From: N295VV@aol.com
Message-ID: <20.7acff0a.2684b775@aol.com>
Date: Fri, 23 Jun 2000 08:52:05 EDT
Subject: New Math?
To: LFrantz@compuserve.com, lancair.list@olsusa.com
Mime-Version: 1.0

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Jim,

I respect your opinions and your ability to figure out things, but in this 
instance, I have to question your formula.

By your reasoning, and by extrapolation,  a solid metal wheel would make the 
soil need to support hundreds of thousands of pounds of weight per square 
foot, and a tire with a fraction of a pound pressure would make the soil need 
to support a very low weight, maybe nothing.

In actuality, the formula should be based on the total airplane weight 
divided by the contact area of the wheel pressing on the soil.  If lower tire 
pressures are used, more rubber may touch the surface, thus lowering the 
weight per square inch.

But, this is not exactly a perfect formula either, since lowering the tire 
pressure lessens the radius of the wheel in the contact area.  Pushing the 
plane then raises the amount of forward pressure to get the wheels to rotate, 
and a "skidding" effect may come into play, causing buildup of soil in an 
inclined plane at the forward point of each wheel.  An example of this may be 
found in trying to push a hay elevator with low tire pressures through a 
muddy field.

Hay elevators with fully filled tires push easier through muddy fields as 
well as through dry fields.   They do maker a deeper furrow, but they push 
easier.

Respectfully,   Farmer Jones
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