Pinewood Derby Stories and Photos from Maximum Velocity
Cheater Bars - Do They Work?
Many years ago, the predominant commercially available track was equipped with a simple starting mechanism. The starting pins were attached to a board which was held in place by rubber bands. To start the race, the operator would rotate the board. Thus, the speed of the operator's movement determined the speed at which the pins would drop. Of course, this speed varied from heat to heat.
Figure 1 - Vintage Starting Gate Source: blog . robinsonmaites . com
It wasn't long before some clever derby car builders realized that by having the car contact the starting pin at a higher point, the car would start more quickly. In fact, this advantage would be significant whenever the operator rotated the board slowly. So, the "Cheater Bar" (also known as a "Spoiler") was born.
Today, starting gates are spring loaded. So, the pins fall rapidly, with a consistent speed, and the speed of the operators hand is not a factor. However, the Cheater Bar concept has continued to be viewed as a way to gain an advantage. In fact, many races ban cars which have a starting pin contact point higher than a set value.
Considering that most racers will run on tracks with spring-loaded gates, and the pins on these gates drop very rapidly, is there any benefit to a Cheater Bar? Let's find out.
IMPLEMENTATION OF A CHEATER BAR A cheater bar is normally a metallic attachment to the front of a car that causes the car to contact the starting pin at a higher than normal location. This can be implemented in several ways. One way is to form the bar out of a piece of coat hanger wire.
Figure 2 - Cheater Bar (Opaque material removed for clarity)
Note the notched front end on the car. This is necessary to ensure that the car only contacts the pin on the bar. Also, the Cheater Bar in the above photo is missing a vital piece. In order for the bar to trip the sensor on an electronic finish line, some opaque material (usually tape) would be wrapped around the bar.
A similar technique is to design the car with the wood creating a high front end (see Figure 3).
Figure 3 - High Nose Car
Although the High Nose will provide the same theoretically fast start as a Cheater Bar, the aerodynamics will be somewhat compromised.
EXPERIMENT SETUP For this experiment a Cheater Bar was implemented in a different way. To minimize the number of factors that could affect the results, an adjustable Cheater Bar was attached to a car. The Cheater Bar was fashioned out of a piece of aluminum plate, two pieces of coat hanger wire, and a small segment of rubber tubing. The metal plate was held in place by rubber tubing, so it could be slid up or down. During the experiment, nothing was changed on the car except for the height of the metal plate.
Figure 4 - Cheater Bar at High Position
Figure 5 - Cheater Bar at Low Position
The car was equipped as follows:
- Extended wheelbase wedge car - Rear weighted to 5 ounces - Three wheels on the ground - Alignment set to rail ride - Pro-Stock Wheels and BSA Speed Axles - Krytox 100 lube
Tests were run on a thirty-two foot Aluminum Freedom Track. The car was staged identically for each run. Five runs were made with the Cheater Bar set at 1-1/2 inches above the track (maximum for the starting pin). Then five runs were made with the bar set at 13/16 inch (low as possible on the car). These tests were then repeated, for a total of ten runs per configuration.
The results were as follows:
High Position - 2.556 seconds average, Standard Deviation at .0037
Low Position - 2.555 seconds average, Standard Deviation at .0030
Thus, the experiment shows that the position of the Cheater Bar did not affect the heat times. (The one-thousandth deviation in average times was well within the Standard Deviation of the data).
CONCLUSION So, if you will be competing in a race that will be run on a track with a spring-loaded starting gate, don't bother with a Cheater Bar. It won't give you any advantage, and may cause your car to receive greater scrutiny or to be disqualified.
On the other hand, if you are in charge of a race that will be run on a track with a spring-loaded gate, then don't worry if a car has a Cheater Bar. It won't provide any advantage.