Science Fair Project

iowastockcars Monday, 2/21/2011

The boys and I are going to do their elementary school fair on the impact different things would have on a hot wheels car on a downhill race track. We plan on picking out a handful of cars and seeing how far they will go over multiple runs.

Then we are going to go back and do different things.

Right now I have come up with:

    weights on different parts of the car Front, Back, or Middle.

I am going to stay away from any liquid materials to prevent damage to the cars and to the track.

I am also throwing around the idea of clear finger nail polish on the wheels (dried). Would this slick up the wheels and cause less friction? Baby powder on the outside of the wheels to again reduce the friction.

Are there any other ideas out there that people have come up with? If you don't want to share with everyone, feel free to drop me a Private Message.




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redlinederby 2/21/11
Site manager

Are you trying to keep the cars as stock as possible? I've always wondered if a 3-wheeled car will out race a 4-wheeled car. In theory, 3 wheels should be less friction assuming all other things on the car are the same.

I've been meaning to test the skinny wheels vs normal wheels too...again all about friction. Four skinny wheels should produce less friction that 4 normal wheels.

The three wheel car has intrigued me as well as I have been told that is one of the tricks with Pinewood Derby cars, only have three wheels touching.

I want to keep them stock, but maybe I can crank up the weight in the opposite corner in the back to lift the front wheel up off the ground just slightly. Im not sure how much would be needed to accomplish this since we aren't talking about a flexible chassis.

The finger nail polish idea came to me since most of the matchbox cars have the "tread" marks on the wheels and I think that does slow them down--but the sound is cool on the orange tracks. So, if you can smoth them out this way, what is going to happen>?

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redlinederby 2/22/11
Site manager

I've wondered about smooth tires too but my thought kind of went the opposite way, thinking that roughing up the tires might create more grip. But now that I'm typing it, that sounds incredibly stupid...but it might be a good comparison for a science fair thing. Smooth nail polish vs stock smooth vs rough.

Any other ideas out there? Planning on picking out cars this weekend for this.

I may grab a FTE and test the idea that was noted elsewhere in another message about them slowing down after multiple runs.

I will post the results that we come up with here.

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JDC442 3/2/11

When I was a scout, my dad helped me win a pinewood derby race by rounding off the wheels of my car so that there would be less surface area actually coming into contact with the track. I believe weight/balance and friction around the axel also play a big part in a car's speed. Dry graphite on the axels works amazingly.

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skaforhire 3/5/11

I just reread this, and see that you are actually looking for distance not speed (although speed is linked to distance...)

I have a lot of experience with producing cars that go "the distance" as we run competitions for this specifically - however, our cars don't stay on the track after the hill and are allowed to "free drive" on linoleum, cement, hardwood, or tile - depending where we run this. So, I don't know how much help some of this will be.

A few things abut stuff that has already been said.

Those Matchbox wheels really do sound cool going down track... And you would think that because there is less surface area on the wheels there would be less friction to slow it down. But, we have found that these type of wheels never travel as far. I think the width on the "tread" in proportion to the wheel is too great, making it essentially a cog with large ruts that hit the ground in a flat manner - its hard to explain without drawing - rather than a tire's smooth motion. So essentially, if you blew up a matchbox car to actual life size, you would have a very bumpy ride, as it would feel like you were constantly hitting a flat tire, or a pothole every few degrees of rotation.

As for needing more tread to get grip - grip is only needed when something is driving the axle and tires. Since we are relying on gravity, I wonder if making the surface as smooth as possible would not be best? Also, the idea to round the wheels sounds like a good one. I did this when I was a scout for the pinewood derby also, it seemed to work. Although, we have always found that thin wheels do not spin as well as normal wheels - I think it has something to do with the way the axle is connected to the wheel. We find them to be neither fast or far ranging in distance. I cant remember the model, but there is a three wheel car that is made by hot wheels that gets alright speed and distance.

There is a picture of it on my website if you look at the third row down, second car from the left... that car does alright in both speed and distance and it runs on three wheels I believe. (EDIT, I just went back and looked - it actually has four wheels... so scratch that.)

I think it goes without saying that cars with straighter alignment, that don't bounce off walls will go the farthest as there would be less friction points.

We don't put anything on our cars' axles or wheels, so I don't have much input on that. IS there a post on how to use graphite on die cast axles?

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