pre-stretched chains
carl...@comcast.net
http://www.stihllibrary.com/pdf/WhyBuySawChain.pdf
The chainsaw pre-stretching may be just marketing or confusion with
load-testing.
But pre-stretched chains do seem to be exactly what they sound like
when it comes to timing chains:
"On the subject of 'pre-stretched' chain, all chains are assembled
with interference fit on some parts and rivets where there is a very
small clearance between fishplates and rivets as they are assembled.
The 'pre-stretch' process takes any initial settling movement one way
and a chain like the Stag they estimate will stretch 2-3mm--the result
is that the chains can be assembled to the engine and run without any
further stretch on initial running, and last much longer in the engine
before needing adjustment/replacing."
http://www.triumphstag.net/start/phorum/read.php?1,13868
That seems to say that timing chains that aren't pre-stretched will
lengthen (not exactly stretching) 2~3 mm when first run--not much, but
a curious detail.
Google shows a fair number of links to pre-stretched timing chains:
http://www.google.com/search?gbv=2&hl=en&q=%22pre-stretched++chain%22+timing&btnG=Search
Pre-stretched chains seem to have been used in transmissions:
"The Turbo-Hydramatic heavy-duty 3-speed automatic transmission, (or
THM400, TH400) came about during development of the Toronado. Called
the TH425 in FWD form, the transmission's torque converter was
separated from its planetary gearset, with the torque converter
driving the gearset through a 2" wide silent chain-drive called Hy-Vo,
riding on two 12" sprockets. The Hy-Vo chain drive was developed by
GM's Hydra-Matic Division and Morse Chain Division of Borg-Warner. The
chains were made from a very strong hardened steel and required no
tensioners or idler pulleys because they were pre-stretched on a
special machine at the factory."
http://en.wikipedia.org/wiki/Oldsmobile_Toronado
Cheers,
Carl Fogel
Sergio
> I'd never heard of pre-stretched chains:
Are you implying that, a few years from now, we'll hear claims to the
effect that bike chains do pre-stretch?
Sergio
Pisa
raa...@gmail.com
> I'd never heard of pre-stretched chains:
>
> http://www.stihllibrary.com/pdf/WhyBuySawChain.pdf
>
> The chainsaw pre-stretching may be just marketing or confusion with
> load-testing.
>
> But pre-stretched chains do seem to be exactly what they sound like
> when it comes to timing chains:
>
> "On the subject of 'pre-stretched' chain, all chains are assembled
> with interference fit on some parts and rivets where there is a very
> small clearance between fishplates and rivets as they are assembled.
> The 'pre-stretch' process takes any initial settling movement one way
> and a chain like the Stag they estimate will stretch 2-3mm--the result
> is that the chains can be assembled to the engine and run without any
> further stretch on initial running, and last much longer in the engine
> before needing adjustment/replacing."
> http://www.triumphstag.net/start/phorum/read.php?1,13868
>
> That seems to say that timing chains that aren't pre-stretched will
> lengthen (not exactly stretching) 2~3 mm when first run--not much, but
> a curious detail.
>
> Google shows a fair number of links to pre-stretched timing chains:
>
>
> Pre-stretched chains seem to have been used in transmissions:
>
> "The Turbo-Hydramatic heavy-duty 3-speed automatic transmission, (or
> THM400, TH400) came about during development of the Toronado. Called
> the TH425 in FWD form, the transmission's torque converter was
> separated from its planetary gearset, with the torque converter
> driving the gearset through a 2" wide silent chain-drive called Hy-Vo,
> riding on two 12" sprockets. The Hy-Vo chain drive was developed by
> GM's Hydra-Matic Division and Morse Chain Division of Borg-Warner. The
> chains were made from a very strong hardened steel and required no
> tensioners or idler pulleys because they were pre-stretched on a
> special machine at the factory."
> http://en.wikipedia.org/wiki/Oldsmobile_Toronado
>
> Cheers,
>
> Carl Fogel
my understanding ( derived from various published resources ) is that
chain stretch comes from accumulative microscopic wear on each pin.
wear as measured by the radius of the pin makes the diametrical size
of the pin twice as small, meaning the pin wears twice as fast. The
pin shifts over in the chain plate to maintain physical contact with
the tangent of the hole in the chain plate meaning it is no longer in
the centre of that hole making the distance between the centre of one
pin to the next twice that of the wear on the radius of the pin;
multiply a wear on a side ( eq the radius ) of a pin of three ten-
thousandths of an inch by 100 and you have a chain that is .06 longer,
or almost 1/16ths of an inch overall, and you are looking at the point
where you should consider replacing your chain.
campa...@yahoo.com
>
> - Show quoted text -
yea, chains don't "stretch", they wear and lengthen. To "pre-stretch"
a bike chain is a ridiculous concept. Sort of like distressed jeans -
yea they look worn-in, but that's because they ARE actually partially
worn out before you buy them.
carl...@comcast.net
Dear Sergio,
From what I read, it sounds as if timing chains would "stretch" 2~3 mm
shortly after installation.
So yes, bike chains probably do lengthen shortly after installation in
the same way, since they're not "pre-stretched".
The lengthening is apparently 2~3 mm for the whole timing chain.
Assuming roughly similar lengths and numbers of links, that's about
1/10th of an inch lengthening for the whole chain.
The usual recommendation is to replace a bike chain of 112~116 links
when 25 links measure 12 & 1/16th inches. That's about 4/16" for the
whole chain.
0.10" = 1/10th inch (2~3 mm for a whole timing chain)
0.25" = 4/16th inches (1/16" per 25 pins on ~100 pin bike chain)
If the timing and bicycle chains are comparable--
--and that's a big if--
Then about 40% of the "wear" before we're supposed to replace our
chains is actually just the initial "stretch" that the timing chain
folk remove by their "pre-stretching" process. Since timing chains run
in sealed oil baths, they last far longer than exposed bicycle chains.
I can't see what difference it would make whether the initial
"settling" is accomplished by factory "pre-stretching" or by just
riding around the block, but it's a curious detail.
Cheers,
Carl Fogel
carl...@comcast.net
Dear R,
That was my understanding, too.
But if timing chains and bike chains are roughly comparable, then
about 40% of that lengthening is due to the initial settling that the
timing folk remove by factory "pre-stretching".
0.25" = 4/16" = 1/16" per 25 pins on ~100-pin bike chain
0.10" = 2~3 mm pre-stretching on an entire timing chain
It's just a curious detail with no practical application that I can
see for bicycles. The result should be the same, whether a bike chain
is "pre-stretched" at the factory or "stretched" by just riding around
the block.
But it's interesting if the initial 40% of chain "wear" before
replacement would occur in a sealed oil bath almost immediately.
Cheers,
Carl Fogel
Leo Lichtman
<carl...@comcast.net> wrote:
(clip) The result should be the same, whether a bike chain
> is "pre-stretched" at the factory or "stretched" by just riding around
^^^^^^^^^^^^^^^^^^
If the manufacturing process leaves some roughness, which disappears during
initial use, resulting in an increase in length/pitch, then "pre-stretching"
would eliminate this. If we presume that the manufacturer includes this in
his plans, and deliberately makes the chain slightly short before
pre-stretching, then the customer would receive a chain that is the proper
length and does not show rapid initial wear. Does anyone know whether new
pre-stretched chains are on pitch or slightly long, as received by the
customer?
Chalo
>
> raam...@gmail.com wrote:
> >
> >my understanding ( derived from various published resources ) is that
> >chain stretch comes from accumulative microscopic wear on each pin.
> >wear as measured by the radius of the pin makes the diametrical size
> >of the pin twice as small, meaning the pin wears twice as fast. The
> >pin shifts over in the chain plate to maintain physical contact with
> >the tangent of the hole in the chain plate meaning it is no longer in
> >the centre of that hole making the distance between the centre of one
> >pin to the next twice that of the wear on the radius of the pin;
> >multiply a wear on a side ( eq the radius ) of a pin of three ten-
> >thousandths of an inch by 100 and you have a chain that is .06 longer,
> >or almost 1/16ths of an inch overall, and you are looking at the point
> >where you should consider replacing your chain.
>
>
> But if timing chains and bike chains are roughly comparable, then
> about 40% of that lengthening is due to the initial settling that the
> timing folk remove by factory "pre-stretching".
>
> 0.25" = 4/16" = 1/16" per 25 pins on ~100-pin bike chain
> 0.10" = 2~3 mm pre-stretching on an entire timing chain
>
> It's just a curious detail with no practical application that I can
> see for bicycles. The result should be the same, whether a bike chain
> is "pre-stretched" at the factory or "stretched" by just riding around
> the block.
>
> But it's interesting if the initial 40% of chain "wear" before
> replacement would occur in a sealed oil bath almost immediately.
While I've not measured the phenomenon is question, it makes sense to
me that some pitch lengthening would occur quickly as a result of
burnishing down asperities at the chain's points of contact, and that
the rest would occur as abrasive wear over a much longer period. No
parts are infinitely smooth or perfectly shaped, after all, and
bringing all the mechanical interfaces into conformity with each other
will naturally cause the chain to grow longer.
