We’re all too use to seeing beautiful builds and process pics on Instagram and social media, but let’s have a fun thread where we talk about when things didn’t go right and what we learned. We’re all human after all and mistakes happen. Are you secure enough to post your failures?
Had this experience tonight working on frame #17 - a gravel bike for myself. I had the front triangle mitered and all ready to weld but had about an hour time limit before wife mandated grocery pickup. Against my usual procedures, I quickly placed a small tack at each top side of the DT/TT instead of my4 tacks on each quadrant. Welded the front triangle just fine but when I sat the frame back up in the jig, my headtube was seriously tilted. Like 10 degrees.
Shit. I’ve never tried cold setting a frame due to various reasons but I decided it’s the only thing I can do. I had some 3/4" threaded rod about 3ft and bent it trying to twist the HT back to no avail. Not messing around, I grabbed my 6ft bar of 1" brass and went at it with all I had.
Until the head tube finally yielded…along with the TT and DT.
More photos here in this imgur album.
Well shit. I ended up cutting out the TT and DT, and will try again. This time making sure the tubes are appropriately tacked before going at it. It’s interesting to note that the tubes gave way at the water bottle holes. And I applied enough force to yield the PMW headtube.
So that’s my mess up for today, what’s been yours?
Here’s a thread I can contribute to. Cut a top tube too short, drilled vent holes in a BB with drive side on the left, tacked the wrong seat tube to a cs subassembly, etc.
Most recently discovered a crack in my personal hardtail after 2 seasons of abuse on the non drive side where the seat stays meet the top tube. On this frame the top tube and stays meet the seat tube below the machined collar, a design flaw that I think contributed. Looking back I had burned a small hole in the seatstay and all the added heat filling it in definitely didn’t help. May rethink hanging bikes front tire up on the ceiling to avoid moisture pooling in that area as well.
When cold setting goes wrong…
These were also the first joints I tried with just gas flux and no paste. Not satisfied with the penetration, so I still use paste(just less) along with gas flux.
Yes, seatstays attached to unsupported/thinner areas of the seat tube is generally a recipe for disaster. It can take a few years, though, so I still see people do it a lot.
I’ve seen an awful lot of frame failures caused by attaching stuff to/drilling excessive holes in downtubes. A few of my own bikes before I started saying no to internal routing and such.
If you do decide to do any of that sort of thing (or attach any sorts of major stress risers/stuff to the downtube) I’d go way, way beefy on it.
For some reason I can’t find any pictures of the frame now, I think there is a real old picture of it in the frame jig in my build thread. I welded up a twin top tube hard tail in the terrible frame jig that I had made back in 2013 or 2014. It was brought to my attention that I really overheated the head tube and downtube joint when welding. I got the brilliant idea to put the whole frame in the heat treat oven at the manufacturer that I worked at, the heat treat guys were happy to run a normalizing (? I forget now) cycle on a Saturday morning. It ended up making the front triangle so droopy, and the ht/bb so out of round that it was ruined, it was a great learning experience. After recently making a frame again and fixing the jig, I think the alignment would have been pretty messed up anyway.
Glad I’m not the only one twisting tubes! Makes me think that cold setting the head tube is a farce.
Got another fail for you guys. Same build. I use my cnc mill to miter. Literally on the last miter of the night, I didn’t reset the Z height when I got everything lined up. When I hit the green button, my mill immediately drove the hole saw into the table making the first table scar on my machine. Shout out to the rock hard blue hole saws. Didn’t damage it at all.
@StratoCycles Argh! Taking me back to the machine shop days! Thanks for making thread, I was thinking we needed a carnage thread in here. This is awesome so far🤘
I make stupid mistakes all the time. I’ve finally made a process document to try and avoid making them twice. Today I got to add: Confirm Headtube Length when I brazed a 190 headtube to a downtube when I intended to do a 170!
Sometimes I like to make the same mistake twice just to be sure I really had it wrong. Note to self: When PMW marks one side of their bottom brackets with a radial groove on the shell face, that means that side is left hand threaded, not that it goes on the left side.
I’m hoping to do internal routing on a full sus I’m working on. I’m planning on using brazed-in brass tubes as guides. Probably 2-3 tubes running down the downtube. It’s butted 1.1/.8/1. Do you think this will cause problems?
I have no idea. All I know is that internal looks cool on instagram, and that I’ve seen an awful lot of broken stuff caused by trying to look cool on instagram.
I just stopped doing internal stuff at all. It’s not worth the stress and I got done trying to be cool a while ago.
That said, tons of people do it, and you’re probably fine. Make sure the guide tubes can’t touch each other and make weird noises while you’re riding.
Thanks Walt, I really appreciate the advice. I might just go for it, as it’s a personal use prototype bike.
I haven’t written any frames off yet, but I’m sure it won’t be long hahaha.
I did weld this brake tab on offset 2.5mm because my IS jig thing is designed for thru axle but with 135 qr the face should be in line with the face of the dropout
Cut off and welded back on with caliper installed to make sure I didn’t cock it up twice hahaha.
This is also the first frame I have made that the bb threads actually needed chasing, I built it just before I read the thread that tells you not to make your vent holes too big, I think the bb shell got a bit distorted.
Too much of everything. Decided to take some brazing lessons after this.
For me, the dumbest was reversing the BB shell. It was for my son so I just installed the BB from the left and he rode it for a year or so and then I cut it up.
The worst was an adjustable reamer that destroyed the seattube. I got frustrated, put it in the rafters for a year. Then I decided to fix it. The ruined ST was oversized so I cut the tube out, added spacers to a smaller standard sized (28.6mm) seattube and then brazed it in. You can see the multiple layers at the BB and ST/TT junctions.
That’s a lot of extra heat and stress risers in the thin part of the tube.
Hahaha I share your pain with the reamer. I had finished my first frame, and my mentor/coworker gave me the reamer, told me to ream the seat tube and left. I didn’t know how to work it and thinned the top of the ST out so much that the braze on saddle bolt snapped off. Luckily I was able to still run a qr seat clamp
Not sure if this will help anyone, I’ve had some success with a piece of round bar with 1.5" long saw cut in one end to hold a strip of emory and winding on the emory. Stick the round bar in the drill and sand the inside of the seat tube. No experience with a brazed frame, but it worked great the frame I just welded. It may be a little less aggressive than a reamer.