robertst
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| posted on 17/7/06 at 07:05 PM |
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bending tubes
how do i go on about bending circular tubes for my chassis?
right now i'm on the rear section and was thinking about the vice, but that will not do...
is there a locost way? i know i can buy a pipe bending machine or take the tube somewhere,
Tom
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big_wasa
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| posted on 17/7/06 at 07:09 PM |
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I tried and failed.
I ended up buying some scrap bends from a firm and cutting and sleeving them. see pic
 
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GaryM
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| posted on 17/7/06 at 07:27 PM |
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I bought a cheap £12 plumbers tube bender.
It did work (with the aid of the heat from a blowtorch) and in the true spirit of Colin Chapman design, broke soon after finishing the last bend!!
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leto
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| posted on 17/7/06 at 09:13 PM |
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Slot tube about 80-90% through at even distances on inside of bend. Bend. Weld up slots. Not the prettiest solution.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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mark chandler
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| posted on 17/7/06 at 09:47 PM |
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Down the tip and look for bed ends, broken climbing frames, old steel chairs infact anything made of 1"tube that has a bend in it.
For the top rail I used 3/4" tube and attacked it with my 22mm copper tube bender... just the job.
Regards Mark
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zetec7
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| posted on 18/7/06 at 03:20 AM |
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We tried with a hydraulic bender...and failed. Several pieces of kinked tubing later, went to the airport & found a chap that bends tubes for
airplane frames. Did a lovely job - if you chat someone up at an airport facility, they may just do it for you for nowt - helps if you show them
photos etc. to get them interested in your project
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bernie955
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| posted on 18/7/06 at 06:32 AM |
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Fill with compacted, completely dry sand (you don't want any moisture in there) and plug both ends (wood plugs), then use an oxy to heat and
bend round something with the right radius. The sand stops the tube from collapsing.
I've seen a guy use this method to build a drag racing chassis from steel tubing.
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robertst
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| posted on 18/7/06 at 11:20 AM |
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interesting.... so i definitely need heat, something with the correct radius to bend,
i'll look for a plumbers tube
thanks!
Tom
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bernie955
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| posted on 18/7/06 at 12:09 PM |
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Depending on the diameter/material thickness you might be able to bend it without heat. The sand will still stop it from collapsing though.
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John Bonnett
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| posted on 19/7/06 at 12:40 PM |
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You can obtain really good and cotrollable bends in 3/4" 16swg round tube (and even square tube) using a bending beam. This is a piece of wood
say 4 x 2 inches. Bore a hole through the 2 inch thickness of the same diameter as the tube. My beam is about 5 ft long and I stand one end on the
floor and grip it in the vice with the hizontal hole facing you. Chamfer the lower edge of the hole front and back to produce a smooth curve that will
allow the bent tube to be removed from the beam. Feed the tube through the hole to the point where you want to start you bend and then gently pull
down on the tube. Feed it in a bit more and bend more. Offer the bend up to the template frequently and you will be amazed how easy it is. One further
tip is to draw a straight line along the length of the tube using a piece of angle placed against the tube as your staightedge. This reference line
will help you to keep your bends in the same plane.
I would attach a picture of my bending beam but despite my best efforts it will not upload. Anyway please feel free to ask if my description is not
clear.
John
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John Bonnett
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| posted on 19/7/06 at 01:11 PM |
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Tube bending using bending beam
Thanks to the learned gentlemen from within the Group i can now attach a couple of pics showing the bending beam.
You need no sand and get no kinks. It is that easy I promise.
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam002.jpg
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam001.jpg
John
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robertst
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| posted on 19/7/06 at 02:13 PM |
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 thats pretty straight forward!
so you put the tube in the hole of the bending beam, and you simply lever it down to bend it?
Tom
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John Bonnett
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| posted on 19/7/06 at 02:32 PM |
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Yes that's all you have to do it really is so easy and if you have a suitable piece of wood, you can do it for zero cost.
Please let me know how you get on.
John
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robertst
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| posted on 20/7/06 at 08:07 PM |
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john, i tried this method...but no luck the hole in the wood got bigger and ultimately the whole thing snapped
as a last resort i did the cutting slots and bending which turned out great... but i have some doubts:
the slots have to be welded after right? i blew massive holes until i made it work.,..
do the slots have to be big, small, widely spaced, narrow spaced??
Tom
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DIY Si
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| posted on 20/7/06 at 08:27 PM |
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It really might be easier to just have a tube with kinks in it. They should get hidden uner the rear skin anyway. That or find some. I cut up an old
bed frame/headboard thing and got 4 nice 90 degree bends in 1" 18swg tube.
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locostv8
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| posted on 20/7/06 at 09:00 PM |
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I've been thinking, really dangerous, but couldn't you bend square tube in much the manner the book shows bending the windshield frame.
