A New Starting Gate

[gatemaker]

Several years ago, I was tasked by my pack to set up a new track. I thought we were set with our new finish line and management software, but it didn't take long to see that the next weak spot was our manually operated starting gate. After some searching, it became apparent that technology for that end of the track was lagging far behind. After several iterations, I believe I've come up with a better mousetrap. Check out http://www.derbygates.com.

By way of intro, my name is Lee Guenther and I'm in the Memphis, TN area. I do have a Bachelor of Science in Electrical Engr, and have been my pack's trackmaster for the last 8 or nine years, and have done several district and Awana derbies as well.

The design is derby tested - it performed flawlessly in my pack's derby this year (56 races), and stood up to the Cubs' banging on it in the pre-race testing (what better endurance test is there?).

Poduction is limited at this time, but can/will grow with demand.

Thanks!

Lee Guenther

[tmbnorm]

That is slick.

You don't want to have your hand in the way when it resets.
Ouch!

[PWD]

Wow that is pretty incredible. I am curious to what inside is the switch that actually starts the timer. Is it a mechanical switch? Or a magnetic switch?

[SlartyBartFast]

The big question is: How Much?

and can it be made modular to support more (or less) lanes?

[gpraceman]

I do like the looks and potential of your start gate.

As I mentioned to you in our PM interchange, I am concerned about how it signals the start of the race (relay) instead of a switch. Any variation with the speed of opening of the gate will show up in the times, which would not be good.

and can it be made modular to support more (or less) lanes?

If you mean being expandable, that would be quite a feat. I think it more likely to make models for different lanes of tracks.

[psycaz]

Add the point of being able to adjust the delay in reseting the gate to the list of questions.

Outside of that, it is very nice and clean design.

[SlartyBartFast]

If you mean being expandable, that would be quite a feat. I think it more likely to make models for different lanes of tracks.

Well, obviously the current design would require a different housing for different sizes of track.

Reason I ask, is I've been messing around trying to make my own automatic resetting starting gate. I won't bother if I can get a built one cheaper...

[gatemaker]

Thanks to all for the warm reception. Some interesting points were raised and to address them:

* - On a reset, your hand might get slapped, but the corners are rounded so there shouldn't be any torn flesh.

* - I use electronics to trip the finish line. My early experiences had kids bumping the starting gate and accidentally tripping the time. Not a problem now.

* - Hmmmm... Modular - maybe in the future.. As for price, I'd like to get $160 for the ones I have now (not even breaking even on materials). I expect my per unit costs to go down when I gear up production.

* - The reset delay depends on the resistor I put on the controller board. Production models probably will be variable.

* - I doubt you could build one as good looking for the above price!

Please don't hesitate if you have any other comments or questions!

Lee

[gpraceman]

* - I use electronics to trip the finish line. My early experiences had kids bumping the starting gate and accidentally tripping the time. Not a problem now.

My concern on using electronics to indicate a heat start will still be that if the gate doesn't open in the same amount of time for each and every heat. If there is an issue with binding of the gate mechanism, temperature effects, or whatever, then that variation will show up in the times (especially timing to 0.0001 seconds like many of the timing systems do). New Directions experienced this issue early on with their solenoid gate and then went with an independent start switch design.

To me, the trigger signal to the solenoid should be independent of the start signal to the timer. The start signal should be based on the actual opening of the gate.

[SlartyBartFast]

To me, the trigger signal to the solenoid should be independent of the start signal to the timer. The start signal should be based on the actual opening of the gate.

The subject of several other threads no doubt, but:
Regardless of how you signal the start to the timer, inconsistent gate opening would affect your timing. No?
If the gate opens quickly, the cars will barely have begun moving when the gate is down and the timer starts. This is the desired outcome whether timing starts with the activation of the gate of use of a gate switch/sensor showing gate fully open.
If the gate opens slowly, the cars will have begun moving when the gate is down. Cars will benefit from a rolling start if a gate open switch/sensor starts the timer, and cars will lose out if the timer started when the gate was activated.
And if gate speed varies, but remains faster than gravity (how many microseconsds of leeway do we have?) and doesn’t slow the cars, I’d see a signal as other than the gate release command as suspect.
To overcome gate timing issues, the only adequate solution IMO is to select the correct gate opening mechanism and adequately rated components (respect the duty cycle of the solenoid).
The solenoid related issues I’ve read about so far seem to all involve using a solenoid to hold the gate open and a spring to hold the gate up. As we can’t see the internals of this gate, we can’t really comment on whether gate speed may become a factor during repeated use. Varying reaction times should be something to be tested and verified.
Of this design, I really like the wide flat gates, and the enclosure. Looks like a really good clean piece of work.

