[NAFEX] Apple pressing

Mark Angermayer hangermayer at isp.com
Sun Dec 7 11:55:39 EST 2008

Del wrote:

"I have a large acme screw and a 14" dia. thick wall plastic pipe I salvaged that I am thinking of making into a screw press for smaller batches, or for grapes. Figure I'll just drill a jillion holes in the pipe."

Hi Del,

I've been considering a screw type press as well.  Roton sell the screws.  The problem is so much mechanical advantage is lost in the inefficiency of a screw.  Acme threads rate at about 30% efficiency.  And that's assuming a good thrust bearing.  Without a thrust bearing on the end of the screw, more mechanical advantage will be lost.  Hydraulic rams are nearly 100% efficient.  I'm still considering a screw, but I'm just not sure if it will deliver enough power.  In short, a typical acme 1 1/4" screw will only deliver about 4 ton of force, and that's with a thrust bearing, if 100 ft/lbs. of torque is applied to the screw.

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