Rebuilding derailleurs
Zeppo
college. He is at an inner city campus so the condition of the bike (beat
up, some rust, flaking paint) is a distinct advantage. The bike was left
outdoors for the last year and is in pretty bad shape. It's a 2001
Performance M207 mountain bike.
I cleaned up the tires, replaced the tunes, brake pads and chain. The
derailleurs seem to be frozen as were the idler pulleys on the rear. I was
able to disassemble the pulleys and clean them up and they are OK now.
How tough is it to rebuild the derailleurs? I adjusted them before but have
never taken one apart. Are there decent instructions somewhere on the web
you could point me too? A Google search hasn't turned up anything useful
yet. Would it be more cost effective to look for a used set on eBay and just
replace them? I don't have a ton of cash to put into this (2 kids in
college) so I'm looking to tap the wealth of your experience.
Thanks in advance for any help you can give.
Regards,
Jon
Simon Lewis
I could suggest you post the make and model of the derailleurs. That
might help.
When you say frozen. Where? They don't move when you shift them or you
cant even move them by hand?
>
> Regards,
> Jon
Zeppo
"Simon Lewis" <simonle...@gmail.com> wrote in message
news:hcmveh$p8b$1...@news.eternal-september.org...
I believe they are Seguno (Shimano) STX-RC components. I tried dousing them
with wd-40 and moving them with the shift levers. Nothing. I can see the
cables pulling on them but they aren't moving. I try moving them by hand
this evening and see if I can get some motion.
Jon
landotter
in addition to replacing the cables doesn't improve their action--then
you might be better off to replace. However--it takes a lot of cycles
to wear out the moving bushing bits on a derailleur. Don't throw away
money on this. Low end Shimano is really pretty great for utility
use.
Simon Lewis
To be honest I'm amazed they have frozen. Much more likely to be a
jammed cable IMO. But we'll see.
Lou Holtman
Wait a little. Soak it again with WD40. If it is still stuck, replace
it. For 20 bucks you have a new one.
Lou
thirty-six
If it's a steel mechanism and it looks aligned about right then it's
likely fine. For cleaning: Take it off and dunk it in diesel fuel
overnight. It has been posted here before that placing it in a bottle
with a cap on and shaking the fuel is sufficient to dislodge all the
muck. Kerosene may also be used.
I think it is likely that the source of your problem lay in the
cable. If releasing the cable at the mechanism frees up the mech,
then that tells you to look elsewhere than the mech. This is so
likely I suggest you do remove both the inner and outer sections of
the wire from the mech despite your declaration "I can see the
Simon Lewis
I really think there is no way in a month of sundays a derailleur will
lock on its own in that time period. That spring is pretty hefty. It must be the cable.
Leo Lichtman
"thirty-six" wrote: (clip) despite your declaration "I can see the
> cables pulling on them but they aren't moving". (clip)
^^^^^^^^^^^^^^^^^^^^^^^^
The statement in quotes tells a lot, and should not be ignored. I may not
have as much bike experience as most of you, but I have 81 years of
mechanical experience. Derailleur cables are able to overcome the built-in
spring tension, but not much more. Add some age, dirt and corrosion, and
the cable will start to deflect the entire derailleur. If you try to get
the cables to do the job, you may also damage the shifter levers. I
definitely recommend pushing the derailleur sideways by hand to see how much
resistance is felt. As you do this, you can province lateral support with
your fingers, so you don't overstress anything. This, along with soaking
with WD-40 or one of the other recommended solvents will probably allow you
to get a little movement at first. As soon as this starts, the action helps
the lubricant penetrate, and begins to break up the gunk. If you keep
adding solvent/lubricant and "worrying" the derailleur, you will probably
get it working in less than a half hour. Patience and good luck.
Zeppo
"Leo Lichtman" <leo.li...@att.net> wrote in message
news:a--dncGJ_IPZhHLX...@giganews.com...
Thanks Lou (and everyone else that replied). I'm going to try testing them
again to see if the cables are the problem or it's just built up gunk.
My unfamiliarity with derailleur construction is the only thing holding me
back from just tearing them down to clean them. If they do need to be torn
down I've reserved two books from the library to use as reference (Todd
Downs and Lennard Zinn's books). Might as well make it a learning
experience.
Thanks to all for your replies. I'll report back on my progress.
Jon
landotter
> "Leo Lichtman" <leo.licht...@att.net> wrote in message
"Tearing down" isn't something anything usually done with derailleurs--
especially as they're not meant to be taken apart, outside of the
jockey wheels, and that the bushings are easily cleaned and lubed in a
minute or two.
RonSonic
Most derailleurs, especially the lower priced models are not designed to be
rebuildable beyond the jockey wheels. I recommend not trying. They aren't meant
to come apart.
My recommendation. Continue the soak, WD40 is fine. Toss the cable, it's the
first thing to rust or otherwise fail in any modern shifting system and they're
cheap. Apparently you've already got the chain off. If not drop it and replace
it after getting the der sorted.
Any used bike, even a free one costs a set of cables and a chain. A rusted or
worn chain chews up drivetrain parts and isn't worth messing with. Cleaning does
not fix the damage to the chain that rust has caused.
With the chain and cable off try exercising the der through it's range of motion
by hand. There's a lot of monkey-motion there but you should be able to feel the
correct swing path and note if there's excess slop or if it isn't moving through
its range. If there are stiff spots or it feels like it's hanging up continue
the lube and exercise to see if it frees up. There are two motions, the cage
swings front to back around its pivot and the body swings in and out, these are
unconnected. See if you can get everything moving freely. If so, you're good.
Replace the cable and chain and check the adjustments. Install and adjustment
info for Shimano is easily googled by the part number stamped on the thing.
Is it too obvious to point out that it will not shift with the wheel chain
mounted and unturning? Thought so, that's why I didn't mention it.
HTH.
--
Oh damn. There's that annoying blog. Again. http://dumbbikeblog.blogspot.com
AMuzi
Most modern changer body pivots are riveted and the things
which look approachable (such as spring pivots) are not
simple for the amateur. Given that a new one is $14.95
there's not much beyond lube, adjustment and alignment that
makes sense.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
Zeppo
Nope, no need at all (furiously writing this downs so I don't forget to
check that later). So it looks as though my best bet would be to replace the
cables as a next step, since that should be done anyway. A plan is starting
to take shape...
Jon
Norman
> Zeppo wrote:
>
> > "Leo Lichtman" <leo.licht...@att.net> wrote in message
Or consider picking up a crap bicycle for $10 or $20
with suntour gt7 (frankly the finest crap derailer ever
made). Resell the bicycle frame on craigslist for
$120 (vintage ross eurotour one of a kind fixie! must
see to appreciate!).
Leo Lichtman
from making something work, in spite of the fact that you may be earning
only 10 cents an hour for the effort. You cannot put a price on the
satisfaction in making something work after it might have been "condemned."
Keep at it.
terryc
> How tough is it to rebuild the derailleurs?
Usually not that hard if you have done all you have. The big problem is
springs going sproing, so if you can get away with out doing that, you
might save a bit of heart ache.
Hint, if you have a digital camera, just take a pictures from various
angles at every step.
Remove "covers" and simple stuff, then agitate, wash scrub(old
toothbrush) in a pint of kerosene is my usual way. If it needs more than
that, might be easier to just spring for a cheap replacement.
Err, if this is for son, why isn't he doing it?
thirty-six
> Is it too obvious to point out that it will not shift with the wheel chain
> mounted and unturning? Thought so, that's why I didn't mention it.
