# Force required to move object on wheels

I'm trying to find the best way to move a heavy weight around. Probably the best way is to put it on wheels but I don't know which physics concepts it involves so I can make a better research.

I have found about rolling force and initial force but it's still unclear for me what can I do to decrease the force needed. What I found but not sure:

• Increase diameter of the wheels
• Wheels/floor made of low rolling resistance coefficient
• Decrease the weight (can't be done)
• Good bearings

Is this correct? What about the number of wheels, moment of inertia? Am I missing something else?

• All those ideas will help. Good bearings are probably most important on a smooth floor. On a rough surface, the diameter and material of the tires could matter more. Make sure the diameter is bigger than any bumps are tall/deep. – EL_DON Nov 15 '16 at 14:06

As you say wheels are usually the first option considered.

Probably the simplest option is to look at an industrial wheel/castor supplier. For example this site has a huge range of wheels castors and other parts for moving and handling.

Wheels are typiacly rated with a maximum load, note that if you use 4 castors it is usual to make sure that they are rated so that 3 are adequately rated for the total load ie if the load is 1000kg you need castors rated to at least 333kg.

Castors are generlaly pretty good for reasonably smooth surfaces like a decent concrete floor. Soft or uneven surfaces may require pneumatic wheels which tend to have significantly larger diameters.

Castors have the advantages of being self contained, vesatile and compact and they can often be fixed directly to th estructure you want to move but only work well on reasonably smooth, hard surfaces.

Typically harder wheels give less rolling resistance on smooth surfaces but are more affected by uneven floors.

Inertia is a fundamental property of matter and there is nothing you can do to decrease it. But when moving things by hand the ability to control heavy loads on wheels becomes a problem before they are too massive to get moving.

If you have a smooth and level floor without drain holes you can instead use an air cushion to move the weight around (think hovercraft).

The air-pressure you need can be calculated with the relation between the footprint of the object and its weight. The flow rate required from the air-compressors will depend on the leakage between the floor and the skirt.

• I saw this idea used effectively, some 20 years ago, when trying to move drilling rigs on a salt lake with weak, wet sediments in the bed of the lake. A special rig was devised that consisted on a hovercraft with very large diameter wheels. The hovercraft part of the rig reduced the pressure of the rig, via the wheels, on the salt lake bed while the wheels propelled & steered the rig. The hovercraft part distributed the mass of the rig over a larger area of lake bed, thus the lake bed didn't fail & the rig didn't get bogged. – Fred Nov 14 '16 at 12:31
• Thanks, but this would be overkill for my case. – Yuri F Becker Nov 14 '16 at 14:49
• @fred do you mean that the hovercraft's weight acting on lake was effectively reduced? – Fennekin Nov 15 '16 at 11:11
• @Fennekin: Yes, the weight that was acting through the wheels, while the rig was being moved. – Fred Nov 16 '16 at 7:33
• For anyone reading this later, a lifting device like this is called an "air caster." – William S. Godfrey- S.E. Nov 16 '16 at 19:00