Grand Prix Racing - The Science of Fast Pinewood Cars

AWANA Kit Wheels

These estimates are based on measurements accurate to about + or - 1/256 inches. The wheel model is not strictly concentric as cylinders 4 an 5, 6 and 7 overlap slightly in radius. However, 5 is on top of 4 and 6 on top of 7 so no material overlaps. "Top" is the face of the wheel when it is laid on a table - a line through the wheel bore would point up.

AWANA wheels are made of a soft plastic that melts easily via mechanical friction. Scraping the material with a sharp implement is likely to cause scuff marks, tears and thin fillaments in the surface. High-speed tools are not recommended. Machining with typical garage tools is difficult.

Axle weight: 0.0416 oz (0.5oz/12axles)

Axle diameter: 0.09375 +/- 0.004 inches (2.38 millimeters)

Axle play: 0.0074 +/- 0.0015 inches (0.19 millimeters)

Wheel weight: 0.07692 oz (1oz/13wheels)

Mechanical advantage: Outer radius/inner radius = 12.667

An Estimate Of The Moment Of Inertia Of An AWANA Kit Wheel

Cylinder Radius (in) Width Volume %Mass Ii/mi Ii/m
inner outer (in) (in3) (in2) (in2)
1 0.047 0.109 0.281 0.00863 5.152 0.007080 0.00036477
2 0.109 0.125 0.094 0.00108 0.644 0.013794 0.00008883
3 0.125 0.250 0.023 0.00345 2.061 0.039063 0.00080501
4 0.250 0.313 0.109 0.01208 7.213 0.080078 0.00577594
5 0.281 0.328 0.094 0.00841 5.023 0.093384 0.00469091
6 0.328 0.578 0.063 0.04449 26.562 0.220947 0.05868739
7 0.516 0.594 0.328 0.08934 53.345 0.309204 0.16494573
Totals V=0.16748 %m=100 I/m=0.23536

Weight(_0.07692_ oz)/386.088 = Total Mass (0.000199237 ozs2/in).

I/m (0.23536) x Total Mass (0.000199237) = I

Total Wheel Moment of Inertia, I = 0.000046892 ozins2.

Wheel Plastic Density, P = mass/volume = 0.000199237/0.16748 = 0.00119 ozs2/in4.

A "Machined" AWANA Kit Wheel

If 3/64 ths inch of tread could be removed down to 1/32 inch (about 50% of it), this would be an estimate of the result. "If" is a big question - it is doubtfull the wheel would remain round or be able to stay that way. So this estimate probably represents an extreme limit. A thin rim is left (the 8th cylinder) so the wheel can maintain its mechanical advantage over axle friction. This rim must be positioned so the wheel is ballanced on the axle under a load.

Cylinder Radius (in) Width Volume %Mass Ii/mi Ii/m
inner outer (in) (in3) (in2) (in2)
1 0.047 0.109 0.281 0.00863 7.023 0.007080 0.00036477
2 0.109 0.125 0.094 0.00108 0.878 0.013794 0.00008883
3 0.125 0.250 0.023 0.00345 2.809 0.039063 0.00080501
4 0.250 0.313 0.109 0.01208 9.832 0.080078 0.00577594
5 0.281 0.328 0.094 0.00841 6.847 0.093384 0.00469091
6 0.328 0.578 0.063 0.04449 36.208 0.220947 0.05868739
7 0.516 0.547 0.328 0.03423 27.858 0.282471 0.16494573
8 0.547 0.594 0.063 0.01050 8.545 0.325806 0.16494573
Totals V=0.12286 %m=100 I/m=0.20251

Wheel weight: density * volume * 386.088 in/s2 = 0.00119 * 0.12286 * 386.088 = 0.05643 oz

Weight(_0.05643_ oz)/386.088 = Total Mass (0.00014616 ozs2/in).

I/m (0.20251) x Total Mass (0.00014616) = I

Total Wheel Moment of Inertia, I = 0.000029599 ozins2.

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Grand Prix Racing - The Science of Fast Pinewood Cars
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