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Post by roosclan on Mar 4, 2012 10:35:20 GMT -6
Our district is having an outlaw race after the district race today, and my Webelo wants to enter his car from a couple years ago in the outlaw race (didn't build one for the cub race). The rules allow for a 16oz. limit. I have my son's car up to 8.5oz. right now, and we can't make it any heavier without gluing weight in areas he doesn't want to put it (damaging the paint).
I thought I read on one forum (can't remember which one), that there was a maximum effective weight before the weight of the body caused too much friction on the axles/wheels and slowed the car down too much. I can't really remember what that limit was, and whether that was stock BSA axles, or needle axles. Does anyone have an idea?
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Post by derbydad3 on Mar 30, 2012 16:51:06 GMT -6
On a local wooden track (40 foot) we found that after about 8 -8.5 ounces we got diminishing returns. The cars that weight 10 ounces and above were consistently slower. Good Luck!!!
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Post by RacerX on Apr 2, 2012 5:46:36 GMT -6
On a local wooden track (40 foot) we found that after about 8 -8.5 ounces we got diminishing returns. The cars that weight 10 ounces and above were consistently slower. Good Luck!!! That's exactly what we found also!  We ended up doing a 8oz car on our RSN wheels (needle axles) believe it not. The small axles would carry the extra weight better up to the 8-9 oz mark. The car was VERY quiet and the axle flex from the additional weight acted a little like suspension. We found that the added weight def made for a noiser car with the added weight and with standard axles it was hard on wheels. For what its worth.  Racer X |
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Post by 5KidsRacing on Apr 3, 2012 8:18:14 GMT -6
My 6th grade Son's science fair project this year was finding out the relationship between speed and weight for a pinewood derby car. The test car was a railrider with BSA wheels, .091" aftermarket axles and Krytox oil lubricant. He started with the car weighing 3 ounces and then added cylinder weights in holes in the top of the car to step it up 1 ounce at a time. He had planned on running 3 ounces up to 10 ounces, but he ended up going to 14 ounces. His car gained speed every time he added an additional ounce. The amount of speed gain was less and less up to 14 ounces, but even at 14 ounces it gained speed over 13 ounces. I am sure the results would be different for variables such as graphite lubricant, modified wheels, etc., but I was surprised by the results because I had always heard that about 9 ounces was about the limit. I think the difference was running oil, not graphite. Here is the car:  |
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