Pinewood Derby Book
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Above we have the screen that you work with on opening the VR Program. Click right on any item on the real screen or in the main menus to go to an extensive help manual. The track parameters are from the standard circular-arc-ramped track from the Physics of the Pinewood Derby book. The car parameters are similar to the ones from the JNTS design on p 219 of this book. The VR program was used to adapt the JNTS car design to the Brett Bullet car which was entered in the National race in Irving, TX, held on May 26, 2005. The liberal race rules were those enclosed in the car kits obtained from the scout shop.
In this example, the designer was interested in how much it would help if a better graphite were used that would reduce the coefficient of wheel/axle friction MU from 0.09 to 0.06. The car with the 0.09 value inserted for the MU parameter was named BRETT_BULLET_MU=0.09. The [Run] button then caused the first row of results which showed that the end-of-ramp time and velocity (T1 in seconds and V1 in cm/sec) and the horizontal run time (T2) gave a net race time (TT) of 2.3821 seconds. When the MU parameter was changed to 0.06 and the new car named BRETT_BULLET_MU=0.06 was run, we see the time has improved to 2.3753 seconds.
The time difference means our design test would improve the performance of the Brett Bullet by 0.18 car lengths (about 1-1/4 inches) at the finish line. All the other 11 parameters may also be changed in the design of a car and the VR program will tell you precisely how much this means at the finish line. Click here for a photo of this high performance car, designed using the VR program, which easily won the National PWD race in Irving. To see a time-only simulation of this race, go to race group of cars. .
A new button has been added in VR-VII that allows the user to display a graph of the results. It shows the distance traveled and the velocity of a car as a function of the time from start to finish.
