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Discussion Starter · #1 ·
Well, I've finished my practice frame as much as I think I need to. Perhaps it is time to move on to some good tubing and build a frame that will actually fit my height. Here's some pictures from start to finish. I'll describe what I learned and what problems I ran into. These are the tubes I cut up from 3 free scrap frames. A couple of forum members told me to buy tubes instead and in hindsight they were right. It was a lot of labour cutting them and cleaning them up.



My jig was made up of two pieces of angle iron welded together in the shape of a 'T'. I got the idea from the 'instructables' website. I modified the jig after building the front triangle in order to fabricate the rear one. Here's a picture of my BB/ST joint. As you can see, I overheated things a bit. I also placed my mitre template 90 deg from where I wanted it by mistake, causing my ST to have the existing bottle braze-ons on the side. I eyeballed the placement of the BB to ST and got lucky, as it looks square. Next time I want to be way more careful.


I think my fillet brazing cleaned up ok, but I have no idea if I have enough metal.


Here's some shots of the completed triangle, and the HT joints. I haven't found it too hard to make tight mitres but then I'm cutting and filing mild steel. I haven't done my fillet brazing on anything except the BB/ST/DT junctions at the time of this posting. Everything is square and true for now. I wonder if doing the fillets will warp everything?



Here's a shot of my chainstays in the jig. (and the seatstays which are still being fit) I messed up here on my measuring because I measured from the shell of the BB instead of the centre. The chainstays are 17.5 as a result. My trig was also bad on the front triangle and I ended up with a 69' HT and a 71' ST. Oh well, it's practice right? As for alignment, it was a PITA. I spent many many hours tweaking things. I used strings, a tape measure and a ruler to get it right.


Here's a shot of my seatstays, the ends of which I hand forged. I cut off the existing slots and then pounded on the end of the tubes with a hammer against the anvil of my vise while rotating the tubing. I had the tubing almost completely closed up on the end. I am most proud of being able to do this, despite the hammer marks. As you can see I then cut new slots.


I had much better luck brazing in the seatstays compared to the chainstays. I figured out where to put the heat on the second run. IMHO brazing is way harder that Oxy/A welding. Here's the completed (almost) frame, minus chainstay and seatstay braces, cable hangers, and brake mounts. It is only brazed too.



I wanted to see if I could build a frame square and true and I think I've succeeded so far. I messed up on my math but know why, so I should be OK with the layout of the next frame. I've proved to myself that I can work with metal accurately and that I like doing it.

I don't see the point of continuing any further with this particular monstrosity because it is very tiny and made of poor quality materials. I think it is time for me to step up to better materials in oversize lengths so I can actually ride what I built.

Drew
 

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Discussion Starter · #5 · (Edited)
Live Wire, in answer to your question this frame is not my first dance as far as a torch goes. Obviously though I am still very much in the beginner stage. I bought a torch a few years ago to fix my car. Since then I taught myself to weld and made up quite a few parts for a stirling engine I designed.

My welds are finally starting to get half decent as far as penetration goes but are quite ugly. I still have a very hard time making gas tight joints I have much better luck with some types of joints than others. I just did my first welds in the vertical position a few weeks ago on my porch railing. I am putting a gate in it. As you'd know the puddle was constantly trying to run downwards.

As for brazing my stirling engine uses about 175 ft of 1/4 copper AC tube for the heat exchangers. These needed to be brazed to my steel flanges I made and welded up earlier. I knew that I'd need to learn to braze the copper tubing so I joined up a few simple parts for the stirling by brazing instead of welding as practice. My first attempt was so bad that I gave up for almost 6 months, but eventually prevailed. Brazing the copper tubes was a nightmare. I had to make 100 connections and needless to say there were a few burn-throughs and leaks.

I also needed to re-profile a camshaft for the engine (I know stirlings don't have camshafts) and built up the new lobes with brass. This part obviously wont last very long if and when I get my engine running but it is a prototype after all.

My work is still crude but getting better with each project. The last thing I made aside from the frame was a new 'impellor' for my cycleops trainer. The stock piece is white metal and it broke at the shaft. I made a new one out of 1/8 sheet complete with brazed fins. It is my nicest work to date. It works like a charm.

I haven't had too much difficulty with brazing up the bike frame by comparison. As you can tell from my very much amateur results, I still have lots to learn as far as overheating, the amount of flux to use, general technique, placement of heat, doing fillets, and a million and one other things.

Drew
 

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OI!!
what's wrong with 69ht 71st??
Unless I miss my guess that's what my dobermann pinscher is!! :D

congrats, you may have just unwittingly mde your first dirtjumping bike!
 
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