Re: Help with disaster cotter pin!

Jeff Potter said:

Re: Jobst's reply: I did check the Google-groups history and the
cranks are straight. We've used an anvil, maul and punch. With the
very first whack I thought I saw the pin move 1mm. Since then,
nothing. We've used a couple different punches. I've considered
that the axle intrudes on the pin-hole and I'm trying not to damage
the axle. Yeah, I can tell the pin is a softy.

Quoted message said:

Re: the 2nd reply: We've drilled out most of the pin, but there's
still some in there. We've drilled all the way through.

Quoted message said:

I wonder if doing the pipes-on-arms jumping routine would help mash
the remaining pin out? Can we use the pin's softness against it?

Well yes... but you must be sure that the cranks are truly 180 degrees
apart so that the cotter has a clear exit when hammered upon. The
cotter will have to shear metal to exit and that's the problem.

Quoted message said:

Will heat maybe help? With about 1/3 of the pin remaining inside
the arm? Solvents advice?

Nothing but mechanical force will do. Get that crank aligned and
drive it out. The only reason for this is to save an antique. I know
of no reasonable cotters available today to replace the ones you have.

Quoted message said:

Once we get the pin out, I suppose I'll need to use the pipes-on-arms
to loosen the crank off the spindle?

I'm not familiar with that routine. The crank should separate
relatively easily, its bore only getting larger from use and force.

Jobst Brandt

You might be able to grind most of it out with a dremel. Finish off
with a hand file. I was going to suggest hot/cold cycles of 30+
degrees swing (sun/shade for a week), but as both metals are steel
this is not likely to produce much of a benefit. It has been known to
work in removing stuck freewheels.

- Don Gillies
San Diego, CA

Is it from a 1974 Raleigh Bicycle ( super course had stronglight
cranks, lower models typically had nervar cranks )?

If so, then might be a 9.5mm cotter pin which would mean there is no
size larger. If you end up drilling it out completely and enlarge the
hole, it may not be possible to install the crank again on a spingle
(cotter will go too deep, washers won't help on threaded side.)

On the other hand, it being a french crankset, it might be 9.0mm which
means that if you enlarge the hole you could use a larger pin for the
next installation. If you have a vernier caliper it would be good to
measure the hole size.

- Don Gillies
San Diego, CA

Donald Gillies said:

Is it from a 1974 Raleigh Bicycle (super course had Stronglight
cranks, lower models typically had Nervar cranks)?

Quoted message said:

If so, then might be a 9.5mm cotter pin which would mean there is no
size larger. If you end up drilling it out completely and enlarge
the hole, it may not be possible to install the crank again on a
spindle (cotter will go too deep, washers won't help on threaded
side.)

Quoted message said:

On the other hand, it being a French crankset, it might be 9.0mm
which means that if you enlarge the hole you could use a larger pin
for the next installation. If you have a vernier caliper it would
be good to measure the hole size.

Hold the phone!

If you drill straight through, the spindle gets its flat removed and
cannot be reused, regardless of cotter size. Besides, the spindle is
hardened steel and should not let itself readily be drilled. I don't
see the room for drilling or Dremel tool in this operation, having
removed a few mushed cotters in the days of yore.

Considering that the cotter is round and has a sloping flat for a
spindle contact, it is apparent that the broad part of the cotter face
should bear pedal torque, not the narrow part. Therefore, cotters
should be installed with the nutted end (broad face) on the leading
face on the left crank and the opposite on the right crank. If not
done so, the cotters will have their narrow face, with about half the
strength, bearing the load.

Jobst Brandt

jeff potter said:

Re: Jobst's reply: I did check the google-groups history and the
crankarms are straight. We've used an anvil, maul and punch. With the
very first whack I thought I saw the pin move 1mm. Since then, nothing.
We've used a couple different punches. I've considered that the axle
intrudes on the pin-hole and I'm trying not to damage the axle. Yeah, I
can tell the pin is a softy.

Since the pin is much softer, you should not have to worry about damaging
the axle unless you resort to explosives.

Quoted message said:

Re: the 2nd reply: We've drilled out most of the pin, but there's still
some in there. We've drilled all the way thru.

The rest of the pin should be malleable enough to collapse it into a
smaller diameter. If not, go through again with a bigger drill bit.

Quoted message said:

I wonder if doing the pipes-on-arms jumping routine would help mash the
remaining pin out? Can we use the pin's softness against it?

Considering the set-up, you are not shearing the pin by doing this, you
are trying to literally cut through it with the crank arm. I don't think
this will succeed.

Quoted message said:

Will heat maybe help? With about 1/3 of the pin remaining inside the
arm? Solvents advice?

Heat will probably not help, since I think the softer pin will expand more
than the hole. Cold might help, but probably not enough.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |

In article <[email hidden]>,

Quoted message said:

Considering that the cotter is round and has a sloping flat for a
spindle contact, it is apparent that the broad part of the cotter face
should bear pedal torque, not the narrow part. Therefore, cotters
should be installed with the nutted end (broad face) on the leading
face on the left crank and the opposite on the right crank. If not
done so, the cotters will have their narrow face, with about half the
strength, bearing the load.

Is this really a consideration? When the torque goes through the
broad end of one cotter, it goes through the narrow end of the opposite
one. So far as just torque through the spindle goes, it doesn't matter
which way you have the cotters - you have to go through a narrow face
whatever the case.
The only consideration would be of the left crank supporting a
bending moment the same time it has a torque, and which orientation
better supports that. But I think that moment is supported (albeit
poorly) by the fit between crank and spindle and not primarily by the
cotter.

