bill meyer

Working on my first frame here and getting the main triangle together. I've got all but the TT done, and per my drawings my HT/ST didn't turn out parallel (both supposed to be 73 degrees) as I had planned, they're about 1-2 degrees off. However, if I squeeze my TT in there it brings them back to parallel, but then things are under tension if you will. Is that ok?

tuz

You can try to cold set the angle... being careful to maintain the HT alignment. But 1-2 degrees is significant so it might be messy. Don't squeeze the TT in, build-in stress will cause failure in the long run. It's better to shorten the TT if you can live with the bad angles.

Or you can start over if you are looking for practice.

bill meyer

Ok, That makes sense, I think I'll roll with the current angles then and shorten the HT a bit. Who know's, I may actually like the slack head angle. It's going to be sort of a gravel/road build anyway with canti brakes, and now the head tube angle will be 71.5-72ish.

Andrew R Stewart 

Do you know where the error is? Which junction? How much too tight is the TT length? Lot's more questions on your process but that's done and now the correction phase is all that counts, with this frame. But the other questions will be wanting answers for the next frame to go better. Andy.

unterhausen

that sounds like a fairly normal amount of spring to me. This is why nobody ever builds this way, even if they don't know that. You can either just jam it in (and pin it?) or witch wand the seat tube and down tube to pull them apart. I wish I remembered the video on youtube of someone witch-wanding a frame into alignment.

bill meyer

It's the HT - DT joint. Just a measurement error on my part when fitting it in the jig, didn't get the angle quite right. I already moved forward and mitered my TT down to fit, had to take about 4mm's off it. A good learning experience anyway.

TiHabanero

The first frame I built had the same problem with the top tube. Commuter and all round bike. I stuck it in and over 20,000 miles later it is still going. I hit the thing with my car with enough force to bend the rear triangle. Realigned the frame and it has been fine. Just not enough pre-loaded tension to make a real difference.

Craig Ryan 

You're working with metal, and it's alive when heated. Get your sequence in order and work on the front triangle as a unit. Make the fit up so it is at peace with itself, then pin it, tack it, and go forward.

Andrew R Stewart 

The joints will close up toward the more heated area. so the DT/HT joint which has more lug on the top of the DT and backside of the HT then on the upper front of the HT means that the HT will cool and move toward the ST. By the same manor the HT will bow after the TT is brazed in place with more heat applied on it's backside with both TT and DT.

As Eric said, few build with the sequence that you have done. A more popular method is to build two "halves" (say the TT/HT and the ST/DT). But most will tack/pin the complete main triangle and braze it in one step.

4mm of placement difference over the length of a ST is about .5* difference. Andy.

unterhausen

I think a more traditional method of building in increments is to braze the DT/HT hockey stick, seat tube brazed to BB shell. Then braze everything together. I think a better practice is to braze everything in the frame but the seat stays. This allows you to mess around with the alignment of the rear triangle after everything is brazed together.

bill meyer

Ok, I didn't realize the DT/HT would close up that much, but I think that's exactly what happened. Not sure why I built it this way, just sort of flying by the seat of my pants and seeing what I learn on the way.

So next time if I were to tack everything first, maintaining angles, what happens to these high heat areas like the HT/DT when I complete brazing, won't they try to pull in, thereby creating built in stresses? Seems like it would create the same result as me trying to stuff the TT in. ..just thinking out loud here

tuz

I think that sequence is suggested in old reynold litterature. I know a builder that uses it; it's fine if you have a good jig.

I try to put 3-4 tacks and that seems to minimize movement during joining. It's usually hard to tell on the HT since it is short.

Certain sequences minimise the build-in stresses but some likely will be in there anyway, it should be fine as long as the tubes don't end up bowed

As Andy said 4 mm ~ 1/2 degree which isn't much; you can partially compensate that by shortening the fork.

