just basically a flat plate with the die and guide mounted to it and the crank bar attached to the die (somehow). the plate could be bolted down flat to a work bench or the bottom T could be bolted to the garage floor. i know it's a super simple MSPaint drawing, but i'm sure you can get the idea. so, question is.... is there something about this design that wouldn't work? AND- where would be the best place to put the handle if this isn't a dumb design? thanks.
it would probably work fine for tube up to 1". maybe 1-1/4" x .063". i am basing this on the fact you can bend conduit by hand in that fashion. you would have to be a bamf to bend 1-1/2" x .120" tube that way.
hmm... i'm beginning to see where the main flaw is. the reason i was having trouble envisioning the leverage (why i stuck the handle right on top, out of ideas...) is because it should be out the other side of the die, right into the floor, the way i have it drawn. so, instead, i'm basically going to order a die, and build sorta the same type manual bender as the JD2 but with the bottom arm (that would mount to the stand) as a wide, flat plate i can bolt to my workbench. i won't need as many holes or pins and such, but i will need to figure out a racheting system of some sort. thanks.
i ordered the plans for that months ago. read everything. it's a pain in the ass. too much involved. i wanted something really simple. in the end, i'll build it and i'll post it.
I am the most crap ass fabricator ever, so I may have no fawking idea what i am talking about but here it goes.
You could use a rocker link(MTB tech) and achieve better leverage ratios. Make an L shape with the pivot at the intersection of the L. short end goes to the die and then the long end could get a straight handle. The ratio of the short compared to the long end of the L should be your mechanical advantage.
a 1 1/4 emt bender has a 5 foot handle, and is hard to bend. Anything larger than that and it can't be done by hand without assistance (electric,hydro).
LOL, you're too kind. I was gonna tell him not to bother. If it's too much trouble to make a real bender, it's obviously too much trouble to bend tube!
Did a little math, at work so I don't have my bender to do "exact" calc's.
Figured from the main pivot point to the hinge point for the ratchet arm is 3". Then figure you have a 4' lever, that your pulling on which applies a moment to another arm that is probably 20" in length that applies a moment to the pin that goes thru the die with its main pivot point thru the center of the die. Then I figured to do more than 90* bend on 1.75 OD .120 wall I can put 100 lbs of force on the handle, maybe more, I don't know. I weigh about 180ish and find myself smoothly pulling not yanking on the handle to get it to bend.
So using these calc's that means with 100 lbs of exerted force on the handle you have roughly 8000 lbs of force being applied to the pin thru the die to rotate it. If your putting about 150 lbs of force on the handle that means your puttin about 12,000 lbs of force. Now when I get home I could get accurate measurements and rework these numbers but I'm just trying to show how much force it takes to bend tubing. Hence why copperhead fab recommend you put the HF 8 ton ram on the bender.
Possibly you could rig something up with a HD hand winch and cable and pullies but the mechanical linkage that these benders use is probably about as simple as you'll find to apply the necessary force manually. Now if you use a simple hand pump hydro cylinder, you could make something like the link below has:
If your objective is to save some money, then I say fail. By the time you buy a die, the material and spend all that fab time, you will more than likely have spent as much or more than if you just buy a bender. If you're just bore and want to fawk around with an idea, then do it.
looks like he made the die. nice job that thing bends tight.
the die in the thread starter is only supported on one side so the bolt/pin that would attach it to the big plate would have to be preaty tight. i would add another side to the bender.
if your looking for a cheap way to bend tube theres a harbor freight tube kinker modification that can turn out was seams like some decnt bends.
actually, my experience with using a single bolt has been good.. i bet i could bend without a nut on the thing at all. once you load the die, the tube finds its center in the shoe and thats it. mine DOESNT work as well with the center bolt tight than it does loose for this reason.
correct, i made the die.
those saying it can't be done, you're just guessing. :shaking: i know this because i've bent 1.75x .120 wall in another homemade manual bender.
the JD2 bender is about as cheap as it gets! they use a 5 foot bar on it and it builds alot of force. we can bend 1 1/2 x .120 wall and only use about three feet of the lever. there unit works so well i cant see any need to build my own. its kind of a wast of time and funds to build one. i would rather use my time to build my rig or one for my wife or 7 year old girl.
Alot of bigger manafacturing benders are single shear on the die side of things. You just need a bigger better alloy pin and a thick enough base plate.
If your really wanted to have fun you could use chain and gears and a gear box to make a cool hand crank bender.
I'm an engineer for company that build cnc tube benders. I ran the numbers on bending 1 3/4" x .120 wall DOM Mild steel tube on a 6.5" CLR. It takes 3800 ft.lbs. of torque to bend the tube. So even if your a bad ass and you can pull with 200lbs. of force, you'll need a pull at the end of a 19' long bar. Good luck with that.
The force exerted on the follower and counteracted by the bend die pin is 4600lbs for the same tube.
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