Chainstay alignment question

[dbohemian]

I don't see a lot of interest in this method in this thread. This is the best, simplest, and cheapest option. Don't overthink it.

Steve is right on. When the problem is a bit too big break it down into an easier problem. I.e. one chainstay is easier than fixturing both at the same time. There are pictures somewhere here of how Doug Fattic uses a simple tool to hold the chainstays at the right angle from the seat tube (BB drop) I think it is called the Barry alignment tool. Use something like this to set the drive side and then use a dummy axle or build wheel to locate the non-drive side. I liked the picture here where Todd Mosley used his surface and a drawing to locate things. That is my go to method when all else fails. I would rather use a known surface and simple measuring tools than a less than precise home brew frame fixture.

[EricKeller]

thread about the Doug Fattic tool right HERE

[Craig Ryan]

There are a lot of different ways to do the rear end of a frame, and a lot of builders do it very differently. With a limited jig, the challenge is setting that first stay in the correct position. Easy if you have a jig. With no jig at all, I'd use a full size drawing, as flat a surface as you can find, math, and squares. With nothing to brace it while brazing, the stay will likely move around on you laterally. Hard to get around that, but maybe a contraption like the vise and bars will help. I've never really done that since my first couple of frames and can't remember what I did, but the key is to hold the stay in place as it's brazed. Once your first stay is in place, work hard to ensure your drop-out is squared up. You need H tools to do this, so you might as well get them as one of your first tools. If the drop-out isn't square it will pull the wheel as you're trying to set your other stay and screw with your head. I put my frame on my table and measure the H tool against vertical from all directions, but this is dependent on having a table and post. --early on I had a machine shop make me three sizes of little bars the size of candy bars. They allowed me to compensate for different tubing sizes. I used them to space my frame above my table, and it worked pretty well.-- Once you have the first stay set perfect, place the second one using as a guide, your H tools, a wheel, and a straight edge. I work the drop-outs so the wheel stays at rest and happy as you tighten the QR. If the drop-out is off a little, it will pull the wheel one way or the other. Visually inspect the wheel/frame from the rear at a distance and when you think you are close get out your straight edge and check with it. I lay the straight edge along my head tube to my seat tube to the top of my wheel right along the brake track. This needs to be symmetric on both sides of the bike. The straight edge doesn't even need to be straight if you measure exactly the same on both sides. For an OS bike the rig I use means 4.5mm. from the straight edge to the rim at dead center top. Doing this will allow you to get your second chain stay height correct. Sometimes this takes a little work to get right, but it will get your rear wheel in line with your seat tube and head tube. Take the wheel in and out a few times to check and see if all is good. Of course your chain stay length needs to be correct also, so check this behind the bottom bracket by measuring the space between the rim and your chain stays. I also use the wheel checker Jeff at Spudnik makes for this, but nothing replaces a good wheel. When brazing (lugged BB) I pull the stay out (make it long) so the wheel is off by about 1mm. at the rim. I find I get a bit of shortening as I braze. I braze with the wheel in place spinning. Get your heat right, get in and out, and heat the outside of the stay more than you'd think to minimize pull in. All should be really close when it cools and you check it. I know this is long, and maybe hard to understand, but problems like this can't be solved by easy answers. You really have to experience the problem. Working without a jig sucks while you're doing it, but gets you good.
Craig

[Doug Fattic]

Brazing the rear triangle so a wheel exactly centers is one of the most challenges aspects of building a frame. Keep in mind that a mm of different in length is magnified out by the rim. I learned a method while I was apprenticing in England that works well without the need of any serious fixtures (an option what was not available to them). Lets see if I can give the cliff notes version of how to do this. The principle is to braze one side of one joint at a time (for example just the non-drive chain stay into the bottom bracket shell), bend any misplacement after brazing back into alignment, make length adjustments on the other free side to center a wheel, spot and/or pin it in place, recheck with a true wheel and then braze the other side, check alignment again after brazing. Here is a wordier explanation of the procedure I follow:

1. Braze the dropouts to the chain stays using a bb shell and an axle to hold them in place. The angle of the dropout to chain stay can easily be bent correctly after brazing if it isn't right.
2. After the end of the chain stays have been mitered, they are fluxed and inserted into the bb shell. I hold them at the right angle to the seat tube with the Berry T tool mentioned previously. An axle can also hold the right length with twisted wire to the seat binder. I correct the side to side position with a Park Frame Alignment Tool. This tool is placed on the head tube and seat tube and the movable pointer adjusted so it just touches the outside face of the dropout on one side. The tool is placed on the other side of the frame to see if the other dropout is equally spaced. The dropouts are pushed back and forth until they are equidistant. Spot it to help hold its position and recheck alignment.
3. Braze the non-drive side cs to bb in place. Recheck the alignment. Bend the dropouts to be parallel to each other with dropout cups (I use Campy H tools).
4. Move the drive chain stay back and forth in the bb socket until a true wheel centers. I use a long straight edge with an adjustable screw to see that it centers. I use it the same way as the Park tool by placing it on each side of the frame until the adjustable screw touches both sides of the rim by the chain stays. One can measure the amount of space on each side of the true wheel's rim other ways including by sight along the seat tube. I have always hated the string method.
5. Spot and/or pin the drive side chain stay to the bb shell when the wheel is centered. Recheck again with a true wheel to make sure it still centers and adjust if necessary (by breaking the spot). Hold the angle of the chain stay to seat tube again with the T tool or some other method. Braze in place. Recheck with a true wheel again.

The seat stays follow the same principles. Braze the top of the seat stays to the seat lug. Braze only one side of a seat stay to a dropout. Check with a true wheel and make adjustments before brazing the other side. Of course alignment checks on the main and rear triangle between any spotting and brazing insures good results.

Doug Fattic
Niles, Michigan

[steve garro]

I don't see a lot of interest in this method in this thread. This is the best, simplest, and cheapest option. Don't overthink it.

K.I.S.S.
Isn't it "Occam's Razor" that states this?
- Garro.

[JimFrain]

Fully attach one stay/drop out to the BB 1st.
- Garro.

^^^ Def the best so far