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
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!
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.
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.
Stuck it in the rig with the
first mark at the end of the half clamp
Took it out and stuck against a plate to take picture.
No kinks at all, nice and smooth so very pleased with
Again checked the squash and
got 41.25 mm so still happy with that.
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
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
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.