DocBlasto

I have a workshop at home, a TIG welder and some fabrication experience accumulated over the years, mostly TIG and MIG on mild steel. I want to attempt my first frame, but I'm really not into the idea of buying or building an expensive adjustable jig for my first build. Basically, I'm trying to build a straight, rideable frame without buying any expensive specialty tools.

So this is a question for all of the cheapskates out there-- how do you get the angles right and compensate for pulling/distortion without having all of the tubes firmly mounted in a precision jig?

unterhausen

My understanding is that Paterek's first edition is online with a cheap fixture. Alex Meade sells a minimalist set of fixturing to be used on a flat surface.

I don't really recommend fixtureless building. However, the traditional method was to make a full size drawing, miter the tubes as well as you can. Tack the hockey stick (head tube/down tube. Then attach the seat tube to the bb shell. Then attach the hockey stick, the seat tube/bb assembly, and the top tube together. Up to this point, it would be best if you were tacking them together and not fully joining.

To put the rear triangle together, I would look up "Doug Fattic t-tool" and make something like that. That allows you to put the chain stays on. At this point, if you have only tacked everything, you should be able to fix any alignment issues. Then fully join the tubes. Check alignment again. When satisfied with that, put on the seat stays. Once the seat stays are on, further alignment becomes much more difficult.

Mitering is very important for alignment.

Andrew R Stewart 

I'll add to Eric's good advice to not trust the tubing to be straight. Early on I thought that the hockey stick method would be fine if I used a Vernier protractor to set the angles Tacking and correcting before completing each joint. But I quickly found that the end points of the tubes, the joint centers, didn't agree with my design. A little bit long or short depending. I muddled through a few frames this way before moving on to more expensive jigging. In hind sight I might have kept to the full scale drafting I used in the very beginnings. I should have tacked more and learned how to braze with less heat distortion too. For main frame alignment before I got a real machinist's flat surface I used my eyes, sighting trough the main frame both ways. The rear end was the low cost string and builder's wheel with a lot of trial and errors. The fork used a wheel clamped to a bench top and the steerer/crown held in the vice. Again a lot of through sighting and nudging about before a tack on one blade.

I find the full scale drawing or at least center to center calculations are better then relying of tube angles and mitered lengths alone is best if doing jigless. Here's some Fork alignment methods I've used and written about in the past.
https://www.bikeforums.net/bicycle-m...ls-left-2.html post #15
Here's a shot of crude but effective rear frame fixturing


This was in 1984. I still use the vice nearly daily and the cabinet now has a couple of grinders on it. This speaks to how long term building can be. Nearly every off riding season (when I do most of my building) I find another way to make a tool or aid. There's a lot that you can do for very little

Here's my Flicker site. I suggest you look through the building and tools albums. There's a lot to give ideas. Andy https://www.flickr.com/photos/73195587@N00/

DocBlasto

That T-tool is really interesting. I can see building one of those on-the-cheap.

DocBlasto

Cool advice on the full-scale drawing. Seems sensible to have a direct reference I can lay the work-piece on.

I like your wood block tube clamp.

My welding table is pretty flat. Not machine-flat, but I think flat enough for this sort of work. It's a tab-and-slot laser-cut table that shipped flat-pack. I clamped the whole thing together and "trued" it, checking it every way with a long straight-edge as I welded it up until I had a torsion box. It's been pretty reliable so far.

I like how much you appear to be doing with very little. I'm looking at my vise on the front-left corner of my workbench and thinking that I could easily have a setup much like yours. The only difference is that I don't have oxy-acetylene, so I intend to TIG-weld my tubesets. I'd love to try brazing if I can get my hands on a torch. It looks a little more forgiving than welding, but I could be mistaken.

Doug Fattic 

I’m a pro with pro tools so I’m not really qualified to answer your question. However I have seen a lot of different efforts trying to make a frame with just a few tools. For many steps trading time for equipment can still get decent results (if you know what you are doing). On the other hand, I have taught frame building classes since the late 70’s and have seen how students struggle even with a knowledgable instructor and great equipment so I know the average person will make a mess of things without a good teacher. However you have a big head start already knowing how to tig weld.

If I was to go to a country where I had only primitive equipment (which actually I have done), the 1st tool I would want is some kind of flat surface to serve as a base for spotting a frame together and alignment checking. For example it is possible to use a table saw top and I have heard of people using a piece of granite countertop that will work if it is properly supported underneath. A better idea is an epoxy designed just for this purpose that can be poured onto a double sheet of MDF board with something on the edges keep the epoxy from running onto the floor before it hardens. If I was really desperate I could use a long straight edge with an adjustable screw on one end. While editing this post I see you have tuned a welding table so that part is taken care of.

I think it would be almost impossible to use vertical dropouts if tig welding a frame without a decent fixture. Using horizontals will greatly reduce your frustration. It is very challenging to get a wheel to center. The slightest amount of chain stay length difference is magnified out by the rim. This is why classic builders rarely used vertical dropouts. I can think of a way to do this tig welding but it would require a lengthy explanation. Brazing with a traditional socketed bottom bracket shell would make things a whole lot easer. Then your chain stay miters don’t need to be spot on perfect and you can slide the chain stays in and out of the socket to get just the right length. Even with that advantage it can still be difficult.

