Robin did some heat calculations earlier on the motor controllers Motor Controller Heat Dissipation with some estimates for the max steady state power, and incorporating an aluminum plate into the aerobody of the chassis. To avoid the manufacturing of an aluminum plate inside a carbon fiber layup, we are doing some more calculations with less assumptions (or at least more accurate ones) and using a heatsink with a fan and forced air.
How much heat will we generate in the motor controllers - we don’t want to do a crazy over designed cooling solution because we know we can do better.
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Aiming for 16.6m/s throughout the race. These calculations of torque requirement are all done done to maintain this given 16.6m/s speed. 16.6m/s = ~60km/h
Average torque is 15.7Nm
Average of all the positive torques is 17.2Nm (treating the distance between each 2 points as identical). I asked Emma for this assuming that there were negative torque showing regenerative braking but I don’t think there actually were.
^Note that the above torques are for each of the motors.
This data is the map from ASC 2018 with waypoints along the route. We will look closer at the hills at the 1.3 and 2.5 markers.
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Angle 13.125 and torque requirement 213.133 over 59.923 metres
Angle 11.526 and torque requirement 188.117 over 28.771 metres
Angle 11.373 and torque requirement 185.715 over 85.577 metres
Angle 10.542 and torque requirement 172.631 over 88.187 metres
Angle 10.435 and torque requirement 170.955 over 29.996 metres
Angle 10.045 and torque requirement 164.805 over 48.502 metres
Angle 9.878 and torque requirement 162.166 over 89.985 metres
Angle 9.744 and torque requirement 160.053 over 57.792 metres
Angle 9.483 and torque requirement 155.932 over 57.288 metres
Angle 9.47 and torque requirement 155.732 over 42.049 metres
Data we will use for calculations:
A 20” diameter tire has a circumference of pi*20in * 2.54(cm/in) / 100 (cm/m) = 1.596m
Travelling at 16.6m/s, this tire rotates at 104.01rpm
Steady State:
Average torque = 15.7Nm
Power(W) = torque(Nm) * speed(rpm) = 15.7Nm * 624 rpm = ~9800W, which is close to the 10kW peak for our motors. If this is what we use in steady state, then we have a problem. Something is going on here, and I probably just made a simple mistake.