Passenger

No, that is not a mandrel bender, a mandrel bender has a mandrel/die that goes on the I.D. of the tube to maintain the I.D. on the radius.

Passenger

To answer the water thing, you can't. The reason being is that the tubing does need compress in the radius. Filling it full of water will not allow it to compress and by either adding more ram pressure(I don't care how strong you think you are you will need hydraulics) or heat to complete the bend you will merely just blow the tube up, literally.

mandrel-bends

Thin wall / Tight Radius cannot be bent on anything but a mandrel bender, and it's not just any mandrel bender that will do it. As the "D" (ratio of tube outside diameter to radius) of the material gets closer to 1, the bender has to become more sophisticated, so it gets even further complicated w/ pressure die assist, direct pressure profiling, boost pressure profiling, early extract points, etc. The material has to be literally pushed and boosted around the outside of the bend. The mandrel itself is only part of the system that prevents the wrinkles or tube collapsing. There is so much more to it.

If you go to page 15 of omni'x mandrel bending guide here (http://www.omnibend.com/pdfs/Omni-X_...ding_Guide.pdf), there is a chart that will help you calculate what you can and cant bend with a normal rotary draw bender, and even just a normal mandrel bender. Say you wanted to bend 1.65" stainless w/ a .065 wall thickness, you would divide 1.65/.065 = 25. Then you go over to your radius chart and look for the first radius that doesnt require a mandrel or wiper. In this case, it's 5D (radius = 1.65*5= 8.25" CLR) can be bent without mandrel or wiper. So any single shot rotary bender could do that. But notice you have to increase your wall thickness to say 0.095 (1.65/.095 = 15) if you want to bend that on 4D radius. Then of course the other problem is, the larger your wall, the larger the torque requirments on the bender. When you start getting to 0.095 ss-304 ... Most normally rotary benders are going to come up lacking in torque. Not to mention .. How useful is a 8" CLR for headers? Not very... (That's a 16" u-bend between centers!)

Tom-Guy

I have a copy of the article on sand bending... somewhere. Be prepared to go through some oxy-fuel as you need a lot of heat.

mandrel-bends

The heat / sand bending technique is basically used in the industrial world with induction benders, where they super heat the material and draw it on a pivot point sometimes over a mandrel as opposed to capping the pipe with sand. Although this works, it won't do thin wall on a tight radius. Most induction bends are 3D or larger.

There's a beautiful picture of an induction bender here:

http://www.pipebending.com/

Eville140

I think I have a couple of them out in the barn, will check later.

Shame there isn't a place that sponsors this site and even gives discounts on these types of materials. And I bet if buying in bulk they might even give a better price? maybe?

Hmmm, shame there is nothing like that.

Captain Bondo

Passenger,

I got ya I think- I can see why you can't just load it up full of something completely uncompressible and expect it to cooperate. Cheers.

Columbia,

Super educational posts, very much appreciated!

Eville,

For all of the 16ga stuff I do, my bends currently come from Racing Solutions/Columbia, just for the record.

The point is that if a guy's volumes keep going up, at some stage it makes sense to start bending his own. Don't misread this to think I'm trying to be some sort of ******** - that's not it all all. I just want to try to run an efficient business - bending my own and being able to do things like pre-bend the more simple runners in one piece, etc. could save me a lot of time and costs, and that means doing it myself ideally.

My best bet is to probably stay on the lookout for a used mandrel bender I guess.

Thanks guys!

malibutwinturbo

since i mandrel bend pipe for a living, once you see how one works, you'll quickly realise how you won't be able to pull anything off using a crush bender

mandrel bending is basically extruding the pipe over a mandrel versus just compressing it around a die like a crusher

Tom-Guy

I've watched a two stroke guy fix a dented exhaust by capping one end, pressurizing the other with shop air, and geeeeeeeently heating the dented area. I think you could manage to uncrush some crush bent by this method.

Smith-02

probably the easiest HMT sort of thing to build now that i think about it. i think i'll put my big ------- hydraulic ram to use on somethin like this