It is also possible to make functional fixturing that can work with whatever you choose as your flat surface. I have stainless steel fixtures laser cut and etched in Ukraine which I use for design set up and spotting frames. They take the place of a full scale drawing and allow adjustmrnts while doing the build. They only cost $1000 (less for an older one) so I wouldn’t want to be bothered making something since they are so awesome but I could replicate them in wood with hand tools if I had to (leaving off the bells and whistles).

Good luck,
Doug Fattic
Niles, Michigan

dsaul

You could build a front triangle on your welding table by using V-blocks and shims to account for the different tubing diameters. You are going to have to build some type of beam style fixture to do the chainstays. You need something that will clamp the bottom bracket in place and something that will hold a dummy axle that is perfectly parallel to and centered on that bottom bracket. Again, you could clamp these parts to your welding table, but it is going to take considerable time and effort to get it all aligned and figure out the proper angle to get the bottom bracket drop correct.

BTW, the jig doesn't do anything to prevent welding distortion. The frame is tacked in the jig and all welding is done outside the jig.

Andrew R Stewart 

I hope the OP does learn how to braze. Attaching "braze ons" (like that name) on the thin sections of tubes (like bottle bosses) is so fast and easy with so little chance of burn through when brazing. I've attached brass or bronze bits (and of course stainless steel ones) with a torch. Then there's the aesthetic aspect of sleeves/lugs or socketed/plug drop outs too. But great frames have been made with either method.

The wood tube blocks are pretty much a standard in most all frame building shops. One can make their own easily. I suggest a hard wood. I like having the same block dimensions for all the various tube sizes as this will speed up the effort to reposition the tubes/frame within the vice as you work on different parts of a frame, say when sanding or filing the tight spots and need that different access angle. The leather hinge also keeps the blocks a one hand item, the other hand in of the frame or vice handle. I place a disposable sheet of material (cardboard) between the two halves of the blocks to both guide the drill bit (I use spade bits) and to allow full tightening of the tube. Andy

Doug Fattic 

Wood blocks are a foundation tool like files in a frame building shop. They are how you hold a frame in the bench vise. Closed pore wood like hard maple works better than open pore oak (which collects flux and tends to chip). 3" X 3" X 1 1/4" is my preferred size. Squeeze 2 of those pieces together with a thin piece of cardboard in-between (like Andy advised) and bore the hole the size of tubing you will be using. Just remember to bore the hole 90º to the grain or they will crack.

If you carefully make the outside dimensions of all the blocks all the same size, they can be part of your fixture holding the tubes on your welding table. I'd probably use 2 half blocks for each tube (one near each end) and drill more small holes in the blocks so they can attach to the holes in your table with long bolts over the full scale drawing. Something can be laid on top of the tubes to hold them in the wood blocks while you tack the frame together.

Paragon Machine Works sells aluminum blocks that can also be used for this purpose (holding tubes on your table, they don't work as well for holding a frame in a bench vise as wood blocks do).

fietsbob

Get the miters cut accurately... and tack weld
and tweak the main triangle into alignment

before doing the joints up fully , Perhaps?

stainless filler wire is commonly used
[Regular steel wire, and you can fillet braze over it]


and you might get the frame to come out OK,,

I have a Touring bike built by a cargobike builder, his shop,
I helped with making parts of it, hands on, in the shop..
not much in the way jigs were used..

It worked out...





....

pwyg

I am a pro with pro tolls and opt to build my frames like my predecessors. First I like the challenge it keep my skills high as torch skill can be the difference between straight and way off. Secondly a frame built in the traditional fixture method builds and traps too much residual stress in to a frame and that is a no go for me. I braze all my joints free hand outside of fixtures. I only build my forks and chainstays in fixtures. if done right they come out of the fixture without pinging thus conforming to the fixture. There is a special technique to do this I only teach my students this trick.
The thing is you can do anything out of a fixture , just expect to have a lot of mistakes and cold setting to be done.
Paul

unterhausen

Paul, do you tack in a fixture?

pwyg

No tacking in fixture. an old school habit. I tack it freehand balanced in a park clamp with checking for square a few times, then tack and check again. goes fast for me but I come from a long line of skill based brazing frame builders. I like the challenge rarely cold set since my checks are thorough and for fillet I can lay quick even fillets so distortion is negated.

JohnDThompson 

Is this with lugs, or TIG welded as the OP asked?

I can see tacking freehand when using lugs, but for TIG welding, wouldn't some sort of fixturing be needed just to keep things in position while tacking?

N.B. I've brazed hundreds, maybe thousands of frames, but haven't tried TIG yet.

pwyg

Yes I have done this with a Tig welder on a few frames and mainly unicycles and recumbents. I really can not build a frame Tig I hate the way they look.

Le Mechanic

I was in a similar situation. Had a tig welder, but not much else frame building wise. I built a welding table with the plan of building bike frames as well as other projects. So far I've built a couple of frames on it. I've been riding/commuting on my first frame for a little over 3 years now. I actually made a little video yesterday highlighting the build process I used, as well my thoughts on the bike overall. At some point I would love to have a nice jig, but for a garage hobby builder, the welding table works great!

unterhausen

my memories are vague, but I'm pretty sure that for my tandem, the only fixturing I used was to hold the bb shell perpendicular to the seat tube. I could do it, I just didn't really like it.