metalanton Posted July 16, 2015 Share Posted July 16, 2015 I recently came across a pile of hydraulic cylinders at the scrap yard that were something like 5" bore and 30" long.. i didn't have a tape measure. anyway, I wanted to build a fairly compact forging press kindof like randy mcdaniel's H-frame so i decided to pass on these. Now that i have been thinking about it, i thought maybe a press could be made in which the cylinders are configured like a KA75, so that the compression stroke of the cylinders would close the dies of the press. I understand that the compression stroke of these cylinders has less strength than the extension due to the reduced surface area from the piston rod on the compression stroke. but In this case i think it would only reduce the tonnage by 5 ton or so, so not a big deal. So my idea was to mount the two cylinders vertically with the pistons pointing up and create a solid base and bottom "anvil" for supporting the cylinders. Then I was thinking that the upper die could be made quite sturdy to alleviate any torsion between the two pistons and ensure that they travel parallel and in synchronicity... but this would require that the pistons take on the guiding of the upper die.. this to me would be a huge advantage in ease of construction since no other framework would be necessary for guiding the upper die. My questions are the following?Has anyone done this? I am thinking if no there must be a good reasonDoes anyone with hydraulic cylinder experience know if the pistons will guide the dies effectively and most importantly safely?Used hydraulic cylinders any good? I have heard of others using cylinders from the scrap yard, are they usually rebuildable, or not worth the trouble.. they are tie rod cylinders probably from a backhoe. i could get them for 40$ each probably Quote Link to comment Share on other sites More sharing options...
LastRonin Posted July 16, 2015 Share Posted July 16, 2015 I haven't built one yet myself, but do work in an industry that deals with pressurized cylinders, so the statement I am about to make comes from solid foundation... If you do not know the pressure rating of the cylinders, do NOT try to use them. High pressure blowouts (especially of flammable things like hydraulic fluid around forge temperature items) is dangerous... Life threateningly. Not just to you, but anyone nearby. Quote Link to comment Share on other sites More sharing options...
metalanton Posted July 16, 2015 Author Share Posted July 16, 2015 thanks, that is definitely sound and very wise advice. How about the idea of using the compression stroke of the cylinder as the forging stroke and/or eliminating guides? Quote Link to comment Share on other sites More sharing options...
arftist Posted July 16, 2015 Share Posted July 16, 2015 The reason is as you already stated, less force. To answer your other question, yes, cylinders are readily rebuildable, especially tie rod cylinders (easier). Quote Link to comment Share on other sites More sharing options...
j.w.s. Posted July 16, 2015 Share Posted July 16, 2015 Depends on what the rod diameter is for the retraction force and what pressure you're feeding into it. A 1" rod at 3000psi would pull at about 56k lbs, a 2" rod would be about 49k lbs. Still, a 25 ton press can move some metal, but it's really going to depend on your engineering skills and I'd take those cylinders and have them repacked before using them which may not be cheap. I thought about doing a ka75 style press, but couldn't find a matching cylinder for the one I already had.-J Quote Link to comment Share on other sites More sharing options...
metalanton Posted July 16, 2015 Author Share Posted July 16, 2015 no that I am thinking about this more, I think I will pass in the junk yard cylinders. I have seen some of the industrial cylinders with mounting plates on the piston end. it seems to me this plate could be simply mounted to some heavy bar, say 2" by 6" ( maybe even using wide channel with a reinforced lower die plate) and holes drilled so that the piston could pass through the bar then a top die plate could be made. the lower plate could be reinforced with steel plate on its sides in a triangular shape or even just heavy plate extending all the way to the ground acting as a base . this base could encase and protect all of the hydraulics. just some thoughts seems extremely simple to build... almost worth losing the extra tonnage form using the pull stroke. J.W.S I would love to hear more about the press you were thinking about designing Quote Link to comment Share on other sites More sharing options...
monstermetal Posted July 17, 2015 Share Posted July 17, 2015 There are real issues about getting both cylinders to pull and push the same, on a guided press the guide helps to keep the cylinders square. Another real concern is bending a rod. A 1.5" rod will not deflect much with all the force straight on it but get a side load and it does not take much, far less than what would be generated by the press. I have one of the only KA150's Grant ever built, one of the reasons why they did not continue to build the 150'lb version was they destroyed themselves. Mine has been rebuilt several times. Quote Link to comment Share on other sites More sharing options...
metalanton Posted July 17, 2015 Author Share Posted July 17, 2015 Thanks monstermetal, that makes a lot of sense, I knew their must be some reason that presses were not built this way Quote Link to comment Share on other sites More sharing options...
JNewman Posted July 17, 2015 Share Posted July 17, 2015 Be careful to do the math on a new press design and or WAY OVERBUILD. Unlike a hammer a press stores energy and a failure unleashes all that energy very quickly. The Jim Batson book is a very good source for how to do the math. Quote Link to comment Share on other sites More sharing options...
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