Starting Gates

[Darin McGrew]

The Cheater Bar topic ended up including discussion of starting gates, which I figured ought to be its own topic.

Our track's starting gate is spring loaded, so that it swings down quickly when the catch is released. It has a metal axle (¼" rod) under the track, perpendicular to the direction of travel. The gates are bolted to this axle, and stick through the slots in the center guide rails when the axle is rotated and latched.

The gates are lightweight aluminum. The aluminum prevents games with magnets (using the motion of the gate to give a car a head start). Since they're lightweight, it doesn't take a very strong spring to rotate the gate quickly.

The spring is oriented to pull the gates down when they're in the latched position (90º), and to pull perpendicular to the axle when the gates are below the surface of the track (-30º or so). The spring was tuned so that the gates don't keep going to hit the underside of the track, but even if they did, they are lightweight and wouldn't disturb the track much. The spring was also tuned so that the gates don't pop back up through the slots in the center guide rails.

Anyway, with this gate, we get consistent starts, and we don't have to worry about the gate's follow-through movement disturbing the race. The gate is in the center of the lane, in the same position as the photosensor for the finish line.

So, what improvements could be made to this design? What other designs work as well?

[Stan Pope]

So, what improvements could be made to this design?

Portability! Walk in and set up on any track in a short time (e.g. 15 minutes) without altering or disassembling the track.

Ideas on how??? (Some were suggested in my cheater bar post.)

[Darin McGrew]

So, what improvements could be made to this design?

Portability! Walk in and set up on any track in a short time (e.g. 15 minutes) without altering or disassembling the track.

Ideas on how??? (Some were suggested in my cheater bar post.)

On any track? Okay...

The gate needs to clamp on top of the starting end of the track, since you can't assume anything about the slots in the track. The pins will extend down to the track surface and will swing up out of the way of the cars.

The length of the pins (or the height of the axle) should be adjustable, to accomodate different heights of center guide rail, different track structures, etc.

The spacing of the pins should be adjustable, to accomodate different lane spacing.

The spacing of the supports that clamp to the track should be adjustable to accomodate different widths of track.

The thing that stumps me right now is how to attach the gate to the track. It has to be generic enough to attach to any track, but you can't interfere with the edges of the track because there may not be enough clearance between the center guide rail and the gate's clamps. My inclination is to have it clamp onto the back of the track somehow, so that it is behind the cars.

[Stan Pope]

Great start, Darin!!! Who else can contribute to this?

[ExtremePWD]

Envision the starting gate as a large C clamp that straddles the track and contacts only the edges. I would probably go with edge clamping in two locations. The C clamps would actually be the starting gate framework. There is a lot of adjustability needed to fit different track widths and lane spacings. To minimize the complexity, a one piece, lightweight bar could go across all lanes. One drawback is it would block the audience and participants' vision of the cars. Plexiglass? Anytime you try and make one device work for a wide spectrum of applications you end up adding excessive complexity and cost or you start compromising performance.

I am working on a portable design for the style of tracks that use a hinged 1x and attached pins. This simplifies the requirements of the device considerably. I purchased the parts today to start experimenting. I'm thinking $5-$10 when done.

[Stan Pope]

I am working on a portable design for the style of tracks that use a hinged 1x and attached pins. This simplifies the requirements of the device considerably. I purchased the parts today to start experimenting. I'm thinking $5-$10 when done.

I'll be interested in the results.

Any other "requirements" that should be listed?

Visibility (audience and participant) is a pretty important issue. That means that the amount of "stuff" above the track needs to be as inobtrusive as possible. Clear plexiglass side panels would be preferable to opaque material, but not ideal because of reflections. Consider 1/4" square cross section steel for side supports.

Would it be reasonable to assume that the underside of the track around the starting area is unobstructed? For the tracks I'm interested in (Piantedosi of various widths) the answer is "yes", but I'm sure that it would not be true for some tracks.

Also, for Piantedosi (and other tracks that I've looked at), there is an edge margin of at least 1" that can be counted on. For my purposes, this could be a "given."

