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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Wondering about air-over-hydralic jack
When an hydraulic jack is used in a press, there is very little stored
energy. So if you're pressing something and it's sticking, but suddenly lets go, nothing happens. But in air over hydraulic, there is a lot of stored energy. Do you get a "lurch" when something sticks and then lets go? Or is there something built into the jack to control this? E.g., a flow-restricting orifice? Thanks, Bob |
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The foot controlled units like Enerpac are a piston arrangement that cycles.
When you press on the treadle the air shuttles a pistion back and forth pumping hydraulic fluid. We have one at work that we use once and awhile when we have to use the porta-power cyuylinder repeatedly. The air is only causing a little hydraulic piston to cycle. On ours if you press the other side of the treadle the cylinder bleeds fluid and retracts. Randy "Bob Engelhardt" wrote in message news When an hydraulic jack is used in a press, there is very little stored energy. So if you're pressing something and it's sticking, but suddenly lets go, nothing happens. But in air over hydraulic, there is a lot of stored energy. Do you get a "lurch" when something sticks and then lets go? Or is there something built into the jack to control this? E.g., a flow-restricting orifice? Thanks, Bob |
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Bob Engelhardt wrote:
When an hydraulic jack is used in a press, there is very little stored energy. So if you're pressing something and it's sticking, but suddenly lets go, nothing happens. But in air over hydraulic, there is a lot of stored energy. Do you get a "lurch" when something sticks and then lets go? Or is there something built into the jack to control this? E.g., a flow-restricting orifice? Thanks, Bob The "stored energy" should never exceed one pump stroke worth of ram travel, probably about 1/8" max. The air cylinder is just operating a second small hydraulic piston pump, one pump stroke per air cylinder stroke. Pete C. |
#4
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Bob Engelhardt wrote:
When an hydraulic jack is used in a press, there is very little stored energy. So if you're pressing something and it's sticking, but suddenly lets go, nothing happens. But in air over hydraulic, there is a lot of stored energy. Do you get a "lurch" when something sticks and then lets go? Or is there something built into the jack to control this? E.g., a flow-restricting orifice? Thanks, Bob Bob, you're confused about AOH jacks. The air motor just pumps for you, they act exactly like a hand pump hydraulic jack, only faster. I have a 20 ton press with a 20 ton AOH bottle jack on it, $79.95 at Harbor Freight a few weeks ago. It is just what you want -- use the air to quickly get the jack down where you want, then use the handle to "feel" the press. Sometimes, of course, you want to just mash it as fast and hard as you can, then the air feature is really boss. - GWE |
#5
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Grant Erwin wrote:
Bob, you're confused about AOH jacks. ... Yes, clearly I am, or was. The question should have been "How do AOH jacks work?". Now I know. Thanks to all - Bob |
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