Hot and cold track question?

[racer1h]

Over the years our has group has noticed that the track is faster in cool, low humidity, days. When it is hot out lap times can be as much as .5sec higher. A 12 sec Car will run 12.5 if the room and track are hot. How can room temp affect a slot car so much. Track is a very clean 130ft Carrera, 12v, silicons.

[slothead]

While many factors are likely involved, I'd guess difference is mostly due to the tires. In F1 they heat the tires before putting them on a car in a pit stop. A way to test this could be to heat up a chassis with a hair dryer on a cool/cold day and see if it makes a difference. A cool track would pull the heat out if the tires pretty quickly, so any effect might only last a lap or two.

Also, test track voltage at the rails with a voltmeter to see if that varies with temperature.

[RichD]

There are a number of possible temperature related issues besides the tires. Tires will leave a deposition on the track and the grip that you get on that may change with changes in temperature and humidity. Another thing that may change is the ohm value of the car's motor, that will go up as the temperature increases and the power output of the motor will go down, but probably not by very much. If the motor is overheating for some reason the reduced power would be more obvious.

[racer1h]

This question was triggered yesterday.......I was running several cars that normally run in the low 11sec. Range. They could barely crack 12sec. The room was hot and the humidity was pretty high.
Cleaned the track, rails, got out the ohm meter checked everything, even changed controllers, same result. Turned on the central air and came back 3 to 4 hours later. The lap times were 3 to 4 tenths better. The motors are a good guess as the hill section felt more lively.

[gt3racerich]

I can't say specifically what part of the car is effected but on my track the temperature of the room absolutely affects lap times.
I basically only use the track in the winter. I have done some extensive testing on many things and always record the temperature as I log my results in. The room is always between 65F and 70F. The warmer the room the faster the lap times (all else being equal).

[slothead]

My initial comments about tire temps was opposite what the original post claimed , that cooler = faster. Others agreed, then the most recent post was faster = hotter.

It was around 80 degrees in my barn loft area yesterday when I was running laps and the times were great. I've also turned laps up here when the temp was below freezing. I came up here once in the middle of winter when the heat was off and it was 4 degrees below zero. A can of Coke that was in the fridge froze and burst it was so cold. I didn't hang around long but had to see if my cars would even move and they did so I ran a few laps using Scalextric and Pioneer cars. Racing in gloves is difficult so I didn't linger or even consider timing them.

For my setup I think warmer = faster, though obviously individual results will vary.

FYI - the coldest it's been at my house in central Maine since 2003 was 30 below zero in January of 2009. It didn't occur to me to go up in the barn and run some laps then, but with yearly temperature swings of 80 - 100 degrees I could conduct some experiments. But maybe just from the low 40's to mid 80's.

[buspor63]

My wood track "feels" to have better grip at 75* than 65*. It's in the garage and I heat and cool it with an open house door with a fan lol

[RichD]

I have noticed that the performance of some tires will change once they have warmed up. I was running in a race that used a spec tire and my car had good grip when I rotated out. When I rotated back in after a few heats I had little grip at first, but by the end of the heat the grip had returned. Other similar tires that I normally run do not do that. I made a comment earlier about tires leaving a deposition on the track. If you run tires on your track that are temperature sensitive they could possibly leave something on the track that makes other brands of tires behave differently. I would really like to test that theory, but I do not have a 1/32nd track. In the interest of having a level playing field when you do club style racing you should probably all run on the same type and make of tires.

[gascarnut]

[chappyman66]

I am going to preface this with "It's not my track". However, I do run on it almost weekly.

My theory is that it has to do with the track joints and power transfer. As the track warms up, the joints expand and some make less efficient contact, so you lose some power. At lower temps, the track shrinks a bit and the joints pull together and give better power transfer. Because it's fully landscaped (ege plastered to the table) it moves where it can, and that's the joints.

Note: I am not saying that Carrera track is bad, that plastic track is bad, or that there is anything wrong with the track. I ran Artin for many years and was very happy with it. And I love racing at Smithtown every week.... it's a great track. I just think it's the difference between sections of track and the continuous strip of tape or braid and the lack of increased resistance at the joints on a taped or braided track. My guess is that taping the rails will make for consistent power.

[HO RacePro]

The takeaway here is that temperature is a factor. Enough of a factor that it can affect lap times by tenths of a second. Which I find a bit surprising because, though almost all physics is affected by temperature, a few degrees difference should have rather small effects.

Things that could contribute to temperature effects, however small:
- Resistance of armature windings
- Heat dissipation of motor
- Heat dissipation of tires
- Traction of tires
- Swelling/Shrinkage of tires
- Balance of tires
- Viscosity of lubricants
- Resistance of power conductors
- Contact resistance of wiring/power conductors
- Surface moisture of track and tires
- Swelling/Shrinkage of track
- Performance of controllers
- Performance of power supply
- Performance of pickup systems
- Accuracy of timing

I said could contribute, and many of these effects should be tiny to the point of being negligable. Which, again, I find hard to reconcile with tenths-of-a-second impacts on lap times. But you start with the data and work your way back to the physics.

My guess is it all comes down to tires. Just which factors make measurable impacts is open to question. It would probably not be easy to tease out which tire factors are in play, but it would be very interesting to find that out.

Ed Bianchi

[slothead]

Though many race fans dislike how engineering has changed things, such as NASCAR now vs. NASCAR then (when you didn't need a million bucks to build a car and the driver made most of the difference), gaining a tenth of a second here and there is about using data. In any data set there will be variance, the difference between measurements. Statistics is about quantifying the variance and trying to find correlations.

If those of us who find puzzles like this interesting started collecting some data we could possibly shed some light on things. When I time trial cars I record the date and try to do all cars in a class on the same day or few days. Next to the date in my spreadsheets I'll start recording the room temperature from my weather station. The weather station also has the outside humidity and air pressure, but the indoor values are likely different. But for now temperature data will be a good start.

If anyone is thinking this would be a waste of time I'll add that anything that keeps your mind active as you get older has value.