If that's the case, then "pre-stretching" would then be better
characterized as run-in.
Chalo
raa...@gmail.com
>
> - Show quoted text -
I will venture to guess that the prestretched chain is a bit of a
marketing concept by someone who really doesn't understand chains; I
can't see how it would be done without requiring some convoluted
process to account for all the variables... consider, in order to have
a prestrecteched chain the correct size, you have to make a smaller
chain then load it- you are having to hope each link ( sideplate) will
elongate uniformly and without damaging the pin, but if you are
tensioning either side of the pin from a single direction you will be
causing a slight bend in the pin, given that the pin is required to be
pressfit into the sideplate and not pop out it has to have stiffer
properties than elastic so the springback from the bending would be
less likely meaning the pin will be permanently bent or damaged by the
loading/ stretching process as would the sideplate, which I imagine
instead of round holes for the pins would be ellipse shaped as well
( not so desirable is it ?). The more I think about it the less I
would want a prestretched chain for my bike. It would be really nice
to hear an engineer from one of those companies try to explain what
they are doing-because it really doesn't seem to make sense to me.
M-gineering
> my understanding ( derived from various published resources ) is that
> chain stretch comes from accumulative microscopic wear on each pin.
Microscope? Try the naked eye first!
--
/Marten
info(apestaartje)m-gineering(punt)nl
carl...@comcast.net
Dear R,
I will venture to guess that you haven't grasped the initial point
that the pre-stretched chains are engine timing chains, not bicycle
chains.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Leo,
I'm not sure that the idea of the pre-stretch is to obtain a "proper"
length.
I _think_ that the idea is to eliminate the initial rapid "wear" that
would occur in a sealed oil bath and throw the initial adjustment off.
After that initial "wear" or "stretch", the timing chains last
amazingly longer than bike chains.
If bike chains behave as the timing chains are said to behave--
--and that's a big if--
--then it may be possible to take a new bike chain, hang it from a
nail, mark the end, install the chain and ride it up a hill or two,
hang it from the same nail, and see 2~3 mm of "stretch" for the whole
chain, achieving about 40% of the popular "wear" limit in less than 1%
of the expected lifespan of the chain.
If so, it's still just a curious detail. Who bothers to measure his
chain for wear after only a single ride?
I wonder how exactly they pre-stretch a chain? Just a brief, heavy
load? A series of impacts, like the buzzing of an air-hammer? Or maybe
more of a running-in process, with the links turning around sprockets
under load?
Cheers,
Carl Fogel
raa...@gmail.com
> On Wed, 13 May 2009 10:19:32 -0700, "Leo Lichtman"
>
the other thing here is the torque on a regular bike chain is said to
be fairly high, higher than a motorbike even and that I expect, is
greater than the load on a timing chain.
jobst....@stanfordalumni.org
>>> I'd never heard of pre-stretched chains:
>> Are you implying that, a few years from now, we'll hear claims to
>> the effect that bike chains do pre-stretch?
> From what I read, it sounds as if timing chains would "stretch" 2~3
> mm shortly after installation.
> So yes, bike chains probably do lengthen shortly after installation
> in the same way, since they're not "pre-stretched".
> The lengthening is apparently 2~3 mm for the whole timing chain.
> Assuming roughly similar lengths and numbers of links, that's about
> 1/10th of an inch lengthening for the whole chain.
> The usual recommendation is to replace a bike chain of 112~116 links
> when 25 links measure 12 & 1/16th inches. That's about 4/16" for
> the whole chain.
> 0.10" = 1/10th inch (2~3 mm for a whole timing chain)
> 0.25" = 4/16th inches (1/16" per 25 pins on ~100 pin bike chain)
> If the timing and bicycle chains are comparable--
> --and that's a big if--
Although many are not roller chains, but that doesn't affect
lengthening by link-pin-to-sleeve wear, which is the problem.
> Then about 40% of the "wear" before we're supposed to replace our
> chains is actually just the initial "stretch" that the timing chain
> folk remove by their "pre-stretching" process. Since timing chains
> run in sealed oil baths, they last far longer than exposed bicycle
> chains.
They don't and they cannot. An (undersized) out of pitch timing chain
will not run on the sprockets whose pitch is unalterable. Therefore,
these chains must have been manufactured undersized and run in a wear
tester until their pitch is the design pitch of the mechanism in which
it is to serve.
> I can't see what difference it would make whether the initial
> "settling" is accomplished by factory "pre-stretching" or by just
> riding around the block, but it's a curious detail.
As I said, you cannot do that because an undersized chain will not run
on standard sprockets. I can imagine that chains whose bushings have
worn to match link-pins might wear more slowly by the larger contact
area between pin and sleeve, something Fogel Labs could determine by
running a new and well worn chain a number of 1000 cycles to determine
if the worn chain wears more slowly than the new one (that sets the
standard.) Of course they should be otherwise identical.
Jobst Brandt
jobst....@stanfordalumni.org
>> (clip) The result should be the same, whether a bike chain
>>> is "pre-stretched" at the factory or "stretched" by just riding
>>> around the block. (clip)
>>^^^^^^^^^^^^^^^^^^
>> If the manufacturing process leaves some roughness, which
>> disappears during initial use, resulting in an increase in
>> length/pitch, then "pre-stretching" would eliminate this. If we
>> presume that the manufacturer includes this in his plans, and
>> deliberately makes the chain slightly short before pre-stretching,
>> then the customer would receive a chain that is the proper length
>> and does not show rapid initial wear. Does anyone know whether new
>> pre-stretched chains are on pitch or slightly long, as received by
>> the customer?
> I'm not sure that the idea of the pre-stretch is to obtain a
> "proper" length.
> I _think_ that the idea is to eliminate the initial rapid "wear"
> that would occur in a sealed oil bath and throw the initial
> adjustment off. After that initial "wear" or "stretch", the timing
> chains last amazingly longer than bike chains.
Do they?
> If bike chains behave as the timing chains are said to behave --and
> that's a big if--
> --then it may be possible to take a new bike chain, hang it from a
> nail, mark the end, install the chain and ride it up a hill or two,
> hang it from the same nail, and see 2~3 mm of "stretch" for the
> whole chain, achieving about 40% of the popular "wear" limit in less
> than 1% of the expected lifespan of the chain.
Can we get rid of that word "stretch" and use "wear"? You needn't
ride to literally "stretch" a chain. Merely load it in tension and
see what you get.
> If so, it's still just a curious detail. Who bothers to measure his
> chain for wear after only a single ride?
> I wonder how exactly they pre-stretch a chain? Just a brief, heavy
> load? A series of impacts, like the buzzing of an air-hammer? Or
> maybe more of a running-in process, with the links turning around
> sprockets under load?
Certainly not a tensile load. They are using the misnomer "stretch"
the same as the bicycle folks do because they don't understand the
process that lengthens chain pitch.
Jobst Brandt
Leo Lichtman
<carl...@comcast.net> wrote: I'm not sure that the idea of the
> length.
If the initial run-in of a chain eliminates minute irregularities early in
its life, and thereby causes it to gain a little length (sometimes called
"stretch," for convenience) then the chain ought to be manufactured so it
reaches the proper length AFTER run-in.
^^^^^^^^^^^^^^^^^^^^^^^^
>
> I _think_ that the idea is to eliminate the initial rapid "wear" that
> would occur in a sealed oil bath and throw the initial adjustment off.
^^^^^^^^^^^^^^^^^^^^^^^
I agree, but eliminating the initial rapid wear is necesarily accompanied by
an increase in length. It would seem that this would need to be
pre-compensated.
Andre Jute
> I'd never heard of pre-stretched chains:
>
> http://www.stihllibrary.com/pdf/WhyBuySawChain.pdf
>
> The chainsaw pre-stretching may be just marketing or confusion with
> load-testing.
>
> But pre-stretched chains do seem to be exactly what they sound like
> when it comes to timing chains:
>
> "On the subject of 'pre-stretched' chain, all chains are assembled
> with interference fit on some parts and rivets where there is a very
> small clearance between fishplates and rivets as they are assembled.
> The 'pre-stretch' process takes any initial settling movement one way
> and a chain like the Stag they estimate will stretch 2-3mm--the result
> is that the chains can be assembled to the engine and run without any
> further stretch on initial running, and last much longer in the engine
> before needing adjustment/replacing."
> http://www.triumphstag.net/start/phorum/read.php?1,13868
>
> That seems to say that timing chains that aren't pre-stretched will
> lengthen (not exactly stretching) 2~3 mm when first run--not much, but
> a curious detail.
>
> Google shows a fair number of links to pre-stretched timing chains:
>
>
> Pre-stretched chains seem to have been used in transmissions:
>
> "The Turbo-Hydramatic heavy-duty 3-speed automatic transmission, (or
> THM400, TH400) came about during development of the Toronado. Called
> the TH425 in FWD form, the transmission's torque converter was
> separated from its planetary gearset, with the torque converter
> driving the gearset through a 2" wide silent chain-drive called Hy-Vo,
> riding on two 12" sprockets. The Hy-Vo chain drive was developed by
> GM's Hydra-Matic Division and Morse Chain Division of Borg-Warner. The
> chains were made from a very strong hardened steel and required no
> tensioners or idler pulleys because they were pre-stretched on a
> special machine at the factory."
