Bike carb conversion; folding the manifold tubes?

[Arsonista]

Carter, I spent most of my apprenticeship making square to rounds. What you need are what we called 'fingers' and a flipper, (old leaf spring). A piece of 4x2 will do at a pinch. The fingers you can make from 2 pieces of angle, say about 30 x 30 x 6, and cut a shallow angle of 30 degs on both legs at one end. The length of the angles needs to be the length of your vice jaws plus the length of the workpiece plus about 50mm. This is getting difficult to describe. Put the angles back to back in the vice with the 'pointed' ends on the left of the vice enough to cover the length of the workpiece. Now drill 2 holes through both legs either side of the jaws and pin them. That's the fingers made. Your pattern development will have 4 'points that are the corners of the square end. You need the triangulation lines now. These are 4 lines that will come from each corner to each quater of the round end. Now pinch the one of the corners in the fingers next to the vice and flipper it over while raising the round end to the the last triangulation line. Do that 4 times and voila. If by some miracle any of this makes sense, draw something up for us to look at. When I was doing this, the technology was marking out blue, dividers and a scriber.

 

[Carter]

Carter, I spent most of my apprenticeship making square to rounds. What you need are what we called 'fingers' and a flipper, (old leaf spring). A piece of 4x2 will do at a pinch.

I think I get where you're going with it. Is it an actual former made of angle or just a bending tool/jig as I think you mean? Not quite sure what this 'flipper' does and where it's applied. Do you mean it's a lever/cheater bar type of thing?

The fingers you can make from 2 pieces of angle, say about 30 x 30 x 6, and cut a shallow angle of 30 degs on both legs at one end. The length of the angles needs to be the length of your vice jaws plus the length of the workpiece plus about 50mm. This is getting difficult to describe. Put the angles back to back in the vice with the 'pointed' ends on the left of the vice enough to cover the length of the workpiece. Now drill 2 holes through both legs either side of the jaws and pin them. That's the fingers made.

Is this what you have in mind?

Thinking about your suggestion how about this? Weld those two lengths of angle back to back but on the actual apex of the angles such that if you cut a section through it you'd have an "X" shape. Grind it down so that the four legs of the 'X' are a perfect fit in the corners of the rectangular port.

Mitre the port end to take up the offset and rise to match the carb position and spacings (ie running upwards and inwards from the ports)

Then taper each of those four flutes away to a 38mm diameter circle and maybe weld a ring at that end to assist with forming.

Basically you'd have made a cheap ghetto-style mandrel/former without all the pricey CNC/pattern making/tooling mularky.

Actually thinking a bit harder, your way sounds a whole lot easier!

 

[Old92ra]

Talk to these people http://www.boggbros.co.uk/fabrication.html

 

[davenport]

my first inlet manifold was made by boggy`s... they do do a very good job..

my lastest 1 (i switched from R6 carbs to gxr1000 bodies) i made myself...

if i was making the items you need i`d probably anneal some tube then beat the bejesus out of it over a square former

 

[Arsonista]

The second pic is pretty much there. The pin hole on the tapered end needs to come back towards the other one to be either side othe vice jaws, with the tapered end clear of the vice. When the jaws are closed it will 'pinch' the sheet at the square you are forming and the round end of the cylinder will be formed at the tapered end of the angles by swiveling the sheet about the pinch point. Grind/cut away any of the taper that foul as the shape comes round. Bloody hell, this is hard to describe. I could have made them by now!. For flipper try looking for panel beating spoons. I've heard them called flippers, spoons, slappers, all sorts. It's just an old leaf spring with a shallow 's' bend on one end and the short bit ground to make a handle. Good luck.

 

[Arsonista]

These are the closest I could find.[/ATTACH]

 

[FASTdan]

How is this coming along now?

You've probably gone too far down that road now but I would personally have stuck with tubing. 1 3/4" alu tube for the carb end, mated to 2" at the head end - formed/squashed to the square shape.

Similar design to below but with stepped up tubes at the join.

 

[gaz_moose]

i dont see why dont buy the required tube and make a tapered square former and bash the tube down onto it.you could lube it with oil so you can pull the tube back off.