Tube bender

for the roll bar

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We always look to do things different from time to time, or to improve on what we have.  One item I have long thought needed changing is the roll bar on the home built car.  It slopes in towards the top, is made from Scaffolding tube and really does not go over my helmet when driving so any chance of a roll over and I think my head would get bashed.

So changing it for a slightly taller one and to try and meet MSA Blue book regulations should mean a better and safer solution.

The Blue book gives minimum sizes for tube of 45 mm x 2.5 mm wall or 50 mm x 2.0 mm wall.  It requires a diagonal on the main loop and two back-stays, but mainly taller then when wearing a helmet and squarer in general shape.  I visited a place that could make one for me and was roughly quoted £300 painted.  I could not easily justify this so looked at making my own bending device for the 45 mm x 2.5 mm wall tube and basically making my own roll bar.

27th December 2012

So I set about going through my metal pieces in the workshop and started to fabricate my own bender.

Looked around my metal pile and found some 10mm plate and some old rusting metal around 18mm thick, formed a sandwich with 3 x 10mm pieces approx 200mm square and then 2 x 18mm pieces across diagonally. Drilled for 6 10mm bolts and one big hole at 1" diameter for the pivot point.

Lots of work on the band saw to rough cut and then down to the job of rounding the piece to a 100 degree quadrant. I completely trashed a dividing table, just was not big enough for the job as I ended up breaking the gears, so had to improvise.

This was my answer.


I had to take breaks from the job to allow the feelings to settle back in my arms and fingers. And to think I should know better being H&S trained.

The next step is to rough cut the groove in the blank before finish cutting. At this rate in a week or so.

4th January 2013

I have sort of finished machining the die, may need a bit of emery work, but will do for a starter.


Will have to do the frame next and see how bits go together!

12th January 2013

I got bored, it's not finished yet, but I had to try and see if it would work, well you would wouldn’t you?  Built up the frame and cut a few guides out of aluminium block, placed things together and had a bend!


The guides are just sat on a base plate as can just be seen.   So started to bend the tube.


I ended up over the 90 degrees with spring back so need to work that out.  There is a slight kink starting on the inner edge of the bend, not sure if you can see this in the pictures.   I think this could be down to the tube guide is not under the die centre line. It needs to have shoulders on the front face to allow it to sit below the die, so at present is 1&1/2 " behind the line, when I have done that I should be able to check for clearances and make sure the guide is as close to the die as possible.

Oval-ation is less then 90% so happy with that.

end bend1.jpg
end bend2.jpg

13th January 2013

The unit is now all but finished, changes to the guide height by lifting it up by 4mm kept the tube tight against the die on the inside bend. Decided to do a proper test bend on a new piece of tube so I marked out rings at 20mm spacing.
final test1.jpg

Stuck it in the rig with the first mark at the end of the half clamp
final test 2.jpg

Took it out and stuck against a plate to take picture. No kinks at all, nice and smooth so very pleased with the result.
final test 3.jpg

Again checked the squash and got 41.25 mm so still happy with that.
final test 4.jpg

Basic measurements are 70 mm (2 3/4") from first mark to start of bend and bend radius 157.5 mm ( 6.2" ) so I have 5 mm ( 0.2") of spring when I take the tension off, the die is 6 inch radius.   I think I will clean and paint the unit before it goes rusty with the cold weather.

3rd February 2013

The frame is painted and I just had to go at the main loop, it worked out OK, so now have to just get on with it.


31st March 2013

long time and no update so about time I caught up.  I had to get more tube, with all the setting up and test pieces I ran out of the stuff.  But anyhow more lengths bought, some plates for the main loop mounts purchased and time on the milling machine with a 45 mm hole saw and I have the following:-


I have also been spending time welding in some square tube and plates at the rear of the car to mount the back stays against.  this was a nervous affair with the petrol tank below it, so drained the tank, sealed the filler, covered with sheets of aluminium and steel to stop molten metal from hitting it etc. and I have got away with it.  There is some damage to the rear paintwork that will need to be repaired and some filling to make the area smooth where I have cut sections of the aluminium top away, but it should look OK when finished.  I am taking the roll-bar to be welded, rather then do it myself, it needs to be correct first time.

2nd April 2013

Back from the welders and all fastened together:


I will get it painted and bolted down over the next few days.  A new boot lid is now required.

A recent Youtube video was done on the operation of tube bender after a forum member asked for the opportunity to borrow it. So it was pulled from the side of the garage and placed on the Milling table at height, not a very good idea really, should be done on the floor, but that makes it difficult to film, well never said it was easy.

 I think that is the end of this tale!

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