> http://en.wikipedia.org/wiki/Oldsmobile_Toronado
>
> Cheers,
>
> Carl Fogel
This is a brilliant post. I have never been at ease with the concept
of a cheap, crude cycling artifact with as many moving parts as a
chain being worshipped, as it is on RBT, as if it were an icon of
watchmaking precision. It has always seemed clear to me that
manufacturing tolerances and slippages, materials differences,
differential wear on assembly machinery, and a hundred other
cumulative factors would cause a chain in use to elongate
fractionally, in the single direction in which power is applied, well
before there was any wear on the rollers, which the likes of Jobst
Brandt claim is the sole factor responsible for chain elongation.
Andre Jute
Coming out of the closet on chains
Andre Jute
Perhaps there's a market for "precision chains" which would in fact be
prestretched chains. We might coin the word "pre-settled" to avoid the
Brandites and other luddites shouting down customers of these chains,
guaranteed to serve at least twice as far than oldfashioned
unstretched, sorry, I mean not pre-settled chains.
Andre Jute
Relentless rigour -- Gaius Germanicus Caesar
jobst....@stanfordalumni.org
>> I'd never heard of pre-stretched chains:
http://www.stihllibrary.com/pdf/WhyBuySawChain.pdf
>> The chainsaw pre-stretching may be just marketing or confusion with
>> load-testing.
>> But pre-stretched chains do seem to be exactly what they sound like
>> when it comes to timing chains:
# On the subject of 'pre-stretched' chain, all chains are assembled
# with interference fit on some parts and rivets where there is a very
# small clearance between fishplates and rivets as they are assembled.
# The 'pre-stretch' process takes any initial settling movement one
# way and a chain like the Stag they estimate will stretch 2-3mm--the
# result is that the chains can be assembled to the engine and run
# without any further stretch on initial running, and last much longer
# in the engine before needing adjustment/replacing.
http://www.triumphstag.net/start/phorum/read.php?1,13868
>> That seems to say that timing chains that aren't pre-stretched will
>> lengthen (not exactly stretching) 2~3 mm when first run--not much,
>> but a curious detail.
>> Google shows a fair number of links to pre-stretched timing chains:
>> Pre-stretched chains seem to have been used in transmissions:
>> "The Turbo-Hydramatic heavy-duty 3-speed automatic transmission,
>> (or THM400, TH400) came about during development of the Toronado.
>> Called the TH425 in FWD form, the transmission's torque converter
>> was separated from its planetary gearset, with the torque converter
>> driving the gearset through a 2" wide silent chain-drive called
>> Hy-Vo, riding on two 12" sprockets. The Hy-Vo chain drive was
>> developed by GM's Hydra-Matic Division and Morse Chain Division of
>> Borg-Warner. The chains were made from a very strong hardened
>> steel and required no tensioners or idler pulleys because they were
>> pre-stretched on a special machine at the factory."
http://en.wikipedia.org/wiki/Oldsmobile_Toronado
> This is a brilliant post. I have never been at ease with the
> concept of a cheap, crude cycling artifact with as many moving parts
> as a chain being worshipped, as it is on RBT, as if it were an icon
> of watchmaking precision. It has always seemed clear to me that
> manufacturing tolerances and slippages, materials differences,
> differential wear on assembly machinery, and a hundred other
> cumulative factors would cause a chain in use to elongate
> fractionally, in the single direction in which power is applied,
> well before there was any wear on the rollers, which the likes of
> Jobst Brandt claim is the sole factor responsible for chain
> elongation.
I have never stated that chain lengthening is wear on rollers: "wear
on the rollers, which the likes of Jobst Brandt claim is the sole
factor responsible for chain elongation". Beside that, new bicycle
chains are highly accurate with a cumulative tensioned length accuracy
small enough not to be visible against commercial steel measuring
tapes or rulers. This is important because the functional piece of
chain length of interest is that which is engaged with driven sprocket
in use, having an even smaller cumulative dimensional tolerance.
Jobst Brandt
datakoll
apologizefor not reading thru but occurs that the chain stretch
machine was PERFECT for breaking ina new chain. And at that level of
awareness, given that many Toro went to the grave waiting for a new ch$
$$ain, incliude statistical analysis of what your machine would do
breakin' a chain.
As for chainsaw users, there's the complete spectrum from neanderhal
unconscious to intellectual incompetence. Again, statisically,
controlling a brealkin period at the factory may quant improve the
factory's position.
"there's a lotta shit on the road"
Tom_Sherman
> [...]
> As for chainsaw users, there's the complete spectrum from neanderhal
> unconscious to intellectual incompetence. Again, statisically,
> controlling a brealkin period at the factory may quant improve the
�ever get suspicious about chain saw oil attracting wood dust? generally
mucking up after two cuts? try dumping hot oil into a container just
right sized for inserting the running blade on the job.
rrrrrrrrrrrrrrrrrrrrr..... plus 750 rpm!" - gene daniels
I want video!
--
Tom Sherman - 42.435731,-83.985007
LOCAL CACTUS EATS CYCLIST - datakoll
Jay Beattie
With a chain saw, you adjust the bar, and there is no sproket
engagement/pitch problem that I know about. I toss a chain when I get
tired of sharpening it. The lumberjacks I know (my wife, actually,
she was in the Forest Service) used to break links. But they were
sawing through some pretty big stuff with giant saws. -- Jay Beattie.
jim beam
how much "undersized" jobst? one micron per meter? two?
> I can imagine that chains whose bushings have
> worn to match link-pins might wear more slowly by the larger contact
> area between pin and sleeve, something Fogel Labs could determine by
> running a new and well worn chain a number of 1000 cycles to determine
> if the worn chain wears more slowly than the new one (that sets the
> standard.) Of course they should be otherwise identical.
rather than imagine, why not consult your friendly local library? there
are tables of chain wear vs. service life showing high initial wear, and
subsequently low service wear of which you're apparently unaware.
carl...@comcast.net
<phil(at)lee-family(dot)me(dot)uk> wrote:
>raa...@gmail.com considered Wed, 13 May 2009 13:09:00 -0700 (PDT) the
>Chain loading would be tension, rather than torque, and would be FAR
>higher on any decent sized motorcycle. Try fitting pedals to a Harley,
>and see how far (or fast) you can move it - in ANY gear ratio.
>If you can get it moving, turn around and try again, because you must
>have been facing downhill!
>Look at the size of the chain on a motorcycle - they wouldn't go to
>the cost (and weight) of a chain that big unless they needed to, and
>motorcycles do genuinely snap chains - through the sideplates, not
>from a pin coming loose.
>Even if cyclists do snap sideplates, it is incredibly rare.
>On motorcycles, it's the normal failure mode.
>Ask anyone who has marshalled at a motorcycle race - chains snap (and
>they are bloody hot when they are fresh off the bike).
>I'd expect timing chain to be similarly stressed to bicycle chain, but
>it runs in a far more benign environment.
>
>I strongly suspect that the initial "stretch" is the squeezing of
>excess assembly lubricant out of the bearings.
Dear Phil,
Actually, even cars don't put out impressive torque compared to
bicycles.
The differences between motorcycles and bicycles are in the gearing
and the RPM.
The bicycle is powered at a pitiful 50~100 rpm by a high-torque pair
of legs.
A single-cylinder motorcycle can often run up to 10,000 rpm, a
thousand times faster. The measured torque is surprisingly low.
With roughly similar-size rear tires, a typical bicycle is a simple
53~30 front to 11~34 rear.
Some motorcycles will almost reverse the 53x11 to a 14x52--just what
you see on a motorcycle involves incredibly low gearing.
Meanwhile, hidden inside the gearbox of the motorycle is the primary
reduction gearing that is then reduced further by ~5 gears.
To give a pair of specific examples, cruising in top gear at 20 mph on
a 53x11 bicycle requires about 52 rpm.
Cruising just as gently in top gear on an elderly trials motorycle,
the same 20 mph requires about 2300 rpm--about 50 times the rpm of the
bicycle.
The bicycle's high-speed gearing, put in 11r x 55f form, is about
0.2:1--that's zero point two to one.
The motorcycle's high-speed gearing ((52r x14f) * 3.714 secondary
reduction * 0.750 fifth gear) is about 9.1:1, about 50 times higher.
Bicycles are high-torque, low-rpm machines.
Motorcycles and cars are low-torque, incredibly high-rpm machines.
You can easily put high torque on a bike--think of just standing on a
level pedal. If you weigh 180 pounds, your weight on a 175 mm crank
produces just over 100 foot-pounds of torque.
That's about what a lot of cars put out. Look up a few torque values
for motorcycles and cars, and you'll be surprised by how low they are.
A typical sedan like the Toyota Corolla puts out only 128 foot-pounds
of torque--but it does so at 4,000 rpm, not at 50~100 rpm:
http://findarticles.com/p/articles/mi_qn4179/is_20000129/ai_n11741185/
Even pathetic engine torque produces wonderful results at high rpm.
