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tube bending

Posted: Tue Sep 23, 2003 12:29 pm
by antt
i'm gonna make a start on my tube bar this weekend, but wanted to ask you guys that have bent with a dodgy pipe bender some q's first.

i'm doing a design similar to the one in the attachment, but i'm not even gonna attempt to bend the top hoop with our crappy supercheap bender. i'll take it to an engineering joint or something and get them to do those bends. (unless someone has a good tube bender in south brisbane that i could do the 2 bends with :) )

anyway, the main bar along the front needs a couple of slight bends in it to follow the bodyline, only 10* at the most, so i'm gonna attempt it with the dodgy supercheap bender. but my question is......whats the best way to do it? i've heard of people using oil on the dies and all sorts of tricks to get em to bend nice. but will this be needed for such a slight bend?

Posted: Tue Sep 23, 2003 12:41 pm
by Wendle
if you are worried about bending the top hoop, just buy 2 cast bends for that.
as for the cheapo bender, use the die that fits nice, not the one with the right number on the side. and yeah chain lube helps, or spray-on cooking oil stuff.
anything that won't run when it is sprayed on..

Posted: Tue Sep 23, 2003 7:38 pm
by V8Patrol
We had this querry a couple of months back......
Here's the link.........

http://www.outerlimits4x4.com/PHP_Modul ... highlight=

hope that helps
kingy

Posted: Tue Sep 23, 2003 10:39 pm
by OzJeeper
You CAN do this with a jack-it-up type bender. U just gottabe brave.

However, what size tube are you bending? It will be supplied as "30mmID" which means 30mm inside diameter - but it's not! It's normally about 32mm. And if it's galvanised pipe, add about 1mm to the OD (outside diameter) of the pipe.

Hmmm... So you walk into the steel merchant and ask for 40mm tube. Can't get it as it's all measured ID (inside diameter) and 40mm ID wil be about, too flippin large to bend with a cheapie bender.
Next is the wall size.
Light wall is a "forget it" size. It's too thin to bend with a cheapie bender. It will kink, splay and be a veritable pain.
Next is medium wall and this is you size pipe. 3mm wall is heavy for a front bar BUT it will be very co-operative in a cheapie bender. Just remember to keep the seam at the BOTTOM of the bend. Your not stretching the welded seam this way.
Oh - just have the barbie on standby as well - it bends cleaner if its warm.

Next is Heavy wall - no it's just too bloody thick to be of use here. 5mm is damn heavy for a front bar.
Now, just think about this. Are you fitting a winch? Sometime? This design looks winch non-compatible. (Maybe?)
You are going to be cutting a heap of rounded joins here. That take lots of time and patience - or are you going to crush end joins?
The welder your going to use is at least a MIG?

In the final washup - is your insurance company going to cover you in this venture? 'Cause if the bar is not SRS Bag compatiable and its a home made jobby....
Just askin'

Otherwise just go for it! You can bend this thing up!

You don't want headlight brushbar type protection????

Posted: Wed Sep 24, 2003 9:36 am
by antt
OzJeeper wrote:You CAN do this with a jack-it-up type bender. U just gottabe brave.

However, what size tube are you bending? It will be supplied as "30mmID" which means 30mm inside diameter - but it's not! It's normally about 32mm. And if it's galvanised pipe, add about 1mm to the OD (outside diameter) of the pipe.

Hmmm... So you walk into the steel merchant and ask for 40mm tube. Can't get it as it's all measured ID (inside diameter) and 40mm ID wil be about, too flippin large to bend with a cheapie bender.
Next is the wall size.
Light wall is a "forget it" size. It's too thin to bend with a cheapie bender. It will kink, splay and be a veritable pain.
Next is medium wall and this is you size pipe. 3mm wall is heavy for a front bar BUT it will be very co-operative in a cheapie bender. Just remember to keep the seam at the BOTTOM of the bend. Your not stretching the welded seam this way.
Oh - just have the barbie on standby as well - it bends cleaner if its warm.

Next is Heavy wall - no it's just too bloody thick to be of use here. 5mm is damn heavy for a front bar.
Now, just think about this. Are you fitting a winch? Sometime? This design looks winch non-compatible. (Maybe?)
You are going to be cutting a heap of rounded joins here. That take lots of time and patience - or are you going to crush end joins?
The welder your going to use is at least a MIG?

In the final washup - is your insurance company going to cover you in this venture? 'Cause if the bar is not SRS Bag compatiable and its a home made jobby....
Just askin'

Otherwise just go for it! You can bend this thing up!

