the book chassis appears to show the lower rear radius of chassis as 2", yet i cant find the upper radius of the top hoop. But as i scroll through the pictures the top radius looks about 2.5/3" which means i could form them on a plumbers pipe bender. any advice please

I used a plumbers pipe bender for both (3", I didn't like the look of the tight radius at the base of the rear panel
Rescued attachment Rear Panel.jpg

If you make them both the same it makes forming the back panel easier. Assuming you are making an ali rear panel, you can make the radii whatever size you like (limited by how the bottom rails are layed out of course).

[note to self; must type quicker ]

Cheers,
David

[Edited on 3/2/05 by flak monkey]

thanx for the reply's as this is tomorrow nites task. I had sort of convinced my self to do both top and bottom the same and go the plumbers pipe bending route, so one more query to put his one to bed having built chassis to book how much if any? of the lower rear rail do i now have to cut away/change to adapt the bigger radius. ps all those using crossflow that whish to upgrade u2u me, re, your old engine box etc

Have you built the lower rail yet? If not, I suggest you make the entire lower rail out of the round tube with the bends. This would be much easier in my opinion and look better too.

Also, when you bend the upper rail and the lower, too--assuming you used my above advice--you may not get the bends on the right side of the tube. The radius will be fin, but the ends that attach to the shock tower may point in different directions. Mine did and I spent an evening bending it by hand to get the end to properly line up to the shock towers.

When I went to sleep that night, it occured to me that I could have cut the tube in half, down the chassis centerline. Then weld the ends to the shock tower, then weld and grind the center section. Would have been much easier than my hercules-like efforts.

--Chris

i did something very similar....

got two bends which i joined in the middle but also put in a inner sleeve. Enabled me to get a strong joint in the middle of the back of the car.

Best I could get was a bend radius of 75mm without too much ovality.
Made thje top and bottom the same, modified the position of RU1 and RU2 accordingly