Failed frame and the start of a new one!

[Reed McFarland]

Hello Everyone,

My frame failed! I’m not all that upset about it because the odds were not in my favor. The frame has had quite the journey just to get built and so the integrity was questionable.

About 10 years ago, I bought a tube and lug kit from Nova (RIP 😢) and used my Jiggernaut to braze up the main triangle. Unfortunately, the bottom bracket shell came out super crooked and I was pretty discouraged. I hung the front triangle up for about 5 years.

After those 5 years, I was inspired to tackle the frame again. The frame had developed some rust but nothing serious. I unbrazed the whole main triangle as a way to restart. At this point I had a more serious frame jig since I was doing a lot of frame modification and repair. I used this to tack the frame together and got a much straighter frame this time around. I ended up finishing the frame but made a huge rookie mistake.

I wasn’t aware at the time that you could not fillet braze stainless steel. At least not easily. And in my inexperience, I just got the dropouts and chainstays as hot as I could. The bronze managed to stick but after finishing the frame, I was discouraged again. The geometry was more of an experiment as well. I made the top tube/reach a little longer thinking it would handle some single track stuff better but after riding it, I would get migraines. Probably from craning my neck or something, but I only rode the bike like 5 times. It sat, unpainted again, for another roughly 5 years.

Fast forward to this past summer, I found I some inspiration to finally put the bike back together. I put a shorter stem on it and a pair of Surly Sunrise bars and it was much better. I relocated some cable guides and removed some cable stops, so once again the frame had a torch to it. I had the frame powder coated and it came out really nice. I built it up with a belt drive, alfine 8-speed hub, dynamo front hub, and made my own decals for it with my wife’s cricut.

I rode it about 2 weeks ago and noticed some interesting marks around where the seat tube meets the bb shell. The braze had cracked. I also noticed that the dropout essentially let go of the bronze. I put a torch to the bb shell and was able to re-melt the silver and fix the crack, but the dropout was unsalvageable.

I started over with fresh tubes, and this weekend I mitered and brazed a set of non-stainless paragon-style dropouts.

Here’s some pictures of the bike that failed and the start of a new one.

[Skip Montanaro]

Reed,

I'm certainly not qualified to comment on any structural/repair issues, and will leave that to the real framebuilders here. I will comment on this statement, as it was a point Doug Fattic made in the framebuilding class I took.

I wasn’t aware at the time that you could not fillet braze stainless steel. At least not easily. And in my inexperience, I just got the dropouts and chainstays as hot as I could. The bronze managed to stick but after finishing the frame, I was discouraged again.

You can fillet braze stainless steel, but you have to use a suitable silver brazing wire. You can't braze stainless steel with bronze. I used stainless steel dropouts and a few other small bits on my frame (stuff I wanted shiny). For that, we used Fillet Pro from Cycle Design.

Skip, Evanston IL

[Reed McFarland]

In the future I’ll use Fillet Pro. Wish I had bought some of that about 6 years ago. 

Reed McFarland

On Nov 13, 2023, at 4:48 PM, Skip Montanaro <skip.mo...@gmail.com> wrote:



[Hahn Rossman]

Reed-

You can also use nickle silver if you get the right flux. It's harder to file than brass, but also stronger. The seattube failure looks a lot like not getting the shell hot enough to flow through. Take a photo of the inside, or better yet hacksaw it in half to see what kind of penetration you achieved.

Hahn Rossman

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[Eric Keller]

I got some of the nickel silver flux from Cycle Design and it makes
nickel silver a lot easier to use. That being said, I'm not sure I
would recommend nickel silver for a relative beginner. It melts at a
higher temperature than brass. We used it instead of brass when I was
at Trek BITD. For no good reason.
Eric Keller
Boalsburg, Pennsylvania

> To view this discussion on the web visit https://groups.google.com/d/msgid/framebuilders/CALhVnia8-3%3DgvNd2Fq2x1Lv4_ap4riUjhdtCHYcpkcODSb_0Vg%40mail.gmail.com.

[Reed McFarland]

Hello Everyone,

Here’s an update from the first thread I started.

1. I got the main triangle mitered
2. I messed with my jig and reconfigured it to give me better/more accurate BB drop while also giving me reference line for the axle height.
3. Since I will be reusing all of the parts from my failed frame back on this one, I will be running a belt drive system with an internally geared hub. This means that my chainline will be pretty tight to the frame. On the old frame, I attempted to dimple the chainstay and under heavy load, the chainring BARELY scratched the paint. So this time I hand filed a section of the chainstay and brazed in a piece of tubing. To achieve placement, I designed and 3D printed a gauge to shows me where a 46t ring passes the chainstay with spacing for the innermost required clearance measurement.
4. I brazed a port for a dropper post. First I cut a piece of tubing, then drilled a hole in the middle. I silver brazed it to the seat tube, then drilled out the hole to accept the cable guide tubing, then silver brazed that in place. I still have some cleanup to do on it.
5. I’m going to re-miter the bottom of the seat tube. I didn’t like the placement of the dropper post port, so it will be rotated about 60 degrees backwards towards the chainstay. (The last picture will be the final placement. Good thing I left the seat tube too long!)

[Reed McFarland]

Next development. I brazed the bottom bracket shell to the seat tube. Don’t worry, I used a lot more flux before brazing.

I designed and 3D printed the tube blocks to hold the seat tube perpendicular to the bottom bracket shell. They bolt to the piece of extrusion and then I gave a long bolt going through the BB shell.

I silver brazed the joint and got good flow and penetration. The last frame failed here so that’s why I pinned this joint. I’ll be pinning all of the joints to help it stay a little straighter.

The last 4 pictures are after cutting and filing down the pins, then hitting everything with a wire wheel.

[tnort...@gmail.com]

Nice!