bottle jack press using air

I saw a picture of a small press and it had a standard looking bottle jack with an air hose hooked up to it for power. Can someone explain
how this works and do you get anywhere near the same force using 100 psi from shop compressor as from using the pump lever. Thanks, Bob
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They are called Air-over-hydraulic bottle jacks and can be purchased for a little more money than a standard bottle jack. The biggest ones available are 20 ton. I used one for my shop press. It cost around $80 for the bottle jack. Northern Tool sells them.
<http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?st oreIdi70&langId=-1&catalogId@06970&PHOTOS=on&TEST=Y&productId 0056 874&categoryId555>
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Ernie Leimkuhler wrote:

Does the "air" cylinder on those kinds of jacks shuttle back and forth when operating?
I once had a vacuum operated car air horn compressor which worked that way, the vacum pulled on a diaphragm which operated a little piston to compress the air to (I'm guessing) 50 psi or so. It purred away and stored the air in what was about a half gallon tank.
Jeff
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An air cylinder, you operate the lever and it goes "swoosh" and smoothly extends or retracts. A lever-operated hydraulic cylinder, you go "pump-pump" and it extends or retracts in little steps. An air-over-hydraulic cylinder, you operate the lever and it goes "phuh-duh-duh" and and it extends or retracts in little steps. They are just like lever-operated ones only faster and less work. In fact, all of them that I've seen (all 2) also operate in lever mode.
I have an 8-ton long-throw one mounted on my engine hoist now. I use my engine hoist a lot, and it saves a lot of work.
Grant Erwin Kirkland, Washington
Jeff Wisnia wrote:

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On 23 Feb 2004 00:17:51 -0800, snipped-for-privacy@mwt.net (Bob) wrote:

The 100 psi basically does the same job as the pump lever. Instead of you pumping it up and down, the air pumps a piston with hydraulic fluid on the other side. From there it operates like normal hydraulic jack.
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