Load weight in pounds - determine if any dead weights adds to the load (such as chain or belts)
Weel, drum or roller diameter on which the load moves or is supported.
The diameter of the axel, shaft or bearing on which the roller, wheel or drum is supported.
Lever arm of the rolling friction:
steel on steel 0.02 wood on steel 0.05
polymer on steel 0.08 hard rubber on steel 0.28
polymer on concrete 0.2 hard rubber on concrete 0.4 - 0.8
medium hard rubber on concrete 0.6 - 1.4    
Coeffecient of friction for support bearings:
  Anti-friction rolling bearings = 0.005
  Slide bearings = 0.08 - 0.1
Additional factor for rim friction on the wheels:
  Wheels with anti-friction bearings c = 0.003
  Wheels with slide bearings c = 0.005
  Guide rollers c = 0.002
Angle of incline
  (+) positive angle is an incline
  (-) negative angle is a decline
Rolling Resistance Force
Variables   Units
W Load weight lb
DW Drum Wheel Diameter in
d Shaft, Bearing, Axis diameter in
f Lever arm of rolling friction in
μL Coefficient of bearing frictions  
c Factor for rim frictions ( wheels )  
α Incline angle °
FL Resistance force load lb