Pipe Bender

Hi Guys
I haven't posted in a while I've been working my tail off here to get my small bussiness moving. I'm trying to put a Professional type mandrel bender together for less then a thousand dollars. This is primarily for bending exhaust tubing not heavy wall pipe. 3" or less, sometimes SS.
The first bender setup I put together didn't work well and just crushed the pipe. I basically took a brand new 25 ton log splitter as a base to work with and tried to do a ram type bender with two swing arms like this one here:


Also it bent the swing arms I had placed improperly.
So I had to go Back to the drawing Board. I looked at the Blind Chicken Bender a friend sent me this link to and I thought I might do that one.

http://www.blindchickenracing.com/Tools/Tube%20Bender/Tubingbender.htm

I kept searching and found this one which I think is a better fit to the log splitter design:

http://www.exm.netfirms.com/Bender/Diagrams.htm

and a whole discussion on building it here

http://www.pirate4x4.com/forum/showthread.php?t=185940&page=12

Its basically a JD2 Model 3 bender.
The JD2 does not bend 2 1/2" or 3" but I plan to make it a bit beefier to accommodate 3" bending Dies, so I can bend the 3" exhaust tubing.
What I am planning to do is instead of using 3/8 plate for the construction I want to cut out 1/2" and double it up making each piece now 1" thick. Then spend half the day drilling holes. The Pins used on the JD only cost about $10 for all of them but would likely be too short for the 1" plate. I was also concerned that 1" pins may not hold up to the stress of 3" bending.
I had made my first 2 1/2" die by stacking 3 plates with layers of plywood and running a drum sander through the curves:


I cant afford the machine I want right now and if I could I'd likely get a big 16" lathe and a Bridgeport vertical mill. It's in the neighborhood of $7-8000.

RMD Model 500-S
http://www.bii1.com/benders_b1b.htm

Anyway after all this explaining I was wondering if someone here could help with any recommendations for the pins.
Diameter of stock? Metal choice?
I have a SouthBend H10 I should be able to cut them without to much issue.
Thanks
John

A #2 Hossfeld has 1" pins. I do know that and somebody recently had a link to plans for a like bender here. You might search the general forum for that link.

I use 1" 4140HT for pins in my hydraulic hossfeld copy.

Real Hossfeld pins are also decent carbon content, and heat treated 1" diameter.
And they wont bend 3".
2" is about the max with the construction of a hossfeld.
I would go up to 1 1/4" pins. Maybe even 1 1/2".

What you want to build is quite a hefty machine- if you dont make it herky, it will continue to break parts.
There is a reason why they cost as much as they do, industrially.

Real Hossfelds do bend 2" iron pipe and I do not think the pins are the limiting factor, its the bending arms. How 3" thin wall compares to 2" pipe in the bender I would like to know.

I have bent the 1" pins on a hossfeld, and snapped the 3/4" pins that hold in the dies.
Guess I dont know my own strength.

I have also bent a lot of 2" schedule 40 stainless. Yep, it can be done, but the hossfeld is working pretty hard to do it.

Dies to bend 3" wouldnt fit in a hossfeld- there wouldnt be enough meat left in em, if you made em only 4" tall.
For tubing, you want a U die and a wiper die- and a lot of oomph to push it.

The commercial model he links to weighs 1800lbs- at current new steel prices, thats almost a grand just in steel. Not counting electrics, a computer, a hydraulic pump that draws 30 amps- whats that, about 3 hp?
That machine retails for 25 grand, not 7 or 8.
http://www.machinetoolsjwk.com/rmd%20rotary%20draw%20bender.htm
For 7 or 8 you can get one that will bend 2".

Forces increase rather rapidly as sizes go up, usually going up by the square in force when the material cross section doubles.

There aint no free lunch- you cant just pick a number out of the air, and say, I want to build a Caterpillar D9 for $6000 from scratch. Or, I have ten grand, and I am going to build a space shuttle.

Big machines cost big money. If those guys could get away building a 3" tube bender for $1000 in parts, believe me, they would.
Of the 25 grand, I doubt they are making more than 5% to 10% in profit, the rest is the cost of building the thing.

For a lot of info on bending and other bending machines, go over to bend-tech.com or offroadfabnet.com
Clint (goes by Bandit) built his own and has a THOROUGH build including adding NC controller, etc.. Very informative.

I have bent the 1" pins on a hossfeld

Click to expand...

Really suprised to hear that. I would have thought they would "snap" like the 3/4"s which I have done myself. Usually takes an interference to even do that. Maybe your 1" pin was a homemade one out of HRS instead of 4140HT.

Professional type mandrel bender together for less then a thousand dollars

Click to expand...

None of the links are to mandrel benders.

