Bending Tech

[N*A*M]

Okay Maths geniuses, here's your chance to shine.

For a basic bow-and-arrow bender, I need to work out how far the ram has to travel to achieve a particular angle. Here are some illustrative diagrams I cobbled together quickly.

Start position:


Finish position:


Let say I want a to be 120*, what is the formula to work out y? What other variables do you need to work it out. Is tube OD relevant?

Some considerations:
1. As the tube bends, the contact point with the rollers will change.
2. As the tube bends, it will crush a little on the contact surface with the die (on the inside of the bend).
3. The smaller x is, the more chance of getting crushing on the outside of the bend where the tube is in contact with the rollers.

To all those that have successfully used this type of bender before, what method did you use to obtain exact and repeatable bends? Cheers.

[Megaman]

Nam,

Forget that type of bender you need the type that holds the tube at one end and bends it around a die. It does not crush the tube and you can readily repeat the bends. They only cost a couple of hundred bucks.

megaman

PS. If you were in sydney we could bend the shit together as I am doing the same to my zuk.

[N*A*M]

Too late Megaman. I bought this one cheap and it should be okay for light duty. With more important things like a roll cage, I will have it bent by a shop so that it doesn't crush on impact. But for doing the front clip, this should be sufficient. Automotive design principles suggest the front should be made to crumple anyway. The bender you speak of is not expensive but the dies are!

[AussieCJ7]

ok if you make this a little more simple,

Split x in half to make a right angle triangle

so we get tan a/2= (x/2)/y (tan=oposite/adjecent)

tan (a/2) * y =x/2

y= (x/2)/tan (a/2)

where a is the angle desired and x is the distance between the 2 points shown on your diagram

a right angel triangle makes for a simple trig equation

This will not take into account for pipe crush and most benders you have to go past the point y to take into account the small estatic property of the pipe but this will give you the starting point and you can fine tune from there

[N*A*M]

I see what you mean but I don't think it's that simple because the tube is not a just line in space and we want to obtain an overall angle. I'm talking about angle that the two straight sections (beyond the rollers) would eventually intersect at. Correct me if I'm wrong but I think what you have given me is more like this:



b = a / 2
m = (x / 2) / tan b
y = ?

Don't forget I want to find out how far the ram has to move. Obviously because the tube is being bent, it's a gradual bend and that the distance it has to move is not as far as m. But how to find this out?

[AussieCJ7]

I Can not see your pic so not sure what you are showing there but.

The distance from on roller to the centre of the die is a fixed distance, if you want to get all speccy about this also subtract the 2 times the radius to the finial value for y as the die is that far from the roller at the starting point


This is your opp in the formula tan=opp/adj

The adj is the distance your are trying to find out.

Tan angle is half of the angle you want the pipe at cause you want a symtrical bend

maybe I am missing something but I think it is that simple try it out on some scrap and let us know

[Wendle]

Dude, get a sliding bevel and a protractor. Set the bevel to the angle you want off the protractor & hold it behind the tube as you bend it. Keep bending till your tube fits tight against the bevel. The other advantage of this is that you don't even have to know what the angle is, you can set the bevel up against some part of your car that you are trying to follow, or set it by eye or whatever...

[RUFF]

Nam,

Forget that type of bender you need the type that holds the tube at one end and bends it around a die. It does not crush the tube and you can readily repeat the bends. They only cost a couple of hundred bucks.

megaman

Dude if you can find me some of these types of benders for a couple of hundred bucks i know about 10 guys in Brisbane that will buy them tommorrow.
Cheapest we have found so far are the Speedworks benders for around $695 without dies. Add about the same again per pair of Dies.
If you know somewhere as cheap as $200 let us know please.

[POS]

NAM you also have to allow for spring back

For the Bootie fab boys, just use a tree.
(dont laugh its been done)

[awill4x4]

