Freewheel removal woes revisited......

On 2008-11-08, wrote:
On Sat, 8 Nov 2008 00:27:13 -0000, "Clive George"
wrote:

"Zog The Undeniable" wrote in message
...

Track riders still (mostly) use screwed-on rear cogs, and a track sprinter
probably screws one down harder than J. Random Cyclist.

Track sprinter in a 90-100" gear vs J Random Cyclist in 30" or less gear?

Dear Clive & Zog,

I'm not arguing, just wondering about the details.

Sheldon's handy calculator suggests
90~100 gear inches for a 53x16 or 53x14
~30 gear inches for a 30x24 or 30x28:
http://sheldonbrown.com/gears/index.html

What kind of forces on the pedal would you expect from a track
sprinter and J. Random Cyclist and how would things work out?

The torque on the rear sprocket is Fls/c where F is pedal force, l is
crank length, s is number of teeth on sprocket and c number of teeth on
chainring.

The pedal force is probably his weight for J. Random Cyclist and 1.5x,
perhaps 2x his weight if we're generous for the track sprinter, since
he's particularly skilled at pulling up on the bars.

Chris Hoy weighs 92kg, so call that 1804N. Assuming his crank is .17m
and he's using 53x14 (does he really use that gear or something higher?)
that's a torque of 81Nm.

J.R.Cyclist also weighs 92kg today and only pushes with 902N. But he
gets a torque of 143Nm in his 30x28.

Ben C? wrote:

Track riders still (mostly) use screwed-on rear cogs, and a track
sprinter probably screws one down harder than J. Random Cyclist.

Track sprinter in a 90-100" gear vs J Random Cyclist in 30" or
less gear?

I'm not arguing, just wondering about the details.

Sheldon's handy calculator suggests 90~100 gear inches for a 53x16
or 53x14 ~30 gear inches for a 30x24 or 30x28:

http://sheldonbrown.com/gears/index.html

What kind of forces on the pedal would you expect from a track
sprinter and J. Random Cyclist and how would things work out?

The torque on the rear sprocket is Fls/c where F is pedal force, l
is crank length, s is number of teeth on sprocket and c number of
teeth on chainring.

The pedal force is probably his weight for J. Random Cyclist and
1.5x, perhaps 2x his weight if we're generous for the track
sprinter, since he's particularly skilled at pulling up on the bars.

Chris Hoy weighs 92kg, so call that 1804N. Assuming his crank is
.17m and he's using 53x14 (does he really use that gear or something
higher?) that's a torque of 81Nm.

J.R.Cyclist also weighs 92kg today and only pushes with 902N. But he
gets a torque of 143Nm in his 30x28.

That is all a bit beside the effect. You can tighten a sprocket (or
FW) with a chain whip with a long handle and not get the engagement as
reticent to removal as continuously rotating torque as applied by
chain pull that rotates relative to the hub.

It is this rotating force and torque that fret the threads together,
displacing lubricant and welding the two together. You can find more
on this in dissimilar metal friction welding:

http://tinyurl.com/6dadfa

Jobst Brandt

On Sat, 08 Nov 2008 15:46:59 +0000, jobst.brandt wrote:

Ben C? wrote:

Track riders still (mostly) use screwed-on rear cogs, and a track
sprinter probably screws one down harder than J. Random Cyclist.

Track sprinter in a 90-100" gear vs J Random Cyclist in 30" or less
gear?

I'm not arguing, just wondering about the details.

Sheldon's handy calculator suggests 90~100 gear inches for a 53x16 or
53x14 ~30 gear inches for a 30x24 or 30x28:

http://sheldonbrown.com/gears/index.html

What kind of forces on the pedal would you expect from a track
sprinter and J. Random Cyclist and how would things work out?

The torque on the rear sprocket is Fls/c where F is pedal force, l is
crank length, s is number of teeth on sprocket and c number of teeth on
chainring.

The pedal force is probably his weight for J. Random Cyclist and 1.5x,
perhaps 2x his weight if we're generous for the track sprinter, since
he's particularly skilled at pulling up on the bars.

