Use of Cupper Tapes in BB/LooseCrank Problem
I know Square Loose Crank is discussed very often here. I have searched and read some of the posts. (And they are helpful might I add?) I understand now the left crank tend to get loose often. I regret I didn't check the crank bolts more often. For that matter, it was stupid of me to not own a crank wrench till ... yesterday. Amazing I didn't have this problem for 20 some years of biking life.
Anyways, right now I am having problem finding dealers who will sell me only left side crank. I can get one used, but it defeats the purpose right? Used Square Cranks is likely to be misshaped right?
I was thinking about replacing the entire system with hallow axial system, but it will set me back 25,000Yen (or approx. 250 USD). So I thought if I were able to fill in the deformation or irregular cavities, cranks won't get loose as easily.
I used to be an electrial engineer and I have seen cupper tapes which can be used for repairing circuit boards or build one. These cupper tapes are real cupper sheet with serious adhesives. I am thinking about taping these tightly to the BB axle and smush it in. (after cleaning of course) Being pretty pure cupper and soft, the cupper tape will deform and fit into the cavities. This came from seeing cupper bushing.
Do you think this is a proper temporary solution (~6 months with periodic monitoring)?
P.S. Is ISIS or Octalink better?
I've never tried anything like what you are suggesting, but if the crank arm is ruined, I don't see that you have anything to lose. You aren't likely to ruin the spindle, as it's steel. Just check the crank arm VERY carefully to make sure it's not cracking, and if it is, don't use it. You definitely don't want to be standing on it near traffic and have it catastrophically fail.
I've heard people say a beer can shim will sometimes work quite well.
That makes a lot to sense. Aluminum against Aluminum may be better than Aluminum against Cupper. I will need a good mechansm to fix against the shaft while the bolting process. This was a part of reason why I originally thought of Cu tapes. Their adhesives are pretty strong.
I need to get the tapes, but I will go take it apart today. If it ain't work, I could at least clean the MOFO.
Thanks for telling me about these things. I am pretty new to bike fixing although I am pretty good with tools. (Thank you, grand-pa Tony.)
I would wonder if the adhesive might "migrate" with use, allowing the arm to loosen again?
I don't know how available "shim stock" is, in your location, but it is readily available at "real" auto parts stores in the US. Maybe that would work?
At this point, I don't think I would be too concerned with dissimilar metals corroding etc. (That MIGHT actually be an advantage, if it "locks" the parts together)
This link is to show some of the thicknesses it comes in-
You should get a used LH crank. It will probably not have a distorted sq taper - it is probably available because the RH one broke or had its threads stripped. I bought a used one once without any problem. Just make sure it is the same length as the RH crank. It will have the length marked on the inside face of the arm - something like 170
I've repaired cranks that way using soda can shims and they worked great. It's worth a try, at least.
No, has to be a beer can, preferrably a German pilsner. And only one shim per can. With luck the shim will require nightly replacement.
Originally Posted by neilG
I took off the cranks today. What I saw was scary. It ain't distorted. There was huge square shaped scar.
First I tried the usual grease the shaft technique. The way the crank went it made me feel pretty good. But when I got on ... Wham! It's loose. I decided against the cupper tape thing, because the problem was HUGE; not a minor fix.
On top of the nastiness, I got something even more. BB was busted. Apparently the bearing fixture broke off and was dancing inside BB casing. This ticked me off. I just lost my head. This means I have to buy the entire drive train. So today afterward, I ran around and install a new hollow-axial cranks / BB.
Sorry, I couldn't come up with positive results. But hey I can ride now.