Re: how to homebrew a 7000-psi mechanical press?

On 20 Apr 2005 00:18:59 -0700, alanh snipped-for-privacy@yahoo.com wrote:


[newsgroup list trimmed away from hobby groups etc.]
Uh, oh!
Here comes another student with a coconut-crusher homework project.
Hint: a screw press with a nice weight on the screw lever does well. Or try my crusher: a wooden lever on the classical nut-cracker design, writ large.
Brian Whatcott
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Anthony wrote: > alanh snipped-for-privacy@yahoo.com wrote in > > >>how to design a 7000-psi mechanical press using standard (preferably, >>Home-Depot) available components? >> >>application is separation of edible-oils from an agricultural crop. >> > > > pressure = force x area > > So you first need to determine the working area of the device. This > will tell you how much force you need total. At that required psi, you > are most likely going to need some power assistance.
If you use a hydraulic ram to provide the force, and the working area of the press is the same as the cross-sectional area of the ram, the oil pressure inside your ram would need to be 7000 psi. This is attainable without too much difficulty. The manually operated hydraulic presses manufactured by Fred S. Carver, Inc. for science laboratories (which essentially use a very nicely made bottle jack to provide the force) go up to 10000 psi on 1 1/4 inch diameter rams and larger. Unless you need the press to be huge, or you need it to open and close very quickly, you can probably manage without power assistance. Power assistance complicates the project because you'll need a fair number of safety features to make sure you can't injure yourself. Your best bet is probably to buy a large bottle jack (here in England you can get a basic 20 ton jack for about 50) and build a sturdy steel frame around it.
Hope this helps,
Chris
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alanh snipped-for-privacy@yahoo.com wrote: > how to design a 7000-psi mechanical press using standard (preferably, > Home-Depot) available components? > > application is separation of edible-oils from an agricultural crop.
This seems to have turned into a huge argument, but don't worry as it's not uncommon on USENET! People have suggested three workable solutions to the problem: hydraulic bottle jacks, screw jacks and gears/rollers. Which one of these is best will depend on how fast you want to process the crop (a press for extracting small samples of oil for scientific purposes is likely to be quite different in design to a press for extracting oil in volume for consumption), your budget, what parts you possess or can obtain and what workshop facilities you have. Can you provide us with any further information?
Best wishes,
Chris Tidy
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I'll type this really, really slowly... [first removing the hobby group list though]
A force of 1000 lbs applied to a die with a 1/7 sq inch cross section exerts a pressure of 7000 psi.
Brian Whatcott Altus, OK

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Gentlemen...........
Since many of you have obviously earned scientific credentials and since you seem to have some familiarity with computer protocol, would it be too much to politely request that you refrain from posting in multiple newsgroups?
Many of your remarks are directed at your friends and acquaintenances in your usual haunts. I know this was originally the "fault" of the OP, but it need not continue endlessly. Please be assured I am aware of the options of ignoring the thread or taking up knitting. But this mindless blather about "When is a pound a pound?" is getting tiresome. Write something interesting once in a while.
Sorry - rant mode off. Isn't the weather nice? - or maybe you're in Michigan. . .
Rich
P.S. Just to piss everyone off equally - it is spelled "hydraulic".
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Posting to rec.crafts.metalworking and sci.engr.mech only.
<snip>

Perhaps my statement was a little too broad. I take your point that if you have a rapid and sustained input of energy to a hydraulic system, you could see a dramatic rupture. But you'd need a large motorised pump or accumulator to supply the energy. I don't believe this is a danger in a small system using a hand pump as discussed here.
Chris
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Posting to rec.crafts.metalworking and sci.engr.mech only.
<snip>

That would be an insane machine to try to build :-).

Maybe it's just me, but I think reliability should always be a design criterion.

I think you'd find that the mechanism would rapidly get worn/distorted to the point at which there was no pressure between the tamper and backplate.
As Rich S. pointed out yesterday, this thread is reaching the end of its useful life, so I'll leave it here!
Chris
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