You know, I was thinking that but forgot to post it. Just flew out of
my mind.
thirty-six
> Most modern changer body pivots are riveted and the things
> which look approachable (such as spring pivots) are not
> simple for the amateur. Given that a new one is $14.95
> there's not much beyond lube, adjustment and alignment that
> makes sense.
Unless your handy with a pipe wrench and hammer.
datakoll
http://www.jensonusa.com/store/sub/1565-Derailleurs+Rear.aspx
scroll dude scroll
buy canuh PC blaster.
a rear wheel spoke guard
anduh seat post mounted chain guard ifn ura usinuh triple CR
Zeppo
Thanks Leo. It is a kick bringing something 'back from the dead'. But it's
also a chance to bond with my teenage son. As he's
now a freshman in college, those moments are getting few and far between.
He's living at school, but close enough to hop the
regional rail to spend a day at home working on his new bike with his dad.
Devious, but it works.
So I was able to confirm the rear derailleur is fine. I didn't have time
last night to play with the front (World Series) but I'll look at it
tonight.
However, the front is very corroded and pitted and might give me more piece
of mind to replace it anyway. We'll see. I'm picking up new brake
and derailleur cables on the way home this evening.
Jon
thirty-six
> "Leo Lichtman" <leo.licht...@att.net> wrote in message
Best to use a silicone spray to lubricate the cables when they have
plastic liners. Use a heavy oil or smearing of grease for unlined
housings.
Zeppo
"terryc" <newsnine...@woa.com.au> wrote in message
news:hcnmhe$v0p$6...@news.eternal-september.org...
He is helping out, when he's home. He's living in a dorm on campus (just 30
minutes away) and has put some time into this as well. He replaced the chain
and brake pads and did some mud removal from the frame and wheels. He's
coming home on Saturday (transit strike dependant) so we can work on
replacing the cables.
He might not normally make this much 'together' time with Dad, but he's
liking the idea of having a bike on campus. As campus is in North Philly,
having a beat-up, rusting but serviceable bike is a big plus.
Jon
Zeppo
>>
>> Thanks Leo. It is a kick bringing something 'back from the dead'. But
>> it's
>> also a chance to bond with my teenage son. As he's
>> now a freshman in college, those moments are getting few and far between.
>> He's living at school, but close enough to hop the
>> regional rail to spend a day at home working on his new bike with his
>> dad.
>> Devious, but it works.
>>
>> So I was able to confirm the rear derailleur is fine. I didn't have time
>> last night to play with the front (World Series) but I'll look at it
>> tonight.
>> However, the front is very corroded and pitted and might give me more
>> piece
>> of mind to replace it anyway. We'll see. I'm picking up new brake
>> and derailleur cables on the way home this evening.
>>
>
> Best to use a silicone spray to lubricate the cables when they have
> plastic liners. Use a heavy oil or smearing of grease for unlined
> housings.
Hi Thirty Six,
I usually use Teflon spray on my bikes to keep the cables lubed and smooth,
but it doesn't have the penetrating capabilities of WD-40. Never thought to
use anything else on the exposed areas but it makes sense.
Thanks,
Jon
thirty-six
When plastic is used as a sliding bearing then silicon is the
preferred lubricant. This works against metals as well as plastic to
plastic. Most good brake cable (otherwise known as Bowden wire)
housing contains a plastic tube inside the spiral wrap, it keeps the
bends smooth and keeps the inner wire generally better protected from
the environment. I believe that silicone is the best lubricant in
this application as it is in all plastic lubrication. I'm not aware
that teflon spray is recommended for plastics. I have used it but
switched to silicone after experiencing a little stickiness. Graphite/
teflon may be used to lubricate rubber if you dont have silicone.
If the cables are without the plastic tube between the inner wire and
outer spral wrap housing, then(sorry, lost it, feels like I'm
programming)
Bad Idea
attached to a bike that is sitting on the ground (especially for
professional mechanics). If you hoist the bike, upright, into a
purpose-built work stand you will find that the bike practically
repairs itself.
Zeppo
"Bad Idea" <w...@2die4.com> wrote in message
news:30b780c2-a059-4dae...@m33g2000pri.googlegroups.com...
It's been sitting on a wall mounted bike rack for weeks now, and the damn
thing still isn't running! :-)
It would be nice to have a work stand, but other things are occupying that
spot in my budget right now.
Jon
Norman
> "Leo Lichtman" <leo.licht...@att.net> wrote in message
The rather extreme upside to all of this is that you get
to fiddle on something that, should it break, won't set
you back more than a Hamilton or so.
terryc
>> Err, if this is for son, why isn't he doing it?
>
> He is helping out, when he's home.
good to hear.
>
> He might not normally make this much 'together' time with Dad, but he's
> liking the idea of having a bike on campus. As campus is in North
> Philly, having a beat-up, rusting but serviceable bike is a big plus.
LBS owner sobbed when he saw the paint job I had applied to a brand new
shiny quality bike frame I purchased of him. Really crappy job, but it
stopped the bike being nicked for the four years I was at uni.
Zeppo
"Simon Lewis" <simonle...@gmail.com> wrote in message
news:hcmveh$p8b$1...@news.eternal-september.org...
> "Zeppo" <ze...@hotmail.org> writes:
>
>> Looking to rebuild an old mountain bike someone gave us for my son to use
>> at
>> college. He is at an inner city campus so the condition of the bike (beat
>> up, some rust, flaking paint) is a distinct advantage. The bike was left
>> outdoors for the last year and is in pretty bad shape. It's a 2001
>> Performance M207 mountain bike.
>>
>> I cleaned up the tires, replaced the tunes, brake pads and chain. The
>> derailleurs seem to be frozen as were the idler pulleys on the rear. I
>> was
>> able to disassemble the pulleys and clean them up and they are OK now.
>>
>> How tough is it to rebuild the derailleurs? I adjusted them before but
>> have
>> never taken one apart. Are there decent instructions somewhere on the web
>> you could point me too? A Google search hasn't turned up anything useful
>> yet. Would it be more cost effective to look for a used set on eBay and
>> just
>> replace them? I don't have a ton of cash to put into this (2 kids in
>> college) so I'm looking to tap the wealth of your experience.
>>
>> Thanks in advance for any help you can give.
>
> I could suggest you post the make and model of the derailleurs. That
> might help.
>
> When you say frozen. Where? They don't move when you shift them or you
> cant even move them by hand?
OK, so the cables are definitely shot and 2 days in WD-40 hasn't helped the
front derailleur at all. It moves, but grudgingly, and not the full range.
It's really corroded. The adjustment screws are pretty much rusted off.
The derailleur is a Shimano STX-RC, Model FD-MC38, a top-pull, top-swing
model that fits a 31.8 tube.
Can you suggest a low cost replacement for this?
Thanks,
Jon
thirty-six
> "Simon Lewis" <simonlewis2...@gmail.com> wrote in message
Your original is likely to be the best choice. I've never seen a
front der in a condition from non accidental causes where it cannot be
revived. I would dunk it in diesel for 48 hours, mount it on a pole/
tube and scrub it with the head of a yard brush. Dont touch the limit
screws, they're likely set right and its best not to move them unless
necessary after full cleaning. after brushing swill it in clean fuel/
kerosene and oil it generously. Leave it for a day, then actuate it.
Michael Press
"Zeppo" <zep...@hotmail.org> wrote:
Almost all front derailleurs are low cost.
Find some that fit, and see.
Sorry, I cannot recommend a specific model.
--
Michael Press
Zeppo
news:rubrum-E7E761....@news.albasani.net...
