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1st frame Alignment issue

1759 Views 17 Replies 10 Participants Last post by A_A, Jul 2, 2009

A_A

Discussion Starter · Jul 1, 2009

Got the front triangle of my frame mitered and brazed and I realized I made a pretty big mistake. I had cut all my miters and layed out the frame on my full sized drawing, everything looked good. I then set up my homemade 80/20 fixture and mounted my tubes so I could tack the frame together, this is where the issues began. After setting all the angles and getting the tubes in place the miters didnt fit snug so I did a bunch of fine tuning and adjusting. I tacked the frame together, took it out of the fixture and went to town doing all the brazing. After everything cooled down I was admiring my work and realized that my bottom bracket was not square to the seat tube (off by about 2 deg). You can tell it is off with the naked eye. To add insult to injury the BB is not centered in the seat tube either (less of an issue in my opinion). So the question is:

Leave it as is?
Heat the whole junction up and try and try to straighten it?
Pull the BB out completely, re-miter and re-braze?
Start over?

AA

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Walt

· #2 · Jul 1, 2009

Questions

Hey A -

Bummer. IMO, it's worth building it up (ie, leaving the front end as-is) with a rear end for practice. Best case scenario, you've got a sweet, if odd, townie. Worst case, you've wasted a little bit of money on stays.

It's generally a good idea to join the ST and BB shell first, check alignment, and then proceed with the rest of the frame. Once you've got the whole front end together, the alignment is very hard to really correct.

2 degrees is a lot, so IMO you've got yourself some wall art and/or a townie. Start over.

-Walt

A_A

Discussion Starter · #3 · Jul 1, 2009 (Edited)

Walt,

Thanks for the input. I may slap the rest of the frame together for practice. I'm willing to bet that I never make that mistake again. I think that my biggest lesson has been that the homemade fixture probably isn't worth using. Sure it looks cool but it is a PITA to setup and prone to errors unless you get everything just right. I should have trusted my original miters and re-adjusted the fixture.

MMcG

· #4 · Jul 1, 2009

Alexis - I think Bob S. also built an 80/20 fixture - but decided to not use it as he found it harder to use than he had thought. Maybe he could offer some good advice for you as well on things. Oh he's Medenveng or whatever his username is on here - I can never get it straight.

But B's a great guy and I'm sure he would be happy to offer some advice based on his foray into frame building.

A_A

Discussion Starter · #5 · Jul 1, 2009

With 1/2 a frame under my belt I can say with some confidence that a full size drawing, a flat surface and some V-blocks is a better method than a home made fixture.

Now back the the frame. I figured that is this thing may end up being wall art so I should see if I can "fix" it. I have successfully removed the BB and the down tube and seat tube are still brazed together. I may gusset the DT and ST together and try to file the BB miter correctly.

I figure I have nothing to loose at this point.

jay_ntwr

· #6 · Jul 1, 2009

A_A said:
With 1/2 a frame under my belt I can say with some confidence that a full size drawing, a flat surface and some V-blocks is a better method than a home made fixture. .

This is the route I went on my first one that is still not complete. So far, I'm very satisfied with it. Also, I'd throw in a Paterk Manual if for no other reason than it is a great read. I'm not going to say that it's taught me a lot, but it's taught me some great tricks and tips that make it absolutely worth the $75.

Now all that said, we've still got no idea if my frame is even kind of straight, so you guys will have to wait until I get it on the alignment table.

Blaster1200

· #7 · Jul 1, 2009

I just finished my first frame. I did this one in sections (BB/ST, HT/DT), making sure each section was aligned before moving on. I didn't use a real jig, other than a bunch of right angle steel. Although I'm building a jig on the cheap, I think I will still do these sections first, then put them in the jig. With my current skill in brazing, a jig will not do anything to ensure I have a straight frame, so I wouldn't really benefit from a jig until I improve my brazing process (order, direction, heat control, etc.).

But my frame - although reasonably straight - has already served its purpose: it was a learning experience. However, my next frame will hopefully serve some use other than as a another learner frame.

Through the process of elimination, I hope my frames will improve. I've already learned a lot of what not to do! (e.g., don't have anything flammable in your flix drip bucket)

jay_ntwr

· #8 · Jul 1, 2009

Blaster1200 said:
I did this one in sections (BB/ST, HT/DT), making sure each section was aligned before moving on./

Sounds like you read the Paterk Manual too.:thumbsup:

TortugaTonta

· #9 · Jul 2, 2009

Frame building is the easy part. I think most people could build a frame and have it be rideable.

Fixtures on the other hand. . . it can take several tries to get one you are truly happy with.

j-ro

· #10 · Jul 2, 2009

What I've found out about frame building is that developing and refining your process ,not just your skills is more than half the battle, You may like your jig better if you start with a st/bb sub-assembly like Walt suggested, you could make it a point to build an inexpensive fixture to hold those two pieces true while tacking and brazing before you start your next frame I built mine out of just a couple of dollars worth of angle iron. I've always meant to build a nicer looking one but you know how that goes..........

spokeywheeler

· #11 · Jul 2, 2009

A_A said:
With 1/2 a frame under my belt I can say with some confidence that a full size drawing, a flat surface and some V-blocks is a better method than a home made fixture.

