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Re: [Shop-talk] math wizards ??? come here

To: "'john niolon'" <>, "'shop-talk'"
Subject: Re: [Shop-talk] math wizards ??? come here
From: "Randall" <>
Date: Thu, 9 Apr 2009 09:22:08 -0700
> If I know the lift with one inch of rise at the
> jack point the multiplication tables will do the rest, right ????

Depends on how accurately you need to know it, and what range you are
working over.  Also how you measure the rise at the jack point.

If the jack, load and pivot are attached to the boom at fixed locations; and
you are measuring "lift" in parallel directions (eg vertically), then the
ratio remains fixed (ignoring boom flex, etc.) within the mechanical limits
of motion.  With the jack 1' away from the pivot and the load 8' away from
the pivot (7' away from the jack), the ratio is 8:1.

But with a typical boom hoist, the "jack" is not vertical and its angle
changes as the boom rises.  Which means that the relative rate of jack
motion (measured along the piston), and load motion measured vertically is
going to change as the boom moves.  In other words, the ratio you are asking
for is not a constant.

Unless you actually need to know the equation for some reason, I would
suggest picking the two extremes you are interested in, and working
backwards from there.

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