Craig Ryan 

Bill, there is a lot of information about sequence out there, and especially in fitting it all up. I don't know anyone who doesn't fit the whole front triangle and proceed from there with either tacks, welds, pins, or some combination. Even without a jig or a good surface it's the way to go. Look at builders photo pages. Order another set of tubes and get right to it, you probably won't ride this one long any way. Early on I never rode a frame for longer than it took to build the next. Good luck!

Andrew R Stewart 

Bill- Yes and, well, no. have you ever cut a frame with a hacksaw? Sometimes the tube ends jump out of alignment, sometimes not. But the reality is that with the full front triangle set up/tacked/pinned then fully brazed you won't know how the stresses are UNLESS you cut the frame apart. (Reminds me of the testing of the Atom Bombs. Once you've tested one it won't do you any more good (like go bomb again)).

But you do talk of one of the goals of good builders. To get all the dimensions and alignments right and also minimize the stresses that remain. How well and fast you braze up a joint is part of it. But how you apply heat not needed to braze with might (or at least i think so) make a difference in the distortions. I will heat up the BB shell's underside and the HT's front side after brazing (not to full brazing temps but more then "warm to the touch") to try to equalize the stresses.

Which brings me to one of my stories about taking a building class many years ago from Eisentraut. He told of a trip to Italy he made to "drink the koolaid". He watched as a famous brand brazed the HT lugs with a hearth furnace. There was a orange hot (brass filler was used) area that covered the HT and a few inches of the TT and DT. Albert was a user of Silver and was taken aback with this totality of very high heat. But then he figured that the heat was evenly distributed over the entire joint(s) and there was no uneven heat distortions. He added that this brand didn't suffer the breakages that others were known for. Andy.

bill meyer

Now that you mention it, yes, I did cut up a Nishiki to do some practice brazing on and I recall the TT sprung a few mm's to one side. Didn't think much about it at the time, but it makes sense now. I've also seen the hearth brazing on a youtube vid and have been shocked by the amount of heat, seems like it would anneal some metals, but I guess not as they've been doing it that way forever.

So hypothetically, if one frame had massive built in stresses, besides being more failure prone, I wonder if it would ride or feel any different than a stress free frame?

I've tried to read the Paterek manual (I learn better by hands on, so not much sinks in really..) and it seems he likes to build in phases and cold set each piece before moving forward, versus tacking everything in place, supposedly to reduce built in stresses.

ok, enough rambling, thanks to all who have responded, this has been a really helpful thread!

Craig Ryan 

Just because the frames noted sprang apart when cut, does not mean it's to be accepted as a standard to build to. If you ensure the tubes and lugs are at peace with each other during fit up, I doubt there will be this so called spring in them.

unterhausen

I've seen some bikes that failed at the head tube, and my guess is that it is because too much stresses were built in. This is particularly true of the bikes that were built with one piece headtubes/lugs. Just speculating, but I think most of us probably leave some stress in the tubes, it's really not hurting anything.

fietsbob

is a tube a bit long? stamped lugs are more flexible than investment cast ones.

ksisler

OP; For first or 100th frame, I am going to suggest that your tubes be cut and fitted to match your design drawing with a fair degree of fidelity. +5 on the other comments about sequence of brazing also.

So now back to the issue of jamming in the last tube. If one were to jam in the tube without the lugs, you would likely see that there is a gap of a mm or two at the top or the bottom of the intersection. This join will be weaker than it should be if brazed, or could be failure point if soldered with silver. You could hide that under the lug and just braze away, or you can fit the pipe correctly (may mean starting with a new pipe) and then do it right.

Being off several degrees is a significant variation from a plan. If you have already brazed some of the joints, then best bet is to file the other tube(s) to fit what you have in front of you and finish it. Having a frame that has well fitted joints and good brazing but has the ST or HT angle a bit off from design is not going to be the end of earthly rotation so to speak.

/k

bill meyer

Thanks K. I didn't jam it in there, mitered the tube down to fit this time. Turns out the head angle is only about .5 off my plan, so it's not too bad and I know where the error occurred this time. Next time I'll try the suggested brazing sequence.