In the 1970s, the Honda SL125 motorcycle produced only 5 (five, not
fifty) foot pounds of torque.
(You can produce 5 foot-pounds of torque with one finger.)
The Honda engine had the mildest, flattest torque curve imaginable--it
didn't rise or fall more than 1/4 of a foot-lb for its tested rpm
range. "We've seen bigger bumps on five-year-old girls" was how the
testers described it.
But applied at 5,000 rpm, that tiny 5 foot-pounds of torque would let
you blow any 50~100 rpm bicyclist into the weeds, even though he was
putting 50~100 foot-pounds of torque by standing on the pedal.
(Try wiggling your finger 5,000 times a minute.)
The cars and motorcycles work by putting out roughly the same torque
per stroke as a bicyclist--but they do it a hundred to a thousand
times faster.
Cheers,
Carl Fogel
M-gineering
> Chain loading would be tension, rather than torque, and would be FAR
> higher on any decent sized motorcycle. Try fitting pedals to a Harley,
> and see how far (or fast) you can move it - in ANY gear ratio.
> If you can get it moving, turn around and try again, because you must
> have been facing downhill!
don't confuse power and torque.
Step on a bicycle crank and you're exerting a torque of .175 x 850=
150Nm. The Harley puts out 100 Nm or so. It'll move fine but slowly,
provided you don't fall over first
--
/Marten
info(apestaartje)m-gineering(punt)nl
carl...@comcast.net
>I'd never heard of pre-stretched chains:
>
> http://www.stihllibrary.com/pdf/WhyBuySawChain.pdf
>
>The chainsaw pre-stretching may be just marketing or confusion with
>load-testing.
>
>But pre-stretched chains do seem to be exactly what they sound like
>when it comes to timing chains:
>
>"On the subject of 'pre-stretched' chain, all chains are assembled
>with interference fit on some parts and rivets where there is a very
>small clearance between fishplates and rivets as they are assembled.
>The 'pre-stretch' process takes any initial settling movement one way
>and a chain like the Stag they estimate will stretch 2-3mm--the result
>is that the chains can be assembled to the engine and run without any
>further stretch on initial running, and last much longer in the engine
>before needing adjustment/replacing."
> http://www.triumphstag.net/start/phorum/read.php?1,13868
>
>That seems to say that timing chains that aren't pre-stretched will
>lengthen (not exactly stretching) 2~3 mm when first run--not much, but
>a curious detail.
>
>Google shows a fair number of links to pre-stretched timing chains:
>
>http://www.google.com/search?gbv=2&hl=en&q=%22pre-stretched++chain%22+timing&btnG=Search
>
>Pre-stretched chains seem to have been used in transmissions:
>
>"The Turbo-Hydramatic heavy-duty 3-speed automatic transmission, (or
>THM400, TH400) came about during development of the Toronado. Called
>the TH425 in FWD form, the transmission's torque converter was
>separated from its planetary gearset, with the torque converter
>driving the gearset through a 2" wide silent chain-drive called Hy-Vo,
>riding on two 12" sprockets. The Hy-Vo chain drive was developed by
>GM's Hydra-Matic Division and Morse Chain Division of Borg-Warner. The
>chains were made from a very strong hardened steel and required no
>tensioners or idler pulleys because they were pre-stretched on a
>special machine at the factory."
> http://en.wikipedia.org/wiki/Oldsmobile_Toronado
>
>Cheers,
>
>Carl Fogel
Yikes, what a sheltered life I've led!
Almost fourteen thousand hits from Google for "pre-stressed" + "chain"
+ "stretched":
http://www.google.com/search?hl=en&lr=&q=%22pre-stressed%22+chain+stretched&btnG=Search
Phrases like "reduce initial chain adjustments" pop up quickly in the
pages about motorcycle, ATV, and timing chains.
"Precision Roller Chain is run and pre-stressed or stretched, which
accurately establishes length, evenly distributes the working load and
prevents rapid elongation during initial run-in."
http://pacificindustries.com/elite/roller.html
Cheers,
Carl Fogel
carl...@comcast.net
Yikes again!
I can't even console myself that pre-stretched chains are something
new that popped up while I wasn't paying attention:
"Certain peculiarities of sprocket chains make it undesirable, it
seems, to use them without a tension idler, especially for large
motors. The chains, as they come from the factories, never correspond
accurately to the length arrived at by multiplying the pitch by the
number of links. According to Renold's own statements, the greatest
care in manufacture still leaves an average difference of 0.025 mm. in
the length of links, when the total lengths of two chains, which
should be alike, are compared. It 'can therefore happen that new
chains refuse to fit upon a construction laid out according to the
above-mentioned formula. Hereto comes the fact that chains stretch.
During- the first loo hours of use the stretch amounts to from 0.2 to
0.4 per cent. After this first "settling" of the chain, the stretch by
wear sets in but ' amounts to only about a one-hundredth part of the
figures mentioned, for the same amount of work. Some manufacturers
therefore sell pre-stretched chains. Nevertheless, the conviction is
growing that a tension idler is the best remedy for the troubles
referred to."
--page 350, "The Automobile", 1913
http://books.google.com/books?id=cNMqAAAAMAAJ&printsec=titlepage#PPA350,M1
The article seems to be talking about industrial motors set at
distances according to formulas, running mostly half-inch pitch chain.
This means that our grandfathers expected a large "stretch" due to
"initial settling" in the first 100 hours of use.
After that, the rate of "stretch" dropped by two orders of magnitude
("only about a one-hundredth part) because the elongation was "stretch
by wear"--which would have been much slower in cleaner conditions than
we suffer with exposed bike chains.
Cheers,
Carl Fogel
pm
> The motorcycle's high-speed gearing ((52r x14f) * 3.714 secondary
> reduction * 0.750 fifth gear) is about 9.1:1, about 50 times higher.
If the question is chain tension, the highest chain tensions are
achieved in the lowest gears. A trials bike will have a pretty low
first, maybe a 10:1 primary * gearbox. 5 foot-pounds of torque at the
crankshaft, going through the gearbox then turning a 14 tooth sprocket
with 5/8" pitch chain nets you 1900 N of chain tension.
> You can easily put high torque on a bike--think of just standing on a
> level pedal. If you weigh 180 pounds, your weight on a 175 mm crank
> produces just over 100 foot-pounds of torque.
Doing this stomp on, say, a 32t chainring nets you some 2100 N of
chain tension. On a 22t chainring, this theoretically goes up to 3000
N. But unless you are cross-chaining a small-small ratio you will find
it nearly impossible to actually exert your whole body weight in the
pedal in such a gear. The rear wheel would slip out, or you would
wheelie; in any case the pedal will move out of the way of your foot
so easily that it will not support your weight until reaching bottom
of the stroke. But the point is, chain tension on an anemic small
trials motorcycle is comparable to the maximum chain tension seen on a
bicycle.
But I thought the original question was timing chains -- these aren't
driving the mass of the vehicle, just the cams. So not much tension at
all in these (and the timing chain on my motorbike has smaller pins
than those on a bicycle chain.)
-pm
Sergio
It 'can therefore happen that
new
> chains refuse to fit upon a construction laid out according to the
> above-mentioned formula. Hereto comes the fact that chains stretch.
> During- the first loo hours of use the stretch amounts to from 0.2 to
> 0.4 per cent. After this first "settling" of the chain, the stretch by
> wear sets in but ' amounts to only about a one-hundredth part of the
> figures mentioned, for the same amount of work. Some manufacturers
> therefore sell pre-stretched chains.
So, let's call it pre-worn to fit: the last step of the machining
process.
Sergio
Pisa
jobst....@stanfordalumni.org
Careful there. Cam drive is full of pulse loading at the moment when
cam followers leave and return to the base circle when lifting valves.
These are the phases where valve float is initiated by elasticity
between crankshaft drive and cam, and cam and valve. That is why cams
must be driven by backlash free chains or belts, and valves must be
direct drive from an overhead cam.
There are no engines being built with hydraulic tappets, push rods,
rocker arms, simple valve springs or valve clearance adjusting screws.
There is a problem there that was ignored by casual thinking of low
speed motion.
Jobst Brandt
RonSonic
Stamping produces some fairly dirty holes and pressing pins into them is going
to be imprecise. I'd expect you'd get a more consistent product after some run
in to settle parts in.
Helmut Springer
> Stamping produces some fairly dirty holes
That depends on technology used, high precision stamping is
amazingly accurate.
--
MfG/Best regards
helmut springer panta rhei
jobst....@stanfordalumni.org
>>> It can therefore happen that new chains refuse to fit upon a
>>> construction laid out according to the above-mentioned formula.
>>> Hereto comes the fact that chains stretch. During- the first l00
>>> hours of use the stretch amounts to from 0.2 to 0.4 per cent.
>>> After this first "settling" of the chain, the stretch by wear sets
>>> in but amounts to only about a one-hundredth part of the figures
>>> mentioned, for the same amount of work. Some manufacturers
>>> therefore sell pre-stretched chains.
I find interesting that the duty cycle envisioned is hours, rather
than repetition of articulation under load.