Not a problem Michael. From what I've been reading almost any top-pull
derailleur that will fit the seat tube can be made to work. I picked up one
on eBay for $10 that will do fine. Same configuration, just a newer model.
Jon
Zeppo
I soaked it in WD-40 for a few days and that didn't loosen it up. Then 2
days in diesel, and it still wouldn't loosen. Picked up a used Shimano STX
on eBay.
Many thanks for you help.
Jon
thirty-six
Did you not try to persuade it first? Pry bar, lump hammer, etc.
Jobst Brandt
components suffer, which is dissimilar metals exposed to corrosive
fluids like sweat and rain-and-sweat. For example, classically quill
stems fail preeminently from this because they are poorly designed,
because the stem is retained by expanding in the steertube at its
bottom end, allowing the upper end to sway from side-to-side.
Fortunately, we have threadless steertubes today so this problem
belongs to out fathers.
Aluminum head bearing shells have similar problems as do aluminum
derailleurs on steel (chromed) pivots. Once aluminum oxide has frozen
the parts in place, frame builders generally saw off the offending
component, bore out the shaft to a thin walled shell and use a Dremel
tool to cut it down one side to pull it out. Solvents do not dissolve
aluminum oxide adequately to free the part and especially enough to
make it work again.
I have pictures and collections of such parts, bu the bicycle industry
is exceedingly slow to recognize the failure and how to fix it. As
you see the threadless steer tube did it so but left hand BB (right
cup) and pedal threads remain a point of failure. Left hand pedal
threads have been explained here at length but the manufacturers don't
seem to read or comprehend what appears here.
Wherever you find a left hand thread that is not part of a turnbuckle,
you are looking at a faulty design. Threads are intended to hold
parts together, not to support radial loads, something they cannot
properly do. Bicycle companies have not discovered that because they
don't hire qualified engineers, believing a bicycle is an inexpensive
and simple device.
http://en.wikipedia.org/wiki/Turnbuckle
Likewise, after years of repairing failed inner tube patch failures
and teaching riders how to avoid it is similarly useless, as we see
from the responses in the tire patch threads. Although bicycle shops
sell "the Bicycle Wheel" they generally avoid reading it, so customers
know more about wheels than the mechanics who build them.
Science is a strange field, as we have seen in the "hot water freezes
faster than cold water" thread that we had here recently. That story
is ultra ancient and all my explanations never make it to the reader.
It reminds me of "how do you ride a bicycle on a frozen lake?":
or why do Shay RR locomotives derail:
http://www.spikesys.com/Trains/grd_loco.html
or why did we ever have air cooled internal combustion engines? All
that is simple to explain but who wants to learn.
Jobst Brandt
Tom Ace
> Wherever you find a left hand thread that is not part of a turnbuckle,
> you are looking at a faulty design. Threads are intended to hold
> parts together, not to support radial loads, something they cannot
> properly do.
Do you deem the left hand thread on the
arbor of a radial arm saw to be a faulty design?
Tom Ace
carl...@comcast.net
> Science is a strange field, as we have seen in the "hot water freezes
> faster than cold water" thread that we had here recently. That story
> is ultra ancient and all my explanations never make it to the reader.
Dear Jobst,
Dunno what you think is "recently" or what your "explanations" were.
Heck, I can't even tell from your post what you think.
But for anyone curious:
http://www.picotech.com/experiments/mpemba_effect/results.html
It's a widely observed and measured effect, with most suggested
explanations involving flaws in the experiments ruled out in the
original paper.
Cheers,
Carl Fogel
Jobst Brandt
>> Wherever you find a left hand thread that is not part of a
>> turnbuckle, you are looking at a faulty design. Threads are
>> intended to hold parts together, not to support radial loads,
>> something they cannot properly do.
> Do you deem the left hand thread on the arbor of a radial arm saw to
> be a faulty design?
I don't have one of those so I cannot inspect its function. A
turnbuckle is an adjustment device that works under pure tension. If
that is what your saw does, it passes the test, while the left hand
thread on a left pedal, a right BB cup or an old fashioned auto lug
nut on left side wheels do not. Re-read (>>) the statement above and
I think you will see whether your saw uses threads correctly.
I don't see where this is ambiguous. You must have missed the thread
on left hand bicycle pedal crank failures and why they occur.
Jobst Brandt
Jobst Brandt
>> Science is a strange field, as we have seen in the "hot water
>> freezes faster than cold water" thread that we had here
>> recently. That story is ultra ancient and all my explanations
>> never make it to the reader.
> Dunno what you think is "recently" or what your "explanations" were.
> Heck, I can't even tell from your post what you think.
> But for anyone curious:
http://www.picotech.com/experiments/mpemba_effect/results.html
You needn't be so condescending, the cause for the more rapid freezing
of warm water than for cold water is insulation, especially in pipes
where there is no evaporation. I explained how hot water makes the
glass clear ice cubes one gets at soft drink dispensers, while whitish
ice, made in one's home refrigerator from cold water is white with
entrapped air that insulates. The "Mpemba Effect" is a hoax, as are
many other such "discoveries".
I am disappointed in Wikipedia for that one.
> It's a widely observed and measured effect, with most suggested
> explanations involving flaws in the experiments ruled out in the
> original paper.
Hot (mostly devoid of entrapped air) water pipes burst sooner than
cold (aerated) water pipes, but they both burst from freezing water.
Also a widely observed effect. Let's put the cause where it belongs
not on folklore. Just because someone with an oddly spelled name
writes an unsupported paper doesn't make it a fact.
Jobst Brandt
Nate Nagel
Saws, grinding wheels, etc. all tend to have left hand threads where the
rotation of the blade/wheel will tend to tighten the arbor nut and not
loosen it. e.g. my bench grinder has a RH thread on the right side and
a LH thread on the left side (the shaft rotates counterclockwise as you
look at it end on from the RH side, so the faces of the wheels are
moving down as you face it.) I really can't imagine it being any other
way; otherwise whenever you developed any significant torque on the LH
wheel it would loosen the nut.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
Jobst Brandt
>> Science is a strange field, as we have seen in the "hot water freezes
>> faster than cold water" thread that we had here recently. That story
>> is ultra ancient and all my explanations never make it to the reader.
> Dunno what you think is "recently" or what your "explanations" were.
> Heck, I can't even tell from your post what you think.
For someone who searches the web for minutia and offers links to them,
you are trying hard to be disparaging in your reply instead of
addressing the subject. I hope you construe further responses to
clarifying the subject rather than ridiculing others.
This is beginning to sound like a jim beam exchange.
Jobst Brandt
Jobst Brandt
>>>> Wherever you find a left hand thread that is not part of a
>>>> turnbuckle, you are looking at a faulty design. Threads are
>>>> intended to hold parts together, not to support radial loads,
>>>> something they cannot properly do.
>>> Do you deem the left hand thread on the arbor of a radial arm saw
>>> to be a faulty design?
>> I don't have one of those so I cannot inspect its function. A
>> turnbuckle is an adjustment device that works under pure tension.
>> If that is what your saw does, it passes the test, while the left
>> hand thread on a left pedal, a right BB cup or an old fashioned
>> auto lug nut on left side wheels do not. Re-read (>>) the
>> statement above and I think you will see whether your saw uses
>> threads correctly.
>> I don't see where this is ambiguous. You must have missed the
>> thread on left hand bicycle pedal crank failures and why they
>> occur.
