M4D-071 Maximum Operating Weight

[MHarryE]

I'm on some pretty serious slopes, so I really want the ballast for extra stability. As long as the tire's psi is the same shouldn't compaction be the same ballasted or not?

Not right. Yes, surface compaction will be the same as tire pressure - Pascal’s Principle. But mass on a tire is transmitted into the soil until everything stabilizes = compaction at depth. An example is trucks. Heavy loads are transmitted deeper into the roadbed than light loads despite tire pressure remaining relatively constant. Keep the tire pressure as low as load/inflation tables allow remembering the planter on the 3 point must be considered.

 

[sea2summit]

I'm on some pretty serious slopes, so I really want the ballast for extra stability. As long as the tire's psi is the same shouldn't compaction be the same ballasted or not?

Think about that for just a minute

 

[Iowa Hillbilly]

NO. The heavier the tire and rim are, the more compaction you have. I do slopes too. I just shift into FWA.

OK, I guess I don't understand compaction as well as I should. I thought it was all based on ground pressure, so that if a tire has 15 psi in it, it would cause less compaction than a tire with 30 psi even if the 15 psi was on a 30000lb machine and the 30 psi tire was on a 10000lb machine. What am I not getting?

 

[sea2summit]

Not right. Yes, surface compaction will be the same as tire pressure - Pascal’s Principle. But mass on a tire is transmitted into the soil until everything stabilizes = compaction at depth. An example is trucks. Heavy loads are transmitted deeper into the roadbed than light loads despite tire pressure remaining relatively constant. Keep the tire pressure as low as load/inflation tables allow remembering the planter on the 3 point must be considered.

For us simple folks: The surface pressure per square inch will remain the same but there will be more square inches touching and more weight carried by the soil=more compaction.

ETA not sure about the truck example. A Tacoma uses 50 PSI, a F-250 80 psi, an F800 100-110 PSI.

 

[sea2summit]

OK, I guess I don't understand compaction as well as I should. I thought it was all based on ground pressure, so that if a tire has 15 psi in it, it would cause less compaction than a tire with 30 psi even if the 15 psi was on a 30000lb machine and the 30 psi tire was on a 10000lb machine. What am I not getting?

You’re thinking that your driving on a hard surface which only weighs that specific point. Soil is more like a fluid that wants to get out of the way, until it can not (compacted).

 

[Iowa Hillbilly]

surface compaction will be the same as tire pressure - Pascal’s Principle. But mass on a tire is transmitted into the soil until everything stabilizes = compaction at depth.

Does that mean if I dual a tractor to reduce tire pressure, I'm actually increasing compaction because I'm making the tractor heavier?

 

[sea2summit]

Does that mean if I dual a tractor to reduce tire pressure, I'm actually increasing compaction because I'm making the tractor heavier?

Depends on the soil composition. If you spread it out enough the weight is better destributed and less compaction. But commonly duals are for more traction not less compaction.

 

[Iowa Hillbilly]

You’re thinking that your driving on a hard surface which only weighs that specific point. Soil is more like a fluid that wants to get out of the way, until it can not (compacted).

I guess that makes sense. I never thought about it in those terms.

 

[5030]

Actually the best bet is a tracked tractor. Kubota made one a few years back, not sure of they still do.

 

[Iowa Hillbilly]

Actually the best bet is a tracked tractor. Kubota made one a few years back, not sure of they still do.

I used to know some rice farmers who swore by the old CAT rubber tracked tractors. They got around real nicely in the fields, but those were big and flat and didn't require much turning around.