Timer accuracy from build

Commercial timing systems
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tmbnorm
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Timer accuracy from build

Post by tmbnorm »

I have built a Microwizard K2 for a Piantedosi Freedom Aluminum track.
After completion, I did some tests and everything seems to work well.

I did some testing with a sheet of paper and I notice that 1 of the sensors is about 1 mm or so infront of the other two sensors. Multiple tests always give 1-2-3 or 1-3-2 as the results using the sheet of paper.

Should I be concerned? I know that you can never get it exact, but is this close enough? I know we are talking about less than 1/10" of an inch over a 40' track (36' or so of race), but I want it to be a good build.

I did not have the adaptor plate to the Freedom track, long story.

I am thinking of getting a new adaptor plate for the Freedom track and a new bottom bar on the K2 timer. I could then redo the timer more exactly.

Thanks for any help.
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gpraceman
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Re: Timer accuracy from build

Post by gpraceman »

Were the holes on the bottom bar not drilled in a straight line? If not, you should contact Micro Wizard for a replacement.

You may want to check up underneath the timer housing and make sure that the IR LED's are pointing straight down. I have seen these get bent out of position. This will make sure each of the sensors is getting the maximum illumination, which is the best condition for detecting a car breaking the beam.

For the paper test, are you sure that you are keeping the paper pefectly parallel to the line of sensors? This is really hard to accomplish.

It is possible to get a tie for 1st place with a Fast Track timer, but it is hard to do. While the timer reports out to 0.001 seconds, there is a secondary timer out to a 0.0002 sec resolution that comes into play when breaking a first place tie. While you cannot tell that this has happened just by looking at the timer (unless it has the times display) but with the data sent to a computer interface, the winning lane is marked with a "!" character. This secondary timer only comes into play with a 1st place tie, not a tie for any other place.
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tmbnorm
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Re: Timer accuracy from build

Post by tmbnorm »

All holes were drilled by me. None of the holes were predrilled.

You can eyeball the line of sensors with a straight edge and see that one of them is just slightly ahead of the others. It is hard to drill the holes in the exact spot when doing it by hand.
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gpraceman
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Re: Timer accuracy from build

Post by gpraceman »

tmbnorm wrote:You can eyeball the line of sensors with a straight edge and see that one of them is just slightly ahead of the others. It is hard to drill the holes in the exact spot when doing it by hand.
I would agree with that. Using a center punch helps, but still it isn't so easy to get all the holes in line.

You can try slotting that hole a bit so you could nudge the one sensor over in line with the other two and then resecure it in place.

Maybe Micro Wizard should predrill those holes on their kits. It is definitely easier to do with a drill press and a fence, than for a customer to try to do so with a hand drill.
Randy Lisano
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Re: Timer accuracy from build

Post by tmbnorm »

Like I said,

I did not have the Freedom adaptor plate when I drilled the holes.
I am thinking getting a new adaptor plate from Piantedosi and a new bottom bar from Microwizard.

I could use the adaptor plate as a guide to drill the holes for the bottom bar.

It is only about a 1-2mm, but I want it to be pretty close.
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Re: Timer accuracy from build

Post by gpraceman »

If you do get another bottom bar, you can use the track mount plate as a guide to mark the holes to get them close. However, I'd recommend that you use a center punch to do the final marking of the hole location so the drill bit won't wander before it takes a bite.

If you've got a buddy with a drill press, then that would be a better way to go for the drilling part. Some type of fence can then be rigged to make sure the holes are in line with each other.

Anyways, before doing all that, you may want to see what you can do with your existing bottom bar.
Randy Lisano
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Re: Timer accuracy from build

Post by tmbnorm »

I used a hole punch, but the drill bit does seem to move around some before taking a bite.

I will look at slotting the one sensor hole a little bit. This is for our Cub scout pack, so I want it to look nice. I will also look into a new bottom bar. It would be easy to do it again, now that I know what I am doing.

Everything is much easier the second time around.

I contacted Microwizard. A new bottom bar is $8 delivered. I am just going to get a new bottom bar.
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Re: Timer accuracy from build

Post by Mr. Slick »

one way to make sure the hole is where it is intended is to take a longer piece of 1/4" metal (steel or aluminum) and drill the holes with a drill press using a fence to get them all straight. Then use this clamped to the track as the guide for the actual holes. If you use a soft metal you won't be able to use the guide lots of times. . . :-)

I have also seen a single lane jig that straddles the center and provides the alignment for the hole. The jig is aligned from lane to lane by putting it between TWO guides that are clamped and perpendicular to the track.

Also remember that the starting pins need to be just as accurate or the same error will be recorded.

What a 1/1000 of a second is: (or what is 1/8 inch)
38ft pin to sensor
3.1 seconds time
==> 147 inches per second
==> .147 inches per 1/1000 second ~ 1/8 inch

ADDED: BTW, a really well tuned car and a track that is as close to perfect as possible will have a variance of 2/1000's of a second over three lanes, 2 runs each.

What is the probability of these "errors" having any meaning in the results? - pretty much nothing.
ALSO- remember that if you have every car doing all the lanes the same number of times, any effect of one lane being "longer" is going to be eliminated if you use time based ranking (total, average, total less slowest) IF you go by POINTS then there could be a difference because of which car is racing in the "long" lane against against which other cars in the heat . . . . this is one of the strongest arguments for the use of total time ranking. (I know I just upset several people, but it is just my humble opinion based on what I know at this time.)
:D
Mr. Slick says: Honey, I am doing this for the kids, not myself.
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