# Force of Tractive Resistance on a Vehicle

1. Oct 22, 2011

### marine345

I have been working on this for a while. I am trying to find the power required to move a 7100 lb vehicle over a variety of scenarios, but am having trouble calculating the force of tractive resistance.

I found what i thought was a pretty exhaustive equation for the force of tractive resistance:
FTR=mg[sin$\alpha$+C0sgn(V)]+sgn(V)[mgC1+($\rho$/2)CDAF]V2+ma
where:
C0=dimensionless coefficient of rolling resistance
$\alpha$=the angle of the surface the vehicle is navigating
C1=Coefficient of rolling resistance while in motion, calculated by (when C0=0.01) C1=C0(V2/100)
$\rho$=air density (lb/ft3
CD=drag coefficient
AF=frontal area of the vehicle (ft2)
V=velocity (fps)
g=32fps2

So far, I have gotten this for one scenario, going 20 mph in sand:
FTR=(7100)[sin(0)+0.35]+[(7100)(0.35(29.3/35))+(0.0718/2)(0.75)(22)](29.3)2=1.06037E6
I used 29.3fps as velocity because that would give me the answer in ft/lbs, and calculated C1=0.35(29.3/35) because I figured '100' would change based on C0. I also thought this number was astronomically large, especially since it would be multiplied by velocity to find the required power to meet the scenario requirements. I have also donr the same with several other scenarios, and gotten really big numbers

2. Oct 22, 2011

### nvn

Last edited by a moderator: Apr 26, 2017