Chasing my tail – the alignment conundrum

I created this framebuilding blog to document my progress, or lack of progress, in becoming a framebuilder.  It’s mostly an online public journal that will at least help me remember what I’ve done when i’m old and forgetful, and it will at least help me remember what I’ve done when I’m old and forgetful. Oh…yeah…oops.

It’s also become somewhat interesting to other budding builders to see how I’ve learned to do things from reading the encyclopedias of information out there on forums and other framebuilder’s blogs, as well as what I’ve learned through trial and error.  So when I post what my welds look like now compared to 2 years ago and they look pretty good…I will also post the stupid crap and how BAD some of the trials turn out.  Full disclosure. This shit ain’t easy.  I’m not expecting after 12 frames that I’m an expert, no way man.  It’ll take 200 or so frames till i even consider using that term, if ever! So here I write about my latest mishap or error or stumbling block.  I’m just going to chalk it up to me still being a relative newbie and now trying to use a new process and frame fixture and trying a new welding sequence (because it’s hard to weld in the fixture).

Frame alignment- For some reason I thought this frame was going to be dead-straight coming out of the fixture. (First mistake = overconfidence.) I took the frame out of the fixture, reamed and faced the BB shell, then screwed down the BB shell to my Bringheli C-channel alignment table and got the height gauges out. The backbone of the bike (seat tube) was said to be 2mm off to the driveside and the head tube is twisted around about the same.  My miters were some of my best yet, and my welds felt and looked pretty good…so how did this happen?? I honestly don’t know.

The weird thing that is confusing me the most, is that when i first took the frame out of the fixture, the seat tube cone (see pics) was centered – meaning it was aligned according to the fixture.  But I figured that the alignment table is perfectly flat and therefore correct, as were my measuring techniques, so I figured I had to do some further work on the frame to get it straight.

This slideshow requires JavaScript.

I cannot figure out why this is happening.  It’s not a ton off,  but it’s more than I want. If 1mm is the threshold for most builders that measure frame alignment (some don’t), then what’s another millimeter anyways, right?  Naw, that’s not how I’m wired. This will bug me until the next frame, or until the backbone of the bike, and head tube are sub-1mm from being dead-on straight.

Cold-setting- Because this frame is me to ride, I decided to try out some stuff to get it back into alignment.  I usually don’t try this but I tried to cold set the seat tube to be straighter.  With the Bringheli small alignment “table”, Joe gives you a very long and heavy metal bar to insert into the seat tube just for this task.  It’s a scary proposition — pulling up on this bar while table starts to lift off the ground.   You think to yourself, ‘this can’t be good’ for the frame.  And this is why some builders appear not to cold-set and just leave it as is no matter how out of alignment – it basically is bending the steel to be in better alignment.  (I read that R.Sachs didn’t have an alignment table for the first 250or so frames be built so didn’t know how out they were – if at all.)

It’s thought that most riders won’t even recognize the 2, 3, 5mm out anyways. So no matter how much I pulled in my comfort zone (not feeling like I was going to break the frame in two), i couldn’t get it to go under about 1.6mm from straight.  Ok, that’s what it’ll be then.  With the the downtube being 8/5/8 OX Plat, I am pretty sure I won’t be able to move this using this small table, and if I do it may fail catastrophically (the frame, not the table!).

Welding a 2nd Pass- Another method I’ve used is to weld a second TIG pass, or even third pass with the pulser and without adding filler.  This is like witch-wanding with a torch and helps pull the tube in the direction you want to move it in.  It’s not the best practice to continue, but I don’t plan to use it forever.  One of these days I won’t need to use it and it’ll phase itself out of my process.

After chasing my tail with cold-setting, laying a couple second passes, and measuring back on the table I got maybe 0.2mm out of it all and thought “well, that was pointless!”
I placed the frame back in the fixture and saw that the seat tube cone was telling me that the top of the seat tube was off to the left….yep, the OPPOSITE direction that the alignment table.

Witch-wanding – So now for the 3rd attempt and method at bringing back the frame into alignment.  This is a technique I first heard from DWF on the mtbr framebuilding forum and since I trust him I gave it a try.  I didn’t know exactly what to try, but I figured, what could possibly go wrong?!  I left the frame in the fixture and moved the seat tube cone up a bit so I could see how centered it was in the tube while heating up the tubes with the torchc.

I started with a 0 tip and a carburizing flame (lower temp), like you use to braze water bottle braze-ons.  I just waved the wand/torch lightly around the BB/ST joint on the side i thought would move it in the direction I wanted, but learned very quickly that I was moving it in the wrong direction.  Apparently heat from a torch pushes and doesn’t pull like a 2nd TIG pass.  It was cool how quickly the seat tube would move to one side, and when I stopped using the torch, it slowly sprung back to its original position.  I did this a few times to try and get the tube to come to rest straight under the seat tube cone, but no luck…it just kept going back to the left (the pictures show in sequence what was happening and the 3rd photo shows it centered but it returned to photo 1 after several seconds).

So I’m not sure what I’m doing wrong, but the witch-wanding didn’t work for me on this frame.  It’s possible that the cold-setting attempts and second passes stifled any further attempts at bringing the frame back into alignment with heat, I don’t know.

So basically, I did a bunch of torture to this frame with no significant improvement to the alignment.  I am finding it hard to believe that by more cranking on the frame I would’ve achieved better results, or that by being a better welder my 2nd pass would have done more.   So I will chalk it up to unequal heat control with my 1st weld passes since I know my miters were tight.

Some days, some frames, are better than others.  I just have to leave this one alone, walk away, and come back to it once the frustration passes. It is frame #13 after all…so maybe this is just how the tubes were meant to be…

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: