anything posted.
> But y'all are right in that I didn't give enuff info to make any case, so
> here goes.
>
> On limited cut-off engines, there is a spot in each direction where
> the valves completely cover both ports. When the engineer opens the
> throttle, the steam chests fill with full pressure steam, thus registering
> on the steam gauge yet, since no steam enters the cylinders, the wheels
> don't turn. Simply moving the reverser to the other direction opens the
> ports allowing the locomotive to move in the opposite direction, enuff to
> allow traveling in the originally desired direction.
>
> explaination, which was part of my reluctance to get into it. I've never
> come across any definative explaination of "limited cut-off," or why some
> engines are set up this way. I've been told that some of the
> larger-cylinder equipped locos were set up for limited cut-off to limit
> the valve from travelling the full distance in its chamber, which, when
> running at full stroke, would allow more steam into the cylinder than the
> boiler could generate.
>
> The last time I saw it happen, the locomotive whistled two, and nothing
> happened. I was watching the wheels, as I had no way of knowing what
> happened in the cab. After about 15 seconds I could see/hear the power
> reverse, the locomotive rolled a bit. Then two more toots, and the thing
> took off. After the run I asked the engineer what happed, and he said "It
> was the damnest thing...."
>
> One of the postings in this or a related thread mentioned a
> three-cylinder engine getting stuck this way. That's interesting, and I'd
> like to know which loco that way, and whether the 3rd cylinder is
> 30-degrees off center of the other two, or not. If so, that could make
> sense as the eccentric cranks on two-cylinder engines are 30-degrees
> either ahead or behind the cylinder travel, and there may be some
> relation.
>
> Sorry for being too ambiguous. ....Mike Del Vecchio
Sorry, must disagree. Assuming the cranks are set at 90 degreees to each
other ie one half a stroke behind, this program will show how many valves are
open for each cylinder position :
10 integer
15 let cutoff = 75
20 let left = 0 : left cylinder start at 0% of stroke
30 let right = 50 : but right is half stroke ahead
40 let right = right + 1
50 let left = left + 1
60 : double acting pistons - don't forget
70 if left = 100 let left = 0
80 if right = 100 let right = 0
90 let open = 0
100 if left < cutoff let open = open + 1
110 if right < cutoff let open = open + 1
120 print left right open
130 goto 40
This gave me the following :-
for 75% cutoff two valves are open for 50% of the wheel revolution
and 1 valve is open for the other 50% - at no time are both valves
shut. For 65% cutoff its 30 and 70, for 55% its 20 and 80. You would
need to get down to below 50% cutoff to have some point at which
neither valve is open.
How about this proposition : sometimes one cylinder won't give you
enough shove to move the train, say on a stiff uphill start - so you
back up until the valves/cylinders are in more advantageous position and
off you go. In his book 'The Locomotive Exchanges' C.J. Allen describes
the driver of a 3 cylinder Bullied Merchant Navy pacific needing 5
minutes worth of backing up to get his 500 ton train started on a 1 in 75
grade.
Phillips, III J.A.
S. A. Lee wrote:
> According to "The Steam Locomotive in America" (A.W. Bruce, 1952) there were about 1,000 steam locomotives built in America with limited cutoff, which Bruce defines as 50% to 60% maximum cutoff in full gear. Interestingly, he says that about half of those were PRR locomotives.
Does Bruce state why limited cut-off appears to have been so popular
with PRR the folks?
JPhillips
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|| N O R T H E R N P A C I F I C R A I L W A Y ||
Route of the Vista-Dome North Coast Limited
pogo
stev...@ix.netcom.com(S. A. Lee ) wrote:
>In <5fimn1$h...@dfw-ixnews8.ix.netcom.com> *igo...@ix.netcom.com (John
>McCoy) writes:
>>(for those who haven't studied up on this - on a normal steam engine,
>>the engineer can adjust the length of time the valve is open - from
>around
>>65 to 70% of the piston stroke in "full gear" down to always closed
>when
>>the reverser is centered.
>Non-limited cutoff engines usually worked at 80%-85% cutoff in full
>gear. Most limited cutoff engines worked 60%-65% in full gear.
Well, at least I had the basic idea right :-)
John
(just say, now where did I put Wood's treatise on the Walschaert
Locomotive Valve Gear?)
S. A. Lee
In <5fnq9l$j...@sjx-ixn3.ix.netcom.com> *igo...@ix.netcom.com (pogo)
writes:
>stev...@ix.netcom.com(S. A. Lee ) wrote:
>
>>In <5fimn1$h...@dfw-ixnews8.ix.netcom.com> *igo...@ix.netcom.com
(John
>>McCoy) writes:
>
>
>>>(for those who haven't studied up on this - on a normal steam
engine,
>>>the engineer can adjust the length of time the valve is open - from
>>around
>>>65 to 70% of the piston stroke in "full gear" down to always closed
>>when
>>>the reverser is centered.
>
>>Non-limited cutoff engines usually worked at 80%-85% cutoff in full
>>gear. Most limited cutoff engines worked 60%-65% in full gear.
>
>Well, at least I had the basic idea right :-)
Yes, you did.
I think you'll find that limited cutoff surfaced in the 'teens and was
adopted by Lima in the mid-1920's, but was discarded later. In fact,
very few locomotives were built after 1930 with less than 70% cutoff in
full gear. There were some notable exceptions to that rule, certain
large Santa Fe engines. And while we're at it, most limited cutoff
engines had relatively larger cylinders to make up for the tractive
effort lost by the limited cutoff arrangement.
According to "The Steam Locomotive in America" (A.W. Bruce, 1952) there
were about 1,000 steam locomotives built in America with limited
cutoff, which Bruce defines as 50% to 60% maximum cutoff in full gear.
Interestingly, he says that about half of those were PRR locomotives.
Steve Lee
S. A. Lee
In <331F34...@ix.netcom.com> "Phillips, III J.A."
<Whst...@ix.netcom.com> writes:
>S. A. Lee wrote:
>
>> According to "The Steam Locomotive in America" (A.W. Bruce, 1952)
there were about 1,000 steam locomotives built in America with limited
cutoff, which Bruce defines as 50% to 60% maximum cutoff in full gear.
Interestingly, he says that about half of those were PRR locomotives.
>
>with PRR the folks?
>
>JPhillips
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> || N O R T H E R N P A C I F I C R A I L W A Y ||
> Route of the Vista-Dome North Coast Limited
No, he doesn't. In fact, he wonders why, as well. Considering that
PRR was so tradition-bound in those days, it may have been a classic
case of "we've always done it that."