tube bending

[pie]

I've got to the almost giving up stage, so would really appreciate some help.
We're trying to bend 30mm tube with a 3mm wall for the trike frame and have been using a hydraulic bender, we've used the 30mm former and the 25mm former and every single time the tube ends up with an indent on the inside of the bend and a slight flat on the outside (a bit like an exhaust pipe) no matter how careful we are and how slowly it's done, the question is how do you get a nice clean bend? what do you use?

[yx600]

Not a hydraulic bender from what I understand, there's another way using an old fiesta rear drum & bar as a bender/former.
Something to do with keeping 1 end of the work static, unlike a hydraulic bender which keeps the centre of the bend static allowing the creases to form.

Will look for the link, but no doubt someone will beat me to it.

add: cant find it at the mo' - one of the mags covered it a little while back. It was a home built unit that allowed the tube to bend without getting those creases in the bends. Will look it out tonight

[pie]

thanks, appreciate it!

[Manky Monkey]

What sort of tube are you using mate? We use ERW -cheap, seamed steam pipe basically, but perfectly adequate for the job. As strong as you'll ever need but it's soft enough not to crease when bent. Welds nicely too. We use 1" bore, (25mm) for the main frame tubes & 1 1/2" bore for the top tube. If you're using a Clarke bender like this the 25mm former refers to the internal diameter, not the external. Pipe is measured by it's bore, tube by it's outside diameter, (O.D).
I'd guess you're either using a more brittle grade of tube -it may be more expensive, seamless, but it's not designed for bending in this kind of bender -you really need a far more expensive bench mounted mandril bender. Or you're trying to use the wrong sized former. You might need to use the larger sized one but pack it with some soft aluminium to reduce it to a good fit -if the tube's a sloppy fit in the former it'll crease.
If you're using harder tube than us it's probably worth warming it with a blow lamp & bending it while it's still hot.
Personally I'd just buy some cheap ol' ERW pipe.

[pie]

Really not sure what the tube i'm using is, it's seamed and was £30 for stock length (dunno if that means anything?) and got it from the local smithy.
The bender being used is the same as in your pic and the tube fits into the former nicely so all i can think is that it's the tube thats causing the problem then.
Do you get perfect bends whithout any deformation using your setup and the ERW (whats that stand for?) tube?

[Manky Monkey]

Electric resistance welded.
The 1" bore bends with no problem at all. The 1 1/2" leaves a very small indent on the back of the bend where the rollers have been if we bend it up to 90 degrees. You might need to space the rollers out further. for 1" we put them in the central position, (there's half a dozen holes on the frame so you can move them about). The further out you put them, the wider the bend will be.
If your tube's from a blacksmith, rather than a tube supplier I'd expect it to be similar grade to ours, rather than top engineering quality. Ours is painted in red oxide. It used to come in black with a blue band painted around it, but was a much coarser grade & didn't weld so well.
Not sure what else to suggest really.

[pie]

I shall carry on tomorrow and try heating it a bit, see what that does.
Thanks for your help.

[brock]

http://www.thefont.pwp.blueyonder.co.uk/bikes/tube_bender.htm

[Manky Monkey]

Hello big bro. 

[pie]

Thanks brock

[toad]

i had the same problem! but the monkey showed me how! £30 a length sounds like the stuff i tried to bend. it wont it,ll just flatten and crease. take andys advice and go for the pipe he use,s! a bit dearer but worth the extra outlay!

[yx600]

http://www.thefont.pwp.blueyonder.co.uk/bikes/tube_bender.htm

Thats the one....   

[ByzMax]

Manky is your pipe a thicker walled one. I thought that you used 4mm-ish rather than 3

It will make a huge difference. I have a compression bender but 1.5mm wall stainless collapses 2mm bends fine!
 

[lunatic]

I guess you dont want the bends looking like the front uprights and the main hoop on this cage, right? I assume having not done much work with tube that kinks weaken the tube as well as lookin crap. I didnt do this!

[klogan45]

Hello Pie,
I had the same problem so I took the former to the steel supplier and asked for some tube that fitted in the former nice and snug. It turned out that tube is measured on the outside diameter and pipe is measured on the inside diameter. It also appears that the size stamped on the former is the inside diameter, so try using pipe with 1 inch or 1.5 inch, or what ever you need, INSIDE diameter. Taking the former to the supplier was the best suggestion that I was given, that was from someone on here, but can't recall who it was . A big SORRY to that person   It worked a treat and the pipe bent just as I needed. Hope this helps, though I did feel a bit silly, giving the appearance that I did'nt know what I needed......... well I did'nt did I
Regards
K