I’d be worried about the rotor warping under heat and hitting the frame. But it does then become a self-solving problem 
So others don’t make the same mistake as me, the inside face of the disc rotor (facing toward the center of the wheel) is 18.75mm from the dropout face or 52.25mm from the centerline of the bike on 12x142mm OLD.
*Edit: Turns out the dura ace caliper from grabcad is wrong by a counmtry mile! Measured my GRX with a vernier and it’s fine…
Not my fail, but a fail that I’ve repaired. Very old, low quality lugged frame. I’d say 40 years old at least, made in a factory during communist times, my guess it was made on friday afternoon shift (or saturday early morning). Frame had a lot of flaws, but someone has decided it needed a rear suspension. It rode like this for all these years, an nobody got hurt. It held on like 5mm dia bronze spot. No penetration at all.
“Suspension”: https://youtube.com/shorts/a9C8fiR6GE0?feature=share
Video with chainstay removal https://youtube.com/shorts/luaPQSMwJdo?feature=share
I’m working on my first frame and got it tacked today, but I burned a small hole in the bottom of my head tube, is this fixable? I have tacks at 12 and 6 o’clock, I burned through the 6 o’clock one. My idea is to add two more tacks, one at 5 and one at 7, then braze the joint and throw bronze at the problem until it goes away, but I’d love to hear y’all’s opinion on what to do.
Probably best to cut the tacks and use a new head tube if you can get one, shouldn’t be too bad if it’s only tacked. Could even trim the end off that’s burned through if you’re able to live with a shorter stack height
Doesn’t look too bad, think I’d support the inside with some alu or copper to dissipate the heat and fill it. It’s gonna get reamed and faced anyway, so shouldn’t be too big of a problem in my opinion
Edit, also agree with @RxDesigns, easy to change it out now too if it saves some hassle, could always try to fix and if you’re not happy with it cut the tacks and do a new one
I second the previous opinions… Probably not the best place for a botch. Easy to put a new headtube in. Maybe shift it a bit lower (increase stack) so it’s easier to weld
Definitely put a new tube on (save that one for a smaller frame!). That spot is possibly the highest point-load on the entire frame, and the hoop stress from having the cup pushed in will absolutely smash it. Best case scenario, it works for a while then you get an nice oval head tube, but it may well crack the joint and cause a crash. It’s also a good idea (though not always practical) to leave HTs long and trim them after welding.
Learn from your mistakes, but learn from other people’s first!
I agreed with everyone’s advice: I would just replace the headtube
A really good surgeon (and now framebuilder) told me something to the effect of “Experience comes from making mistakes”
Making mistakes is part of the process! When I build a new design, I always order spares, anticipating I will screw up something… It hurts more with titanium 
Did you clean those tubes? they should be sanded to bright metal then wiped clean prior to welding.
Thank y’all so much for the advice! I’m gonna order a new headtube and start over, i’d much rather buy a new tube than new teeth when this one inevitably fails catastrophically.
@Neuhaus_Metalworks I hit the ends of the tubes with a wire wheel and cleaned with acetone, but I only took ~1/2" of them to shiny metal, would you suggest cleaning more?
You don’t need to clean more than an inch from where you weld but that area should be very clean. I would get some emery cloth or sand paper in the 220 range to sand the outside and inside of the welded area. Wipe with IPA before you sand so you don’t just push oil and grit into the tube, sand, then wipe again.
Bah, I should’ve taken a picture of this. But at least I have a story.
Last weekend I was welding up a personal bike. As I always do, I threaded a BB into the shell as my first step to confirm that it’s oriented correctly (direct result of another early frame building fail). I made a mental note to deep clean the BB but neglected to leave a note to myself.
Can you all see where this is going?
I have blown holes through lots of tubes but never through the middle of a thick piece of tubing. Now I have. A quick examination showed a nice greasy/oily sheen on the threads of the BB. My guess is that I was running a bit hot, hit the grease and shit went sideways. Tube was unharmed (NDS CS) so I cut the tacks, cleaned, filed, cleaned, filled, filed, cleaned, cleaned, cleaned, cleaned again.
Chasing the BB threads was a bit scary but patience and copious amounts of cutting fluid helped. BB goes in, not as smooth as I’d like but this is a personal bike. . . and one more of those mistakes I’ll never make again.
#3 suffered from a reversed BB shell - it was for my 9yo son at the time so no harm really other than a good learning moment.
My first step is putting holes in the bottom for venting and hole in top for ST vent. I do this as soon as I start assembling and measuring tubes.
When you think you’ve seen it all…introducing the buckled headtube!
Pictures don’t do much justice on how badly that thing stretched…it probably went from a 75* ha to 78.
Bearing race went all potatoes…
Frame was about 1 month old and being ridden by someone who makes a living of riding bmx, or dare I say a “pro”.I already put him on a replacement.
There is a lot to process, 1.5mm wall thickness headtube shouldn’t fail like that, I’ve done many frames with the same headtube, some of them took some nasty crashes, some of them were thrown away mid jump, but never anything like that happened.
I consider the tubes fit and weld was as my average, could be improve but neither of them failed.
Also to keep thing blurry, this bike was lost by an airline on this dude last travel and the rear end got mashed in the process …could be something to consider.
Anyway live and learn, I’m already planning to machined some thicker wall headtube for people that goes really hard.
The weak point is going to fail. The TT and DT both with gussets looks very stout. Based on the failure mode, they seem overbuilt. Nothing wrong with that. As a repair, replacing that headtube would be easier than replacing top/downtubes so, I’d count this as a win if you want to repair it.
I’d say the guy stuffed the front end into something pretty hard.
Totally agree , the weakest point failed. Top and downtubes are pretty common for bmx, 1mm wall straight gauge.Gussets are bit long and overkill, but bmx riders are hard believer in gussets
I’m all up for repair on any bikes but BMX, they have such a short lifespan it’s not even worth the money I would charge ( if I had to charge), and it’s usually easier for me to make a new frame ( this one in a rush I have to admit )
Yes if he rode into a wall I would have believe it but from what he said it was from doing a big " frontflip" over a box jump
I’m making a couple spare 2mm wall headtubes as soon as I get a minute
That’s not a fail, that’s a win. How many youtube vids have we all seen where the HT gets ripped off because the DT and TT joints cracked? I’d much rather have this happen than lose my whole front end - and my teeth.
Yeah, classic fail, happened to me multiple times, especially with metal rulers when you have same size 10 segments numbers as 1 segment (in or cm). Also built too short rear end, had to cut the whole part off and build a new one CS and SS
