Calculate Torque 4wd vs 2wd

General Discussion
21

60 / (2 * pi * 220 KV) = 0.04340 KT (Torque in Newton Meters Per Amp of Motor Current)

70 Motor Current Limit * 0.04340 KT = 3.03841 Peak Motor Torque in Newton Meters

48 wheel teeth / 20 motor teeth = 2.4 gear ratio

3.03841 Peak Motor Torque in Newton Meters * 2.4 Gear Ratio = 7.29219 Wheel Torque in Newton Meters

(7.29219 Wheel Torque in Newton Meters * 1000mm) / ((1/2) * 107 Tire Diameter in MM) = 136.30261 Thrust in Newtons, 1 Motor

136.30261 Thrust in Newtons, 1 Motor × 0.22480 = 30.64204 Thrust in Pounds, 1 Motor

30.64204 Thrust in Pounds, 1 Motor × 0.45359 = 13.89898 Thrust in Kilograms, 1 Motor

30.64204 Pounds Thrust, 1 Motor * 4 Motor Quantity = 122.56819 Pounds Vehicle Thust <—

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22

Dude this was so helpful. If my calculation are not off, 4x 250kv on 3:1 gear ratio with 6.5 inch wheels will put the vehicle thrust at about 93.65576 Pounds Vehicle Thrust.

Is there a formula to calculate how fast a vehicle will hit top speed with vehicle thrust?

23

if there was no air, you could use this:

Force (Newtons) = Mass (KG) * Acceleration (m/s^2)

therefore:

Force (Newtons) / Mass (KG) = Acceleration (m/s^2)

A = acceleration (m/s2) B = the final velocity (m/s) C = the initial velocity (m/s) D = the time in which the change occurs (s) E = the change in velocity (m/s)

A = ((B - C) / D) = (E / D)

therefore

(B - C) / A = D the time in which the change occurs (s)

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24

I wonder if my set up can reach the theoretical weighted speed of 49mph with 4 6374, 12s8p 30q pack and 16/42 pullies on 152mm wheels.

25

what are the kv and current limits?

26

190kv running 80motor amps and 40 constant battery amps per Focbox.

27

it looks like with 2 motors, you’d hit 49-50mph, judging from where the yellow line, bottom left chart (vehicle thrust pounds, 2 motors) dips below the blue line, bottom left chart (wind drag force, pounds) (2 motors thrust force @ 50mph = 34.99lbs – wind drag force @ 50mph = 35.08lbs).

with 4 motors, it looks closer to 54mph, judging from where the red line, bottom left chart (vehicle thrust pounds, 4 motors) dips below the blue line (wind drag force, pounds).

The peak vehicle thrust of 124.88lbs (red line, bottom left chart) begins to drop off at about 25mph, because due to the increasing back emf voltage with increasing speed (red line, top left chart), sustaining 80a motor current above ~25mph would require more than the 40a battery current limit per motor.

(46v battery, 0.050ohm winding, (4) 190kv motors, 152mm tire, 42 wheel teeth, 16 motor teeth, 2.625:1 gear ratio, 100% throttle, 95% max duty cycle, 80a motor current limit & 40a battery current limit per motor)

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