I'm in the process of constructing the rear of my book chassis, and have come to the bit where I need to bend the 19mm tube that forms the luggage compartment ..

For the upper rail, a 3 inch radius is required. Luckily, I hired a conduit bender that had a 20mm forme. With this I managed to bend the tube very neatly and with the right radius.

Anyway, the bottom corner tubes need to be bent with a 2 inch radius. I'm having trouble bending these neatly...

Can anyone give me any tips?

That's pretty tight for that size of tubing even if you could find a 2" radius bender tool.

If you have access to a welder, though, you could kerf all but the outer side (pie shaped wedges cut out), bend toward the inner side, weld the kerfs shut, and grind down the welds. The more kerfs, the smoother the outside and inside radii.

I've never seen this method used with round tubing, but if you can hold it still while cutting the kerfs, it might work.

It's easier to panel if both radii are the same. I used a plumbers bending tool and for the bottom just bend a piece of tube with 2 right angles and cut the bits you need out of that.

yours, Pete.

Yip, I agree with Peteff. I just used a 3" form and used a section from a 90 degree bend which gave me the 2" bend I needed. It's not perfect but it will be covered with aluminium anyway. I think Mark Allanson did this too and then welded a piece of flat bar on the outside of the round stuff to form the exact 2" radius profile. That seemed to be a good idea to me.

Cheers,
Craig.

Picture shows it all really, the 25x3mm flat bar gives a smooth radius
Rescued attachment RearPanelRadius.JPG

Thanks all...

Looks very tidy Mark...have you panelled it yet ? (if so did the different radii cause a prob)

Isn't there also a SVA rule about no radii less than 3" on any exposed part?

Isn't there also a SVA rule about no radii less than 3" on any exposed part?

I think you will find that it is 2.5mm, 3" might be a bit more of a problem!

I havent panelled out yet, I am going to put in a pair of rollbar braces before that (got to have them if your seatbelts are attached to the rollbar, I could not get the height requirement by attaching to the chassis unless I built 2 little eiffel tower thingies on the bulkhead top!)

My lower radii on the back panel are also 3", I thought that trying to wrap 1.6mm ally aroud a 90 degree bend with disimilar radii top and bottom was just making life difficult for no reason!

quote:

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Originally posted by Mark Allanson
(got to have them if your seatbelts are attached to the rollbar,

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Originally posted by Mark Allanson
got to have them if your seatbelts are attached to the rollbar

I haven't. My rollbar is welded on and the mounts are on a crossmember between the uprights with a thread tapped into a 5mm plate welded to it.

yours, Pete.

I read it somewhere on here, I took it as gospel.

I also want the rear braces in case of a rear ender, I live on the main A30 and just outside the 40 limits of the village. What has happened before is some holiday maker sees a fast car indicating right after just leaving a restricted zone and assumes they are overtaking, and go to follow in my wake - but I am turning right into my drive! - you can imagine the near misses I have had, it is a bit of a worry!

Mark