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!

[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]

"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?

[eschallenberg]

Sounds like a great incremental plan. Thanks.

[David Tollefson]

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

Fe = Iron
Al = Aluminum

[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]

"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?

[GrayJay]

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... =)

THis is pretty much how I did chainstays on a MTB to fatbike re-build. Dummy axel was just a piece of all-thread from hardware store with jam-nuts to set spacing. Once the CS are brazed to the BB, then remove the angle iron + dummy axel, put a wheel in the dropouts and you can sight any small mis-alignment of the verticle plane between the rim and the front triangle, easy to correct with just very minor bending of the CS if needed before attaching the seatstays.

chainstays.jpg

[eschallenberg]

I have some sort of jig ... but not as precise as what you've got.

[eschallenberg]

I haven't used the Park dropout tool, but I've seen photos. Does it bend the dropout only, or the whole CS? I was hoping to bend just the DO.

[suhacycles]

I haven't used the Park dropout tool, but I've seen photos. Does it bend the dropout only, or the whole CS? I was hoping to bend just the DO.

Yeah, you can just tweak the dropout with it. What GrayJay has is kinda similar to what I've done except I use Anvil dummy axles which are machined perfectly and have just enough extra width to compensate for the inevitable contraction that happens after things cool down.

[Todd Mosley]

On my first build I got my chainstays to come out aligned, but I had to stare at it for an hour before the solution came to me, which is pretty simple. I'm using a surplus marble countertop as my flat surface and I'm holding the main triangle with 3 v-blocks on top of (2) 1-2-3 spacers so my left chainstay has enough clearance from the countertop surface.

Stick your dummy axle in the dropouts spaced to correct spacing plus a few mm (132mm for 130mm final spacing), divide the axle width by two (= 66mm). Find the height of your bottom bracket center from the countertop surface ( say ~ 150mm). The inside of your right dropout will need to be 66mm higher than the BB center, so 150mm + 66mm = 216mm. Now, I took the 1-2-3 block and placed it under the left chainstay until my right dropout was at 216mm. I took my 90 degree straight edge and lined up the chainstay until it was straight over the blueprint and my bottom bracket drop was correct. Now, tack your chainstays with silver, then put it in your bike stand and finish it the rest of the way.

Or, you can do it GrayJay's way, which doesn't involve math, which I suck at, but you'll need to come up with a way to set your BB drop. If you can line it up over the blueprint like I did, that should work.

[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.