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Index of calculation results:

An aero and friction power load chart is found in post #152.

A chart showing aero and friction effect on ET and speed for 700lbs and 3.3GR is found in post #161.

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Initial post

We need some performance requirements:

Is this a 1/8 mile or 1/4 mile run? Answer: 1/8 mile = 660 ft

How quickly do you want to run, what is your target ET? Answer: min ET = 6.9 sec

Is there a maximum speed limit for this class? Answer: 110 mph

Do you want to include a cooling system or do without? He wants one.

We will get the answers from the previous thread:

Drag racing is about E.T. not mph. Jr Comp cars are restricted to 6.90 seconds or slower based on either an e.t. dial-your own

or heads-up basis; breakout rules apply. In qualified events, no racer can

qualify quicker than 6.900. Any racer running faster than 110.00 mph at any time

during an event is disqualified.

Most Jr Comp cars weigh 550 - 600 lbs. plus driver.

Calculate E.T.: 755 pounds and HP of 114 (85 kW)

[edit]

Constants and Constraints:

race distance: 1/8 mile = 660 ft

max speed: 110 mph = 161.3 ft/sec

minimum ET: 6.9 sec

tire diameter: 22" , Circumference = 5.76 ft

weight: 755 lbs; Mass = 23.4472 lb-sec^2/ft

pulley ratio: 10:3

YASA 400 motor torque at 450A: T~360 N-m = 265 ft-lbs up to 3000 RPM at 500V

Preliminary Calculatus Eliminatus:

Acceleration based on ET(min) and distance from x = .5 A t^2 ;

A = 27.72 ft/s2 = 0.86 g

Velocity from A and ET(min): v = At = 191.3 ft/sec = 130 mph exceeds max speed limit, therefore too high.

Acceleration based upon V(max) speed and ET(min):

A = v/t = 23.38 = 0.726 g

Power based upon Force and speed:

P = M A V(max) = 88405 lb-ft/sec = 161 HP

Energy of mass at V(max) from 1/2 M V^2:

E = 304956 lb-ft

Energy of pack: 500V at 500A

E = 250000 kW

Average Power from Energy over ET(min):

P = dE/dT = 44197 lb-ft/sec = 80.4 HP

Bottoms-Up Look:

Need 548 Lbsf to accelerate and meet 6.9 sec ET and not break out Vmax

Torque at axle = r x F = 11/12 * 548 = 502.5 ft-lbs * 3/10 pulley ratio = 150 ft-lbs at motor

And current will be 150/285 * 450A = 238 Amps, easily provided by the 500V/500A pack.

This is all without aero, friction and other losses.

So the pack and motor size appear to have a good margin to meet the requirements with some margin for losses.