Ground Pressure 2

[TNdigger]

Can anyone tell me how to figure ground pressure of a S185 for comparison to my eariler post. Again I will ask to everyone what I m comparing is 8915lbs @5.0psi and 7890lbs @3.7. The heavier is a case 440 CT and The lighter is Asv SR 70. This will be my first big machine purchase so all advice is appreciated. Just to let you know Bobcat dealer?-poor service Cat dealer? -to proud. All others are not a consideration for me. Disposables. Thanks Again

[Scag48]

I can't give you an exact number, but the tracked machines, while heavier, are going to have less ground pressure than an S185 due to a much larger ground contact area via the tracks. Maybe someone else knows better than I, but I'd take a stab and say a wheeled machine, such as the S185, is probably around 8-9 PSI. I know it's going to be greater, I'm just not sure by how much. I'll do some number crunching here in a minute and post anothe reply.

[Scag48]

Okay, pulled up some specs. Case 440CT has 56" of track on the ground, per side. ASV SR70 has 71" of track on the ground, per side, and ASV provides the square inches of track on the ground, which is around 2,100 square inches.

Now, an S185 weighs about 6,200 pounds, substantially lighter in comparison to the Case and ASV. Case 440CT is 8,900 pounds or so depending on how it's equipped, SR70 is 7,900 pounds.

Figure a standard tire for the S185 is 12 inches wide and 16 inches around. Figure half the diameter of the tire is on the ground, could be more, could be less. So, 8" multiplied by 12" is 96 square inches per tire, multiplied by 4 tires is 364 square inches of contact. Divide that number by 6,200 pounds and the PSI for an S185 is around 16. Pretty large number, it's kind of surprising. This is all assuming that my tire calculations are correct, figuring out exactly how much tire is on the ground is the hard part, the math from there is easy.

[AWJ Services]

A tired machine will do leave much deeper impressions in the ground.
My Machine weighs close too 10k and I go across lawns quite often.It leaves lug marks more than ruts.
It will leave depressions if the ground is soft enough too move under your foot.

[Digdeep]

Can anyone tell me how to figure ground pressure of a S185 for comparison to my eariler post. Again I will ask to everyone what I m comparing is 8915lbs @5.0psi and 7890lbs @3.7. The heavier is a case 440 CT and The lighter is Asv SR 70. This will be my first big machine purchase so all advice is appreciated. Just to let you know Bobcat dealer?-poor service Cat dealer? -to proud. All others are not a consideration for me. Disposables. Thanks Again

Ground pressure= machine operating weight/total square inches of track surface.....SR70 7890/2100=3.75psi. A rough rule of thumb for a skid steer is that the ground pressure will be pretty close to the air pressure of the tires.

[raschmid07]

TN Digger- Can't help you on your post, but were are you located in Knoxville? I'm from there but go to Auburn, I'll be heading back that ways for work this summer here in a few weeks.

[hansondirtman]

digdeep is pretty right on this:
http://www.michelinag.com/agx/en-US/htbuyt/reduce_soil_compaction/reduce_soil_compaction2.jsp

[ksss]

I had read somewhere that the average pounds per square inch on a skid steer was around 35 psi, a lot of variables in that so I don't know how accurate that is.

[Digdeep]

I had read somewhere that the average pounds per square inch on a skid steer was around 35 psi, a lot of variables in that so I don't know how accurate that is.

I think that if the sidewalls are more rigid it adds a couple psi to the equation.

[Digdeep]

I had read somewhere that the average pounds per square inch on a skid steer was around 35 psi, a lot of variables in that so I don't know how accurate that is.

I think you're right ksss.

[Ausman]

There is another thing to consider in that the ground pressure on a CTL is calculated as an average over the entire length of the machine track. All other CTL's apart from ASV are rear heavy to gain lift advantage, what this means is tha the other machines have a much higer ground pressure over the rear of the machine. Cat for instance has 80% of its weight over the rear torsion axle, the ASV is 50% this give less over the entire length.

As far as tyres go they have 6 x 2 inches on the ground per corner and they also have all the weight over thr rear, put that suckers rear axle over the scales that is its ground pressure.

There is a lot of smoke and mirrors with figures, the proof is pick up a load and go drive and turn on turf and you will see.

[AWJ Services]

Also the rigid frame machines evenly distrubute the load over the whole track when loaded while a suspended track tends too tilt forward and apply the pressure more on the front part of the rollers.
If an ASV/Cat had a track similar too a Takeuchi(Lug design wise) it would really make a mess.
More smoke and mirrors.

[hansondirtman]

Also the rigid frame machines evenly distrubute the load over the whole track when loaded while a suspended track tends too tilt forward and apply the pressure more on the front part of the rollers.
If an ASV/Cat had a track similar too a Takeuchi(Lug design wise) it would really make a mess.
More smoke and mirrors.

Uh, that makes no sense - the suspension allows the chassis to tilt forward some while the undercarriage ramains flat on the ground, where a rigid machine has to pivot on the front idlersm putting all the weight on the front when loaded or on the back when unloaded. That's why people like the suspension - where's bobcatron to back me up on this?

[bobcat_ron]

Uh, that makes no sense - the suspension allows the chassis to tilt forward some while the undercarriage ramains flat on the ground, where a rigid machine has to pivot on the front idlersm putting all the weight on the front when loaded or on the back when unloaded. That's why people like the suspension - where's bobcatron to back me up on this?


Yup, totally nailed it there, especially when going over dips and bumps, the torsion axles (suspension) keep the ground pressure more consistent and evenly distributed.