Glare off lanes interfering with a timing system

[gpraceman]

However, the bottom color may impact timer systems using incandescent light sources. Theorietically at least, a reflective bottom surface could allow light to bounce off a track then off the bottom of the car and then into the sensors thus slightly delaying triggering. We will typically paint the bottom of our cars with ultra flat black paint for this reason. Another stone turned over.

This can also be an issue with Awana tracks since the lanes are typically color coded. The yellow lane, especially if glossy, can cause glare problems with the sensor in the way you indicated. It can affect any timing system using photosensors, even the IR ones, since sunlight or incandescent room lighting can have a lot of IR.

I always recommend that a black stripe be painted across the finish line, centered on the sensors and about 2 inches wide. This helps cut the glare. It also helps if the sensors are recessed into the track as much as possible so the liklihood of a relective bounce of light hitting the sensors becomes unlikely.

[M7 Racing]

This is actually an interesting topic. What is the thoughts out there. If you paint the bottom of your car flat black will you eliminate the glare to make sure the timing system does not get interfered with or does it not matter?

[mrvoltz]

Never had problems with glare using IR.
I don't think painting the bottom of your car will make any difference.
My holes for the sensors do not exceed 3/8" so there isn't much room for reflection.

[Mike Doyle]

I think sensitivity issues with finish line sensors have more impact on "barge" or high nosed car designs. Depending on the set-up, cheater bars might not even register at all until the bulk of the car obscures the sensor, negating any gain from an earlier start.

If you have access to a timer you can sweep various profiles past the sensors at different heights, speeds, and lighting conditions. Try a section of coat hanger to simulate a cheater bar, a popcicle stick for a frontal wing, ect. You will find mixed results since some objects can pass the sensors without detection under the right conditions.

My point is this, if you're going to concentrate on every other aspect of car construction towards perfection, spend 15 seconds to spray some flat black on the bottom of the nose on the far off chance that reflective bounce could rob you of true timing.

[M7 Racing]

How much of a nose of a car do you need to trigger something like the Fast Track sensor? I look at Warp Speed's car and the nose looks like it is only a 1/2" at most. Is there any risk of the sensors not picking it up?

[M7 Racing]

My point is this, if you're going to concentrate on every other aspect of car construction towards perfection, spend 15 seconds to spray some flat black on the bottom of the nose on the far off chance that reflective bounce could rob you of true timing.

I agree. We did that this year...extremely easy to do and it is cheap security. Another added bonus was it confused everyone. I caught one of the car stagers checking out my sons car and spinning the wheels and comparing them to his son's car. This happened right before he was racing in the championsihp. He spun each wheel around 4 times which I assume made it lose a little graphite, however I hope it was not the reason why he was 7/1000ths of a second slower than his brother (I don't think so). Well as my son was going up to him to ask him why he was messing with his car you could see him turn over the car an mouth, "why did they paint it black"? Kinda funny, all he had to do was ask my son for some advise and he would of got all that he needed to run a fast car however he was more worried about figuring it out on his own. The black bottom just made him think there was some big secret thing that was done to the car.

[gpraceman]

How much of a nose of a car do you need to trigger something like the Fast Track sensor? I look at Warp Speed's car and the nose looks like it is only a 1/2" at most. Is there any risk of the sensors not picking it up?

The Fast Track sensor is only 1/8" in diameter, so it won't take much to block the beam.

[M7 Racing]

How much of a nose of a car do you need to trigger something like the Fast Track sensor? I look at Warp Speed's car and the nose looks like it is only a 1/2" at most. Is there any risk of the sensors not picking it up?

The Fast Track sensor is only 1/8" in diameter, so it won't take much to block the beam.

Is that a single beam in the middle of the track? If so, you could have a needle nose type car miss it and maybe catch it on the side of the body?

[gpraceman]

Is that a single beam in the middle of the track? If so, you could have a needle nose type car miss it and maybe catch it on the side of the body?

Yes. It is a single beam centered on the lane. If you do a needle nose, you do run the risk of the sensor not triggering until the side of the nose blocks the beam. That is if the car is not centered on the lane when it crosses the finish line.

[Mike Doyle]

Don't forget to consider distance above the track when you're thinking about width. You can run narrower profiles closer to the track that might not be detectable when mounted higher up.

I'd wager many of the high wire cheater bar cars aren't registering the wire itself at the finish line but the first major portion of the body to cross instead.

If you look at our car from last year (in photos, "My Sons 2005 car), it had a thin high wing on the front with nothing vertically behind it to block the beam until just ahead of the front axle. We experienced erratic timing last year and didn't discover the potential for error in the timing registration of that design until we started playing with a timer this year in our basement.

[gpraceman]

We experienced erratic timing last year and didn't discover the potential for error in the timing registration of that design until we started playing with a timer this year in our basement.

This would be more prominent of an issue if the IR sensor was 1/4" diameter instead of 1/8". Most timer manufacturers are using 1/4" sensors. Micro Wizard is the only one that I know of using the 1/8" sensors.

The higher the "cheater bar" is mounted above the track, the more likely it will not be reliably detected by the finish line sensor.

[craig_newbold]

We experienced erratic timing last year and didn't discover the potential for error in the timing registration of that design until we started playing with a timer this year in our basement.

This would be more prominent of an issue if the IR sensor was 1/4" diameter instead of 1/8". Most timer manufacturers are using 1/4" sensors. Micro Wizard is the only one that I know of using the 1/8" sensors.

The higher the "cheater bar" is mounted above the track, the more likely it will not be reliably detected by the finish line sensor.

The two most common sizes for IR Emmitters and Detectors are 5mm and 3mm diameters. These are the same standard sizes that regular Green or Red LEDs are built to also. I don't know of any detector in use that would be larger than 5mm.

For the DTX000 and TURBO products we use the 3mm size detector and emitter, which is just under 1/8 inch in diameter. The mount that holds the detector are larger, but obviously that doesn't have anything to do with detector accuracy while the diameter of the detector itself could have a small impact.

- Craig

[gpraceman]

For the DTX000 and TURBO products we use the 3mm size detector and emitter, which is just under 1/8 inch in diameter. The mount that holds the detector are larger, but obviously that doesn't have anything to do with detector accuracy while the diameter of the detector itself could have a small impact.

Thanks for clarifying that with your timers. Since they are mounted inside a plastic sleeve probably was why I was thinking that they were the larger sensors. That's what happens when I try to go by memory .

[Watch-out-for-that-frog]

Thanks to this thread our latest derbyh went off PERFECT! We raced in a mall with all sorts of lighting issues. A little tape and an exacto, poof no more issues! Made me look like a pro hehehehehe THANKS!!!!!!!!!!

[Pack38dad]

Build a Wedge!
No problem with blocking the sensors that way.
We also take a Sharpie and color the first couple of inches of the nose on the bottom black. Matte black paint might also be an option, but the Sharpie will do.