Chris Hoy weighs 92kg, so call that 1804N. Assuming his crank is .17m
and he's using 53x14 (does he really use that gear or something
higher?) that's a torque of 81Nm.

J.R.Cyclist also weighs 92kg today and only pushes with 902N. But he
gets a torque of 143Nm in his 30x28.

That is all a bit beside the effect. You can tighten a sprocket (or FW)
with a chain whip with a long handle and not get the engagement as
reticent to removal as continuously rotating torque as applied by chain
pull that rotates relative to the hub.

It is this rotating force and torque that fret the threads together,
displacing lubricant and welding the two together. You can find more on
this in dissimilar metal friction welding:

http://tinyurl.com/6dadfa



jobst, austenitic and ferritic steels are not very "dissimilar" for this
kind of thing. besides, in the type of welding cited there, high
temperature is involved. not that you let little things called "facts"
get in the way of your presumptive ignorant bull****ting.

On Fri, 07 Nov 2008 23:00:50 +0000, Zog The Undeniable wrote:

JCrowe wrote:
wrote:
Jim Crowe wrote:

A while back I detailed the woes of removing an old SunTour Winner
Pro from a wheel. I finally got it off using chain vicegrips after
removing the pawls from the body. Sad to destroy the freewheel.
Somebody recommended the Interloc Racing Designs freewheels and I
ordered one.

Leave your vices at home. In the shop, use Vise-Grips.

Yeah....it took chain vice-grips followed by a pipe wrench.
Breaking it loose was a challenge, but then it was easy as pie. Of
course, being in the shop of a friend who restores vintage BMW
motorcycles didn't hurt any.

I think you should consider the design aspect. No part of a drive
train should transmit torque through threads. Threads that only get
tighter and tighter in use. If you look at good freehubs, you'll see
the sprockets are on splines, the sprocket retaining cover plate is
not the last sprocket but a separate part that screws into the
rotating body with snap-in detents. Drive is transmitted to the
aluminum hub via press fit splines.

I understand this, but given that my 28 year old Campy hubs are
serviceable, I don't see the point of changing.

Track riders still (mostly) use screwed-on rear cogs, and a track
sprinter probably screws one down harder than J. Random Cyclist. Of
course, a fixed-wheel sprocket is somewhat easier to remove because the
sprocket itself is used with a big chainwhip to unscrew it. With a
freewheel, you have a small tool in the middle of the assembly which is
liable to strip. I remember knocking them loose with a big mallet - it
sometimes took a few minutes, although it was satisfying when they
finally broke away. Fortunately my freewheels used the many-splined
Shimano tool, not the 4-spronged type that tends to break.

Sometimes the threads get destroyed on a track hub, which is an
advantage of a fixed/fixed flip-flop hub in a dishless wheel; you can
use the other side.

if it's fixed/fixed, yes, but not fixed/free as some people try. trying
to use fixed without the proper l/h thread lockring is not very safe -
it's not "fixed" at all.

On Sat, 08 Nov 2008 03:54:35 -0600, Ben C wrote:

On 2008-11-08, wrote:
On Sat, 8 Nov 2008 00:27:13 -0000, "Clive George"
wrote:

"Zog The Undeniable" wrote in message
...

Track riders still (mostly) use screwed-on rear cogs, and a track sprinter
probably screws one down harder than J. Random Cyclist.

Track sprinter in a 90-100" gear vs J Random Cyclist in 30" or less gear?

Dear Clive & Zog,

I'm not arguing, just wondering about the details.

Sheldon's handy calculator suggests
90~100 gear inches for a 53x16 or 53x14
~30 gear inches for a 30x24 or 30x28:
http://sheldonbrown.com/gears/index.html

What kind of forces on the pedal would you expect from a track
sprinter and J. Random Cyclist and how would things work out?

The torque on the rear sprocket is Fls/c where F is pedal force, l is
crank length, s is number of teeth on sprocket and c number of teeth on
chainring.

