Correct brazing sequence for flat mount caliper mounts on chain stay

[BigPoser]

Looking for a little guidance here. I'm trying to figure out the best way to braze the NDS CS so that I can minimize movement in the stay itself as well as shortening. I'm using these mounts BK13 - stainless Steel Flat Caliper Mount, have internal hose routing, and am using Syntace dropouts. My first sequence went like this: braze stay to dropout (so I can mount to CS fixture), cut hose routing and braze in tube. Miter BB. Everything is tight. Then cut and braze in caliper mounts. When I put the stays back in the frame fixture notice the gap as well as the stay pulled to the center of the BB. Here is the pic:

Stay Gap.JPG

I was very curious about this and wanted to try to different sequence to see if I'll get a different result. So I made a second set and performed my sequence like this: braze stay to dropouts, cut hole for internal routing and caliper mounts, braze in caliper mounts and brake hose tubing, then cut miter at BB. The exact same thing happened.

What is the best way to braze everything up to minimize the shortening and pull to the BB center?

I liked the second set I built better than the first and actually tried to bend the first set back to it's desired position at the BB and it broke the joint at one of the caliper mounts. So either I put too much English on it, or I did do a very job on the joint in the first place. I'm really scared to try to cold set the second set now, but am also afraid that if I braze the stay to the BB in the proper place then the dropout will move inward in the process.

I've been told there are caliper mounts out there that you braze around the entire stay so they won't pull inward, but I've not seen anything like.

Sorry for the long post. I'm just looking for some guidance on this.

Thanks in advance. And not sure why the picture is turned 90 degrees either.

Brandon

[niknak]

I've only used the prefabbed flat mount dropouts, so I'm also curious what others do when they cut the stays and braze in the mounts. I do have a couple of thoughts based on your experiences so far:

- Try accounting for the change to alignment of the CS by making it meet the BB further outboard by the amount you've seen the CS get sucked toward the center. That way there's no stress in the system and CS moves to your mark post braze.

- The other thing to think about is floating your flame on the outside of the CS next to the brake mounts to make sure that whole area gets the same temp applied. This works wonders for preventing the rear triangle from sucking in when brazing in bridges.

Also, it appears we have the same frame jig. The 1/2" screw on my jig isn't straight, tested on my surface plate, so the BB doesn't sit perfectly parallel with the dropouts. I'm planning to move to a sub-assembly for the BB/CS brazing a la Kris Henry to increase rigidity and accuracy when working with this crucial part of construction.

Good luck and please let us know if you find a solution.

[BigPoser]

Thanks for the reply Nick. Yeah so I do heat up the whole area on the the CS to try to keep even heat all over. The CS moved inward 3.5mm so not a ton, but still something that I had to deal with. I had thought that maybe I could just tack up the CS to the DO, braze in the caliper mounts, finish the DO braze and then miter the BB.

[steve garro]

The CS moved inward 3.5mm so .

Bend the sucka back !!!!

- Garro.

[BigPoser]

Bend the sucka back !!!!

- Garro.

I did. Got it back to where it needed to be, but a bit scary.

[steve garro]

I did. Got it back to where it needed to be, but a bit scary.

That's how it's done - carefulllllllly

- Garro.