Help, need advice on inconsistent times

[FastBob]

How much variation in times do you guys with practice tracks see? On our old home made 32 foot track the average variation was .0305 sec. I bought a new aluminum 32 foot track a few weeks ago and so far the average variation is .0412. Times on both tracks are in the 2.6 range. We usually make 10 runs to get an average and have seen as high as .066 variation in the 10 times with all conditions being equal. Our least variation so far in a 10 run test has been .020. I was hoping for that number or better with our new track. We had a car in Tigers and Cubs this year and at the district race the Tiger cars times only varied .014 sec. across all 4 lanes which I thought was extremely consistent. The Cub varied .026 across all 4 lanes.
Thanks for any info.

[pwdarchitect]

The inconsistancy isn't that far out of line if the car itself is not aligned to it's maximum potential.

One thing you will want to check is how level the track is in both directions. A laser level is a tool that will help with this. You might have to put a shim here and there in order to get your track as level as possible.
You also might want to consider making fixtures to support the track at each track joint such that you can make slight adjustments via a screw type of foot.

[Stan Pope]

Variance looks high.

Look for alignment issues that put a rear wheel against the guide at varying distances down the track.

[FastBob]

Thanks guys,
Don't think it's the cars. Both are aligned pretty good per Stan's method. Cars roll straight and wheels pretty much stay put rolling forward and backward. No rail riders yet. Both are very fast. Tiger won at pack, district and council and cub won at pack, district and was 2nd at council.

Here are there times at the district race:

cub car
time
2.6134
2.5873
2.5957
2.5938
2.5976 avg. .0261 variation, faster car than tiger but less consistent, better wheels & axles than tiger car.

tiger car
2.6375
2.6354
2.6232
2.6230
2.6298 avg. .0145 variation, more consistent but slower than cub car, lower CG than cub.

These times were on 4 different lanes. Our times are all on 1 lane which should make it easier to be more consistent. We have leveled the track side to side with a bubble level and filed some rough joints. Why would leveling it end to end matter about consistency? Is a laser level better?Will continue to tweak track. Could the timer or starting gate influence our times this much? We relube lightly every 10 runs with hobby lube.

Track is a Best Track
Timer is a Judge

So far we've made over 100 runs, 13 sets, between the 2 cars with7 to 10 runs each set trying to get the times more consistent.

Here is an average set of times on our 1 lane track.
2.671
2.642
2.652
2.679
2.672
2.660
2.668
2.684
2.655
avg. 2.665, variation .042

Greatest variation in 13 sets was .066. Least variation was .020. Average was .041

Thanks again for any input

[PWD]

.305 and .0412 iare on the high side from our experience. Especially on a 32 foot track. What would be interesting is to see the difference if you turned it into a rail rider. I think what is happening now in some lanes it is a natural rail rider and others the rasied wheel is rubbing.

I am willing to bet that if you turned it into a rail rider you would see more consistent times and the times would be close to the faster times you are seeing.

On our 32' Pianadosi wood track a well built and aligned car has no more than .0100 of variance in speed. This is even true from year to year. Kind of boring. Glad we have gone to a 49' alumimnum track. On this track we have variances of .0300 and sometimes even higher. Far more interesting.

Personally I think to continue to have PWD remain as interesting as it has been in the past we are going to need to go to longer tracks.

[Mike Doyle]

One thing that can cause a huge variance in times is the start gate switch. If you have a spring loaded gate and the wrong switch arm alignment then you'll get irregular "switch bounces" sometimes that will yield inconsistent times.

We modified our Piantedosi start gate with two layers of foam- one very soft layer to absorb the first impact and a second layer of firmer foam to arrest the gate movement. We also aligned the microswitch for minimum contact with the gate was closed and ensured the gate didn't swing back and re-strike the switch once it was released.

Our times are very consistent now and the slightest adjustment in alignment is clearly registered, we can even observe the graphite break-in and fatigue over multiple runs.

[Stan Pope]

Don't think it's the cars. Both are aligned pretty good per Stan's method. Cars roll straight and wheels pretty much stay put rolling forward and backward. No rail riders yet. Both are very fast. Tiger won at pack, district and council and cub won at pack, district and was 2nd at council.

Then I will revise my suggestions...

Way to go! Good job!

Cars aligned "dead on" will show more variation than cars aligned for "optimized rail riding."

A rail rider tend to be subjected to nearly identical track imperfections each trip down the track. Variance due largely to initial staging and when and how first rail impact occurs.

"Dead on" aligned car is subjected to different track imperfections almost every trip depending on when and how each rail iimpact occurs, as dictated by initial staging.

Sounds like your team has done a very good job of achieving "dead on" alignment! The obvious next step is to develop proficiency with advanced alignment techniques. "Dead on" alignment is a great "stepping off" point for "rail riding."

Variance differences between your home track and the pack/district/council tracks can come from a lot of sources. Consistency in the starting mechanism, rail and running surface smoothness are the most likely sources.

[SuperDave]

How do you know the timing is correct? With a photo detection system, car shape and room lighting can (may not, just ask some others) affect the results. Especially without a 'rail rider', the car can cross to the center or left or right randomly. At the very least, try a dark room during the race.