Though you might want to make a bit stouter pieces.
http://wrangler.rutgers.edu/gallery2/v/7slotgrille/hssss/
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John Bonnett
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| posted on 20/7/06 at 09:08 PM |
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Hi Robert,
My beam is hardwood. I thought softwood would work just as well but seemingly not. Do perservere because believe me it does work well. The tube needs
to be a reasonably tight fit in the hole. I made a 3/4" hole with one of those flat wood bits that fit an electric drill. The lower part of the
hole needs to be flared out downwards. The trick is to bend a little bit, pull the tube out half an inch and then bend a bit more and so on. A little
bit at a time. Try to be precise and sensitive as you bend the tube. Don't try to just pull the tube down in one shot. If the tube sticks you
need to chisel a bit more of the wood from the lower front edge of the hole. I have used this method to bend both 3/4" and 1" round tube
and also 3/4" square tube as well. It is really useful for the tube on the scuttle and round the back of the car.
It is difficult to explain the tecnique without being able to demonstrate it but I can post some stage by stage pictures which i will do tomorrow. I
hope that will help.
Regards
John
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marc n
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| posted on 20/7/06 at 09:11 PM |
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are these for back panel supports ??? , if so could bend a batch up in 19mm tube on our machine for a couple of quid which will be dead easy as i bend
the stuff all the time Postage is the problem though, will be bending 19mm on tuesday next week if anyone wants one let me know what dimensions etc
best regards
marc
please email rather than u2u
direct workshop email ( manned 8am till 6pm )
www.mnrltd.co.uk enquireys to :-
chrismnrltd@btinternet.com
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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John Bonnett
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| posted on 21/7/06 at 09:46 AM |
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Hi Robert and everyone else interested in bending tubes.
First a big apology. My instruction was wrong. You gradually feed the tube into the beam and not out of it. The rest is ok but that is actually really
important so sorry for that. They say a picture is worth a 1000 words so I've taken a few that might help the explanation.
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam001Medium.jpg
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam002Medium.jpg
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam003Medium.jpg
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam004Medium.jpg
http://i93.photobucket.com/albums/l57/bonnett_2006/bendingbeam006Medium.jpg
cheers
John
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timf
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| posted on 21/7/06 at 11:46 AM |
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quote:
Originally posted by John Bonnett
Hi Robert,
My beam is hardwood. I thought softwood would work just as well but seemingly not.
you can get away with laminating several layers of plywook togeter to achive the same effect of using hardwood
[Edited on 21/7/06 by timf]
A prisoner of war is a man who tries to kill you and fails, and then asks you not to kill him."
- Sir Winston S. Churchill, 1952
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leto
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| posted on 21/7/06 at 05:20 PM |
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quote:
Originally posted by robertst
john, i tried this method...but no luck the hole in the wood got bigger and ultimately the whole thing snapped
as a last resort i did the cutting slots and bending which turned out great... but i have some doubts:
the slots have to be welded after right? i blew massive holes until i made it work.,..
do the slots have to be big, small, widely spaced, narrow spaced??
Well, depends... You have to remove the difference between the length of the outside radius and the inside radius of the bend. Many thin slots will
make a smother bend but will take more welding.
To get theoretical:
The number of slots needed for a 90° bend is pi(Ro-Ri)/(2t).
Were Ro is the outer radius, Ri the inner radius (Ro – tube diameter) and t the width of the slots.
c/c distance of the slots should be ((pi Ro/2)-t)/(No-1), were No is the number of slots.
The bend starts and ends with a slot.
Boring isn't it? So boring I can't be bothered to check it
I'm a little surprised that the bending beam didn't work at all, even if it was made of softwood. You haven't by any chance got
hardened tubes?
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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robertst
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| posted on 21/7/06 at 07:53 PM |
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.... dunno... i was using a short tube though. so the levering force was not too high...
the tube is 1.5mm by 20mm diameter.
if i use the 2 metre tube. it will bend... but i wont really have much control of the accuracy of the bend...
i'll try hardwood and your formulae in case of deep frustration
thanks!
Tom
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Mark Allanson
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| posted on 21/7/06 at 08:50 PM |
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Is this what you are all after? Did all the bends for my car, wishbones included, cost £1.50 at a boot sale - Ideal
 
Rescued attachment PipeBend.jpg
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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robertst
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| posted on 21/7/06 at 11:34 PM |
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yeah i saw this pic of yours on an earlier thread... isnt that for fixed radii though? you get 90º bends, but which are really long right?
Tom
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John Bonnett
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| posted on 22/7/06 at 06:01 AM |
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The bender shown in the picture will only bend one radius determined by the mandril. This is an excellent way of producing consistent bends say for
the rear corners of the frame.
The bending beam allows whatever radius you require and by offering the tube up to a template you can accurately produce the bend you need.
The secret of success using the bending beam is bend a little bit, push the tube in say no more tha 1/2" and the bend a bit more and so on. If
you bend too much in one go, it will distort and then you will not be able to push it in any further.
I'm sure everyone is totally bored with my rabbitting so unless you have any more specific queries, I'll shu up on this subject.
Best of luck with you bends
John
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