TiHabanero

Frame needs the top tube brazed in at this point, however the head tube is twisted. Need to move it 1mm and am finding that it won't budge. Have a solid steel bar inserted in the head tube with about 12 inches sticking out one end. pushing on it fairly hard, and am afraid of damaging the down tube with too much force. Any advice?

Doug Fattic 

Are your tubes thin heat treated or normal 9/6/9?

8aaron8

Doug's question is very important regarding the force. Another tactic that can help with alleviating the twist is how you braze the top tube, specifically the tt/ht joint. Depending on which way the head tube needs to twist back focus on brazing that side of the lug first then finish the other side and finally bring the heat back to the first side just for 10-15 sec, don't remelt the filler material. For example if the headtube is twisted to the left wrt the ST while looking from the front of the frame, braze the right (Non-drive side in this case) side of the lug first, then finish on the left and bring heat back to the right for a few seconds and done.

TiHabanero

OK, I get using heat to move the heat tube over at the other end of it. Will try that. The head tube is an old 531 and the down tube is an OS 7 4 7 Columbus Life.

unterhausen

you aren't going to get it to move by bending, unfortunately

If it wasn't twisted, but moved over, then bending would work

Nessism

The down tube will buckle if you try to bend it into alignment (don't ask me how I know.)

e-RICHIE

The head tube linearity on some frames (the main triangle) will stretch into alignment (Read: with enough force something will bend). It all depends on how the frame is clamped, how long the error you want rectified is over (Read: is the miscue 1mm at the head tube OR is it at the very end of an alignment rod that's a meter long), and how you fulcrum and pulley the tools in order to activate the remedy. Oh - the most important component to enable this at all is the elongation factor of the material in the frame.

TiHabanero

Update: With the application of heat I was able to move the head tube, however not enough for a perfect alignment. I have moved head tubes before, but they were all 28.6mm 9 6 9 tubes, this one is 7 4 7 and 31.8mm. Seems to make a difference. Looks like this one is going to either be pulled apart or put on the wall unfinished. Back to the drawing board.

e-RICHIE

What was heated, and where?

TiHabanero

Heated the bottom head lug and that is all. Did not heat the down tube or head tube other than what is inside the lug. Remember, the top tube is not installed yet and the head tube is "twisted" out of alignment. Right now I feel lucky to have moved it and don't want to risk damaging any tubes as the frame can be finished and ridden, it just won't be 100%.

calstar 

Good plan, I bet it will be close enough that you won't notice it when riding. I also think there are a lot of production bikes ridden daily that aren't close to being 100% in alignment and the riders don't notice it. Please keep us posted as you progress with the build.

regards, Brian

e-RICHIE

oh okay. You’re assembling the triangle in sections. I thought you aligned/realigned the unit after it was fully done.

e-RICHIE

@TiHabanero I have another question because I'm not able to visualize what you're working with. If the main triangle wasn't completed, and only the head tube and down tube were assembled, and you saw a misalignment, what's being measured against what? If there's no seat tube and or bb shell as part of the equation, you only have the two tubes and the lug. Am I missing something here? Thank you.