Oh, yes, another requirement: the gate must be setable and releaseable from either side! The starter needs to be positioned across the track from the audience, and the track orientation can't be dictated by the starting gate!

[ExtremePWD]

Operable from either side is easy to accomodate. How much space behind the cars can be counted on with the Piantedosi track? Can I assume 1 " also?

The consideration with any part of the mechanism or attachment that is behind the cars is allowing for a clear line of sight for alignment of the cars.

[Stan Pope]

Operable from either side is easy to accomodate. How much space behind the cars can be counted on with the Piantedosi track? Can I assume 1 " also?

The distance from the pins to the rear edge of the track is around 12". Your concerns about visibility are valid.

[Darin McGrew]

Oh, yes, another requirement: the gate must be setable and releaseable from either side! The starter needs to be positioned across the track from the audience, and the track orientation can't be dictated by the starting gate!

We set up the audience seating in a "U" shape, with the track running down the center, and with the seats for the four racers at the bottom of the "U". With this configuration, "across the track from the audience" is behind the starting gate, which is where the starter (who also stages the cars) stands.

[Darin McGrew]

Would it be reasonable to assume that the underside of the track around the starting area is unobstructed? For the tracks I'm interested in (Piantedosi of various widths) the answer is "yes", but I'm sure that it would not be true for some tracks.

Also, for Piantedosi (and other tracks that I've looked at), there is an edge margin of at least 1" that can be counted on. For my purposes, this could be a "given."

Ours is an atypical track from what I've seen, but it's built with a 1x4 frame on the edges and ends of each section of track. It's like your typical drawer, only upside down. The cross-section looks something like this:

Code: Select all

|__----_____----_____----_____----__|
|                                   |
|                                   |

There is a similar 1x4 at the end of each section, including the start and finish.

[Stan Pope]

Oh, yes, another requirement: the gate must be setable and releaseable from either side! The starter needs to be positioned across the track from the audience, and the track orientation can't be dictated by the starting gate!

We set up the audience seating in a "U" shape, with the track running down the center, and with the seats for the four racers at the bottom of the "U". With this configuration, "across the track from the audience" is behind the starting gate, which is where the starter (who also stages the cars) stands.

My environment is a bit different: 3 basketball courts side-by-side. About 2 1/2 of these are quartered with a track in each one. Bleacher seating for older folks around periphery of the courts (not along dividing lines, tho). Boys on floor with track between boys and older folks. Boys in the current heat stage their carsn then wait at finsh line. For viewing the staging and starting activity, we feel that older folks and the boys who in this heat are the ones who need totally unobstructed visibility.

I think the point is that release control needs to be operatable without reaching up to the starting line above track level.

[ExtremePWD]

Another consideration for a portable starting system / attachment is the presence of a timer start switch. A totally separate, above the track system would not trigger an existing starting switch. A solution that builds on the existing starting gate addresses this issue as long as the additional hardware does not need to occupy the same location as the switch assembly. A little research will be needed to understand at least the standard variations provided by the leading timer manufacturers. There will be the occasional home-brew timer setup that would be unpredicatable in design.

[Stan Pope]

Timer start switch interface! Excellent addition to requirements!

Microswitches stsill come in DPST form? Or are microswitches still made?

[ExtremePWD]

There are many kinds of small/micro switches on the market. However, for this application the best design appears to be the type that has a flexible lever arm sticking out that provides some tolerance for the location of the feature it is sensing. These are pretty difficult to find in the right pole/throw/open/closed combination. I have tried using a direct acting switch and it must be finely tuned for the contact.

[Stan Pope]

Most of the microswitches I've encountered are of the 3 contact variety, so they can be treated as either Normally Open or as Normally Closed. This makes them very versatile in this applicaiton. It has been a lot of years since I scavenged any of them, but the flexible lever arm with a roller at the end were pretty common.

The next question about them is whether their switching times are consistent enough to be useful in this clock-start signal application. If not, then I'd go with an LED - photodiode arrangement (I set up arrangements like that about 20 years ago to help count mouse exercise wheel revolutions in a science project with eldest daughter. along with a building a 4-channel strip chart recorder!)