Chain slack idler

[spyfoxy]

As per the plans, I used an old derailleur to pick up the slack in the return chain. It seems to make an awful lot of noise though, and it bent twice. After the first time I rewelded it very securely. Both times it was welded parallel to the main boom. I'm thinking of just changing it out for another v-belt pulley, but before I do, does anybody see anything wrong with it? Keep in mind the photo is AFTER it bent slightly the second time.

On a related note, we already know it's okay to replace the derailleur with another pulley, is it okay to replace the front pulley with a derailleur?

[TheKid]

Those little plastic sprockets on a derailer would never hold up. Stick with the pulley on the drive side of the chain. Your chain may be a little short, which puts too much pressure on the return side idler, as well as the rear derailler. Here's a link to Sheldon Brown's derailler adjustment. It includes the proper way of determining the chain length. First, the chain length part, then the link to the article

Chain Length

If you replace your chain or sprockets, you should check your chain length. New chains come longer than they need to be for the vast majority of bicycles. You will almost certainly need to shorten a new chain before installing it on your bicycle. If your large sprocket sizes are anywhere near the maximum your rear derailer can handle, the chain length can be quite critical.
The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that they could be connected (outer link meets inner link), then make the chain one complete link (one inch) longer than that. In almost all cases, this will give the optimum length.

http://www.sheldonbrown.com/derailer-adjustment.html

[SirJoey]

Hi Spy,

Also, your chain is routed through the idler wrong. Prolly the reason for the noise.

Try it like this: http://joeywallace.spaces.live.com/photos/cns!9D0D4DF6F50AAFC2!1326/?&_c02_owner=1&_c02_vws=1

[TheKid]

It's the same routing Brad used on the Streetfox

http://www.atomiczombie.com/product/streetfox/streetfox-lg.jpg

I ran into the same problem on the meridian, and bent both the idler and the rear derailler. My chain was about 3 links too short. After lengthening the chain, I had no problems.

[SirJoey]

Well, wrong compared to the way it was originally supposed to run through that thing, anyway....

[spyfoxy]

I see. Well I must have missed the chain routing, I'll definitely try fixing that. If it still gives me trouble I'll just go for a pulley because it's easier. :) Thanks!

[spyfoxy]

Thanks for the advice all. I didn't change the routing, but I did correct the chain length (it was WAY too long) following the instructions on Sheldon Brown's web page. It seems to have corrected the problem. I still have an ongoing chain problem of a different variety, with the front pulley. When going through a hard turn, the chain likes to slip out of the pulley. I think it only happens when coasting, but I'm not sure. Anyone else have this problem? Think I just need to re-check the chain length? We've tried adjusting how far from the main boom the pulley sits using spacer nuts to no avail.

[TheKid]

You could bend a piece of 3/4" - 1" wide x 1/8" thick aluminum (or 1/16" thick steel)into a U shape, wide enough to span the pulley bearings on top, wide enough to just clear the width of the pulley on the bottom, and long enough to just clear the chain on the pulley. It will stop the chain from coming off the pulley

[spyfoxy]

You could bend a piece of 3/4" - 1" wide x 1/8" thick aluminum (or 1/16" thick steel)into a U shape, wide enough to span the pulley bearings on top, wide enough to just clear the width of the pulley on the bottom, and long enough to just clear the chain on the pulley. It will stop the chain from coming off the pulley

Yup, that totally did the trick. Check out the photo of the finished pulley. We even put a spring between the metal guide and the pulley, so the pulley can slide back and forth on the bolt like a derailleur. It's nice because as the front sprockets change, the pulley stays in line with it. :)