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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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