>> So, let's call it pre-worn to fit: the last step of the machining
>> process.
> Stamping produces some fairly dirty holes and pressing pins into
> them is going to be imprecise. I'd expect you'd get a more
> consistent product after some run in to settle parts in.
The art of making precision roller chains has been well developed and
is not as hit-and-miss as depicted. Let's get back to the original
subject, which is, chain elongation from frictional wear and the
effects of load.
Jobst Brandt
carl...@comcast.net
<phil(at)lee-family(dot)me(dot)uk> wrote:
>carl...@comcast.net considered Wed, 13 May 2009 22:29:07 -0600 the
>perfect time to write:
>
><loads of stuff about the internal gear rations of the engine/primary
>reduction/gearbox which is utterly irrelevant>
>
>Try hooking up pedals to the same rear sprocket (on the motorcycle) as
>the normal drive uses. Use whatever chainwheel you like.
>
>Can you break traction, with the normal weight on the normal
>motorcycle tyre?
>
>The motorcycle can.
Dear Phil,
You might as well ask if I can lift a car with jack.
A typical bicycle's lowest overall gearing is probably a 30x34, about
1:1 gearing.
A trials motorcycle's lowest overall gearing with the two external
sprockets and the primary and secondary reduction is around 35:1.
So yes, I can break traction by stomping on a pedal with 35:1 gearing.
Leverage is a wonderful thing.
Of course, the traction will break for only a fraction of an inch
because I have only a single power pulse available, not a thousand.
The duration of the tension is not the same thing as the tension.
Cheers,
Carl Fogel
Michael Press
carl...@comcast.net wrote:
What does torque have to do with chain tension?
They are different units.
You should study a year of physics,
and stop talking about these things
as if you know. Being corrected all
the time is no substitute for doing
the exercises.
--
Michael Press
datakoll
PEOPLE TELL ME FOGEL IS A NINY BUT LOOK HERE THERE'S PROOF HE'S SNOT.
souds like the Armstrong approach, no ? pass the ATP
Carl, try it holding the crank and rod !
Now for the electric motor Indy controverysey....
"a bird in hand is worth .3 euro"
jobst....@stanfordalumni.org
>>>>>>> (clip) The result should be the same, whether a bike chain is
>>>>>>> "pre-stretched" at the factory or "stretched" by just riding
>>>>>>> around the block. (clip)
>>>>>> If the manufacturing process leaves some roughness, which
>>>>>> disappears during initial use, resulting in an increase in
>>>>>> length/pitch, then "pre-stretching" would eliminate this. If
>>>>>> we presume that the manufacturer includes this in his plans,
>>>>>> and deliberately makes the chain slightly short before
>>>>>> pre-stretching, then the customer would receive a chain that is
>>>>>> the proper length and does not show rapid initial wear. Does
>>>>>> anyone know whether new pre-stretched chains are on pitch or
>>>>>> slightly long, as received by the customer?
>>>>> I'm not sure that the idea of the pre-stretch is to obtain a
>>>>> "proper" length.
>>>>> I _think_ that the idea is to eliminate the initial rapid "wear"
>>>>> that would occur in a sealed oil bath and throw the initial
>>>>> adjustment off. After that initial "wear" or "stretch", the
>>>>> timing chains last amazingly longer than bike chains.
>>>>> If bike chains behave as the timing chains are said to behave
>>>>> --and that's a big if-- then it may be possible to take a new
>>>>> bike chain, hang it from a nail, mark the end, install the chain
>>>>> and ride it up a hill or two, hang it from the same nail, and
>>>>> see 2~3 mm of "stretch" for the whole chain, achieving about 40%
>>>>> of the popular "wear" limit in less than 1% of the expected
>>>>> lifespan of the chain.
>>>>> If so, it's still just a curious detail. Who bothers to measure
>>>>> his chain for wear after only a single ride?
>>>>> I wonder how exactly they pre-stretch a chain? Just a brief,
>>>>> heavy load? A series of impacts, like the buzzing of an
>>>>> air-hammer? Or maybe more of a running-in process, with the
>>>>> links turning around sprockets under load?
>>>> the other thing here is the torque on a regular bike chain is
>>>> said to be fairly high, higher than a motorbike even and that I
>>>> expect, is greater than the load on a timing chain.
>>> Chain loading would be tension, rather than torque, and would be
>>> FAR higher on any decent sized motorcycle. Try fitting pedals to
>>> a Harley, and see how far (or fast) you can move it - in ANY gear
>>> ratio. If you can get it moving, turn around and try again,
>>> because you must have been facing downhill!
>>> Look at the size of the chain on a motorcycle - they wouldn't go
>>> to the cost (and weight) of a chain that big unless they needed
>>> to, and motorcycles do genuinely snap chains - through the side
>>> plates, not from a pin coming loose.
>>> Even if cyclists do snap side plates, it is incredibly rare. On
>>> motorcycles, it's the normal failure mode. Ask anyone who has
>>> marshalled at a motorcycle race - chains snap (and they are bloody
>>> hot when they are fresh off the bike). I'd expect timing chain to
>>> be similarly stressed to bicycle chain, but it runs in a far more
>>> benign environment.
>>> I strongly suspect that the initial "stretch" is the squeezing of
>>> excess assembly lubricant out of the bearings.
>> Actually, even cars don't put out impressive torque compared to
>> bicycles.
>> The differences between motorcycles and bicycles are in the gearing
>> and the RPM.
>> The bicycle is powered at a pitiful 50~100 rpm by a high-torque
>> pair of legs.
>> A single-cylinder motorcycle can often run up to 10,000 rpm, a
>> thousand times faster. The measured torque is surprisingly low.
>> With roughly similar-size rear tires, a typical bicycle is a simple
>> 53~30 front to 11~34 rear.
>> Some motorcycles will almost reverse the 53x11 to a 14x52--just
>> what you see on a motorcycle involves incredibly low gearing.
>> Meanwhile, hidden inside the gearbox of the motorcycle is the
>> primary reduction gearing that is then reduced further by ~5 gears.
>> To give a pair of specific examples, cruising in top gear at 20 mph
>> on a 53x11 bicycle requires about 52 rpm.
>> Cruising just as gently in top gear on an elderly trials
>> motorcycle, the same 20 mph requires about 2300 rpm--about 50 times
>> the rpm of the bicycle.
>> The bicycle's high-speed gearing, put in 11r x 55f form, is about
>> 0.2:1--that's zero point two to one.
>> The motorcycle's high-speed gearing ((52r x14f) * 3.714 secondary
>> reduction * 0.750 fifth gear) is about 9.1:1, about 50 times
>> higher.
>> Bicycles are high-torque, low-rpm machines.
>> Motorcycles and cars are low-torque, incredibly high-rpm machines.
> What does torque have to do with chain tension? They are different
> units. You should study a year of physics, and stop talking about
> these things as if you know. Being corrected all the time is no
> substitute for doing the exercises.
Well, I don't know how it is meant, but with the rear wheel roughly
the same outside diameter among bicycles and motorcycles, torque
required to slip the rear wheel depends on vehicle total weight.
This, considering the drive sprocket diameter on the wheel, can give
chain tension.
However, all this is off the mark, because as writers have mentioned,
the speed and continuity of power pulses makes these two applications
a poor comparison.
Jobst Brandt
carl...@comcast.net
<phil(at)lee-family(dot)me(dot)uk> wrote:
>carl...@comcast.net considered Thu, 14 May 2009 11:59:48 -0600 the
>So you can only do it by increasing the torque by use of gearing.
>
>Now try the experiment I originally stated, connecting the pedals
>directly to the same rear sprocket as the motorcycle ordinarily uses,
>with whatever chainwheel you like.
>
>You will not be able to break traction.
>The motorcycle will.
>Therefore the motorcycle is capable of applying more force through
>it's chain than you are.
>
>How many riders do you think would be capable of breaking (through the
>sideplates, by pure tension) the size of chain on a typical large
>motorcycle?
>Yet motorcycles do this with a fair degree of regularity.
>
>It makes no difference how much gearing comes before the final drive
>stage - it is the tension in that chain we are interested in.
Dear Phil,
Try this thought experiment.
One rider stomping 100 ft-lbs of torque on a typical bicycle can't
break traction. He can manage only 50~100 rpm after he gets going and
faces gearing of ~1:1 at best. (A typical motorcycle's gearing is
twenty times lower than that.)
But now let's have 100 riders stomp down on 100 pedals--not
simultaneously, but one after another, all within one second, all
connected to the same rear wheel, each with 100 foot-pounds of torque.
That's 100 foot-lbs at ~6,000 rpm, like a motorcycle.
What do you think the bicycle's rear tire will do when 100 riders try
to spin it within one second?
The chain tension is limited by the traction--once the tire slips, the
chain tension drops.
Of course, I could be mistaken. Or we could just be missing each
other's point. If so, some calculations would help to illustrate your
point.
