Are my 3 speed cottered cranks bent?
09-04-21, 04:07 PM
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Are my 3 speed cottered cranks bent?
I've noticed an odd lopsided feeling when I pedal my Armstrong 3 speed. It feels almost as if the cranks are bent or the pedals are bent. Or perhaps it's something inside the bottom bracket? I'd be grateful for any thoughts or opinions. Thank you!
09-04-21, 04:25 PM
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It LOOKS like the left crank is bent inwards from the angle of the pedal but always hard to tell if there is any optical distortion from photos. If so an old steel crank like that can be bent back. A good sturdy vice and a cheater bar with the crank/pedal removed will make it much easier.
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09-04-21, 04:30 PM
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Try "new" pedals first. You'll probably need 1/2" spindles.
A pedal spindle will bend well before those steel cranks will, and will give the wobbly sensation in the feet.
A pedal spindle will bend well before those steel cranks will, and will give the wobbly sensation in the feet.
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09-04-21, 06:14 PM
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Generally 1/2" pedal threads are for 1 piece cranks. These 3 piece cranks will most likely have a 9/16" pedal thread. I do agree that either the LH arm is bent, the LH pedal axle is bent or the camera lens is distorting things. Nice bike BTW. Andy
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09-04-21, 08:33 PM
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I have seen a few cottered cranks that were off a little bit in thier alignment. It was not much, no more than 2°. I was converting them over to a square tapper spindle and on close inspection of the old spindles I noted that the face of the spindle where it engages the pin was well worn. I think that the cotter had become loose and worn out the face. Then when repairing with a new pin the crank arm was off a little in the direction of the wear.
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09-04-21, 08:42 PM
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I have nothing constructive to offer but I love the patina in this photo. Please don't ever try to clean this up.
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09-05-21, 03:06 AM
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The only thing i see is that the cotters are „reversed“. I don‘t think that‘s a big deal generally and also shouldn‘t cause the feeling you describe. I have this feeling sometimes when i start riding a different bike than the day before. It usually goes away after a few km. So i guess in my case it‘s a perception thing rather then a mechanical problem.
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09-05-21, 05:32 AM
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See Dave Moulton's page on cotter pin cranks for details on cotter pin maintenance.
Last edited by Trakhak; 09-05-21 at 05:36 AM.
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09-05-21, 05:32 PM
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The pins have an angled contact face. This angle is not a "standard" amount and as it's this face that gets filed as needed to best fit the pin (depth wise) these angles can drift WRT to each other.
I've heard both pin directions as being the "correct one" over the years. These pins reversed from what I do but having inserted pins in both directions many times I find that as long as they are well installed it really won't matter. Andy
I've heard both pin directions as being the "correct one" over the years. These pins reversed from what I do but having inserted pins in both directions many times I find that as long as they are well installed it really won't matter. Andy
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09-06-21, 09:52 AM
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Thanks for all the thoughtful replies! I tried swapping out a different set of pedals from another 3 speed of that era and the wobbly-ness was great improved. Now I'm on the hunt around for another pair of pedals. Thanks!
