Chainstay alignment question

[eschallenberg]

Newbie, here ... building first frame with minimal jigging and wondering about best ways to ensure properly aligned rear triangle.

Was thinking of this:

Before coping chain stays, inserting them into the BB and putting in a wheel with a larger tire, 35mm instead of 23. Pushing the wheel in so that the tire makes contact with the DT and making sure it is in the same vertical plane as the DT.

Is this stupid?

[JimFrain]

make a plywood jig with an old steel axle. tack it, then pull it out of the jig. finish your brazing with the axle still bolted on.
Good Luck!

[ToddFarr]

I used the string method and a dummy axle on my first frame. Tacked it check it with a wheel and brazed on. I did use horizontal dropouts though, which are more forgiving.

[eschallenberg]

I'm planning on track drops. Had read that they were trickier, but couldn't figure out why.

[suhacycles]

You mean the seat tube, not down tube right?

Do you have a dummy axle? One way would be to get some angle iron/aluminum and hold it against the TT-ST plane and try to align the dropouts relative to the angle Fe/Al and try to get the spacing even. Of course, even if you mess up a good whack and/or some leverage can get the chainstays back in alignment if you don't mind doing that... =)

[steve garro]

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

[eschallenberg]

Sounds like a great incremental plan. Thanks.

[Dallas Tex]

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

[Mike Wanner]

Hmmmm, every time I visit this forum I learn something new. This is great stuff.

[veryredbike]

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.

Worked for me twice so far. Get one just the length you want it and mitered, braze it in. Do a slightly long miter on the other and insert it. Put in a perfectly trued and dished wheel and tug it back and forth until it's centered between the CS at the BB. angle as necessary to get the wheel parallel to the seat tube. Pin in place (if you're doing that), braze. If the wheel tilts a little to one side or another once the seat stays are in place., a tiny bit of filing will fix that. Not ideal, but if that's the worst thing that happens on your first bike...

[Andrew R Stewart]

IMG_1065.jpgThis is how i built a number of bikes. Wheel clamped to bench top. Frame in vice so that the chain stays and seat stays are of correct lengths. Move the frame around until it is in line with the wheel, eyeball or string to get drop out centering, eyeball or straight edges for wheel to be in plane with the seat tube. Lot's of playing around until all lines up and measures out. Then tack and recheck, tack again and recheck.

This is about simple as it gets. Andy.

[Jonathan]

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.

Me three. When I had a bringheli fixture I did it this way to make up for any limitations in fixtures accuracy.

[JimFrain]

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

^^^ Def the best so far

[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

[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.

[eschallenberg]

"Fe/Al"? Unfamiliar with the acronym ...

And concerning the good whack technique, is that really a viable method? Is brute force a good way to fix misalignments?

I'm also concerned about how to bend the dropouts back into plane with the hub ... I've seen folks just clamp them in a vise and bend. Is that really how it's done?

[David Tollefson]

"Fe/Al"? Unfamiliar with the acronym ...

Fe = Iron
Al = Aluminum

[suhacycles]

"Fe/Al"? Unfamiliar with the acronym ...

And concerning the good whack technique, is that really a viable method? Is brute force a good way to fix misalignments?

I'm also concerned about how to bend the dropouts back into plane with the hub ... I've seen folks just clamp them in a vise and bend. Is that really how it's done?

Well, if the alignment is pretty good to start with then after the thing cools down I doubt the force would have to be very 'brute' anyway, especially with an oval chainstay. They bend quite easily. Bending dropouts shouldn't be a problem either if it's not extreme. Ever use a Park dropout alignment tool?