02 03 Pinewood Derby Stories and Photos from Maximum Velocity 04 05 15 16 19 20 21 22 23 24 25 26 27 28 31 32 33

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

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.

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

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.

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.

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.

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)

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

From Pinewood Derby Times Volume 2, Issue 6

To subscribe to this free e-newsletter, please visit:

(C)2011, Maximum Velocity, Inc. All rights reserved.
35 36 37 38