Require a Peg on Bottom of Car?

[SlartyBartFast]

Looking at how to place finish line sensors the low center of lane design of the all metal tracks struck me. Couldn't the car specifications be altered to allow lower riding cars?

But, there's another possible use of that. Given the clearance available in the center of the track, why not use standard optical switches and install a wood dowel in the bottom of every car?

Previously an idea came about in a discussion about car alignment and starting gate issues. I had proposed using something similar to the BSA axle guard to guide the placement of the car at the top of the track. If a dowel was placed at each end of the car, a slotted block in the start are would ensure decent car alignment every race. Not important for races where participants stage their own cars, but if officials stage the cars it certainly levels the playing field.

The holes for the dowels could be pre-drilled in the kit block and the dowels supplied. Put the dowel holes between the axles, and you have a new variable to play with as to how to get the fasted time.

(And yes, I know this would require different stopping mechanisms and would only be a good idea if the same method of timing was used in all races the car would participate in.)

[SlartyBartFast]

Please note that simply voting doesn't give me any info. If you're driven to vote please join the conversation and say why you voted.

[batstar70]

I voted bad idea 'cause in my way of thinking its just another rule to adhere to and all tracks would need to be the same (clearance in the center). Just my 2cents worth. batstar70

[Darin McGrew]

It might work if you distributed kits with the pegs already in place, or if you held workshops where you helped everyone install the pegs. But it would mean that the cars could not race on tracks with a solid guide rail.

[SlartyBartFast]

Absolutely Darin. If your track has a solid center rail, the idea is (probably) out of the question.

Drilling two holes in the bottom of each block centered at the axles and providing dowels is very little to have to do.

As for the solid rail issue, I said "probably" because it depends on the thickness of the rail. Too close to the 3/8ths minimum car clearance at the idea is not possible. With just a small amount of clearance, the idea becomes possible.

Don't glue the dowels in and the car could be reused on other tracks too. With the inherent problems of maintaining weight, CG, and overcoming any track/timer specific design decisions.

[gpraceman]

Absolutely Darin. If your track has a solid center rail, the idea is (probably) out of the question.

There would also be a problem with Micro Wizard tracks, since they have screw heads that stick up in the centers of each lane.

I only see this idea working on BestTracks.

[SlartyBartFast]

they have screw heads that stick up in the centers of each lane.

Know by how much? One slot sensor requires only 2.5 mm to reach the sensors. So say 5mm from the bottom of the car would be required.

[ohiofitter]

If this is for your pack race and you are the PWD chairman you could make it happen........But does the council and district race use your track..........I have to say it's a bad idea right now just for the simple fact there are so many variances in the track right now

[SlartyBartFast]

there are so many variances in the track right now

Not sure what you mean. You mean from track to track?

How do people feel about reflective IR sensors? With a daylight filter, shouldn't they be better than or just as good as DIY break beams?

A very short distance sensor and a small white mark on the nose of cars and it should be perfect.

BTW, for those that haven't figured out my MO, I've sketched out a starting light and results display tower and would like to get rid of the bridge required by break beam timers to have a clear unobstructed view of the race.

[gpraceman]

Know by how much? One slot sensor requires only 2.5 mm to reach the sensors. So say 5mm from the bottom of the car would be required.

The heads are probably about 3 or 4 mm tall.

How do people feel about reflective IR sensors? With a daylight filter, shouldn't they be better than or just as good as DIY break beams?

With any type of reflector mounted to the car, you will end up with issues of nose design, angle of the reflector, and so on. You'd be better off sticking with something that wasn't dependent on the cars (other than them breaking a beam).

BTW, for those that haven't figured out my MO, I've sketched out a starting light and results display tower and would like to get rid of the bridge required by break beam timers to have a clear unobstructed view of the race.

Overall, it seems you are making more work for yourself than you need to. If you are building a timing system, just make it low profile. Minimize the thickness of the bridge span and supports. Even consider making the supports out of plexiglas.

[SlartyBartFast]

With any type of reflector mounted to the car, you will end up with issues of nose design, angle of the reflector, and so on.

Interesting you should bring that up. A rigid square stuck to the car would eliminate design and construction issues IMO.

Nose design is a big, but seemingly ignored, issue with break-beams as well.

How wide is the beam? How much of the beam needs to be blocked before the circuit reports the break?

A fast car that wants to ensure that the beam is broken as quickly as possible, should have a nose design that is:
- flat
- square
- low as possible
- a minimum width equal to the maximum side to side displacement of the car.

I would think that an interesting test would to be to see what the tolerance and lane to lane deviation really is for a track using a straight edge and square.

[gpraceman]

Interesting you should bring that up. A rigid square stuck to the car would eliminate design and construction issues IMO.

What of the angle of the nose? If your reflector is angled with respect to the IR emitter/receiver unit, then you can be inducing timing problems. So, to counter act that issue you will have to change your rules so racers cannot have angled noses. To me that is an unnecessary design restriction.

[SlartyBartFast]

What of the angle of the nose? If your reflector is angled with respect to the IR emitter/receiver unit, then you can be inducing timing problems. So, to counter act that issue you will have to change your rules so racers cannot have angled noses. To me that is an unnecessary design restriction.

The reflective pair sensors are aimed to detect paper at a given distance (used in photocopiers and printers).

True that means a low flat surface would be required. The idea I had was card stock affixed near the axles. Then everyone would have the same reflective surface aligned with the front of their car.

I don't see this or inserting a pin/dowel to be anymore invasive than areas left flat and unpainted for stamps or other requirements.

I don't expect to encounter any of the pineheads on here and pinewood seems rare around here. So what ever I try is really just on my head.

It's more a question of technical and enforcement feasibility that I'm concerned.

[gpraceman]

The reflective pair sensors are aimed to detect paper at a given distance (used in photocopiers and printers).

That is fine in a photocopier, but a different story on a Pinewood Derby track. In a photocopier you can ensure the sensors are tangential to the paper.

True that means a low flat surface would be required. The idea I had was card stock affixed near the axles. Then everyone would have the same reflective surface aligned with the front of their car.

What about extended/regular wheelbase issues?

I don't see this or inserting a pin/dowel to be anymore invasive than areas left flat and unpainted for stamps or other requirements.

Those measures are not critical to how the cars are timed.

I don't expect to encounter any of the pineheads on here and pinewood seems rare around here. So what ever I try is really just on my head.

Are you sure that will always be the case?

It's more a question of technical and enforcement feasibility that I'm concerned.

Personally, I think you are far better off going with regular IR beams than some system that relies on the cars themselves to be a component of the detection system (again, other than blocking a beam).

So, what happens when you move on and someone else has to run the race and use the equipment? The less complicated it is, the easier it will be on them. You certainly cannot depend on them to read any documentation you leave behind (likely to not get read or will get lost).

If you do end up building some system like you propose, I hope you do some good testing prior to make sure that the finish detection will be reliable.

[FAST Racing]

Having a "pin/dowel" protruding below the nose of
the car will cause the car to tumble when it gets
to the stop section.

On an aggressive rail-rider, it can cause the car to
corkscrew into another lane when the wheels drop
away in the stop section.