You don't want headlight brushbar type protection????


thanks for that ozjeeper. the tube i'm getting off a mate and i think it's 50mm OD with a 3mm wall. when you say keep the seam at the bottom of the bend, do you mean have the tube so the seam sits in the lowest part of the die?

my old vitara doesn't have airbags, so thats not a worry

Posted: Wed Sep 24, 2003 9:41 am
by Area54
antt wrote:when you say keep the seam at the bottom of the bend, do you mean have the tube so the seam sits in the lowest part of the die?


Yes. The welded seam is more resistant to stretching than the rest of the tube.

Posted: Wed Sep 24, 2003 10:49 am
by V8Patrol
Area54 wrote:
antt wrote:when you say keep the seam at the bottom of the bend, do you mean have the tube so the seam sits in the lowest part of the die?


Yes. The welded seam is more resistant to stretching than the rest of the tube.


put the seam on the inside of the curve/bend, its better to "crush" the seam than to try and "stretch" it around the curve/bend.

Posted: Wed Sep 24, 2003 11:09 am
by N*A*M
i'd have to disagree with you kingy.

i've tried it with the seam in various locations and found the tube bent best when the seam was on the side. i know it probably cause funny effects through assymetrical force loadings around the tube and along the seam but it was the method with least deformation.

i've had a pipe fail with bad kinking with the seam on the inside of the bend but i've never had a seam split from being on the outside of the bend.

just take it slowly and order plenty of spare materials antt.

Posted: Wed Sep 24, 2003 11:47 am
by antt
well, went to start on the first easy bends this morning, get it all set-up. oil on the die, seam to the inside, start jacking, then NOTHING :? . bloody thing has no oil in it or the seals must be buggered :x :x :x . might just see if i can borrow a mates bender

Posted: Wed Sep 24, 2003 11:49 am
by V8Patrol
disagree ??????????? thats what makes the world go round :D
I have had failures and on expensive pipe aswell as the "cheaper imported" stuff.

Posted: Thu Sep 25, 2003 7:30 am
by OzJeeper
For most of the applications I have used/bent pipe that HAS a seam I have positioned the seam on this inside radius of a bend. That is with the seam sitting downward in the former.
For someone who is unsure of what result theu are goingto get, I strongly suggest placing the seam downward, but hey! Give it a go either way (said the Actress to the Bishop)

For a chrush/power bender, it's really not an issue but for a hand former the slow and easy way is best.

As I asked earlier, you doing cut ends (sorta half circle in the pipe end) or the quick way of bashing the pipe end flatish and then welding?

Posted: Thu Sep 25, 2003 8:49 am
by antt
OzJeeper wrote:For most of the applications I have used/bent pipe that HAS a seam I have positioned the seam on this inside radius of a bend. That is with the seam sitting downward in the former.
For someone who is unsure of what result theu are goingto get, I strongly suggest placing the seam downward, but hey! Give it a go either way (said the Actress to the Bishop)

For a chrush/power bender, it's really not an issue but for a hand former the slow and easy way is best.

As I asked earlier, you doing cut ends (sorta half circle in the pipe end) or the quick way of bashing the pipe end flatish and then welding?


i'll use a die grinder to curve the ends of the tube where it meets. i know it'll take a bit, but it'l be easier to weld and be stronger

Posted: Thu Sep 25, 2003 10:29 am
by bubs
just cut it like the pic below

Posted: Thu Sep 25, 2003 1:43 pm
by N*A*M
bubs notching method works but is also time consuming. it's what i've been doing to notch the joints on my skate rails.

but now i'm getting lazy and i'm just hammering the end so that they become more ovular. it works fine for non-critical applications and is pretty quick and easy. looks sort of like the attachment but i wouldn't recommend it for automotive use.

Posted: Thu Sep 25, 2003 1:56 pm
by bubs
nam - like this :?:

Posted: Thu Sep 25, 2003 2:31 pm
by N*A*M
exactly bubs :cool:

just whack the end flatter so it has a better match to the straight tube which you're joining to. works better if the straight tube is bigger in size but even if they're the same, you don't need to flatten it that much.

dodgy but effective ;)

i'd do it for sliders and bumpers but not for cages

Posted: Thu Sep 25, 2003 6:57 pm
by antt
well, got the main bit done tonight, bent with the seam to the inside witha bit of oil on the die, and it bent perfect. we'll see how the rest goes on the weekend

Posted: Thu Sep 25, 2003 8:21 pm
by V8Patrol

OI ..... N*A*M......
NER NER NER NER NER
:finger: :finger: :finger: :finger:
:rofl:

Posted: Thu Sep 25, 2003 9:45 pm
by N*A*M
maybe i'm just retarded :roll:

Posted: Thu Sep 25, 2003 10:14 pm
by antt
it wasn't the worlds sharpest bend, something like this

\
|

if you get what i mean :finger:

Posted: Thu Sep 25, 2003 10:18 pm
by V8Patrol
yeah but dont tell N*A*M that !!! :roll: