No heat needed Patrick. Each side of the back end of an M20 frame will bend cold as long as you can hold the main frame somehow. You can see how I held it. I remember another forum member held his frame in the fork of an Apple tree Ron

email (option): ronpier@talk21.com

Hi Ron

That's brilliant! If I find mine isn't true then I'll follow this approach. I didn't get to work on her this weekend, got sidetracked with IT support at home...which has consumed all of Sunday, still I'm sure I'm more educated now.

Anyway, next weekend I'll check, measure, re-check, re-measure and only then plan some well aimed brute force.

Cheers

Richard

email (option): dickie.bobbie@hotmail.co.uk

Hi Ron

Looking at your first photo, the short strut on the top of the rear frame, just below the seat looks as if it has been cut and re-welded, or re-enforced in some way. The second photo shows a hole drilled through the same strut.
When I straightened my frame, I cut this strut so that I could straighten each half separately, first using the "tree" method then using a vice with half round anvils, all cold. When everything was straight, I re-assembled and found a twist in the frame. To fix this, I bolted it to my work bench and pulled it straight using square tube and threaded rod, then heated the stress points with oxi-acetylene. On cooling it remained straight. One should use heat reservedly, consider carefully where to apply heat, use the correct size nozzle and avoid butane as it has not got enough heat.
The two halves of the short strut then lined up. I fitted a spool and brazed it up. I do not have a hole in the strut and fix the mudguard using a saddle.
All dimensions are now within a millimeter or two of the frame drawing.
Most important is that the lugs holding the rear axle are parallel and horizontal to each other and in-line with the frame. I also used heat to correct this.

Cheers
Peter

email (option): pvlietstra@gmail.com

Hi Peter. The first picture I posted is actually after I'd straightened the frame and welded up that hole. I've also used a correct saddle clamp. Here is that frame under construction. I've done over 5000 miles on it since I built it and it handles very well. Ron

email (option): ronpier@talk21.com

Can someone supply the relevant dimensions for the piece that fits between the wheel mounts when carrying out this frame straightening?....

I should think it would be useful info. for the technical page as well...Ian

email (option): ian@wright52.plus.com

Here is my rear frame gauge. I'll ask Henk to post it into the technical page. Ron

PS I just noticed that the threads are nearly 1/16" longer than I quoted, hence the discrepancy in the added total, but it was early However the threads can be any length!


free html images

email (option): ronpier@talk21.com

I think I posted something about this loooong ago; Robb Nortier should know about this. Are you there Robb...

Yes Hans Robb actually made and gave me this gauge. I'm just passing on the dimensions for anyone who wants to make one. I didn't notice anything about it in technical, but Henk is looking into it. Ron

email (option): ronpier@talk21.com

Thanks Ron....Ian

email (option): ian@wright52.plus.com

Hi Chaps,
I have made a frame gauge to Ron's dimensions and measured my rear frame, only 3mm off, not bad considering the state of it! However there is more to this than meets the eye, the diameter of the down tube is 38.11mm and the seat down tube is 34.81mm a difference of 3.3mm. As all the measurements are being taken from the tube centres the straight edge is not running parallel to the centres, I would suggest using a 1.6mm spacer on the rear tube in order to achieve parallelism.
Hope this all makes sense and helps.
Cheers
Jim

email (option): johnboywalton13@msn.com

Well spotted Jim...It all makes sense...The discrepancy in tube diameters could be easily missed..Ian

email (option): ian@wright52.plus.com