[gpraceman]

Regardless of how you signal the start to the timer, inconsistent gate opening would affect your timing. No?

Yes, it could, if the pins did not clear the cars before they started rolling. It also depends on what "event" is being used to start timing.

Activation of the solenoid is not the same event as the actual opening of the gate. There is some delay between the two events (reaction time of the electronics, operation of the solenoid and operation of the mechanical linkage to drop the pins). With this delay there can be variation from heat to heat which can very well show up in race times if the solenoid trigger event was used to start timing.

Whether timing should start when the gate is fully open or has just started opening, is something else that can be debated. IMO, I think it better to start timing just as the gate opens so variation in the speed of it opening will not cause a timing problem. This still assumes that the pins will swing away before the cars can start to roll.

There is just too much potential for timing issues if the solenoid trigger event is used as the start signal. Case in point is the initial problem with the New Directions start gate, until they added a start switch to their design.

[gatemaker]

My two cents on race starts:

Ideally, when the start mechanism is engaged, that is when the timer should start and the posts should move away fast enough that they don't interfere with the movement of the cars. Given the ideal situation of a perfectly frictionless car, then the posts would need to have an acceleration of 9.8 m/sec/sec tangential to the axis of rotation of the gate at the lowest possible point of contact with the cars. This is the criteria that should be met with a good starting gate.

The use of mechanical swtiches that are typically used do not provide an absolute time in that some rotation of the gate is necessary to open the switch, and even then, the time required to open will center around an everage time. But then again, we're looking for relative times for the cars, and it is hoped that the time for tripping the timer is consistent across the races. Using a relay is no different -- it is after all a switch. However, the time required to engage the relay falls well below the resolution of the timers used currently, providing greater consistency in triggering the timer.

[gpraceman]

Maybe I can explain my concern more clearly this way.

If timing starts based on solenoid triggering, then here are the possible variations:

1. Δc - Start gate circuit reaction time - Timing starts at the end of this
2. Δs - Solenoid reaction time (from when current applied until solenoid starts to move)
3. Δm - Mechanical linkage reaction time (removal of any slop in the linkage until pins are away from cars)

A car's time (as measured by the timer) = Δs + Δm + "real" run time

If the start gate opening is the start of timing, the variations would be:

1. Δc - Start gate circuit reaction time
2. Δs - Solenoid reaction time (from when current applied until solenoid starts to move)
3. Δm - Mechanical linkage reaction time (removal of any slop in the linkage and until pins are away from cars)
4. Δsw - Start switch reaction time - Timing starts at the end of this

Of course, there can be variation in start switch reaction time, but you've removed two other possible sources of variation that potentially can be of much greater magnitude (especially when combined).

What if the solenoid starts sticking? Then the solenoid reaction time goes up and variability will likely increase.

What if there is some binding in the mechanical linkage or rubbing of the pins against the track slots they protrude through? Then the mechanical linkage reaction time goes up and variability will likely increase.

Keep in mind that most timer brands time to 0.0001 sec resolution. Can these possible variations exceed 0.0001 sec (separately or combined)? If so, then starting timing based on the solenoid triggering will measure these and affect the end results. If scoring by points, that is not a problem, as it effects everyone in the heat equally. However, that is not the case if scoring by times. I would not want the start gate to decide who gets a trophy (or who goes to the next level race) in a close race.

BTW - I'm seeing more and more why Fast Track timers only use a 0.001 sec timing resolution. There is much less chance (a factor of 10 less) for these variation sources to be measured by the timer.