> Saws, grinding wheels, etc. all tend to have left hand threads where
> the rotation of the blade/wheel will tend to tighten the arbor nut
> and not loosen it. e.g. my bench grinder has a RH thread on the
> right side and a LH thread on the left side (the shaft rotates
> counterclockwise as you look at it end on from the RH side, so the
> faces of the wheels are moving down as you face it.) I really can't
> imagine it being any other way; otherwise whenever you developed any
> significant torque on the LH wheel it would loosen the nut.
That's because they are, like bicycle pedals, doing what others have
without proper analysis. You'll note that Shimano no longer transmits
pedaling torque to the back wheel through screw-on sprockets because
it was a horrible design. The same goes for saws and grinding wheels
that are not properly located and tend to get tighter with torque.
That fits the description of a faulty design.
Have you noticed how small hyper-crackers are in comparison to chain
whips to remove rear wheel sprockets? They are an example of
improvement and a proper design.
Jobst Brandt
thirty-six
>
> If the cables are without the plastic tube between the inner wire and
> outer spral wrap housing, then(sorry, lost it, feels like I'm
> programming)
For cables without liners use a regular grade of oil or grease. The
reliable long service method is to use graphited grease pumped in to
the housing with a special applicator for bowden wires. The case of
grease is warmed and a pump applied to pressurise the 'piston', the
cable moved to and fro until the grease appears at the other end.
It's a neat device if you can use it.
Nate Nagel
It may be inelegant, but "faulty" is a bit of a stretch... I've used
bench grinders inherited from my great-grandfather that used the same
design and managed to hold together all these years. (my dad has one
bolted to a workbench into his barn that is likely older than he,
although I think I replaced the motor sometime back when I was in high
school, the grinder head just got a clean up and some fresh oil - it's a
belt driven head so you can hide the motor under the bench and have more
access to the wheels for odd shaped parts.)
I am trying to think of an alternative method (not using the rotation of
the wheel to keep a nut tight) to keep the wheel from loosening its
attachment mechanism without adding parts or complexity, and am coming
up dry.
carl...@comcast.net
>Carl Fogel wrote:
>
>>> Science is a strange field, as we have seen in the "hot water
>>> freezes faster than cold water" thread that we had here
>>> recently. �That story is ultra ancient and all my explanations
>>> never make it to the reader.
>
>> Dunno what you think is "recently" or what your "explanations" were.
>
>> Heck, I can't even tell from your post what you think.
>
>> But for anyone curious:
>
> http://www.picotech.com/experiments/mpemba_effect/results.html
>
>You needn't be so condescending, the cause for the more rapid freezing
>of warm water than for cold water is insulation, especially in pipes
>where there is no evaporation.
Dear Jobst,
Nope, two containers, same freezer, well-known phenomenon.
Cheers,
Carl Fogel
z
Cotter pins?
RonSonic
>I have pictures and collections of such parts, bu the bicycle industry
>is exceedingly slow to recognize the failure and how to fix it. As
>you see the threadless steer tube did it so but left hand BB (right
>cup) and pedal threads remain a point of failure. Left hand pedal
>threads have been explained here at length but the manufacturers don't
>seem to read or comprehend what appears here.
>
>Wherever you find a left hand thread that is not part of a turnbuckle,
>you are looking at a faulty design. Threads are intended to hold
>parts together, not to support radial loads, something they cannot
>properly do. Bicycle companies have not discovered that because they
>don't hire qualified engineers, believing a bicycle is an inexpensive
>and simple device.
More likely they understand it perfectly well but are uninterested in attempting
to introduce a new standard that replaces pedals and crank arms. It doesn't
matter how many of what kind of engineers they hire, they would first have to
convince riders that there is a problem and that this is the solution. Then they
get to convince buyers that they won't find themselves with an orphan crankset
that no pedal will fit in five years.
Perhaps Shimano could pull this off. If they tried very hard and invested a huge
amount of money. Nobody else has the breadth of pedal types and market levels to
even think about it.
The threadless headset is simpler, less expensive and requires less labor to
install than the system it replaces, regardless of its other advantages. That
won't be true of your new pedal system.
--
Oh damn. There's that annoying blog. Again. http://dumbbikeblog.blogspot.com
thirty-six
Vibration will shake pretty much anything loose and that is why the
screw fastening is the correct one.
Tom Ace
> >> Wherever you find a left hand thread that is not part of a
> >> turnbuckle, you are looking at a faulty design. Threads are
> >> intended to hold parts together, not to support radial loads,
> >> something they cannot properly do.
> > Do you deem the left hand thread on the arbor of a radial arm saw to
> > be a faulty design?
>
> I don't have one of those so I cannot inspect its function.
I can't imagine you haven't seen this kind of arrangement.
Millions of saws in the USA use a threaded 5/8" arbor.
A pic (with the nut loosened a bit) is at
http://minortriad.com/rsaw.jpg
You said in another response that "The same goes for saws
and grinding wheels that are not properly located and tend
to get tighter with torque."
Tightening in use is a non-issue. The nut comes off with a
short hand tool, with the same torque I put it on with.
If this is a faulty design, describe one that would be better.
Keep in mind that it has to be able to mount one blade or a
whole stack (for dado or rabbet joints).
Tom Ace
datakoll
load for your roses. Flatworms anyone ?
I bought 3 at $10. such a deal right ? like good bones, 3 derays ...
aluminum oxide iza bear.
on two forks, desil fuel for 2-3 weeks, torch, CO2,
tied er down and applied the max lever
pretzelville !
gets the neck muscles loose.
Jobst Brandt
> It may be inelegant, but "faulty" is a bit of a stretch... I've
> used bench grinders inherited from my great-grandfather that used
> the same design and managed to hold together all these years. (my
> dad has one bolted to a workbench into his barn that is likely older
> than he, although I think I replaced the motor sometime back when I
> was in high school, the grinder head just got a clean up and some
> fresh oil - it's a belt driven head so you can hide the motor under
> the bench and have more access to the wheels for odd shaped parts.)
> I am trying to think of an alternative method (not using the
> rotation of the wheel to keep a nut tight) to keep the wheel from
> loosening its attachment mechanism without adding parts or
> complexity, and am coming up dry.
To make up for that the wheels keep tightening until thread friction
exceeds the load as it did for years on old freewheels, and on this
forum we heard from people who didn't like to see the change, even
though sprockets got close to infinitely tight and distorted into
conical plates while some even fractured.
We can find plenty of dissenters today for the splined sprockets used
by Campagnolo and Shimano with a retaining screw with ratchet face.
I'll bet your saw has off center blades once the nut is tight because
they have smooth bores with clearance. That is not in the intent of
the designer.
I think how many years we put up with air cooled IC engines with all
the motor engineers supporting the failed proposition. I worked at
Porsche and recall when Mr. F. Porsche asked me what people would say
when they scrapped air cooling. My response was "It's about time" and
it occurred.
There are still many air cooled engine fanatics that love the expense
and sound of a rattling engine assembled of many individual parts that
all change fit with heat. In the 1960's we could never achieve the
reliability and power of water cooled competitors, no matter ho hard
we tried.
Jobst Brandt
Jobst Brandt
>>>> Science is a strange field, as we have seen in the "hot water
>>>> freezes faster than cold water" thread that we had here
>>>> recently. That story is ultra ancient and all my explanations
>>>> never make it to the reader.
>>> Dunno what you think is "recently" or what your "explanations"
>>> were.
>>> Heck, I can't even tell from your post what you think.
>>> But for anyone curious:
http://www.picotech.com/experiments/mpemba_effect/results.html
>> You needn't be so condescending, the cause for the more rapid
>> freezing of warm water than for cold water is insulation,
>> especially in pipes where there is no evaporation.