You'd probably have to go to a radius of at least 4x the diameter to bend 3" exhaust tubing without crushing or wrinkling if you were using a JD2 type bender. Someone *might* make the die and follower block of that size for a thousand bucks, but I wouldn't and I've made a bunch of dies for use in those types of benders.

Check out this site. I found it looking at boats one evening and it has a link to a site with pics or cad files for a homemade hydralic pipe bender.

Glen's backyard boat building

Good luck,

Todd

Ok, I'll admit I just put my foot in my mouth with the price on the 500.
I went Back and looked at the pricing for the different models and the price that stuck in my head was for the RMD-150 Bender not the RMD 500
RMD - 150 Hydraulic Rotary Draw Bender
Capacity is up to 2 inch Schedule 40 Pipe, 2 inch square tubing, 2-1/2 inch Chromolly (up to .083 wall)
List Price: $5850. Optional Angle-Autostop.
But Note the wall thickness of the 2 inch.
Exhaust tubing, even 3" has a wall of no more than 1/16 th of an inch 0.0625 and I'm not positive but I think its more like 0.045 wall. most guys just want aluminized welded seem steel tube.
The SS is $38 a foot for 2 1/2 inch around here and the 3 inch is like $44 per ft.
I'm looking to bend radius's of no tighter than say 6 inch dia as the only thing that would require a tighter bend would be a header and I don't see anything coming way that's got 2 1/2 inch or 3 inch ports on the heads. Most will be 8 or 10 inches.

This isn't an Earth mover and I'm not trying to Build a Saturn V rocket here.

Todd - Glens bender id a variation of the BlindChicken bender. As I don't have a mill to cut the roller block I opted for the JD2 which is more easily achieved with a welder, plasma cutter, drill press, and a 10 inch lathe. In the 4x4 thread which is 22 pages long there was discussion of the problems associated with the BlindChicken bender such as the roller block binding.
I didn't want to over think the thing the more parts you have the more the likelihood of a part failure.
The Hosfeld & JD2 designs seem to only be limited by the pins and the thickness of the plate stock you choose. As for the leverage arm I'm Partial to the 5hp Briggs and Stratton &the 25 ton hydraulic ram. I like to remind myself too that a good fulcrum and lever is tough to beat.
Also I did read somewhere a guy was using pins from Caterpillar Tractors.
I think I'm going to go with the 4140HT
I was also thinking the same thing Ries suggested as far as 1 1/4 or 1 1/2 inch for the pins.
Thanks for the input
John

Power, or the lack of it, isn't the problem. Bender strength isn't the problem either.

If you're using a die with a 6" centerline radius and bending 2" OD tubing, the absolute minimum wall tube you can bend with this type bender will be .095". Anything thinner will wrinkle and flatten on the heel (back side of the bend). As tube OD increases, the ratio of minimum wall to tube OD does not increase in a linear manner. For example, you can easily bend 1" OD x .030 wall tube on a 6" radius, but when you double the diameter to 2", the min wall increases by 3x. These are numbers based on actual bends and not calculated results. I've never seen any formulas for calculating minimum wall for a given tube OD and bend radius. But, one quickly finds the trends are consistent as diameter increases and bend radius is held constant. Going up to 3" tube on a 6" CLR, the trend would predict a minimum wall greater than .200" You *might* bend 3"x 3/16 wall successfully, but I'd bet you can't bend anything thinner. You actually said you wanted to bend on a 6" diameter. If that's what you really meant, that's a 3" centerline radius. About the only 3" stock you would ever bend on a 3" CLR would be solid bar.

If the wall is heavy enough, then the limit for this type bender is strength of the bender itself and the available power. Thin wall material carries its own limitations and the only way to overcome them is to use a larger bend radius. That's why I made a WAG up above of 4x tube diameter for a min bend radius on 3" exhaust tube. FWIW, a die of that size would start with a 24" burnout at least 3.5" thick, weighing over 450#.

MANDREL bender is a whole 'nother thing. Perhaps you are confused, as yes those machines you show bend piped around mandreds, or dies,
but MANDREL BENDING refers to the process of having a slug drawn through INSIDE the tube as it is being bent preventing the collapse of the tube.

