Force Required

[mach6]

What would be the approximate force required on the perimeter of a 30 ft diameter table that weighs 200,000 lbs to move it? The table is sitting on twelve wheels (10" diameter each) that are mounted to ball bearings.

[edgepflow]

A quick approximation would be:

Force = coefficient of static friction X weight.

The rubber-to-road friction is likely larger than the bearing friction (assuming the bearings are in good condition).

My old physics textbook lists for coefficient of static friction = 1 for rubber on dry concrete.

Edit:

The method above will significantly over-estimate the force since this would only apply if the tires could not roll.

I will look into this a little more...

[Bob S]

The rolling resistance coefficient (RRC) for rubber automobile tires is about 0.01 (less if the tires are inflated more). Thus for a car weighing 3000 pounds, the horizontal force needed to push the car (overcome the RRC) is about 30 pounds.

For your case, I would guess about 0.01 x 200,000 pounds = 2,000 pounds tangential force on the perimeter of the table.

Bob S

[AlephZero]

I don't think you are going to support 200,000 lbs on 12 10-inch-diameter rubber tires. The weight on each tire would be about 7.5 tons. Compare "one 10-inch diameter wheel" with the wheels and tires on a typical 7-ton road truck!

The question is impossible to answer unless we know more about the wheels, and what surface they are running on. You would probably need a specially built track to support that weight with such a small contact area. Otherwise, the most of the force will be overcoming the deformation of the ground and/or the wheels, not overcoming rolling resistance or friction in the bearings.

[Travis_King]

Where the heck do you have a 100 ton table and why would such a table have wheels?

[AlephZero]

There are plenty of mobile engineering structures that weigh more than 100 tons. That is only the weight of three large "standard" road trucks. But supporting them on twelve 10-inch diameter wheels is not so common.

[Travis_King]

I don't mean to get off track here, but I hotly disagree that there are plenty of 100 ton TABLES that are required to be mobile, 10 inch wheels or not.

[Bob S]

The gross weight limit of a standard US rail freight car is about 286,000 pounds, supported on eight 33" diameter steel wheels (35,750 pounds each). The rolling resistance coefficient of steel wheels on a steel rail (without deformation) is about 0.1%.