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Getting back to your slot car, if its mass is in proportion to the linear scale of 1/24, we can expect it to weigh about 100 g. At 70 m.p.h. (31.3 m.s-1), its kinetic energy is 49 joules. To get that much energy into the car in 0.25 seconds, the mechanical output of the motor must be 200 watts. For a typical small motor, not really desiged for efficiency, the electrical input would have to be 300 to 400 watts. The average acceleration is 125 m.s-2. The force required to give this acceleration is 12.5 newtons. With only a little more than one newton (100 g force) holding the car down on the track, you need a coefficient of friction of 12.5. Are you

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I'm not a physicist, nor a mathmetician but I think I understand your point. My belief is that there is no way that the mass of this slot car is anywhere near 1/24 of a real car. I believe the weight isn't, however the way I'm calculating this scale thing must be bogus. It's not just a matter of dividing real world by 24 is it? Your estimated weight of 100 grams leads me to believe that there is some logarithm involved. Your estimate seems low if 1 gram equals .035 oz. This car weighs probably less than 12 ounces and most of that is motor. I think the 1/24 scale definition may possibly be derived only from the body length and width. The body shape and the fact that they put glue on the track help to keep the car on the track. My thinking is based on remedial math. Oh no. Not another word problem!!

They slotcar raceway has a 160 foot track. The fastest lap time I've ever recorded there was 1.7 seconds. If I divide 160 feet into 5280 I get 1/33 of a mile. This makes some degree of sense in that it would be close to one scale mile track for the 1/32 scale cars which are the most popular ones in the world. Again this may be meaningless if my scale calculation is in error. If I multiply 33 times 1.7 seconds I get 56.1 seconds to theoretically go a real, not scale, mile. Is my logic correct here so far? If I divide 56.1 seconds into 3600 (number of seconds in an hour) I come out with an average speed of 64.1 mph (O.K. not 70). Did I screw up yet? I got the 70 mph figure from the salesman who sold me the car who said that it would probably max out at 70-75 mph.

This lap time is really only possible in the first few laps around the track because as the motor gets hotter, the speed decreases. This is an average lap speed because there 1080 degrees of turns (in varying degrees banked) that need to be negotiated so maximum speed must be somewhat higher. These cars seem to reach maximum speed in well under a second. I have what is called a G7 class car made by Koford Engineering. It cost me about $400. This is quite a different speed experience to the one I remembered in the '60s when I was a kid. The races are quite thrilling. Eight of these cars on the same track at the same time. It really is a blur! Better than any video game! here's a web site that has more info that might help.

http://www.oldweirdherald.com/slotcars/slotcars.html

Mark

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