> Nope, two containers, same freezer, well-known phenomenon.
I see you clipped the essential points I made and what I learned in
college physics. Hot water is not aerated while cold water is, and
aeration constitutes lower thermal conductivity, the reason why hot
water pipes often burst before cold water pipes because they are air
free, an effect non scientific people believe is caused by an abnormal
strange "Mpemba" effect.
I also learned in many winters, locally and in Europe that hot water
pipes often burst before cold water pipes for that reason. It is as
mysterious as the use of bubblers to keep boats from being damaged by
freezing lakes. That was also filled with myth and lore until schools
began teaching the temperature in frozen lakes... why Lake Tahoe
doesn't freeze, for instance. It is not as people liked to believe.
As I often mention, science is a foreign subject to most people, even
those who seem to have some scientific education. Van der Waals
forces remain a major stumbling block for many who never question why
a wet finger turns a page of a newspaper while a dry one doesn't, or
why moisture remains stuck to walls.
Jobst Brandt
Nate Nagel
But now we're talking about a saw blade or grinding wheel, and I've
never had one get too tight to remove (unlike a freewheel) - the design
works. And a grinding wheel gets dressed after installation, so precise
location is not required.
>
> We can find plenty of dissenters today for the splined sprockets used
> by Campagnolo and Shimano with a retaining screw with ratchet face.
> I'll bet your saw has off center blades once the nut is tight because
> they have smooth bores with clearance. That is not in the intent of
> the designer.
very small clearances... probably as much clearance or more in the
grinder head's bearings or bushings.
I guess the point is, what's the alternative? Four or five cap screws,
like a wheel hub? More expense and parts for no noticeable advantage in
service.
> I think how many years we put up with air cooled IC engines with all
> the motor engineers supporting the failed proposition. I worked at
> Porsche and recall when Mr. F. Porsche asked me what people would say
> when they scrapped air cooling. My response was "It's about time" and
> it occurred.
>
> There are still many air cooled engine fanatics that love the expense
> and sound of a rattling engine assembled of many individual parts that
> all change fit with heat. In the 1960's we could never achieve the
> reliability and power of water cooled competitors, no matter ho hard
> we tried.
But there is an advantage to air cooling... I'm surprised Colin Chapman
never tried it. And I certainly wouldn't kick a glycol-deficient car
out of my driveway for leaking oil...
Jobst Brandt
>> I have pictures and collections of such parts, bu the bicycle
>> industry is exceedingly slow to recognize the failure and how to
>> fix it. As you see the threadless steer tube did it so but left
>> hand BB (right cup) and pedal threads remain a point of failure.
>> Left hand pedal threads have been explained here at length but the
>> manufacturers don't seem to read or comprehend what appears here.
>> Wherever you find a left hand thread that is not part of a
>> turnbuckle, you are looking at a faulty design. Threads are
>> intended to hold parts together, not to support radial loads,
>> something they cannot properly do. Bicycle companies have not
>> discovered that because they don't hire qualified engineers,
>> believing a bicycle is an inexpensive and simple device.
> More likely they understand it perfectly well but are uninterested
> in attempting to introduce a new standard that replaces pedals and
> crank arms. It doesn't matter how many of what kind of engineers
> they hire, they would first have to convince riders that there is a
> problem and that this is the solution. Then they get to convince
> buyers that they won't find themselves with an orphan cranks that
> no pedal will fit in five years.
You are assuming they recognize the problem but talking to them, I am
sure they don't understand thread precession. It took the auto
industry many years to switch to the conical lug nut... and they knew
or should have.
> Perhaps Shimano could pull this off. If they tried very hard and
> invested a huge amount of money. Nobody else has the breadth of
> pedal types and market levels to even think about it.
I doubt it. I talked to upper level managers with examples of failed
cranks and modified parts (often seen here) at InterBike. There was
interest but no results. Enough people have fallen and gotten injured
from these left hand thread pedals to make it worth while.
> The threadless headset is simpler, less expensive and requires less
> labor to install than the system it replaces, regardless of its
> other advantages. That won't be true of your new pedal system.
Why not? It screws in just like the current standard. It's just like
tightening lug nuts on a car, truck r trailer. I can assure you of
that because I and others use this modification that would only be
simpler if it were part of the OEM part.
--
Jobst Brandt
Norman
> > and sound of a rattling engine assembled of many individual parts that
> > all change fit with heat. In the 1960's we could never achieve the
> > reliability and power of water cooled competitors, no matter ho hard
> > we tried.
>
> But there is an advantage to air cooling... I'm surprised Colin Chapman
> never tried it. And I certainly wouldn't kick a glycol-deficient car
> out of my driveway for leaking oil...
>
Correct me if I'm mistaken, but some of the old Gleaner combines
had air-cooled V diesels: them silly things just sit out there from
September through May, & rarely, if ever, get run in freezing
conditions.
Jobst Brandt
>>>> Wherever you find a left hand thread that is not part of a
>>>> turnbuckle, you are looking at a faulty design. Threads are
>>>> intended to hold parts together, not to support radial loads,
>>>> something they cannot properly do.
>>> Do you deem the left hand thread on the arbor of a radial arm saw
>>> to be a faulty design?
>> I don't have one of those so I cannot inspect its function.
> I can't imagine you haven't seen this kind of arrangement. Millions
> of saws in the USA use a threaded 5/8" arbor. A pic (with the nut
> loosened a bit) is at
http://minortriad.com/rsaw.jpg
Try to imagine someone who does no wood work and doesn't use machine
tools in my own repairs. The above picture seems to no center the saw
blade with any precision and if it loosens so readily, it doesn't need
a left hand thread, there being no practical torque that wold tighten
it.
> You said in another response that "The same goes for saws and
> grinding wheels that are not properly located and tend to get
> tighter with torque."
> Tightening in use is a non-issue. The nut comes off with a short
> hand tool, with the same torque I put it on with.
Then why use a left hand thread?
> If this is a faulty design, describe one that would be better.
> Keep in mind that it has to be able to mount one blade or a
> whole stack (for dado or rabbet joints).
I'm not in th saw business but I could come up with a collet that
would accept one or more blades and fit on a conical spud with a right
hand thread.
Jobst Brandt
Nate Nagel
there is a small torque that tightens the nut, and it WILL loosen it if
run backwards.
Frank Krygowski
>
>
> Dear Jobst,
>
> Nope, two containers, same freezer, well-known phenomenon.
>
> Cheers,
>
> Carl Fogel
The one time I tried it with two ice cube trays, one filled hot, one
filled cold, it yielded no surprises. The cold water froze faster by
a wide margin.
Has Fogel Labs joined the fray yet?
- Frank Krygowski
Jobst Brandt
>>> There are still many air cooled engine fanatics that love the expense
>>> and sound of a rattling engine assembled of many individual parts that
>>> all change fit with heat. In the 1960's we could never achieve the
>>> reliability and power of water cooled competitors, no matter ho hard
>>> we tried.
>> But there is an advantage to air cooling... I'm surprised Colin Chapman
>> never tried it. And I certainly wouldn't kick a glycol-deficient car
>> out of my driveway for leaking oil...
That's because you don't understand why air cooling was ever used and
is no longer to be found on newer engines.
> Correct me if I'm mistaken, but some of the old Gleaner combines
> had air-cooled V diesels: them silly things just sit out there from
> September through May, & rarely, if ever, get run in freezing
> conditions.
THis was once in Wikipedia, but the air cooled faithful deleted the
entire article with picutres. The air cooled religious live!
