Chainstay alignment help
Hello - first time frame builder here, working without a jig trying to make my first bike rideable and safe. The brazing is going well - my problem is in my chainstay alignment. There's a few pics I uploaded to flickr here: http://www.flickr.com/photos/24722787@N00/
So I've gotten the general "eyeball" of the alignment straight (see pic aiming down top tube). I had to do some minor "cold setting" using the Sheldon Brown 2x4 method, but it seems pretty straight to the eye at this point. I've got it to where using the string from dropout, around head tube, to other dropout is within 1mm (see pics, it's actually 1 mm further away on the drive side). Problem is, the wheel is clearly still closer to the drive side (see pics with toothpick with a hash on it to show difference) - which makes even less sense given the "string test" shows that dropout slightly further outward compared to the non-drive side. My dropouts appear flush to the axle (see pics). I haven't brazed in seat stays yet, but when I hold them in place, they're equidistant from the wheel rim. Lastly - when I measure from the tip of the BB lug to the dropout, they appear to also be equidistant, so it doesn't appear that one CS is longer than the other. Also - the wheel is true and dished fine (same issue if I flip the wheel over, and when the wheel spins, the difference doesn't change).
Not sure at this point what could be causing it to be closer on one side than the other, but it's about 5mm closer to the drive side than the non-drive side. I'd like it to be even, but I guess I'm not sure what to do at this point. If this will ride straight, then it's probably not worth breaking the braze and re-brazing one of them, but I'm not sure if this difference will make it ride poorly, or if I'll be alright.
Any idea/suggestions on why it might be closer to one CS, or how this will effect ride quality would be greatly appreciated.
Thanks for listening to my noobie ramblings and for your help.
It's a pretty sure bet that if the dropouts are equidistant from the bike's centerline and the wheel closer to one stay than the other that one of the c-stays is a shade longer than the other. This would be VERY difficult to measure properly and accurately as it takes only a very small difference to make the wheel a good ways off center.
The way to make things are work out well is to slightly file the dropout slot so that the axle can slip just a bit further back on one side and then land in the center of the c-stays. It will take just a few file strokes and the wheel will move over. A little goes a LONG way so go slow.
I would strongly consider adding the s-stays before you do this. Heat will make things move around some and you will likely need to do the same thing (file the slot to get the wheel to center) between the s-stays so if you wait you can do it all at the same time. Less tail chasing this way.
This would make sense - and would also explain why no matter what I tried to do, I couldn't get the wheel to center. I can definitely do the seat stays first, I just wanted to make sure I didn't need to totally remove one of the chain stays before I brazed in the seat stays as that seemed like it would complicate things further.
So just so I'm clear - you're suggesting I take a half round file or something of that nature and on the side that's further away from the wheel right now (non-drive side) make some file strokes on the back end of the dropout one or two at a time and test between each for alignment.
I believe the most difficult part of making a frame is getting the chainstays to be exactly the same length so a wheel precisely centers in the plane of the frame. This is why beginners should use horizontal rather than vertical dropouts that can't be adjusted. I can't tell if you used vertical dropouts in your frame but if you did, you do need to pull one of the chainstays out and do it over again. You can't file vertical dropouts back to increase chain stay length. Sometimes the slot in a vertical dropout angles back instead of straight up. In that case you can file the dropouts as David (one of the builders I'd have make a frame for me if I didn't myself) suggested (the time honored way of equalizing chainstay length with horizontals). However you absolutely must do that before the seat stays are attached since you would also be effecting seat stay length as well if they were already attached. That would result in the wheel not centering by the brake bridge. As a matter of fact I would encourage you to do that before the seat stays are attached anyway in case you can't get it right with filing. it is possible to get chainstay and seatstay lengths exactly right outside of an expensive fixture but it requires doing each joint one at a time and checking in-between with your true wheel. It is actually a fairly long process to explain and the specifics are too much for a single post.
Thanks Doug. I figured that despite my desire to not unbraze the chainstay, it was probably the more proper way of going about this, especially since I just have totally vertical dropouts (not semi-horizontal as you were describing above). So I took out the chainstay that was longer, and re-brazed it with quite decent results. I had to shave some extra off my miter where that chainstay meets the BB, then I re-fluxed, re-brazed, and I'm now quite centered all around. Thanks for the advice. I'll be sure to upload pics when I'm done. Seatstays are next!
My suggestion is that you braze the seat stays to the seat lug first and then after that attach them to the dropouts one at a time. That way you can check to see that your rear wheel centers up by the seat stays before the 2nd stay is brazed in. iIf there is a discrepancy, it is still easy enough with one loose to make a change without having to unbraze anything.
To those who posted above - thanks for your advice. I've totally finished the frame and the build. Did a rattle can job using SprayMax 2K clear coat for now. Only ridden about 30 miles on her so far, but it's my first time riding steel and it's awesome. Took it to a shop for the facing/chasing/reaming and they put it on an alignment tool and I only ended up about 2mm out of alignment without using a jig, so not bad. Can ride it comfortably without hands, so it must be pretty straight! If the brazes all hold through the New England riding season, I'll consider having it professionally painted this winter. Thanks again for all your comments and help!
Grumpy Young Coot
Nice! I hope mine turns out that well!