I tried using my

http://enginuitysystems.com/EVCalculator.htm for a 4000 lb (1818 KG) vehicle, and for 0 acceleration I get

**504** Newtons (113 lb force) of thrust at 100 kM/h (62 MPH), and

**356** Newtons (80 lb force - rolling resistance) at 0 MPH (after fixing my formula):

Code:

```
fForce = (fMass*fGrav*fRoll) + ((fAir*fDrag*fArea*(fSpeed/3.6)^2)/2) + (fMass*fAccel);
fPower = fForce*fSpeed/3.6;
```

The power required seems to be about right, with

**5.46 kW** at 31 MPH and

**18.8 kW** at 62 MPH, so it is somewhat a square law function related to speed.

But the most force will be from the acceleration (or incline), which is

**4901 Newtons** (1100 lb force) for a 25% grade or 2.5 m/sec/sec acceleration.

I think I see the error in my formula - a misplaced parenthesis - since the sum of all the speed terms should be squared.

Bottom line, however, seems to be in favor of keeping the transmission and 4WD and using a smaller motor.

[edit] I found some references for estimations of power and force for vehicles:

http://craig.backfire.ca/pages/autos/drag
http://www.engr.colostate.edu/~allan/fluids/page8/page8.html
The second document shows the following formula:

F = Cr*m*g + 0.5*p*Cd*A*V^2

Where g = gravity constant (9.8), Cr = Coefficient of rolling resistance (0.015 typ), p = Density of air (1.2), and Cd = Coefficient of drag (0.3 typ)

My formula appears to be correct, but perhaps there is a problem with operator precedence in JavaScript.

[edit2]

The problem was that JavaScript does not use ^2 for square. I corrected the calculator and the correct (AFAIK) values are as above.