Cheers,
Carl Fogel
datakoll
chainsaw people, stihl 041 here, tend toward chain brutality. More
power, less traction.
cycle people are chain sensitive: 9 grams grit per chain and urout.
motorcycle technology may have leveled the field, 1975> ???, toward a
more egalitarian engineering: more power is more power forget the
chain. Come gather...
visit the ER saturday night.
jim beam
eh??? so pushrod valve trains don't exist???
>
> There are no engines being built with hydraulic tappets, push rods,
> rocker arms, simple valve springs or valve clearance adjusting screws.
ok jobst, you're losing it.
>
> There is a problem there that was ignored by casual thinking of low
> speed motion.
or in your case, the problem seems to be low speed thinking.
jim beam
but carl, you're talking about the input, not the output. at the output
end, in order to accelerate several hundred pounds more motorcycle
faster than faster a bicycle, you will have had to have had the gears
"magnify" torque, and thus chain load, most substantially.
Carl Sundquist
Nor desmodromic?
jim beam
you're cruel.
jobst....@stanfordalumni.org
> Nor desmodromic?
The last major desmodromic engines of note were pre WWII Mercedes W196
and post WWII, 300SLR and basta, because cam profiles could be
developed forward from the "jerk" curves, integrated to give the
acceleration curves, integrated to give velocity curves, integrated to
give lift curves, something that was not possible before the advent of
computer modeling.
Before computer can modeling, engineers manually drew lift curves from
which they made cams and measured, as accurately as possible, actual
lift that was then differentiated twice to give acceleration (F=Ma) to
assess valve train forces. Differentiation is a "noisy" process and
yielded no useful information from the enormous "hash" it generated.
That is why we had horrible Iskanderian (square headed) cams.
That is why desmodromic is OUT. There are no F1 car engines that have
even remotely considered desmodromic valve drive with its springy
rocker arm cam followers and horrible springs. I don't understand
what engineers at Ducati use for valve design or that they haven't
noticed, under high speed photography, what their valves are doing at
high speed, however you can hear it when their engines run, as loud
thrashing (lift-off and backlash).
>>> There are no engines being built with hydraulic tappets, push
>>> rods, rocker arms, simple valve springs or valve clearance
>>> adjusting screws.
>> ok jobst, you're losing it.
>>> There is a problem there that was ignored by casual thinking of
>>> low speed motion.
In the realm of high performance engines, inertial forces are far
greater than was formerly believed and is now known from computer
modeling in which grotesque elasticities can be observed in slow
motion.
>> or in your case, the problem seems to be low speed thinking.
Jobst Brandt
Carl Sundquist
Springs in desmo systems?
jim beam
???
> because cam profiles could be
> developed forward from the "jerk" curves, integrated to give the
> acceleration curves, integrated to give velocity curves, integrated to
> give lift curves, something that was not possible before the advent of
> computer modeling.
>
> Before computer can modeling, engineers manually drew lift curves from
> which they made cams and measured, as accurately as possible, actual
> lift that was then differentiated twice to give acceleration (F=Ma) to
> assess valve train forces. Differentiation is a "noisy" process and
> yielded no useful information from the enormous "hash" it generated.
> That is why we had horrible Iskanderian (square headed) cams.
>
> That is why desmodromic is OUT. There are no F1 car engines that have
> even remotely considered desmodromic valve drive with its springy
> rocker arm cam followers and horrible springs.
???
> I don't understand
> what engineers at Ducati use for valve design or that they haven't
> noticed, under high speed photography, what their valves are doing at
> high speed, however you can hear it when their engines run, as loud
> thrashing (lift-off and backlash).
??? er, actually jobst, that is the dry multi-plate clutch, and it only
only makes a noise when the clutch is disengaged because the plates are
loose enough to rattle. the noise disappears under load.
>
>>>> There are no engines being built with hydraulic tappets, push
>>>> rods, rocker arms, simple valve springs or valve clearance
>>>> adjusting screws.
>
>>> ok jobst, you're losing it.
>
>>>> There is a problem there that was ignored by casual thinking of
>>>> low speed motion.
>
> In the realm of high performance engines, inertial forces are far
> greater than was formerly believed and is now known from computer
> modeling in which grotesque elasticities can be observed in slow
> motion.
how do you "know" this jobst? you evidently don't know shit about
ducati - and they've been known to win a race or two.
>
>>> or in your case, the problem seems to be low speed thinking.
>
what's next for our entertainment this weekend jobst? can we have a
repeat of your van der waal's forces and brake squeal comedy?
_
>
> Springs in desmo systems?
Yes.
Little ones to finish closing the valves - clearance issues with thermal
expansion.
http://www.ducati.com/bikes/techcafe.jhtml?artID=2&detail=article&part=technical
Carl Sundquist
Then where does Jobst's clattering noise come from? (Rhetorical question)
jobst....@stanfordalumni.org
>>> Nor desmodromic?
>> have even remotely considered desmodromic valve drive in the last
>> 50 years with its springy rocker arm cam followers and horrible
>> compensating springs.
> Springs in desmodromic systems?
There must be compliance for thermal expansion somewhere and
desmodromic has that. The whole desmodromic concept was a failure in
assessing what the problem was and dodged and wove around it finding
that some sort of spring somewhere was necessary to take up occurring
changes from nominal dimensions... but it doesn't work well as can be
heard.
>> I don't understand what engineers at Ducati use for valve design or
>> that they haven't noticed, under high speed photography, what their
>> valves are doing, however it is audible as loud thrashing when
>> their engines run (lift-off and backlash).
>>>>> There are no engines being built with hydraulic tappets, push
>>>>> rods, rocker arms, simple valve springs or valve clearance
>>>>> adjusting screws.
>>>> ok jobst, you're losing it.
>>>>> There is a problem there that was ignored by casual thinking of
>>>>> low speed motion.
>> In the realm of high performance engines, inertial forces are far
>> greater than was formerly believed, and is now known from computer
jobst....@stanfordalumni.org
>> Springs in desmo systems?
> Yes.
> Little ones to finish closing the valves - clearance issues with
> thermal expansion.
http://www.ducati.com/bikes/techcafe.jhtml?artID=2&detail=article&part=technical
Or:
http://members.chello.nl/~wgj.jansen/text/Maserati.html
http://members.chello.nl/~wgj.jansen/text/MaseratiV8.html
Jobst Brandt
jobst....@stanfordalumni.org
Jobst Brandt
jobst....@stanfordalumni.org
>>> Springs in desmodromic systems?
>> Yes.
>> Little ones to finish closing the valves - clearance issues with
>> thermal expansion.
> Then where does Jobst's clattering noise come from?
As I said, from lift-off and backlash. This, in a system where
without high speed photography and more importantly, computer
modeling, the enormity of deformations in valve drive was terribly
misunderstood. It reminds me of so many other technical matters that
were left to "common knowledge" in the days of yore. The stress
analyses in "the Bicycle Wheel" also went untested by common knowledge
for a long time as popular as the bicycle has been over more than a
century.
Valve drive was only understood when enough interest (money) was at
stake to computer model the whole affair. Desmodromic is an
anachronism (an artifact that belongs to another time) that should not
be found in any current engine, just as air cooled internal combustion
engines for vehicles have no excuse for existence today, the carbon
water pump sealhaving been introduced long ago, so there are no more
boiling engines on mountain roads. The War Department took care of
that at the outset of WWII, insisting that military vehicles didn't
boil.
Technology is full of such misdiagnoses and I have had the job of
working on them.
Jobst Brandt
jim beam
> Carl Sundquist wrote:
>
>>>> Springs in desmodromic systems?
>
>>> Yes.
>
>>> Little ones to finish closing the valves - clearance issues with
>>> thermal expansion.
>
> http://tinyurl.com/29mpn
>
>> Then where does Jobst's clattering noise come from?
>
> As I said, from lift-off and backlash. This, in a system where
> without high speed photography and more importantly, computer
> modeling, the enormity of deformations in valve drive was terribly
> misunderstood.
really? so when cams get flat spots associated with excess loading,
that's not easily understood? so when cams need to be carburized or
nitrided because of the above, that's not understood? because you do
know that point loading from mere spring pressure on a cam is trivial
don't you jobst?
> It reminds me of so many other technical matters that
> were left to "common knowledge" in the days of yore. The stress
> analyses in "the Bicycle Wheel" also went untested by common knowledge
> for a long time as popular as the bicycle has been over more than a
> century.
really??? "analyses" like failing to understand that rim deformation is
responsible for spokes unloading at the contact point? "analyses" that
allows the misunderstanding of the above to lead to errors on spoke
tension "as high as the rim can bear" that cost an industry millions of
dollars and spawned the pre-built wheel industry? "analyses" that lead
to laughable mistakes about anodizing [not anisotropy and excess spoke
tension] causing rim cracking? "analyses" that completely failed to
figure out that spokes fatigue because of bending, not "residual stress"?
>
> Valve drive was only understood when enough interest (money) was at
> stake to computer model the whole affair.
???
> Desmodromic is an
> anachronism (an artifact that belongs to another time) that should not
> be found in any current engine, just as air cooled internal combustion
> engines for vehicles have no excuse for existence today, the carbon
> water pump sealhaving been introduced long ago, so there are no more
> boiling engines on mountain roads.
is that what you really believe??? it was just the seal??? and
temperature control and uniformity has nothing to do with it???
jobst, that is right up there with your bizarre bullshit on van der
waal's forces and brake squeal!