Nam, take it from someone who bends tubing for sprintcar chassis and try to keep it as simple as possible. Although the bender we use is a purpose built electric/hydraulic tube bender, I have used your type in the past.
Get yourself a "line of chords" 2 foot rule (it's like a 1 foot rule which opens up to 2 feet) , a good bevel gauge and a 2 foot flat plate carpenters square.
The chords rule will allow to set any angle you wish in degrees, the bevel gauge I use for getting in tighter areas my rule wont fit.
When using your bender, bend your tube to any angle you wish by using the 2 foot rule along the top or centreline of your tube as you bend it. When the tube is bent to this angle simply look through the frame on your bender where the die comes through.( I usually use the top of the frame) and mark the die with texta. Release the pressure until the tube is no longer under any pressure on the outer rollers. Check the angle, it will be under bent.
Next, start pumping again to the mark you have on the die, but take it a little further and mark again. . Repeat this process till you have a correct angle with pressure released on the tube. You now have a mark on the bender die which you can repeatedly bend tubes to the same angles. Remove the previous marks on the die with thinners. Note these marks change as you change thicknesses so it's a good idea to write these in a notebook with a sketch of die position and tube thickness. Try bending a tube by 10 degree increments and writing down positions on the die. You now have a tube and thickness guide you can readily bend quickly to any angle you require.
It's a little finicky and time consuming but once you have data written down it's easy to repeat it time and time again.
Regards Andrew.
ps sorry for the long post.

[N*A*M]

Andrew and Carlton

Thanks for your contribution. I guess a lot of the maths mumbo jumbo can be junked if there is a good practical and easy to follow method. I'll get set up like suggested.

Also, does anyone know if coating the contact surface between tube and die with something would make a difference in the quality of bend? I tried a thick spray of WD40 on the die before bending some tube - because I thought it would make it easier to remove the die from the tube afterwards. Funnily enough, it seems to get a better result. This was a bend of more than 90* and it looked pretty decent. Would some grease on the die help?

Nam

[Wooders]

Megaman,

I'd also be interested in the few hundred$$ bender....Any details??

[Megaman]

I'll get the details of the bender including photos on the weekend.
And post them on monday.

Megaman

[Damo]

I got more buyers for you. Any details????

[Cheezy4x4]

Just ordered a Speedwerx one with dies. I hope the one you are talking about is crap. No offence but I payed a bit more than a couple of hundred.

[OVERKILL ENG]

Cheezy let me know how your bender goes.The trouble with the cheap ones is that after a while the dies open up and the pipe then kinks.I'm on my second cheap bender whithin 6 months.

[Cheezy4x4]

Sam I had the same prob with mine, so Im biting the bullet and getting a good one.
The dies are $670ea so why dont we all buy a different size and sway around.

[OVERKILL ENG]

How much was the bender?
What size pipe are you using?

[N*A*M]

Whoa expensive! But good idea Cheezy. Cover all bases and get a variety of dies. Where did you order your bender from?

The good thing about the bender I got is that the engineering shop sells the dies separately as well. I could've chosen imperial or metric dies when I bought the bender.

[Cheezy4x4]

Sam the bender was $670 but I also got a notcher. Speedwerx.
Im using 2" Dom for most of my cage with a 120 thou wall.
Im also going to use some 11/2 Dom for other bits.
Some people are saying 2" is to big for the cage, but my POS is heavy and I want to be safe while doing back flips.

[moose]

just bend up some wheelie bars !!!!!

[Hoonz]

bend a round roll cage so when u roll its smooth all the way to the bottom
hah

[OVERKILL ENG]

Cool I will buy one i think. All my tibing is 1'1/4 so I'll buy that die.And if you need that size we can swap.

[Cheezy4x4]

Sam I have 2" die, and soon hope to be moving alittle closer to you.

[Ferwoaza]

Your emigrating from mexico cheezy??

Sam..where do you get your tube from? I'm just getting into fabricating and dunno a good place to get steel, tube, metal in general Gunna need some to space up my front n rear bars after the body lift too :|

Megaman, any news on that cheap bender yet?

[M&M Custom Engineerin]

Megaman, any news on that cheap bender yet?

I second that.

[OVERKILL ENG]

Cool Cheezy where are you moving to?
Ferwoaza Firequip is where I get all my tubing from, They are fairly cheap but reliable and deliver.

[Strange Rover]

So what sort of tubing is everyone using. Is it called DOM tubing?? Seemless pipe?? What sort of dollars is the stuff worth?

Sam

[bj on roids]

Megaman, any news on that cheap bender yet?

I second that.

can i third it?

[Wooders]

So what sort of tubing is everyone using. Is it called DOM tubing?? Seemless pipe?? What sort of dollars is the stuff worth?

Sam

At this stage I'd be happy to be able to work with plain pipe.....I can't see myself going the DOM tube route.....at this time...