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SW Ontario | Omar - 10/16/2007 19:28
Just a couple of thoughts: If you take the tire and rim off the buggy, and let all the air out of the tire, does the sidewall completely collapse? If not, then the sidewall does carry some of the load. Second, if what you are saying about the footprint expanding as the load increases is true, then there should be absolutely no difference in damage taking a fully loaded cart across the field versus an empty one. I've never talked to anyone who believed that. If psi is the only factor in field damage, then my bicycle would cause far more damage to your field than a fully loaded grain cart.
Well, of course the sidewall carries some weight, but as the axle load goes up, this becomes an insignificant amount. Actually there is VERY LITTLE difference in a full buggy to an empty buggy with the michelins.
I did another experiment last year to prove this point to another farmer who thaught like you do. We were combining in a VERY wet field and I asked him if he thaught the combine would make deeper ruts when it was full or empty. He answered full, like most people would. I explained that the as the load got heavier, the footprint got proportionetly bigger to compensate for it and you would not be able to see a difference.
So... I made a pass at the back of the field where is was very wet, standing water and all with both a full combine and a empty one. I then took the guy for a ride and asked him to tell me which tracks were which. He actually chose the empty combine tracks, but ultimately you could not see any difference. To be as fair as I could, I overlaped the tracks so that one pass was not on slightly drier or firmer ground than the other.
Things that make you go Hmmm.
Oh and the bicycle analogy...
If you were to take a machine with low pressure Michelins into a very wet field, I would bet that you could follow it with your bike and the tires would sink in deeper. This is not the full story though, as a machine travels over the ground the weight radiates outward and down a larger area of soil starts to bear the load. Since bike is very light, you would not do any damage at much depth.
Edited by kinzepower 10/17/2007 14:23
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Compaction and PSI of Tires