You might consider:
Why automobile engines were air-cooled -----------------------------
Cars and trucks using direct air cooling (without an intermediate
liquid) were built over a long period beginning with the advent of
mass produced passenger cars and ending with a small and generally
unrecognized technical change. Before World War II, water cooled
cars and trucks routinely overheated while climbing mountain roads,
creating geysers of boiling cooling water. This was considered
normal, and at the time, most noted mountain roads had auto repair
shops to minister to overheating engines.
ACS (Auto Club Suisse) maintains historical monuments to that era on
the Susten Pass where two radiator refill stations remain.
http://en.wikipedia.org/wiki/Image:ACS_water_Susten.jpg
These have instructions on a cast metal plaque and a spherical bottom
watering can hanging next to a water spigot. The spherical bottom was
intended to keep it from being set down and, therefore, be useless
around the house, in spite of which it was stolen, as the picture
shows.
During that period, European firms such as Magirus-Deutz
http://de.wikipedia.org/wiki/Magirus-Deutz
http://www.magirusdeutz.co.uk/
built air-cooled diesel trucks, Porsche
http://porschediesel.stereofx.org/
built air-cooled farm tractors, and Volkswagen became famous with
air-cooled passenger cars. In the USA, Franklin built cars with
air-cooled engines.
"What changed and when?"
The change occurred at the start of World War II when the US military
needed reliable vehicles. The subject of boiling engines was
addressed, researched, and a solution found. Previous radiator.
"Air-cooled automotive engines existed for lack of a water pump seal!"
Jobst Brandt
Norman
I don't know about Fogel Labs, but I have to say that the
other side of the thermodynamic equation makes this
mixture of amaretto, OJ, & soda just about perfect.
Cheers.
Jobst Brandt
>>> There are still many air cooled engine fanatics that love the
>>> expense and sound of a rattling engine assembled of many
>>> individual parts that all change fit with heat. In the 1960's
>>> working in the Porsche racing department, we could never achieve
>>> the reliability and power of water cooled competitors, no matter
>>> how hard we tried.
>> But there is an advantage to air cooling... I'm surprised Colin
>> Chapman never tried it. And I certainly wouldn't kick a
>> glycol-deficient car out of my driveway for leaking oil...
That's because you don't understand why air cooling was ever used and
andis no longer to be found on new engines.
> Correct me if I'm mistaken, but some of the old Gleaner combines
> had air-cooled V diesels: them silly things just sit out there from
> September through May, & rarely, if ever, get run in freezing
> conditions.
You might consider:
This article was once in Wikipedia, but the air cooled faithful
deleted the article and its picutres. The air cooled religion livesq!
Frank Krygowski
> Tom Ace wrote:
>
> http://minortriad.com/rsaw.jpg
>
> Try to imagine someone who does no wood work and doesn't use machine
> tools in my own repairs. The above picture seems to no center the saw
> blade with any precision and if it loosens so readily, it doesn't need
> a left hand thread, there being no practical torque that wold tighten
> it.
It centers the saw blade well enough. I just measured the ID of the
blade and the OD of the arbor on my radial arm saw. OD=0.624",
ID=0.626" and we're cutting wood, not milling steel. A couple
thousandths runout is negligible for woodworking.
And a good reason for the left hand thread is this: If the woodworker
changes the blade but forgets to tighten it down, then begins a cut,
the blade would rotate in the direction to spin the collar and loosen
a right hand thread. I think the danger is not that the blade will
spin completely off; rather, that the now wobbly blade will grab the
workpiece and kick. That kick is the great danger of both table saws
and radial arm saws in woodworking.
I think it's one of those situations where you have to examine not
only normal service, but abnormal service, including faulty
installation, to understand the design.
> I'm not in th saw business but I could come up with a collet that
> would accept one or more blades and fit on a conical spud with a right
> hand thread.
Since this existing design has succeeded for, oh, 100 years, there's
no need; there'd be no market. It would be a textbook example of
"overengineered."
BTW, another example of a good left hand thread application: The
chuck of a reversible drill is screwed on with a normal right hand
thread, but retained by a left hand screw inserted axially into the
open chuck. And we can probably come up with others.
- Frank Krygowski
z
Tom Ace
> > Tightening in use is a non-issue. The nut comes off with a short
> > hand tool, with the same torque I put it on with.
>
> Then why use a left hand thread?
I should've said it comes off with roughly the same torque,
close enough to not feel different when using the wrench.
As Nate Nagel said, there's a small effect that would
loosen the nut were it threaded the other way.
It's a small enough effect to not make removal hard;
it's nothing like removing a threaded sprocket or freewheel.
> > If this is a faulty design, describe one that would be better.
> > Keep in mind that it has to be able to mount one blade or a
> > whole stack (for dado or rabbet joints).
>
> I'm not in th saw business but I could come up with a collet that
> would accept one or more blades and fit on a conical spud with a right
> hand thread.
That would expand to hold and center the blade but unless I'm
missing something, it wouldn't keep a thin blade square to the axis.
Tom Ace
Michael Press
"Zeppo" <ze...@hotmail.org> wrote:
> "Michael Press" <rub...@pacbell.net> wrote in message
> news:rubrum-E7E761....@news.albasani.net...
> > In article <7lk7tuF...@mid.individual.net>,
> > "Zeppo" <zep...@hotmail.org> wrote:
> >
> >> "Simon Lewis" <simonle...@gmail.com> wrote in message
> >> news:hcmveh$p8b$1...@news.eternal-september.org...
> >> > "Zeppo" <ze...@hotmail.org> writes:
> >> >
> >> >> Looking to rebuild an old mountain bike someone gave us for my son to
> >> >> use
> >> >> at
> >> >> college. He is at an inner city campus so the condition of the bike
> >> >> (beat
> >> >> up, some rust, flaking paint) is a distinct advantage. The bike was
> >> >> left
> >> >> outdoors for the last year and is in pretty bad shape. It's a 2001
> >> >> Performance M207 mountain bike.
> >> >>
> >> >> I cleaned up the tires, replaced the tunes, brake pads and chain. The
> >> >> derailleurs seem to be frozen as were the idler pulleys on the rear. I
> >> >> was
> >> >> able to disassemble the pulleys and clean them up and they are OK now.
> >> >>
> >> >> How tough is it to rebuild the derailleurs? I adjusted them before but
> >> >> have
> >> >> never taken one apart. Are there decent instructions somewhere on the
> >> >> web
> >> >> you could point me too? A Google search hasn't turned up anything
> >> >> useful
> >> >> yet. Would it be more cost effective to look for a used set on eBay
> >> >> and
> >> >> just
> >> >> replace them? I don't have a ton of cash to put into this (2 kids in
> >> >> college) so I'm looking to tap the wealth of your experience.
> >> >>
> >> >> Thanks in advance for any help you can give.
> >> >
> >> > I could suggest you post the make and model of the derailleurs. That
> >> > might help.
> >> >
> >> > When you say frozen. Where? They don't move when you shift them or you
> >> > cant even move them by hand?
> >>
> >> OK, so the cables are definitely shot and 2 days in WD-40 hasn't helped
> >> the
> >> front derailleur at all. It moves, but grudgingly, and not the full
> >> range.
> >> It's really corroded. The adjustment screws are pretty much rusted off.
> >>
> >> The derailleur is a Shimano STX-RC, Model FD-MC38, a top-pull, top-swing
> >> model that fits a 31.8 tube.
> >>
> >> Can you suggest a low cost replacement for this?
> >
> > Almost all front derailleurs are low cost.
> > Find some that fit, and see.
> > Sorry, I cannot recommend a specific model.