-Luns

On Wed, 27 Sep 2006 23:31:14 +0000 (UTC), [email hidden]

(Luns Tee) said:

In article <[email hidden]>,

Quoted message said:

Considering that the cotter is round and has a sloping flat for a
spindle contact, it is apparent that the broad part of the cotter face
should bear pedal torque, not the narrow part. Therefore, cotters
should be installed with the nutted end (broad face) on the leading
face on the left crank and the opposite on the right crank. If not
done so, the cotters will have their narrow face, with about half the
strength, bearing the load.

Is this really a consideration? When the torque goes through the
broad end of one cotter, it goes through the narrow end of the opposite
one. So far as just torque through the spindle goes, it doesn't matter
which way you have the cotters - you have to go through a narrow face
whatever the case.
The only consideration would be of the left crank supporting a
bending moment the same time it has a torque, and which orientation
better supports that. But I think that moment is supported (albeit
poorly) by the fit between crank and spindle and not primarily by the
cotter.

The cotter itself is not tapered, only the flat.

And for those who still use 'em, silver steel makes nice cotters that
can be easily hardened.

Luns Tee said:

Quoted message said:

Considering that the cotter is round and has a sloping flat for a
spindle contact, it is apparent that the broad part of the cotter
face should bear pedal torque, not the narrow part. Therefore,
cotters should be installed with the nutted end (broad face) on the
leading face on the left crank and the opposite on the right crank.
If not done so, the cotters will have their narrow face, with about
half the strength, bearing the load.

Quoted message said:

Is this really a consideration? When the torque goes through the
broad end of one cotter, it goes through the narrow end of the
opposite one. So far as just torque through the spindle goes, it
doesn't matter which way you have the cotters - you have to go
through a narrow face whatever the case.

Quoted message said:

The only consideration would be of the left crank supporting a
bending moment the same time it has a torque, and which orientation
better supports that. But I think that moment is supported (albeit
poorly) by the fit between crank and spindle and not primarily by
the cotter.

Major lapse the on my part. Talking with Sheldon brought back
history. What I wrote in the paragraph above is entirely wrong and I
did that exercise many years ago in a similar manner.

No matter which way the cotters are installed, front-to-rear or
rear-to-front one each crank, one small face will be the load bearing
one on one crank or the other.

When realizing this it two problems occurred to me. First that the
angles must be the same so the cranks are truly 180 degrees apart, and
that achieving this is not well done with a file, all cotters being
only partly finished when new.

For this purpose I made a 0.25" thick tooling plate having a 5 degree
sloping ramp on one side ending with a 90 degree end stop, so that
when a cotter was laid in it and clamped in a milling machine vise it
could be reliably skimmed to the same face depth and angle. By using
a 5 degree angle, the face of the cotter had a more uniform width,
much so that the flat ran off the head end of the cotter.

This reduced force of installation, gave an accurate angle, and gave a
broader contact face. I used this for my cranks and those of my
friends until the steel cottered crank went away, aluminum cranks not
allowing such high stress contacts.

The problem is still current as we see Shimano and Campagnolo produce
solutions for crank-to-spindle attachment.

Jobst Brandt

Luns Tee said:

Quoted message said:

Considering that the cotter is round and has a sloping flat for a
spindle contact, it is apparent that the broad part of the cotter
face should bear pedal torque, not the narrow part. Therefore,
cotters should be installed with the nutted end (broad face) on the
leading face on the left crank and the opposite on the right crank.
If not done so, the cotters will have their narrow face, with about
half the strength, bearing the load.

Quoted message said:

Is this really a consideration? When the torque goes through the
broad end of one cotter, it goes through the narrow end of the
opposite one. So far as just torque through the spindle goes, it
doesn't matter which way you have the cotters - you have to go
through a narrow face whatever the case.

Quoted message said:

The only consideration would be of the left crank supporting a
bending moment the same time it has a torque, and which orientation
better supports that. But I think that moment is supported (albeit
poorly) by the fit between crank and spindle and not primarily by
the cotter.

Major lapse the on my part. Talking with Sheldon at InterBike brought
back history. What I wrote in the paragraph above is entirely wrong
and something I did many years ago thinking in a similar manner.

No matter which way the cotters are installed, front-to-rear or
rear-to-front one each crank, one small face will be the load bearing
one on one crank or the other.

When realizing this two problems occurred to me. First being that the
angles must be the same so the cranks are truly 180 degrees apart, and
that achieving this is not well done with a file, all cotters being
only partly finished when new and at what I consider an unsuitable
steep angle.

For this reason I made a 0.25" thick tooling plate having a 5 degree
sloping ramp on one side ending with a 90 degree end stop, so that
when a cotter was laid in it and clamped in a milling machine vise it
could be reliably skimmed to the same face depth and angle. By using
a 5 degree angle, the face of the cotter had a more uniform width, so
much so that the flat extended through the head of the cotter.

The 5 degrees reduced force of installation, gave an accurate angle,
and a broader contact face. I used this for my cranks and those of my
friends until the steel cottered crank went away, aluminum cranks not
allowing such high stress contacts.

The problem is still current as we see Shimano and Campagnolo produce
solutions for crank-to-spindle attachment.

Jobst Brandt