The pedal force is probably his weight for J. Random Cyclist and 1.5x,
perhaps 2x his weight if we're generous for the track sprinter, since
he's particularly skilled at pulling up on the bars.

Chris Hoy weighs 92kg, so call that 1804N. Assuming his crank is .17m
and he's using 53x14 (does he really use that gear or something higher?)
that's a torque of 81Nm.

J.R.Cyclist also weighs 92kg today and only pushes with 902N. But he
gets a torque of 143Nm in his 30x28.

Dear Ben,

Yes, I was thinking that about 3-to-1 would be the ratio for ~90
versus ~30 gear inches.

What I'm wondering about is the force. We tend to talk about body
weight and adding to it by pulling up on the bars and so forth, but I
don't really know what J. Random Cyclist puts onto his lowest gear (or
if he even uses it), nor what sprinters put out.

A typical bicyclist just riding around might put out 200 watts, while
sprinters will break a thousand watts for a couple of seconds, five
times as much.

In other words, 3 x 200 watts 1 x 1,000 watts

But that's watts, not raw torque.

The sprinter's cadence is probably higher, so he may just put out more
(or longer-duration) pulses at lower force than J. Random puts out
just riding around in low gear. In motorcycles, a rouhg analogy would
be the difference between a low-gear, low-speed trials machine versus
an overpowered high-geared street bike.

In terms of tightening the screw-on gear, I don't know which would get
things tighter, a couple of hefty high-torque impulses from J. Random,
or lots of lower-torque impulses from a sprinter.

In practical terms, I suppose that only a bike shop with lots of
experience could tell us which gears are actually harder to unscrew,
higher-gear sprinters or low-gear ordinary riders.

Cheers,

Carl Fogel

Carl Fogel wrote:

In practical terms, I suppose that only a bike shop with lots of
experience could tell us which gears are actually harder to unscrew,
higher-gear sprinters or low-gear ordinary riders.

It's the freewheels that were installed with dry threads.

As a personal observation, I have noticed that my friend Pardo, whose
weight has fallen somewhere between 30% and 40% of my own during the
entire time I've known him, can jam a freewheel every bit as tight on
its threads as I can. I know this because I have had to remove a
couple of them for him, and I almost herniated myself doing so. I
seriously doubt that he would install a freewheel without greasing the
threads first, and I know he is not an exceptionally powerful rider
even for his size.

Pardo has a few riding habits that differ from mine and might have a
bearing on freewheel removal torque. He uses small granny rings
frequently, while my usual bikes have rings between 36 and 49 teeth.
He puts a larger number of miles on a smaller number of bikes than I
do. And he rides extravagantly in the foulest sloppy conditions that
the Pacific Northwest can provide, while I try to minimize riding in
the rain and avoid riding in mud altogether. Which one of these
factors has the most pronounced effect on sticking the freewheel to
the hub, I can't say. I will note, however, that in principle a 33
inch gear pushed by me should screw on a freewheel a whole lot tighter
than a 19 inch gear pushed by Pardo. In practice, his freewheels seem
to be at least as difficult to remove as mine.

Chalo

aka Jobst Brandt wrote:
[...]
We don't need more ratios. We need a wider spread of ratios. I
regularly see people with more than 30 gears riding only one
sprocket up long grades... Oh that's easy, you have 33 gears.
[...]
Oooh! You coast? Any real man pedals hard all the time, as I have
noticed with the 30+ gear folks. That's when I realized I was an old
fogy with a 50-13 as top gear. That became clear when descending the
steep back side of Mt. Hamilton the other day, where I was generally
one of the fastest descenders.

Starting the descent, after Copernicus Peak, I passed a guy who
subsequently passed me leaving me to wondered how he was getting
around those curves so fast, only to notice that he sprinted out of
every turn and pedaling on the strait sections, making headway while I
was coasting. Not having shifted into my top gear I could only go a
little faster out of some turns in my 50-15 gear.[...]

I thought that 50-15 was also your climbing gear? Why not ride a
single-speed or fixed-gear then?

--
Tom Sherman - 42.435731,-83.985007
If you are not a part of the solution, you are a part of the precipitate.