>
> Not a problem Michael. From what I've been reading almost any top-pull
> derailleur that will fit the seat tube can be made to work. I picked up one
> on eBay for $10 that will do fine. Same configuration, just a newer model.
Happy to hear it.
--
Michael Press
Michael Press
Jobst Brandt <jbr...@sonic.net> wrote:
> There are still many air cooled engine fanatics that love the expense
> and sound of a rattling engine assembled of many individual parts that
> all change fit with heat. In the 1960's we could never achieve the
> reliability and power of water cooled competitors, no matter ho hard
> we tried.
Those VW engines sound like sewing machines.
--
Michael Press
Michael Press
<ed8aedc5-9973-4615...@l13g2000yqb.googlegroups.com>,
"carl...@comcast.net" <carl...@comcast.net> wrote:
> On Nov 11, 2:21 pm, Jobst Brandt <jbra...@sonic.net> wrote:
>
> > Science is a strange field, as we have seen in the "hot water freezes
> > faster than cold water" thread that we had here recently. That story
> > is ultra ancient and all my explanations never make it to the reader.
>
> Dear Jobst,
>
> Dunno what you think is "recently" or what your "explanations" were.
>
> Heck, I can't even tell from your post what you think.
>
> But for anyone curious:
>
> http://www.picotech.com/experiments/mpemba_effect/results.html
>
> It's a widely observed and measured effect, with most suggested
> explanations involving flaws in the experiments ruled out in the
> original paper.
Show us one where the mass of the frozen water is measured.
--
Michael Press
Jobst Brandt
>> There are still many air cooled engine fanatics that love the
>> expense and sound of a rattling engine assembled of many individual
>> parts that all change fit with heat. In the 1960's at the Porsche
>> racing department we could never achieve the reliability and power
>> of our water cooled competitors, no matter how hard and what we
>> tried.
> Those VW engines sound like sewing machines.
They were the 804 opposed eight cylinder F1 engine that won one race
with Dan Gurney at the wheel in Francochamps (F) before the project
was canceled.
Jobst Brandt
datakoll
farmers likum.
Tony Maggs ! reads like Porsche at Indy.
thirty-six
Citreon 2cv and VW Beetles would be running well in sub freezing
conditions in two minutes. Using a lighter lubricant meant these
things were off the mark before most cars were started.
thirty-six
> The reason it's no longer found is simple - noise limits.
> There's reasons that most of the engines in general aviation are
> air-cooled - it's reliable and light.
> Just think of how many reliability problems on cars are down to the
> cooling system, but only on liquid cooled cars.
Unfortunately, commonly missed during 'diagnosing' running problems.
thirty-six
Even on engines with a water cooling system, the circulating oil does
have a role to play in stabilizing engine temperatures.
Zeppo
>>
>> >> Thanks,
>> >> Jon
>>
>> > Your original is likely to be the best choice. I've never seen a
>> > front der in a condition from non accidental causes where it cannot be
>> > revived. I would dunk it in diesel for 48 hours, mount it on a pole/
>> > tube and scrub it with the head of a yard brush. Dont touch the limit
>> > screws, they're likely set right and its best not to move them unless
>> > necessary after full cleaning. after brushing swill it in clean fuel/
>> > kerosene and oil it generously. Leave it for a day, then actuate it.
>>
>> I soaked it in WD-40 for a few days and that didn't loosen it up. Then 2
>> days in diesel, and it still wouldn't loosen. Picked up a used Shimano
>> STX
>> on eBay.
>>
>> Many thanks for you help.
>>
>> Jon
>
> Did you not try to persuade it first? Pry bar, lump hammer, etc.
Yes, and I was on the debating team in college.
It would move very reluctantly, and with a great amount of force, and
soaking and scrubbing didn't loosen it at all. I realized I had put about 4
hours into the part and decided to cut my losses.
Jon
thirty-six
Ha ha ha, Of course, what I shoulda dun was look into my 'breaker
box', it contains all my heavy tools, including a can of Plus-Gas.
The Plus-Gas is the standard aid to free corroded and gummed bolts
etc. It's been a while since I opened the box, I forget sometimes.
Zeppo
"thirty-six" <thirt...@live.co.uk> wrote in message
news:5a986269-9bd0-4b70...@p35g2000yqh.googlegroups.com...
As does air.
Zeppo
"thirty-six" <thirt...@live.co.uk> wrote in message
news:d590a448-02c1-4855...@r24g2000yqd.googlegroups.com...
> On 3 Nov, 16:13, thirty-six <thirty-...@live.co.uk> wrote:
>
>>
>> If the cables are without the plastic tube between the inner wire and
>> outer spral wrap housing, then(sorry, lost it, feels like I'm
>> programming)
>
> For cables without liners use a regular grade of oil or grease. The
> reliable long service method is to use graphited grease pumped in to
> the housing with a special applicator for bowden wires. The case of
> grease is warmed and a pump applied to pressurise the 'piston', the
> cable moved to and fro until the grease appears at the other end.
> It's a neat device if you can use it.
Thank God the housing had liners. I can't imagine how much that pump would
have set me back. :-)
carl...@comcast.net
Dear Frank,
Maybe "Krygowski" isn't oddly spelled enough to work?
:-)
Actually, anyone who looks past the oddly-spelled name that worried
Jobst (!) will find that the Mpemba effect is well-recognized, harder
to demonstrate than expected, and even harder to explain.
Anyway, Fogel Labs was beaten to the punch by Descartes Labs and some
fly-by-night publishing house called "Scientific American" (apparently
"Jearl" and "Debenedetti" are spelled oddly enough to make things
work):
"Descartes made careful observations of the freezing of water that
enabled him to identify the liquid's unusual density maximum at 4 �C.
These studies convinced him that 'water which has been kept hot for a
long time freezes faster than any other sort'."
"But were all these reports just the result of bad experimental
technique? Surely it should be a simple matter to settle the issue
once and for all by carrying out experiments? That turns out to be
surprisingly difficult, not least because the statement 'hot water
freezes faster than cold' is ill-defined. In a recent paper, Jeng
suggests a more precise wording (arXiv.org/abs/physics/0512262v1):
'There exists a set of initial parameters, and a pair of temperatures,
such that given two bodies of water identical in these parameters, and
differing only in their temperatures, the hot one will freeze
sooner.'"
[ . . . ]
"In 1977, for example, Jearl Walker reported in Scientific American
that he had observed the time it took a beaker of water to cool to 0
�C from different initial temperatures under various conditions. These
tests provided some clarification of the effect (see figure). But
although Walker reported that he could reproduce most of his results,
he still obtained large deviations in some of them. 'I have not been
able to resolve the controversy,' he said."
"However, despite the continuing uncertainties surrounding the effect,
Pablo Debenedetti, a physicist at Princeton University and a
specialist in phase transitions of water, is happy to believe Mpemba's
account. 'I do not see any reason to doubt observations showing that
under some circumstances hot water can freeze faster than cold
water,'" he says.
http://physicsworld.com/cws/article/print/24493
(Access to that link with an embedded graph of Jearl Walker's
measurements may require a free sign-up, but it's worth the slight
fuss to read the whole article.)
Some other Mpemba links:
http://www.physics.adelaide.edu.au/~dkoks/Faq/General/hot_water.html
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/freezhot.html#c3
Cheers,
Carl Fogel
carl...@comcast.net
>Carl Fogel wrote:
>
>>>>> Science is a strange field, as we have seen in the "hot water
>>>>> freezes faster than cold water" thread that we had here
>>>>> recently. �That story is ultra ancient and all my explanations
>>>>> never make it to the reader.
