You are kidding, I hope. The angular momentum of the wheel would be tiny; and any force you would save by not generating it would be a drop compared to the rest of the forces.
I have heard that raising a wheel reduces friction, but the odds of having it track as well as 4 wheels is not good.
The increased friction would be where the wheel and the axel come in contact with each other. The carried weight would be 1/3 greater for each wheel and axel if 1 wheel were eliminated.
As a grandfather I have made many Pinewood Derby cars for scouts in our family. The kids designed them, I did the body work, they painted and finished wheels and hop-up. We had many winners. My daughter was Den Mother for her son's Cub pack and helped run the derby. In her final year she entered the race against the dads, and she smoked them! The track always had a 3/8" center strip to keep cars on track so our main concern was clearance underneath the body. Glenn
Except for paying for the weddings, I am now more glad than ever that all I had was daughters.
Not kidding. It can produce a measurable result. That's not to say it's particularly important in the grand scheme of things, and I did try to make that clear.
Well, it doesn't reduce friction, and it is true that it's harder to get the car to track as well with only three wheels. But not impossible.
Since I haven't seen it mentioned here, I should point out a very important performance factor that is usually neglected, and that is the track itself. A car which could perform extremely well on a top- quality track often fares poorly on a bad track. For example, on a bumpy track, you can't push the weight back as far as you'd like (and could get away with on a smooth track).
Jim
True. The axle load on a car with four wheels would be 1/4 the car's total weight. It would be 1/3 on a car with a lifted wheel. But the axle- wheel friction is directly proportional to the axle load. That is, for any given wheel:
f = c * (1/4)m = cm/4
where f is the friction, c is a constant, and m is the car's weight.
So t_4 = 4f = 4cm/4 = cm
where t_4 is the total friction from wheel drag in the 4-wheel case.
Similarly, with three wheels, as you noted, we have, f = cm/3, but now there are only three wheels, so the total friction is
t_3 = 3f = 3cm/3 = cm
Since c is the same in both scenarios, t_4 = t_3. That is, the total friction is the same in both cases.
Jim
Thank you all for your input we will be keeping all four wheels on the track Joe
You get more accurate results. :-)
Certainly!
Ideally, the rules are devised so as to limit the available performance improvements to those that can be accomplished by an eight to ten year- old boy with a reasonably knowledgeable mentor and rudimentary tools.
When I was doing this stuff, we added open and unlimited categories to give the more zealous mentors the opportunity to satisfy their urges without taking over their boys' cars.
Jim
Yes, Virginia, there are really fast cars.
Scouting has a huge presence on our military bases overseas. While we were in Japan, my son participated in large pack races two years in a row. Each year, over 90 cars raced a double elimination tournament with the winner of each race determined by a best 2 out of 3 trips down the track against the same opponent. That meant the slowest cars went down the track at least 4 times and the fastest cars went down several dozen times.
Each year, there was one car that crossed the finish line first every single time it ran. The first year, it was someone else's car. The second year, it was my son's.
When we came back to the States, we repeated the feat two more years at smaller pack races.
Fast cars don't just exist in the fantasies of kids young and old. They are real, and we built 'em.
DonkeyHody "A poor workman quarrels with his tools." - American Indian Proverb
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