Milestone 2 Calculations

I did up a neat excel sheet which allowed me to calculate some simple approximated values from a few given parameters:

Constants/Inputs Value Units
Wheel Radius 0.0508 m
Gear ratio 0.333333333
kv 149
Input Voltage 28 V
Max Current 40 A
Mass of rider and kart 100 kg
Drag coefficient 0.804
Frontal Area 0.6 m2
How many motors? 2
Density of Air 1.225 kgm-3
Resistance of Motor 0.021 ohm


Derived Constants
kt 0.064089293
wheel circumference 0.319185814 m
no load rps 4172 rps
Max power output 2240 W
Max Stall Torque 2.563571719 Nm-1
Graph Slope -0.000614471 Nm-1rps-1
At Standstill
Max Wheel Torque 7.690715156 Nm-1
Force exerted on ground 302.7840612 N
Acceleration @ Standstill 3.027840612 ms-2
wheel rps @35kmh 27.85211504 rps
motor rps @35kmh 83.55634512 rps
Drag @35kmh 23.35161459 N
Power loss @35kmh 207.5958537 W
Torque @35kmh 2.512228793 Nm-1
Power Output @35kmh 209.9126561 W

Since the power output of the motor is roughly equal to the fudged approximated power loss due to air drag of the kart at 35kmh, and given that the motor would definitely not perform at 100%, I can say that our kart will not even remotely hit 35kmh. I might be wrong though.

I actually secretly hope it does go above 35 =/


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