> The War Department took care of
> that at the outset of WWII, insisting that military vehicles didn't
> boil.
>
> Technology is full of such misdiagnoses and I have had the job of
> working on them.
"working on" and "understanding" or "solving" are sadly not the same -
as you repeatedly insist on demonstrating. if you understood even 10%
of the fundamentals you really should, you'd not make the gross mistakes
you do. and if you had even 1% more smarts, you'd bother to open a book
and learn stuff rather than have to be corrected on the same old howlers
time and time again.
Michael Press
jobst....@stanfordalumni.org wrote:
I read the Wikipedia article on desmodromic engines.
The article states that high speed photography shows
that most often valve float is not caused by elastic strain
in "rigid" parts, or by too weak a valve spring. It is
caused by a standing wave solution in the valve spring
that is excited at particular speeds resonant with one
of the harmonics in the valve spring. This is cured
by installing a snub spring concentric with the valve
spring or by designing a spring that varies from a
straight helix along its length, thus varying the spring
constant at different spring excursions.
--
Michael Press
jobst....@stanfordalumni.org
>>>>> Springs in desmodromic systems?
>>>> Yes.
>>>> Little ones to finish closing the valves - clearance issues with
>>>> thermal expansion.
>>> Then where does Jobst's clattering noise come from?
>> As I said, from lift-off and backlash. This, in a system where
>> without high speed photography and more importantly, computer
>> modeling, the enormity of deformations in valve drive was terribly
>> misunderstood. It reminds me of so many other technical matters
>> that were left to "common knowledge" in the days of yore. The
>> stress analyses in "the Bicycle Wheel" also went untested by common
>> knowledge for a long time as popular as the bicycle has been over
>> more than a century.
>> Valve drive was only understood when enough interest (money) was at
>> stake to computer model the whole affair. Desmodromic is an
>> anachronism (an artifact that belongs to another time) that should
>> not be found in any current engine, just as air cooled internal
>> combustion engines for vehicles have no excuse for existence today,
>> the carbon water pump seal having been introduced long ago, so there
>> are no more boiling engines on mountain roads. The War Department
>> took care of that at the outset of WWII, insisting that military
>> vehicles didn't boil.
>> Technology is full of such misdiagnoses and I have had the job of
>> working on them.
> I read the Wikipedia article on desmodromic engines. The article
> states that high speed photography shows that most often valve float
> is not caused by elastic strain in "rigid" parts, or by too weak a
> valve spring. It is caused by a standing wave solution in the valve
> spring that is excited at particular speeds resonant with one of the
> harmonics in the valve spring. This is cured by installing a snub
> spring concentric with the valve spring or by designing a spring
> that varies from a straight helix along its length, thus varying the
> spring constant at different spring excursions.
As I mentioned, standing waves (slinky) in springs was an old issue
that was addressed with variable coil spacing in springs and later by
"bee hive" springs which are progressive through their smaller coil
diameters at the moving end. Thus the resonant frequency changes
throughout the valve stroke preventing resonance.
More damaging is elasticity in push rods, rocker arms, and cam drive
such as (torsion bar) shafts or stacked gears with elastic backlash in
their gear teeth.
Besides, high performance engines (>10,000 rpm) use pneumatic springs.
Meanwhile, back at the ranch, desmodromic is an anachronism... with
springs.
Jobst Brandt
jim beam
have you read the wikipedia article's history? jobst has been writing
and re-writing his version of reality over there for ages now and refers
to any corrections of his mistakes as "vandalism".
jim beam
never been near a japanese motorcycle in the last 30 years then jobst?
> Meanwhile, back at the ranch, desmodromic is an anachronism... with
> springs.
>
meanwhile, back at the ranch, a tired ignorant old man is still trying
to wring the last drops of turnip juice out of his alma mater, even
though he doesn't know what the fuck he's talking about.
Michael Press
jobst....@stanfordalumni.org wrote:
Let's consider overhead cam engines. Do you think that the
rocker arm should be eliminated and the cam drive the
valve directly? Is this done?
--
Michael Press
jim beam
> Michael Press <rub...@pacbell.net> considered Sun, 17 May 2009
not "any", just some.
Carl Sundquist
> Michael Press <rub...@pacbell.net> considered Sun, 17 May 2009
> 18:30:53 -0700 the perfect time to write:
>
8000 hp top fuel dragster engines still use pushrods and rocker arms.
RonSonic
Since about 1904, "most."
_
> Let's consider overhead cam engines. Do you think that the
> rocker arm should be eliminated and the cam drive the
> valve directly? Is this done?
Frequently - with a DOHC arrangement, the cams push the valve stems through
"buckets"; so called because there is usually a clearance adjusting shim
contained within.
jim beam
no, just some. to have a cam follower run directly by the cam requires
special management of valve lash. that was addressed with hydraulic
lifters at one point, but they're out of fashion again. meanwhile
manufacturers like honda with 100hp/liter engines continue to use
rockers [accommodates vtec]. and check out the variable valve lifters
on bmw - can't do that with direct lift.
Brian Huntley
> Jay Taylor wrote:
> >> Springs in desmo systems?
> > Yes.
> > Little ones to finish closing the valves - clearance issues with
> > thermal expansion.
>
>
> Or:
>
> http://members.chello.nl/~wgj.jansen/text/Maserati.html
> http://members.chello.nl/~wgj.jansen/text/MaseratiV8.html
>
> Jobst Brandt
Ah, there's nothing quite like a nice cut-away engineering drawing. I
especially like hand-drawn ones, a disappering species. Sometimes I
wish I'd squirreled away some from my rail-car building days.
Michael Press
jim beam <m...@privacy.net> wrote:
A web search for this stuff comes up with so much information
that I find it impossible to find good diagrams and descriptions
of valve trains and cam followers in these configurations.
Do you have any URL's to these kinds of pages?
--
Michael Press
Michael Press
_ <jtayNO...@hfDONTSENDMESPAMx.andara.com> wrote:
Do you know of a page with good diagrams and descriptions of
cam follower buckets?
--
Michael Press
Kerry Montgomery
"Michael Press" <rub...@pacbell.net> wrote in message
news:rubrum-997875....@news.sf.sbcglobal.net...
Michael,
Here's a page with a photo and some description (and some opinions, too):
http://tinyurl.com/q9wgc9
And another with some photos and diagrams and text, too:
http://tinyurl.com/p4a5tv
Kerry
Tim McNamara
Carl Sundquist <carlsun...@cox.net> wrote:
And a complete rebuild between runs not infrequently.
Carl Sundquist
Wouldn't you say there is a correlation between the amount of power you
can wring out of an engine and the frequency of rebuilds?
AMuzi
Bicycle racing or drag racing?
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
Carl Sundquist
That's why today was a rest day in Lombardy.
jim beam
best go to the library. the bosch automotive handbook is concise but
descriptive, especially of the bmw system. but it doesn't cover things
like honda's vtec or toyota's vvt:
http://asia.vtec.net/spfeature/vtecimpl/vtec1.html
http://www.billzilla.org/vvtvtec.htm
thirt...@live.co.uk
> RonSonic wrote:
> > On Sun, 17 May 2009 22:00:06 -0700, jim beam <m...@privacy.net> wrote:
>
> >> Phil W Lee wrote:
> >>> Michael Press <rub...@pacbell.net> considered Sun, 17 May 2009
> >>> 18:30:53 -0700 the perfect time to write:
>
is that naturally aspirated 100hp/litre?
Kerry Montgomery
<thirt...@live.co.uk> wrote in message
news:57f320d1-f1a8-49f3...@s20g2000vbp.googlegroups.com...
<end of previous postings>
thirty-six,
Yes.
Kerry
jim beam
yes. and some hondas go to 120, stock from factory.
and if you know where to go non-factory...
http://www.theoldone.com/articles/Larryscivic/MondayDyno.jpg
http://www.theoldone.com/articles/Larryscivic/Larrys_Civic.htm
Carl Sundquist
All four of the Japanese motorcycle manufacturers offer 600 cc engines
that are rated at more than 100 hp at the rear wheel.
Michael Press
"Kerry Montgomery" <kamo...@teleport.com> wrote:
> "Michael Press" <rub...@pacbell.net> wrote in message
> news:rubrum-997875....@news.sf.sbcglobal.net...
> > In article <w7oj37iiebi5$.es28y9l2skm9$.d...@40tude.net>,
> > _ <jtayNO...@hfDONTSENDMESPAMx.andara.com> wrote:
> >
> >> On Sun, 17 May 2009 18:30:53 -0700, Michael Press wrote:
> >>
> >>
> >> > Let's consider overhead cam engines. Do you think that the
> >> > rocker arm should be eliminated and the cam drive the
> >> > valve directly? Is this done?
> >>
> >> Frequently - with a DOHC arrangement, the cams push the valve stems
> >> through
> >> "buckets"; so called because there is usually a clearance adjusting shim
> >> contained within.
> >
> > Do you know of a page with good diagrams and descriptions of
> > cam follower buckets?
