Pinewood Derby Stories and Photos from Maximum Velocity
Solenoid Start Gate: Are Races More Consistent? By Randy Davis
Solenoid Start Gates came on the market a few years ago. These mechanisms use a solenoid (electrically activated switch) to release the starting gate at the press of button. The benefits of a Solenoid Gate include:
1. Enabling the computer software to release the gate (as opposed to a computer operator activating the heat, and then another operator opening the gate).
2. Allowing audience members or car owners to activate the gate remotely (adds some additional fun and participation to the pinewood derby).
3. Potentially improving the consistency of heats. Depending on the type of gate release mechanism, by eliminating the need for a person to operate the gate, consistency may be improved.
This latter benefit is what intrigued me. I run several experiments per year, and a big issue with experiment validity is eliminating factors that can adversely influence the results. So, eliminating inconsistency in gate operation should improve the validity of experimental data.
FREEDOM TRACK START GATE I have a two lane, aluminum, Freedom track. The gate on the track works fine, if the operator uses care when opening the gate. But if the operator is not careful, the track will be shaken when the gate is operated.
Photo 1 - Freedom Track Gate
Referencing Photo 1, if your hand is placed at point A and then slightly rotated, the gate releases and the track remains stable. However, if the gate lever is pulled at point B (the natural place to operate the gate), the starting section of the track will shake.
SOLENOID START GATE FROM NEW DIRECTIONS For the testing I acquired a MWG-1 Start Gate from John Shreffler at New Directions.(1) This gate was specifically designed for the Freedom Track start gate. The gate installed with minimal effort; I had it up and running in 20 minutes.
Photo 2 - Underside of Start Gate
Photo 3 - Top Side of Start Gate
In Photo 3, for reference the manual release arm is still present. It can be removed, but like the photo I left mine in place so that I could switch back and forth from manual to auto. For manual testing I used a rubber band to pull the solenoid latch out of the way.
TEST SETUP The car used in the test (Photo 4) was equipped as listed below. I chose this car as the needle axles and outlaw wheels result in very consistent performance from heat to heat.
- Five ounces with a one inch balance point - Extended wheelbase - Three wheels on ground, set to rail ride - Needle Axle Outlaw Wheels - Krytox 100 Lube
Photo 4 - Test Car
For the experiment, I ran five heats with the manual gate (carefully rotated at "A"), then five heats with the Start Gate. Next, I ran five heats with the manual gate (quickly pulled at "B"), then five heats with the Start Gate.
RESULTS The standard deviation(2) was calculated for each of the four sets of five runs. The results are shown below:
Figure 1 - Results of Testing
As seen in the chart the deviation was smallest when the Solenoid Start Gate was used. The deviation was larger when the manual gate was used carefully, and even greater when the gate was used in the natural way.(3)
CONCLUSION Clearly, gate consistency does affect heat times. So if gate consistency is important to you, consider adding a solenoid start gate to your track.
(1)See New Directions for more information on the MWG-1 Start Gate. New Directions offers a similar gate for other tracks.
(2)A statistical calculation showing how much the data deviates from the average. A larger number means that the data has a greater deviation from the average.
(3) The results of this test are only applicable for a two-lane Freedom Track. Results may be different for Freedom Tracks with more lanes (more stable), and for tracks using a different type of manual gate.