Refurbishing cranks
 

Hi

We have a mixed set of cranks on the tandem being, three CPi cranks (two for captain and left hand for stoker) and a stronglight triple crank (for the stoker). We are in the process of "rebuilding" the tandem. There were some scuff makes on the Stronglight crank. I sanded the crank with 800/1000 and 1200 grit carborundum paper and polished the aluminium alloy with Brasso. It ended up looking much better than the crank originally was. The CPi cranks looked like it was a brightly polished aluminium alloy. I thought sanding out the scuff marks would be easy. It now seems that the cranks has some coating (chrome??? or anodizing) on it. I seems that I now will have to sand down all three cranks to obtain similarity, a very labourious process. If it has a coating would it be ok to leave it uncoated or would they wear down??? Can I stop where I am now and have all three anodised??? Is there an easier way to get rid of the anodising or chrome???? Help and suggestions would be appreciated.

Big H

Years ago, 14 to be exact, I ran into a similar problem with a set of Dura Ace cranks. The left crank got scuffed up in a wreck; instead of purchasing a new arm, I decided to polish out the abrasions. If that looked too bad, I'd buy a left arm and be no worse for the attempt. As it turns out, the Dura Ace also had some kind of clear-coat...not paint...over the aluminum. We polished right through it and after some effort, the dings in the arm looked pretty good. With the two arms side-by-side, I could see that the polished left arm was slightly more lusterous and "brighter" than the original right arm and spider. However, once mounted on the bike, where you can't see both crank faces at the same time, you never notice. I was worried that the clear protectant missing from the left arm would cause it to tarnish over time.

Years went by and I forgot all about the two dissimilarly finished cranks until I read this thread.

Well, it's been 14 years as I mentioned, and tens of thousands of miles later, and the cranks both look just the same as they did after the touch-up work.

So...I'd say go for it.

However, I live in very dry Utah, USA(merica), not humid USA(frica)...therefore your milage may vary.

Full-strength, heavy-duty oven cleaner will remove the anodized finish. You apply it cold and let it sit until the anodizing turns black, after which it can be wiped off with a wet sponge. You must be careful not to let it sit on any bare aluminum too long as this stuff is caustic enough to cause pitting. I've had the anodizing loosen up in as few as 20 minutes but in other intances have had to let it sit for up to 45 minutes.

If after the initial treament some patches of anodizing remain, recoat and let sit for another 5 or 10 minutes and if necessary use some steel wool to "motivate" the removal process.

Once you've got it all off, hit the parts with a high-speed buffing wheel and polishing compound to brighten them back-up. You can leave them "nekkid" with a coat of polish and wax and then repolish with someting like Semichrome or Mother's when they start to tarnish, or you can have them re-anodized.

Here's a link to a snap-shot of a Stratos FR-4T fork that I expected to to have a nickel silver finish but which arrived with a grey-blue finish. To get that nickel silver finish, I stripped off the anodizing and then polished to compliment the rear swing arm on our 1st Ventana off-road tandem.

http://home.att.net/~mark.livingood/...4_polished.jpg
http://home.att.net/~mark.livingood/...tana/ecdm2.JPG

You can see the grey-blue anodized finish on the ends of this FR4T fork:
http://www.ne.jp/asahi/julesandjames...se/stratos.jpg

It took a few hours, but the results were rather stunning. I've used the same process on a variety of bicycle and motorcycle parts with equally good results. Far easier than trying to buff or sand-off the finish.

Usual disclaimers apply. This is definitely an "at your own peril" type of process that is not necessarily fool proof. Be sure to use rubber gloves, eye protection, lay out newspaper, and work in a well ventilated area, etc....

Thanx for the help. I have just finished sanding and polishing the cranks and they look amazing. With the brightly polished alloy we are now contemplating to have them anodised black. We are redoing the whole tandem and the frame is being painted black with a touch of silver in it with yellow decals. I will post a picture as soon as the tandem is completed.

Keep those wheels spinning

Big H

Howdy from Tucson!
Big H: the black paint job is a great idea. Most of our tandems have been black (with some gold hi-lites). With black paint it is easy to touch up if you chip/scratch the finish. A can of gloss back spray paint and . . . PHFFTT! . . . it is fixed.
Also for the fashion conscious: You can wear any color jersey with black paint job!
Finished the 59 mile Tour of the Tucson Mountains today; about 1000 riders and quite a few tandems. Anything from a '70s Gitane to brand new machines.

Thanx for all the help.

I will be seeing the Surgeon today. I had a ventral hernia repaired on 15 April and that is why I have so much time on hand, the stitches will most likely come out today. Cannot wait to start cycling again.

Zonatandem... congrats on your race!!!!!! It is alway fun.

Keep those wheels spinning!!!!

Big H