My time, your time... What's in a time?

[emptyd]

Over the years I've encountered here a fair number of posts that started out something like "What is a good time for [fill in the track type and dimensions]. Lots and lots of time comparison requests.

Our Grand Prix was a week and a half ago and we just used a new Fast Track timer. It uses a laser trigger which we set up to be tripped by the starting pins. We also put the finish line sensor holes about 3 feet further down the track than the old timer. Everything else was the same: slope, track material (same track), straightness…

An excellent time in the past on our track/old timer setup was 2.96 “seconds”. As I compared that time to those posted around here I concluded that if we were to ever advance to any “regional” events we get our behinds kicked!

This year, the top time on our track was 2.33 seconds! What a difference. The times were up all across the board despite having a 3 foot LONGER racing surface.

I have come to conclude that trying to compare times from various brands of timers, various mounting/triggering methods, and various start methods… throws so many variables into the mix that it is virtually impossible.

We learned that our old timer (which was commercially purchased through Awana) was really more of a “counter” that a “timer” or better stated “chronometer”. It counted “in the neighborhood” of one whole number per second, but not anywhere near exactly.

As another metric, that same (old) timer on an aluminum track of the same length as used in our competition turned in a time of 3.04 “seconds” for the car that ran 2.33 seconds (best time – average was more like 2.39).

So, for what it is worth, I’ll never again pay any attention to the “my car ran thus and so…”, or “how fast is a ‘good’ time…” posts. What an education.

[Stan Pope]

Great post!

Both times seem unnatural. 2.96 seems unnaturally slow, and 2.33 seems unnaturally fast.

It is important that the times be "consistent" with one timer ... important so that competition is judged "by the same yardstick" and important that you be able to compare the effect of car changes when you are tuning. It appears that each of your timers, separately, satisfy that aspect

[TAL]

I totally agree that a time on your track is no comparison to a time on my track even thou you and I might have the same track make , timer make or what have ya.

Reason being some fail to include that the laser gate is actually 4 or 5 inches away from actual starting gate and some will fail to tell you that the factory stacking blocks under track that were originally 3/8" thick have now been replaced with now 1/2" stacking blocks .

Many will also fail to include the fact that the finish line has been moved back or forward 2 or 3 inches.

Their a just some many different variables that can effect the situation that to me times are only comparable when done on the same track and equipment at about the same time without upsetting the track in any way.

[3 Cub Dad]

I'd have to respectfully disagree a little. IF given all of the qualifying information, (example; 42' BestTrack, microswitch, K3Microwizard time, first set of sensor holes), it can be beneficial for comparison. We ran the above last year for our pack, but with no districts, we had no way of knowing how the speed of our cars compared to others. A few of the postings here gave us some comparison numbers, (as well as video from last years Lima race for the PWD league).

I agree that on built tracks, or older tracks, you can't really compare times, but for the newer purchased "standard" tracks, the numbers should be pretty comparable.

[TAL]

Best track ; I have seen 2 in my life and can't really comment as to set-up requirements.

We do have a Freedom anodized that can be Time manipulated very easily.

Examle: We can set the bottom of the 4 legs level with the flat running surface of the track or sometimes we put a 3/4" (1x4) up under the 4 legs for floor protection from sharp edges of the aluminum.

Also the stacking blocks of the track sections are standard 3/8" but if are replaced with say 3/4" or even 2" stacking blocks would that not make a difference in times?

Yes it does, On our track a Stock car that will cut a 2.9 on the standard blocks will cut a high 3.0 win using 3/4" stacking blocks and about the same differences will accure when leveling , raising 3/4" or even a 3/8" sheet of plywood on the 4 bottom legs.

Even with the pre-bent curve of the best track It could probably be manipulated in these effects also?

[knavekid]

While most of the timer manufacturers specify the resolution of their timers, I could not find a specification on timer accuracy. I looked at Newbold, Microwizard, and New Directions. I saw resolutions specified as fine as 10 microseconds. However, a 100 microsecond resolution doesn't mean that the total elapsed time will be accurate to 100 microseconds. It all depends on the accuracy of the time base.

Most microprocessors have an internal clock capability and also support an external clock source. The internally generated clocks can vary by more than 5%. The external clock may be a crystal oscillator, a quartz crystal, a ceramic resonator, or a simple resistor/capacitor network. Crystal oscillators have a specified accuracy that can be as good as 25ppm (parts per million). For a 3 second ET, this would correspond to about 75 microseconds. Quartz crystals can be as good as 20ppm or about 60 microseconds. Ceramic resonators are only accurate to about 0.5% or about 15 milliseconds for a 3 second ET. The 5% internal clock could be off as much as 150 milliseconds.

These time base inaccuracies may be small compared to design latencies due to sampling and software. The latencies due to the sense circuit and start gate sensor can introduce even more error.

In conclusion, the displayed ET for any particular track can vary greatly compared to any other track of the same length and construction due to several factors.

[sporty]

Emptyd,


You make a good statement !


I do think we both are in a wider gap of agreement on certain matters though.

But let me first say where I am coming from.


Many post times, with little or no info, in regards to tracks and set up, software and so forth.

So I have been hoping that some kind of general time data can be gathered or the information of the track and so forth.

Not so much for seing who really is faster. But to let it be known that there is going to a range.

That what appears to be a fast time may not be a fast time.


However the more data and good data gathered. Esp from newer standard track that are sold. you can get somewhat of a better chart together. Than no chart and just guess work.

Data and information is everything though !


I never totally focus on the time. We each much find a system or process that works for us and the kids.

No one knows the track you race on better than you and the people who set it up and run it.


I use the time as a comparison to the others who raced on the track my kids raced on, and save the data from year to year to go buy.

Then it's always racing the cars from last year against this year. As also a way to compare progress.


But yes, if the track times you see are not your make and model of track and set up is different. The times are going to be pretty different to try and compare too.

But you did bring up a very good point on the timers and microseconds.


That was great to point out to all of us !


Sporty

[PWD_addict]

We only compare times to the same track in previous years. In a recent post, it appeared that our cars were a full 1 second slower on a similar sized track than doct1010's cars (I think it was Doc). I had assumed that our track was really rough given that it is a homemade "Challenger" track with rough joints. Perhaps it is just the timer that is giving us the discrepancy in times with other similar-sized aluminum tracks.

All I know for sure is that my son and I have won his Pack Derby the last two years and my daughter's car set the all-time track record this year. We haven't had district derbies to see other cars from other packs but will see them all on April 19th this year.

I also know that my son's last year car was faster than any car in another pack that let us test on their track after their Derby. Well, faster than any other car except for the car we built with my Godson with ultra-light wheels that won that Pack.

So, I'm in agreement with emptyd.