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-   -   Tubing bender (http://www.risingsun4x4club.org/forum2/showthread.php?t=18494)

OilHammer 09-14-2012 03:09 PM

Tubing bender
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Anyone know much about bending rectangular tube, both steel and aluminum?

I'm looking to bend 1x2 in both the long and short dimension, but I would rather it not distort. Wondering what my min radius is to do that. I assume that radius is tighter for steel than aluminum.

And if distortion is unavoidable, how tight can I bend it regardless?

Oh, found this interesting article on the web. Guy made a bender out of an old brake drum and that gave me an idea. http://www.thefont.info/tubebender/tube_bender.htm

Why not take two brake rotors, one off of a tiny econobox and then find a slightly larger rotor to fits over the top of the raised "hat". Then you have an adjustable tubing bender! Well, the basis of one anyway.

nakman 09-14-2012 03:19 PM

You know there's this guy in Durango who bends square tubes to make cargo barriers... nah, that'd be too easy. :bolt:

OilHammer 09-14-2012 04:02 PM

I don't think it's that easy. I think my radius on the end is too tight for either Al or MS. I may need to CNC that whole end and then sleeve a larger tube onto it about where the line is in the drawing. The long "bow" bend in the middle is much easier.

Uncle Ben 09-14-2012 04:23 PM

Your rotor idea will work if you design a follower that keeps the tube feeding onto the curve of the bender at a consistent height. You could also use the rotor set up in a press with consistent followers on each side to ensure uniformity. I'm sure you are aware that square or rectangular tubing will distort along the sides because of the top and bottom parallels bending on different radius. If your die has immovable sides that are the width of your material the distortion will be a nice trough inward on both sides. If you die is wider than the material the distortion will be outward and the material will flatten. You might try the filling the tube with sand (cheap mandrel) trick....not sure that will work or not, it depends on how compressible your sand (media in the void) is. I have no idea of how to make a real mandrel bender for square stock but I would bet someone does!

Looking at your cad....have you considered chatting with the Millers at Epocs? The unit could be made by cad laser cutting the 4 sides of the tube and welding them together!

OilHammer 09-14-2012 04:50 PM

I'm looking to make my first unit myself if I can, or at least make sure I'm designing something that can be manufactured easily enough. While laser cutting and then welding together is an option, my guess would be the cost will skyrocket if we have to do that. It would probably be cheaper to just change the design and put in hard angles and just weld in those places. But....if I can get it all bent and minimize the welding, it will be a lot better looking and cheaper to make/sell.

Thanks for the input though, keep the ideas coming! I can't disclose what it is just yet, but once I have a functioning prototype in my hot little hands, I will. :)
This is by far the most complicated component of the device, so once I have this resolved, the rest will happen pretty quickly.

Corbet 09-14-2012 07:08 PM

The JD Squared model 32 bender I use does not offer dies for rectangular tubing just square.

What radius are you attempting to bend at? For example the 3/4" square I use for barriers is bent at 3". That is the tightest they offer for the tubing size. Round can be bent tighter, I have a 3/4 round at 2.25" radius. Mine indent both the inner and outer surfaces while the sides remain pretty much as is.

Building one is definitely possible but might be more of a PITA than its worth depending on how much bending you want to do and how accurate it needs to be. I can reproduce things pretty consistently, you may not be able to on a home made unit.

You might be able to get two square dies and stack the tubes to achieve 1x2" It just depends what your trying to do. I've never seen a rectangular bending die but honestly have never looked.

OilHammer 09-17-2012 09:58 AM

Decided to just go ahead and build the first proto with round tube. I will need to smash the ends to mate up with what I was thinking design wise, but that's really not the end of the world, and likely far cheaper. I was so caught up with the look of it, I forgot that what I'm really after for now is functionality. So...that would mean the first one is steel and round. If I get it worked out, I'll want to go aluminum and honestly, I'm not sure the square is necessary at all.

Overlander 09-18-2012 02:23 PM

I've learned a neat trick from one of the videos on the internet: you can fill the square tube with sand before bending it - to minimize the squashing effect. The sand keeps the walls from collapsing.... you should probably heat the outside of the tube to allow it to stretch.

Secondly, if the esthetics don't have to be perfect, you could cut small notches on the inside of the bend - this allows the outside of the material to stretch normally and the inside to be compressed naturally into space (where some of the material has been removed) - once you achieve the radius you want, you can then weld over the cuts and smooth out with the grinder - that's what I did for my sliders and it worked fine - since I didn't have a tube bender.


frontrange 09-18-2012 03:42 PM

Cerrobend works better than sand for a one-off setup, it's a very low temperature melt alloy.

My bending dies for square tube have a convex inner contour to push in the inside of the tube as it wraps around the die. I'd think you'd get a mess of a bend without that action.

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