Cotter pin removal... Too easy!
#26
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Additional tips for those using the hammer method:
To avoid bending or mushrooming the threaded portion of the cotter pin, unscrew the nut and add washers such that (1) the top of the nut is flush with the end of the cotter pin and (2) there's a gap of about an eighth to a quarter of an inch between the washers and the surface of the crank arm. The small gap ensures that the threaded part has no room to bend sideways upon impact.
As an alternative to the pipe/flange support method, which can result in the pipe absorbing a large proportion of the impact energy, I like to (1) stand the bike on the floor against a bench or wall with a sheet of cardboard protecting the chainring (with the cardboard cut out so that only the crank arm is exposed); (2) orient the crank arm vertically (with the cotter pin on the horizontal); and (3) stand over the crank arm such that, when I hit the cotter pin nut, my arm is at full length (making it easy to guide the hammer to the point of impact with the greatest force).
Resting the bike on the floor is better than clamping the bike in a stand or otherwise restricting its movement because it guarantees that the maximum force goes into dislodging the cotter pin rather than the force being partly absorbed by the bike stand, pipe, etc.
To avoid bending or mushrooming the threaded portion of the cotter pin, unscrew the nut and add washers such that (1) the top of the nut is flush with the end of the cotter pin and (2) there's a gap of about an eighth to a quarter of an inch between the washers and the surface of the crank arm. The small gap ensures that the threaded part has no room to bend sideways upon impact.
As an alternative to the pipe/flange support method, which can result in the pipe absorbing a large proportion of the impact energy, I like to (1) stand the bike on the floor against a bench or wall with a sheet of cardboard protecting the chainring (with the cardboard cut out so that only the crank arm is exposed); (2) orient the crank arm vertically (with the cotter pin on the horizontal); and (3) stand over the crank arm such that, when I hit the cotter pin nut, my arm is at full length (making it easy to guide the hammer to the point of impact with the greatest force).
Resting the bike on the floor is better than clamping the bike in a stand or otherwise restricting its movement because it guarantees that the maximum force goes into dislodging the cotter pin rather than the force being partly absorbed by the bike stand, pipe, etc.
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They're just so. Immaterial, though, since I specified that the crank arm should be oriented vertically, thus ensuring that the force from the hammer blow is horizontal, allowing the bike to roll an inch or two as a result of the hit, representing a minute amount of ancillary energy loss. Less energy absorbed by a pipe or the bike stand means more energy applied to the cotter pin.
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They're just so. Immaterial, though, since I specified that the crank arm should be oriented vertically, thus ensuring that the force from the hammer blow is horizontal, allowing the bike to roll an inch or two as a result of the hit, representing a minute amount of ancillary energy loss. Less energy absorbed by a pipe or the bike stand means more energy applied to the cotter pin.
When I want to hit something hard, I don't want it to able move at all; "an inch or two" sounds like way too much, but they're your bikes...
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I disagree. The pipe to the floor is not to protect the bearings, which cannot be harmed by hammering (I've done that experiment!). The pipe is to give you the sharpest or shortest-duration impulse (in the physics sense of the word). Without the pipe, your impulse gets spread out in time, with the peak force attenuated, by passing through the frame, bike stand etc. (or the tires if the bike is sitting on the ground.
Still, I foresee a lot of mallets rounding out the tops of cotters - especially if whoever reads this does not see your caveat about using a concave-ended cottered spindle as a punch. Even then, I always back out the cotter nut just up to the edge of the threads when using my Bikesmith press.
I still prefer the press over a hammer for overall control and the ability to stop and reconsider the present approachif the cotter starts to deform.
-Kurt
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The other trick is to use a stout punch with a concave end that holds it centered on the cotter. My punch is actually a cottered BB spindle that has dimples on the ends, that just happen to match the curved ends on cotters (most cotters anyway; maybe not all have curved ends). Whatever metal that spindle is made of, it's about perfect, hard but not brittle. Been using that same one since about '72.
Mark B
Mark B
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Lots of methods work - sometimes well - sometimes not so well. My preferred method is to use measured clamping force with penetrating oil and a light tap now and then.
#33
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Another reason to buy a Bikesmith press is that Mark Stonich who makes them is a great guy, very knowledgeble and helpful on many subjects including internal gear hubs, recumbents and crank shortening in addition to being The Source for all things cotter related.
Mark B
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#34
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I didn't mention eye protection, hopefully goes without saying whenever you hit something with a hammer. But if your spindle or whatever you use as a punch is hard and brittle, then flying shrapnel is a possibility.
Mark B
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They also appreciated being shown that it's far easier to snug up cranks onto square-taper bottom brackets by using a torque wrench on one side and a socket wrench on the other rather than using the torque wrench on each side in succession, although it sometimes took a while for them to understand why that method simultaneously tightened both bolts to exactly the same degree.
#36
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I would say it supports the crank arm, forcing the hammer blow to concentrate energy into shearing the pin relative to the arm and spindle end. It takes the hammer force from the arm directly into the floor and not into the bearing races.
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#39
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Unfortunately the original crank and spindle just aint right. Combination of worn spindle, perhaps slightly bent crank arm, and general low quality cottered crank. So I installed an older 1960's Stronglight crank with a nicely machined spindle that I removed from a Gitane Hosteller years ago.. Used the still nearly perfect original cotters. Oh what a difference it makes. Bearings run smooth. Crank arms are true.
EDit: and now I see I am missing a bolt on the crank spider! What the? I rode a pretty good pace for 15 miles and no issues. Chainrings ran true. No noises from cranks. I'm sure I have a bolt that will work.
EDit: and now I see I am missing a bolt on the crank spider! What the? I rode a pretty good pace for 15 miles and no issues. Chainrings ran true. No noises from cranks. I'm sure I have a bolt that will work.
Last edited by big chainring; 05-08-21 at 07:38 PM.
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I used the pipe and flange method on an old three speed a while back. But I was afraid the hammering would crack my garage floor, so I took it outside, tied the frame up on a chain link fence, sat a cinder block under the frame, put a 1/4" steel plate on the block, and sat the pipe flange on the plate. Also had another plate that I held on top of the cotter, and hammered on the plate. I got the cotters out with 3 or 4 blows each, but I imagine all the different pieces probably diminished the effectiveness of my hammer blows.