>
>>>> Dunno what you think is "recently" or what your "explanations"
>>>> were.
>
>>>> Heck, I can't even tell from your post what you think.
>
>>>> But for anyone curious:
>
> http://www.picotech.com/experiments/mpemba_effect/results.html
>
>>> You needn't be so condescending, the cause for the more rapid
>>> freezing of warm water than for cold water is insulation,
>>> especially in pipes where there is no evaporation.
>
>> Nope, two containers, same freezer, well-known phenomenon.
>
>I see you clipped the essential points I made and what I learned in
>college physics. Hot water is not aerated while cold water is, and
>aeration constitutes lower thermal conductivity, the reason why hot
>water pipes often burst before cold water pipes because they are air
>free, an effect non scientific people believe is caused by an abnormal
>strange "Mpemba" effect.
>
>I also learned in many winters, locally and in Europe that hot water
>pipes often burst before cold water pipes for that reason. It is as
>mysterious as the use of bubblers to keep boats from being damaged by
>freezing lakes. That was also filled with myth and lore until schools
>began teaching the temperature in frozen lakes... why Lake Tahoe
>doesn't freeze, for instance. It is not as people liked to believe.
>
>As I often mention, science is a foreign subject to most people, even
>those who seem to have some scientific education. Van der Waals
>forces remain a major stumbling block for many who never question why
>a wet finger turns a page of a newspaper while a dry one doesn't, or
>why moisture remains stuck to walls.
>
>Jobst Brandt
Dear Jobst,
I see that you are still talking about hot water pipes and not the
Mpemba effect.
Cheers,
Carl Fogel
russell...@yahoo.com
wrote:
> >That's because you don't understand why air cooling was ever used and
> >is no longer to be found on newer engines.
>
> The reason it's no longer found is simple - noise limits.
> There's reasons that most of the engines in general aviation are
> air-cooled - it's reliable and light.
> Just think of how many reliability problems on cars are down to the
> cooling system, but only on liquid cooled cars.
Propellor airplanes with air cooled engines operate in very different
environments than automobiles. That is why air cooled engines can
work in airplanes, but not automobiles. Airplanes generally do not
have traffic jams where they essentially idle or move at 10 mph for
30-60 minutes twice a day. Cars do in all big cities. If the car is
not moving, its not going to get enough air moving across the block to
cool it down. Airplanes sit for a few minutes warming up and then
take off. They don't idle for an hour. And then of course you have
the propellor. Its blowing air across the engine at 50-100 mph or
whatever. An airplane provides its own method of air cooling by its
propellor. Cars don't have big fan blades sticking out of the
radiator blowing air onto the block. If they did then air cooling
would work fine.
Norman
<russellseat...@yahoo.com> wrote:
. . .
> Cars don't have big fan blades sticking out of the
> radiator blowing air onto the block. If they did then air cooling
> would work fine.
You missed the thread titled "Here squirrely squirrely squirrel!"
Of course, the French are/were insane, which is why we love
them so.
thirty-six
Yes, but the rotational movement of the goldfish scales is really
important, and nobody knew anything about it until I pointed it out.
carl...@comcast.net
<frkr...@gmail.com> wrote:
>On Nov 11, 6:58�pm, carlfo...@comcast.net wrote:
>>
>>
>> Dear Jobst,
>>
>> Nope, two containers, same freezer, well-known phenomenon.
>>
>> Cheers,
>>
>> Carl Fogel
>
>The one time I tried it with two ice cube trays, one filled hot, one
>filled cold, it yielded no surprises. The cold water froze faster by
>a wide margin.
>
>Has Fogel Labs joined the fray yet?
>
>- Frank Krygowski
Dear Frank,
Just a note to point out another nice article on the Mpemba effect by
yet another fellow with what Jobst would consider an oddly spelled
name:
http://arxiv.org/PS_cache/physics/pdf/0512/0512262v1.pdf
As the article points out, demonstrations of the Mpemba effect are
fairly common in science fairs.
Cheers,
Carl Fogel
Frank Krygowski
> On Wed, 11 Nov 2009 19:48:27 -0800 (PST), Frank Krygowski
>
> >filled cold, it yielded no surprises. The cold water froze faster by
> >a wide margin.
>
> >Has Fogel Labs joined the fray yet?
>
> >- Frank Krygowski
>
> Dear Frank,
>
> Maybe "Krygowski" isn't oddly spelled enough to work?
>
> :-)
>
> Actually, anyone who looks past the oddly-spelled name that worried
> Jobst (!) will find that the Mpemba effect is well-recognized, harder
> to demonstrate than expected, and even harder to explain.
Hmm. The harder it is to demonstrate, the less it requires
explanation.
>
> Anyway, Fogel Labs was beaten to the punch by Descartes Labs and some
> fly-by-night publishing house called "Scientific American" (apparently
> "Jearl" and "Debenedetti" are spelled oddly enough to make things
> work):
>
> "Descartes made careful observations of the freezing of water that
> enabled him to identify the liquid's unusual density maximum at 4 °C.
> These studies convinced him that 'water which has been kept hot for a
> long time freezes faster than any other sort'."
That's apparently not saying the same thing. Has it been kept hot for
a long time (to, say, expel gases) then cooled to room temperature,
_then_ timed to its freezing?
> Surely it should be a simple matter to settle the issue
> once and for all by carrying out experiments? That turns out to be
> surprisingly difficult, not least because the statement 'hot water
> freezes faster than cold' is ill-defined.
Certainly, we need a precise statement of the problem. As usual.
> In a recent paper, Jeng
> suggests a more precise wording (arXiv.org/abs/physics/0512262v1):
> 'There exists a set of initial parameters, and a pair of temperatures,
> such that given two bodies of water identical in these parameters, and
> differing only in their temperatures, the hot one will freeze
> sooner.'"
Even that is a bit imprecise. Are we talking about a fixed mass of
water, or are we allowing for possible reduction in mass by
evaporation?
>
> [ . . . ]
>
> "In 1977, for example, Jearl Walker reported in Scientific American
> that he had observed the time it took a beaker of water to cool to 0
> °C from different initial temperatures under various conditions. These
> tests provided some clarification of the effect (see figure). But
> although Walker reported that he could reproduce most of his results,
> he still obtained large deviations in some of them. 'I have not been
> able to resolve the controversy,' he said."
Of course, cooling to 0 °C is not the same as freezing.
> "However, despite the continuing uncertainties surrounding the effect,
> Pablo Debenedetti, a physicist at Princeton University and a
> specialist in phase transitions of water, is happy to believe Mpemba's
> account. 'I do not see any reason to doubt observations showing that
> under some circumstances hot water can freeze faster than cold
> water,'" he says.
That too seems vague. He implies, but does not state, that he's
referring to equal masses of hot and cold water under equal
environmental conditions.
I can envision some secondary effects changing cooling rate. People
have mentioned evaporation (more of a factor when rinsing a car in the
winter than making ice cubes in a freezer, I suppose) and better
conduction with surrounding ice in a freezer, once a hotter container
has melted its way into the ice. I can envision dissolved gases
having an effect on the crystallization process itself. We know that
liquids can become super-cooled without freezing, if they lack proper
triggers or nuclei for crystal formation.
But if conditions are truly equal, it's very hard for me to believe
that, say, 100 grams of water at 50 °C is going to freeze before 100
grams of water at 18 °C. That's what I thought before I put the hot
and cold water into my freezer, and that's what I still thought after
I took them out.
This bears more than a grammatic similarity to "cold fusion."
- Frank Krygowski