I want to build a hydraulic press, basically an over sized "H" frame press. Shooting for 50" between centers so can get something 48" inside to bend. Hopping to bend 1/8" material full 48". Hope to bend ¼" at 12"±. Am expecting to use 3 cylinders across the top - each end and center. Besides bending things, want to use also like a plain shop press. Looking to make the attachments/adapters to switch from bending to pressing. Expect uprights to be maybe 8" "H" beams. Tons? What do I need for 50 ton? Or is this realistic? I have a pump rated for 10kpsi. 1/2 or 3/4 hp I think. 8" stroke should me plenty. Or am I dreaming. The welding.... no problem. Plumbing... I think I can handle. Just don't have a clue what rams or size needed to do the job. So.... If there is anyone out there that kinda knows some about this stuff and can pass along any suggestions, thanks. Or if this is not feasible to build... say so. But thanks for any input.

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Regardless of age this thread might get, feel free to add to it please.

It's feasable. Hell, anything is feasible if it's budgetable. . lol.

Do you mean something like this, but with rollers for bending the material?

Well the one in the pic is advertised as a 50 ton press. I know exactly what you're talking about building. pins should work, but I'd suggest trying to find some chomemoly to make them from. They do make Porta-Powers that are rated for the kind of tonnage you want (I used to use them to align 12 and 14 cyl engines weighing 20 tons dry after we set them on the skids) but they are pricey.

you could possibly valve two or three of them in tandem as long as you had a sufficient reservior. Also remember that most of these cylinders are directionally valved meaning they dont just retract. you have to power them back to zero extension.

One obstical may be the length of stroke you want. You may have to settle for a max extension of about 5".

Other than that, proper metallurgy will be absolutely vital. (How will you be welding this thing) Pre-heating and controlled cooling are going to be vital whenever you start welding this thing out, and stock alloy will be just as important. With kind of operating pressures you're talking about being capable of, one flawed weld could cause a catastrophy.

Just a side note, We have a 100 ton press in our machine shop at sherwin thats as tall as my house. I mean this thing is MASSIVE. It was machined, welded, and built cylinders (2) and all inside the building back in the early 70's. It was used to press on brass bearings that were in what ammounts to the worlds largest rock tumbler... So at this point I have to ask... what in the world are you bending?

Sorry for the ten year long post.

-Kenny

This is interesting... http://www.gregsmithequipment.com/50-Ton-Air-Hydraulic-Shop-Press-p/ht0811.htm

Could maybe be modified.....

I used to have a friend that built trash dumpsters, and I was able to go mouch the press brake and shear - both would bend/chomp ¼" 8' long. Man, that was nice. Well, he isn't in business any more. So... I was thinking of making my own press brake that would bend 1/8" up to 48" long, and maybe ¼" up to 12" wide... Mostly just odds and ends when I am making something, nothing specific. And wanted to make attachments so could also us it as a "shop-press" to push things apart and together when needed. The little "porta-press" I have just don't cut it most of the time. Just not big enough sometimes. So, I was thinking of just building something that I could do various things with.
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5" stroke would/should be good. Just some of the shortest cylinders I've seen were 8". I just didn't see any need for anything longer... I'm not looking to split fire wood woth it.. As I already have a home made log splitter...
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Thought I'd look at the scrap yard for some old bridge beams to make it from... 8" to 12" beams maybe? H beams prefered. Had considered 1" grade 8 bolts to put it together. Or a combo of bolts and (mig) welding. My mig will handle 200~ish amps on single phase. Miller XMT-304 CC/CV with S-12 4-roller drive. Or could stick weld with the Lincoln 355 square wave tig machine...
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And this might be just more of a project than is worth or that I can handle.... I am expecting this monstrosity to weigh 1k to 2k
# when done. I have a fork lift, and also am going to build a overhead chain hoist. Have the Hoist - 3 ton I think, or is it 6 ton... don't remember - but its thrown back in a corner waiting... Something else to do.
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Ok so, not going to try and quote pascals law (I believe thats the "father" of Hydro) the pressure can be made by changing the initial push piston size to the force piston size. Think of your break system. The power booster pushes a 1/4" inch piston but at the force side (caliper) your pushing a 1-2" piston to compress the shoes on the rotor. The total pressure is well over 100 psi. (would have to calculate I'm using general number here, based of ford system....i.e. Jeep noob) anyways, If you make this with a small piston at the lever side so that your piston pushing down at the bending side is larger, the force pressure increases exponentially while maintaining low line pressure. This will increase function but maintain safety.
As for smooth bends you'll need to create a jig for the basic bend, then set a compass measurement to measure degree of bend angle while bending. (think tube bender tool) I agree with going chromolly. It is stronger and can handle pressure better without warping itself.

hope this helps, I am not an engineer. Just using physics class and getting idea from brake system function. I do work with engineers and can ask them how they would do it for ya.