AA, Just curious about your 8020 jig problems. I was thinking about building one and have found some good fittings for the head tube and BB shell but is there anything I should know about making a jig from the stuff? It seems as though there are some folks using their 8020 jigs for their main frame jig, so was your problem with the material itself or with the fixtures you used to hold the tubing in place? Thanks

BeatAFool

· #12 · Jul 2, 2009

I use a 8020 jig and it's fine for what I do. It's not nessary but it helps speed thing up a little. One thing I do is.. tack the st/bb outa the jig (as already mentioned), tack the ht/dt (hockey stick), align both and set the jig to these NOT the tubes to the jig, tack the dt/bb together, check alignment, tack tt in place, check alignment, weld bb area, check alignment, weld ht/dt, alignment, weld ht/tt, alignment, weld tt/st, alignment........................ I'm not sure this is the best way but it's been working for me so far. I haven't really figured out the best way to do the rear end yet. but this is what I've been doing, weld the dropouts on the cs, align, tack to bb, align, tack on ss, align, weld ss/do, align, weld cs/bb align, weld ss/st, align.

All that said.. my frames are only as straight as my surface plate (marble countertop), and skill level (beginner, with 5 frames, 4 rideable).

MDEnvEngr

· #13 · Jul 2, 2009

5

Mark threw me in...

I'm a newbie with 7 frames done and the 8th on the table right now. The first 3 were totally jig-less. Four and five used my 8020 jig. Six - 7 and now 8 on my alignment table fixtures. See pics below for the 8020 jig.

My process has changed with every frame and is *starting* to come together. Unfortunately, I do not have an pics of the new fixtures (perhaps I'll take some tonight). Basically, the frame is set up on the alignment table. The fixtures index off of the table. I tack the frame horizontal on the table. Then, I remove it from the fixtures and verify alignment. The 2 I've built so far have come off perfectly straight. See the other image of Doug Fattic's flat fixture...this is what I used for inspiration (though my fixtures are much simpler). Seems like I'm collecting a whole bunch of doodads and doohickeys that each do a particular function. I know what they are for, and how to use them, but they would probably appear useless to someone else. That's all part of the fun...coming up with a method that works for you.

The 8020 jig was nice, and looked good but I found it difficult to set up. And the couple of frames I tacked in it needed tweaking. Someone else might find the jig the best thing since sliced bread.

When developing your method...think about what works for you and not what looks good in Pro builder's blogs. Keep it as simple as possible. Keep it cheap so you don't feel bad going in a different direction.

Good luck. B

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A_A

Discussion Starter · #14 · Jul 2, 2009

Here is how I used my 80/20 jig.

I have not made any indexes or guides for the ST & HT angle so I level the jig then set the angles using a protractor. I then set the rear axle location and made a level line to the front of the fixture. I adjusted the BB drop based on the level line as well as the head tube location mocking up the AC height of the fork (and taking into account the headset stack up). With all these settings done I make sure my ETT length matched my drawing and I set the tubes in place.

Once the tubes were in place I noticed the miters were not 100% correct, I then made the adjustments to the fixture.

Mistakes I made:

*Re-cutting miters without double checking the fixture
*Did not tighten the BB axel in the fixture and check for square
*I made the fixture for a 68mm BB, I used a 73mm BB and forgot to adjust the BB cones to the correct location to make BB centered.
*I made no sub-assemblies, I put the front triangle tubes in the fixture and started tacking
*I took the front triangle out of the fixture and didnt check for obvious errors, I just stated brazing

The only other issue with the 80/20 jig is that there are some major heat sinks at each tube junction. You need to take into account that a lot of heat is sucked into the fixture. This is probably only an issue for newbs like me.

Last night I was able to salvage what I have done. I successfully removed the BB while keeping the DT and ST brazed together. I cleaned the tubes inside and out (took 2 hours). I was able to adjust the miter and I re-brazed the BB in. I even managed to get it centered and square.

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TortugaTonta

· #15 · Jul 2, 2009

Sounds to me like you had a good learning experience, that counts for something.

Walt

· #16 · Jul 2, 2009

For future reference...

The seat tube/BB shell subassembly is pretty important - you really want to have that joint (assuming you're compound mitering the DT to the BB/ST) completely brazed/welded. Sticking everything together and running a bead around all the joints will leave a weird unbrazed spot on the front side of the seat tube/BB, which is not a good thing for a variety of reasons.

-Walt

A_A said:
Here is how I used my 80/20 jig.
*I made no sub-assemblies, I put the front triangle tubes in the fixture and started tacking
*I took the front triangle out of the fixture and didnt check for obvious errors, I just stated brazing

j-ro

· #17 · Jul 2, 2009

2

seat tube bottom bracket fixture

Its not much to look at but here are a couple of shots of my ST/BB welding fixture, I usually set the pieces in , tack the center, flip it over tack the center and then the two sides, flip it once again and start welding, when i'm done, there is usually a minute amount of squaring to do which I can acomplish by putting a piece of 1 1/4" round stock in my vice and 'tweaking the subassembly into alignment.(which is checked with a square from both sides and measured with mikes) once this step is complete the lineal orientation is more clear and i can layout and install bottle bosses at this point before setting it into the jig, someday i'll build one with a better clamping system for the bb , but given the amount of time I have for frame building this one is doing fine for now.

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A_A

Discussion Starter · #18 · Jul 2, 2009

Walt said:
The seat tube/BB shell subassembly is pretty important - you really want to have that joint (assuming you're compound mitering the DT to the BB/ST) completely brazed/welded. Sticking everything together and running a bead around all the joints will leave a weird unbrazed spot on the front side of the seat tube/BB, which is not a good thing for a variety of reasons.

-Walt

I guess that answers the other question I was going to ask......

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