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Is this crank toast?

Old 02-21-21, 06:10 AM
  #1  
kross57
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Is this crank toast?

I am working on a mid-80s Peugeot. There is play in the crank where shown by the arrows. Is there any way to fix this, or is the crank arm shot?

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Old 02-21-21, 06:18 AM
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Originally Posted by kross57 View Post
I am working on a mid-80s Peugeot. There is play in the crank where shown by the arrows. Is there any way to fix this, or is the crank arm shot?
If the swage between the arm and the spider has become loose it's effectively toast; with the same tooling and press as used to make it it might be fixable, but who has that.
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Old 02-21-21, 06:45 AM
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Originally Posted by oneclick View Post
If the swage between the arm and the spider has become loose it's effectively toast; with the same tooling and press as used to make it it might be fixable, but who has that.
Thanks! That's what I figured, but I wanted to be sure.
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Old 02-21-21, 07:31 AM
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How much play is there? You could try peening the swage to tighten it up; however it's probably a better idea to scrap it. Sooner or later, you'll find yourself trying to get though an intersection with both crank arms in the 6 o'clock position. Better vintage cranks are not that expensive. French ones are a bit harder to find, though.
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Old 02-21-21, 08:41 AM
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Originally Posted by Moe Zhoost View Post
How much play is there? You could try peening the swage to tighten it up; however it's probably a better idea to scrap it. Sooner or later, you'll find yourself trying to get though an intersection with both crank arms in the 6 o'clock position. Better vintage cranks are not that expensive. French ones are a bit harder to find, though.
They would stay at 180, they're fixed to the crank.

If it slips what happens is pedal, no go.
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Old 02-21-21, 09:01 AM
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Stick a fork in ‘em to check but I think those cranks are done.
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Old 02-21-21, 09:17 AM
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Originally Posted by oneclick View Post
They would stay at 180, they're fixed to the crank.
Perhaps not. See: Swaged Cranks

Originally Posted by DiabloScott View Post
I remember it well - I was first in line at a left turn lane. When I got the green arrow I attempted my usual explosive acceleration so I could get through the intersection and into the bike lane without holding up the cars behind me. Instead, I got half a revolution of the crank and then suddenly both legs were at 6 o'clock and I had no propulsion. I had to dismount and walk through the intersection while the cars behind me laughed and sneered.
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Old 02-21-21, 09:36 AM
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Originally Posted by Moe Zhoost View Post
Perhaps not. See: Swaged Cranks
I had a look at that. There is no physical way the two crank arms can fail to be aligned at 180 degrees if they each remain attached to their and of the axle - assuming that axle remains intact. The ring - and its swage - are outboard of the crank/axle interface.

And as axles can and do break, I suspect that this is what happened; that the crank was swaged may only be relevant to the point that such cranks are usually built to a lower price-point and their axles may thus be more prone to failure - which may have been the OP's (indirect) point.
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Old 02-21-21, 11:34 AM
  #9  
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Cheap bb spindles can and do fail on occasion. This one let go just as I accelerated onto the main road after ascending from the American River Canyon.
Thankfully not a complete break, and I was able to soft-pedal the two miles to the ride's start/finish!
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Old 02-21-21, 11:36 AM
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There is a peugeot branded stronglight crank for sale in the C&V for sale forum.
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Old 02-21-21, 11:49 AM
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Looks nothing like toast. But since going low carb, I haven’t seen a slice in months —-

​​​​​​—— but even if I drizzled melted Kerrygold Irish butter all over it, - that still looks like a damaged crank arm not worth salvaging- whether for a bike or for breakfast
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Old 02-21-21, 11:49 AM
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French toast.
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Old 02-21-21, 12:54 PM
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Anyone ever try to have one Tigged?
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Old 02-21-21, 12:59 PM
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This is toast those are cranks. Those cranks are probably not one I would want to ride on but not toast, do not eat.
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Old 02-21-21, 01:51 PM
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That's a Stronglight 5470 crankset that's a look-alike for the Stronglight 104. The 104 was a solid spider, not swaged and the chainrings are fully interchangeable.
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Old 02-21-21, 03:45 PM
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Originally Posted by oneclick View Post
I had a look at that. There is no physical way the two crank arms can fail to be aligned at 180 degrees if they each remain attached to their and of the axle - assuming that axle remains intact. The ring - and its swage - are outboard of the crank/axle interface.
You are absolutely correct. The thread I referenced sent my head on a detour. A failure of the swage would at worst result in the crank arm spinning on the motionless chainring.

Cheers, mate.
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Old 02-21-21, 04:25 PM
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I had that same crank on a late 80s UO10 and it started to loosen up then the drive side crank arm broke right in half.Never saw that before.Very low miles
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Old 02-21-21, 04:30 PM
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Post a pic of the other side. Strong possible I may have a replacement I can send over. Can't tell if it's one of the Nervar arms or if it's one of the Peugeot-branded Stronglight cranks, although I don't think the latter came in swaged format. I can't recall which ones were swaged otoh.
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Old 02-21-21, 04:44 PM
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I am not one to give up on bike parts without trying to fix them. If it was me that had this issue I would put the arm on a solid surface and find a socket or pipe that is just a little smaller than the crank arm flange on the back of the arm and give it a good whack with a sledge hammer to see if it would tighten up. Once I tried that and found out that it didn't work (most likely result) I would toss it.
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Old 02-21-21, 04:56 PM
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FWIW, @marius.suiram has a Peugeot-branded Stronglight 104 crank in the "For Sale": forum:

Stronglight model 104 crank set, marked Peugeot , 170 mm, 52/40

This is a one-piece (not swaged) crank; not sure if it is forged or cast, but either way a step up from the failed swaged crank.
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Old 02-21-21, 08:53 PM
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Originally Posted by rjhammett View Post
I am not one to give up on bike parts without trying to fix them. If it was me that had this issue I would put the arm on a solid surface and find a socket or pipe that is just a little smaller than the crank arm flange on the back of the arm and give it a good whack with a sledge hammer to see if it would tighten up. Once I tried that and found out that it didn't work (most likely result) I would toss it.
Maybe it will be better to use a nice big brnch vise (with a cheater pipe to increase amount of pressure) to press the socket against the flange, instead. A vise will provide a similar even pressure that the press in that factory did on the flange that hitting it with a hammer won't likely do.
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Old 02-21-21, 09:22 PM
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It's done. That's it. That's all. Done deal. Be good. Have fun.
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Old 02-21-21, 10:48 PM
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Originally Posted by merziac View Post
Anyone ever try to have one Tigged?
I think it's not wise, but unlike many welders, I will tell you why. The alloys may be different between the crank arm and the spider, and either or both might be "not weldable" alloys. You _could_ weld them, but they wouldn't have much strength due to the way the metal grain precipitates after welding. I'm guessing a crack would start somewhere.

If I ever have access to tig equipment again, I'm happy to try!!
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Old 02-21-21, 11:32 PM
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Old 02-22-21, 12:43 AM
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Originally Posted by scarlson View Post
I think it's not wise, but unlike many welders, I will tell you why. The alloys may be different between the crank arm and the spider, and either or both might be "not weldable" alloys. You _could_ weld them, but they wouldn't have much strength due to the way the metal grain precipitates after welding. I'm guessing a crack would start somewhere.

If I ever have access to tig equipment again, I'm happy to try!!
Atta boy!
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