>
> Michael,
> Here's a page with a photo and some description (and some opinions, too):
> http://tinyurl.com/q9wgc9
> And another with some photos and diagrams and text, too:
> http://tinyurl.com/p4a5tv
Okay, thanks.
--
Michael Press
someone
The only original part is the block which has been extensively
modified, a compression ratio of 13.4 to 1 running at 9000rpm. I was
thinking of a standard road engine pulling a medium saloon, not a
missile launcher.
someone
jobst....@stanfordalumni.org
That is the only type being built today. As I said, push rods, rocker
arms, valve adjusting screws, hydraulic valve lifters and shaft and
stacked gear drive for overhead cams has been thrown out as missing
the problem. The Wikipedia item was written by desmo faithful. As I
pointed out, the most advanced high performance engines (Formula One
racing) recognized these mechanisms as basically flawed, all being too
elastic.
Jobst Brandt
jobst....@stanfordalumni.org
>> no, just some. to have a cam follower run directly by the cam
>> requires special management of valve lash. that was addressed with
>> hydraulic lifters at one point, but they're out of fashion again.
>> meanwhile manufacturers like honda with 100hp/liter engines
>> continue to use rockers [accommodates vtec]. and check out the
>> variable valve lifters on bmw - can't do that with direct lift.
> A web search for this stuff comes up with so much information that I
> find it impossible to find good diagrams and descriptions of valve
> trains and cam followers in these configurations. Do you have any
> URL's to these kinds of pages?
Just drop by you local engine re-builder and note that Volvo, Honda,
Subaru, and a slew of other cars use overhead cams directly above the
line of valves and need no maintenance for the next 200,000 miles. No
one has removed the head or valve cover on 200,000 mile Volvos of
which I know in my circle of car owners.
Jobst Brandt
Ben C
> thirt...@live.co.uk wrote:
>> On 18 May, 13:47, jim beam <m...@privacy.net> wrote:
>> is that naturally aspirated 100hp/litre?
>
> All four of the Japanese motorcycle manufacturers offer 600 cc engines
> that are rated at more than 100 hp at the rear wheel.
I've often wondered about the high specific output of motorbike engines.
Is it partly because they have a much lower torque requirement than car
engines?
Tom_Sherman
Honda VTEC engines [1] require periodic (i.e. 30,000 miles) adjustment
of valve lash.
[1] What I have personally owned for the last 15 years, both SOHC
16-valve I-4 engines.
--
Tom Sherman - 42.435731,-83.985007
LOCAL CACTUS EATS CYCLIST - datakoll
Tom_Sherman
> On 19 May, 06:42, jim beam <m...@privacy.net> wrote:
>> thirty-...@live.co.uk wrote:
>>> On 18 May, 13:47, jim beam <m...@privacy.net> wrote:
>>>> no, just some. to have a cam follower run directly by the cam requires
>>>> special management of valve lash. that was addressed with hydraulic
>>>> lifters at one point, but they're out of fashion again. meanwhile
>>>> manufacturers like honda with 100hp/liter engines continue to use
>>>> rockers [accommodates vtec]. and check out the variable valve lifters
>>>> on bmw - can't do that with direct lift.
>>> is that naturally aspirated 100hp/litre?
>> yes. and some hondas go to 120, stock from factory.
>>
>> and if you know where to go non-factory...
>>
>> http://www.theoldone.com/articles/Larryscivic/MondayDyno.jpg
>>
>> http://www.theoldone.com/articles/Larryscivic/Larrys_Civic.htm
>
> The only original part is the block which has been extensively
> modified, a compression ratio of 13.4 to 1 running at 9000rpm. I was
> thinking of a standard road engine pulling a medium saloon, not a
> missile launcher.
The stock Honda S2000 has 240 hp (SAE net) from a 2.0L I-4.
Tom_Sherman
>> yes. and some hondas go to 120, stock from factory.
>
> which?
S2000 sports car.
someone
wrote:
The engine is specific to this vehicle? Does not appear to be
thermally efficient by the fuel consunption figures. Also rather a
low production run for what is a very limited vehicle(two seater rag
top), not a medium saloon. Block used with Accord? Any good info on
the S2000 engine specifics anywhere? Out of production next month.
Rather large displacement for a four.
someone
> On 2009-05-19, Carl Sundquist <carlsun.rem...@cox.net> wrote:
>
> > thirty-...@live.co.uk wrote:
> >> On 18 May, 13:47, jim beam <m...@privacy.net> wrote:
> [...]
> >> is that naturally aspirated 100hp/litre?
>
> > All four of the Japanese motorcycle manufacturers offer 600 cc engines
> > that are rated at more than 100 hp at the rear wheel.
>
> I've often wondered about the high specific output of motorbike engines.
> Is it partly because they have a much lower torque requirement than car
> engines?
It's because sports bikes attract loonies. Tyre failures at 150mph+
tend to remove complete bikes from the market. So there is good
demand from new riders for a specialist market which is not country
specific. Investment for race and road motorbike engines is a good
gamble despite general economic variance. And wot you said.
jim beam
jobst, you're amazing. either you're lying about your having physically
inspected, or you don't understand what you see. [much more likely].
because this is bullshit of thew highest order. seriously - you're
losing it old man.
jim beam
no, it's that they rev high and don't need to last as long. oh, and
they're not built by idiots using 1950's technology whose management
won't invest in any research.
jim beam
jobst, what fucking planet do you live on? that amazing miss-statement
surpasses your "brake squeal is caused by van der waal's forces" classic.
> The Wikipedia item was written by desmo faithful. As I
> pointed out, the most advanced high performance engines (Formula One
> racing) recognized these mechanisms as basically flawed, all being too
> elastic.
sure - this is a totally credible statement coming from a guy that
doesn't recognize an ohc rocker arm when he sees one!
jobst - your brain hasn't gotten out of the 50's. and it didn't contain
much before that point either apparently.
Ben C
> On 20 May 2009 06:33:57 GMT, jobst....@stanfordalumni.org wrote:
>
>>> Let's consider overhead cam engines. Do you think that the rocker
>>> arm should be eliminated and the cam drive the valve directly? Is
>>> this done?
>>
>>That is the only type being built today. As I said, push rods, rocker
>>arms, valve adjusting screws, hydraulic valve lifters and shaft and
>>stacked gear drive for overhead cams has been thrown out as missing
>>the problem.
>
> are many, many engines being built with SOHC or DOHC with rocker arms
> and adjustment screws or hydraulic lifters.
Can you name any engines on cars currently in production that are like
that?
[Not rhetorical-- nothing surprises me about the datedness of the Ford
POS-100 pickup trucks that are popular in America].
In my experience Jobst is right about this. My stinking feeler gauges
have been gathering grime in the bottom of the toolbox for quite a few
years.
>> The Wikipedia item was written by desmo faithful. As I
>>pointed out, the most advanced high performance engines (Formula One
>>racing) recognized these mechanisms as basically flawed, all being too
>>elastic.
>
> Formula 1 racing engines may go that way, but at other levels you find
> lots of rocker arms.
Not desmodromic though. That really is a bit of a Ducati quirk.
jobst....@stanfordalumni.org
>>> Let's consider overhead cam engines. Do you think that the rocker
>>> arm should be eliminated and the cam drive the valve directly? Is
>>> this done?
>> That is the only type being built today. As I said, push rods,
>> rocker arms, valve adjusting screws, hydraulic valve lifters and
>> shaft and stacked gear drive for overhead cams has been thrown out
>> as missing the problem.
> That's incorrect or incorrectly qualified as to which engines. There
> are many, many engines being built with SOHC or DOHC with rocker
> arms and adjustment screws or hydraulic lifters.
Let's qualify that to mean the only kind of automotive engine being
developed today. There are many old, still in production, engines
that hail from an earlier era. Just consider how long VW and some
others continued to build air cooled engines after the last vestige of
hope for the concept had disappeared. The same goes for swing axle,
rear engine, torsion bare suspended cars.
>> The Wikipedia item was written by desmo faithful. As I pointed
>> out, the most advanced high performance engines (Formula One
>> racing) recognized these mechanisms as basically flawed, all being
>> too elastic.
> Formula 1 racing engines may go that way, but at other levels you
> find lots of rocker arms.
Only in antique designs and Ducati rocker arm cam followers. That
these engines works has be demonstrated over many years, that there
are reasons for not following that design any longer are well
developed but is not enough to cause some commercial products to
change, but in time they will vanish.
Jobst Brandt
Andre Jute
> Only in antique designs and Ducati rocker arm cam followers. That
> these engines works has be demonstrated over many years, that there
> are reasons for not following that design any longer are well
> developed but is not enough to cause some commercial products to
> change, but in time they will vanish.
>
> Jobst Brandt
Judged by their racing results, the guys who designed the current GP
Ducati aren't romantics.
Me, now I'm an unrepentant romantic. I reckon that steam is smooth and
silent and clean, and with today's technology can be made to be
instant-starting and fully recycling as well. We could rationally
bring back steam cars...
Andre Jute
Reformed petrol head
Car-free since 1992
Greener than thou!