Ok
With all the exacting measurements flying my way I was compelled to measure the stock out in the back of the shop. Both the 2 1/2 and 3 inch have a wall of .090 inch not 0.0625 or 0.045 wall as I said earlier.
I also checked the radius of the allow-able hop over the Firebirds axle I have sitting up waiting to get done. The stock pipe was 2inch with 4inch radius bends. This would be 3" and I have 20 inches of room for the 180 deg hop. Minus the 6 inches for tube and I will be at 14 for diameter, but that’s real tight.
Many dies for these benders tend not to stop at 180 deg, more like 220 deg. I have even seen full circular dies for both the center and the follower. Also from all the reading on the forums the followers work best wet (greased). Some guys are using white lithium for lube. Some of the Industrial machines are using Teflon blocks instead of steel.
To get the best fit for some cars the pipes will have to be pieced together and I was expecting this with the firebird particularly because the Guy squeezed a 2001 LS1 corvette engine in it. He's not paying for stainless and is aware that this is a tight fit. I prefer to work trucks as there’s lots of freedom to fit stuff underneath, but the real money is coming my way from the modified cars. I am looking for a used standard machine maybe even a leased one down the road but right now I need a working Tube bender for exhaust that’s 2 1/2 and 3 inch. A decent slip roll would be nice too.

Back before Cad/Cam and DRO calibrated Mandrel benders: How the hell did the guys bend 3" exhaust tubing if they needed a tight bend?
Hand form two Pieces and weld up the seem?

That doesn't come off as practical only if you have no other choice and it can be done, but can we agree it's a time consuming PITA!
I know they didn't worry about fuel economy but even on the real old bikes, trucks, & cars I've seen I don't recall seeing 1/8-inch pipe used for the exhaust. The only heavy part of an exhaust I can recall would be cast headers and couplers (flange plates and such.

Muncher:
You said the pipe would wrinkle anything tighter then a 6 inch on 2 inch with a .095 wall.
Most exhaust benders do leave wrinkles throughout the bend radius.
I do respect you know more about bending equipment then I do, and appreciate your advice. Its not falling on deaf ears.
My Bending experience is based primarily in hand forming metal furniture such as Iron beds, tables, chairs, railing, and brass lamps & chandeliers. For the Brass we would fill the tube with lead/tin mix and then pull the rod around a mandrel to get the desired scroll. Iron pipe worked fine cold but if you placed it into a rod furnace or used a rosebud tip torch you could follow the form pretty easily without crushing the pipe.
Even though the ram setup I started with bent the swing arms the partial bend I got went smooth for what it bent. It was the 1/2inch plate that failed not the 2 1/2" tube. I set it up by gusseting the plates for strength but my pivot points were too far out and it twisted the plates.

The JD2 is more like a roll form then a ram and the appeal of the design particularly for the guys in the 4x4 forum was that there is no indentation on the inside of the tubing’s radius like with the ram type. That weakens the Roll cages and Framework they were building they are building. The NHRA type Roll cages Ive installed are usually only 1 7/8 to 2 1/4 inch max pipe with .125 wall.
For now I just need a rig that will get me by for a while till I can sock away enough to get the machine I really want and need.
I need the bender for smaller stuff anyway. Stock exhaust is usually smaller the 2 inches too. So in the event that this really doesn’t work I can always go pick up pre-bends and piece the jobs together till I can get a better machine.
Thanks
John

One thing you gotta remember- they didnt do this in the old days.
I have never seen an old car, like even a 60's or 50's car, that came stock with 3" exhaust tube.
More like 1 1/2" from the factory.
Hot rodders ran as little exhaust as possible back in the 50's. Straight pipes if possible, cutouts when they had to have a muffler.
Old time hot rods are often amazingly crude in real life- they were scabbed together by guys who didnt have any tools, much less machining or welding experience, from $25 cars. I have seen a few originals, like Robert Williams old 32 ford, that he hot rodded way back when, when he was art director for Big Daddy Roth- no slick 3" exhaust in that baby, believe me.

We know a lot more about how engines work now, and use materials and sizes that were never used either stock or custom back in the old days.

Anyway, I think Metalmuncher is right in that you should build your dies with the largest radius you can get away with.
For a one shot, you just might be able to get your plywood die to work. And you can certainly heat the stainless to bend it. Wet down the die first with water- this is an old glassblowers trick- they blow hot glass into short run dies made from old oak pallets- just soak em with water.

Depending on your alloy of stainless, if its a 300 series, you could anneal it first to make it bend easier- run it up to red hot with a forge or a rosebud, then immediately quench in cold water. A big washtub or something. This will anneal 304, to its softest state, and make it a lot easier to cold bend afterwards.

If it was me, rather than trying to re-invent the wheel, I would buy a JD2 bender- they are only a few hundred bucks- then make spacer blocks for it to fatten the gap up enough to get your bigger homemade die in it- a stock hossfeld has a 4" gap between the top and bottom bending arms, and I think that is what a JD2 is also- so jack it up to 5", build your one shot plywood die, and bend one.

While it is not as complicated as a space shuttle, building a really decent working hydraulic bender is not as easy as just slapping a cylinder on. How much is your time worth?