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Ground Pressure (tiny bug?)


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BTS,</p>

I noticed in Reisberg that my US tanks had two different ground pressure values. The M4A3(75)W has 14.3 PSI (1.0 Kg/ccm). The heavier + version has listed 15.5 PSI (1.9Kg/ccm). </p>

One of these conversions is wrong isn't it? I don't have a calculator on me, or I would tell you which :-Þ</p>

I'm also a bit confused about the Kg/ccm measure. Shouldn't that be Kg/scm? or Kg/sm in SI units?</p>

I know I'm getting really picky now :)</p>

Bruce</p>

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Guest KwazyDog

Id say that the ccm is metric Bruce. Its kilogram per cubic centimetre... smile.gif

[This message has been edited by KwazyDog (edited 11-16-99).]

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Guest Madmatt

Hmmm I am not sure which number you are having a problem with but the PSI ground presure numbers coincide with 4 different sources that I was able to locate in about 5 minutes of searching. Well truth be known one souce qouted 14.5 PSI so shoot me! wink.gif

I would assume that the Kilogram to cubic centimeter kg/ccm seems right as well but i will check on it some more. Anyone else with a better grasp of mathematics/measures wish to jump in?

Madmatt out....

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Generally pressure is a force per unit area, so I would think that it would be M/A or Kg/scm. It is not readily apparrent to me what force per volume would be. As to the conversion, I was never any good with USCS units. Someone else will have to pick that one up. -Sorry

- Bill Carey

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Well, assuming that they were trying to show both English and Metric, then I think it should be 14.3 PSI (98.621 kPa) and 15.5 PSI (106.9 kPa). If I recall, Kg/ccm is a density measurement, so I'm not sure how that info is important. I'm pretty sure that Moon is right about it being possible that 15.5 PSI can equal 1.9kg/ccm, but since the last time I had to figure stuff like that out was in high school, I wouldn't have a clue off hand as to if that figure is accurate.

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Don't _ever_ post on topics like this when a physicist is around. smile.gif Sorry, nobody's gotten it right yet. The correct metric mass/area (which is not a pressure) is 1.09 kg/square cm. A 0 was dropped, and this should be easy to fix. If you really want all the gory details, read on -

If the W weighs 35 tons = 70000 lb, and has a ground pressure of 14.3 psi, its footprint is 4900 square inches - about 34 square feet, which is reasonable. Converting these to metric, one gets 1.0 kg/cm squared, which is what is noted (ccm is a somewhat archaic notation for square centimeters, NOT cubic... the c's are both "centi". It's like p. for a page and pp. for several pages) BTW, don't even get me started on the fact that this is not a pressure... pounds (a force) and kilograms (a mass) do not measure the same thing, a metric pressure would be kg/m/s^2. Doing the same for the W+, assuming the same footprint, one gets 15.1 psi - close enough given the precision of the data provided. This then becomes 1.09 kg/cm^2, NOT 1.9. Someone dropped a 0. I would expect, since this is so simple, it can be fixed easily.

[This message has been edited by Beamup (edited 11-16-99).]

[This message has been edited by Beamup (edited 11-16-99).]

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