Derby Talk

Questions that confront us in designing next years car(s): I'm not sure if you were looking for answers to these questions or not. The answer to many of them may be in the rules for your PWD - don't do anything that is not allowed. Assumming your PWD allows all the modifications you mentioned - her...

:arrow: Friction really is independent of surface area. :arrow: Wheel alignment does make a difference. :arrow: Aerodynamics only plays a very small part in PWD car speed. :arrow: Make the car as heavy as the rules allow. :arrow: What makes a car faster on one track may not work on all tracks. :arro...

I have removed my reply.
I did not have anything more to contribute to this discussion.

I don't think a father who spends about 95% of the construction time on the car is neccessarily a bad thing. Sorry to keep harping on this. Our pack has an unwritten rule that the scout is supposed to mostly build the car with a little parental assistance. Other packs may have different rules. I th...

This software stinks If you are unhappy with the scheduling provided by that software, I posted a link to some FREE software that I developed using the Young & Pope PPN/CPN charting methods. The link/explanation is in the "Software" forum. I would be happy if someone out there used it...

The judges are told to pick out the car that looks like the boy did most of the work.

Are the boys/parents told that this is how they will be judged before they start working on the car?

Wouldn't the "wing" also act like a parachute and slow your "decent" down the track?
Would the energy gained by reduced friction be overcome by that lost due to the parachute effect?
I would like to see the results of this experiment.

It seems like you must be talking about a very small lane bias. I would wonder if the lane bias isn't insignificant in comparison to the staging at the top of the track, and the release mechanism. Maybe you have got all these things down to very minor differences. I believe our track has a much more...

The experiments that I've seen support the theory that you want as much mass concentrated in as small a central location as possible. Thanks for explaining that. I've always suspected that these ultra-thin, ultra-light cars with a large mass of metal near the rear wheels were faster for a reason. B...

These calculations are the real world measurements Now that I understand how you measured it, and what you used to do it, I see that is was more precise than balancing on an edge. Just curious about the term you used "1-2-3 block", I gather from your description that is is a rectangular p...

The wheels that were DQ were the ones that had most of the edge knobs off Ahhh. So it was rounding inside to outside, not making the wheels round about the center of rotation. The inside to outside rounding would cause less of the tread to contact the surface of the track (just the top of the round...

Our 60' wooden track has a similiar 8' long raised center guide covered in felt. It works well. I'm not sure what you consider "common materials" but this was built with the same wood used for the rest of the track. It's the 9th 8' section of the track, with the finish line in the middle o...

The cub-scouts don't do it, but the Y-Guides race we participate in give out the "Turtle Award" to the slowest car that actually crosses the finish line. The timers only go to 9.99 seconds, and the "Turtles" usually take longer, so there is always a "finals race" to see...

How did these calculations compare with real world measurements? Did you try and balance the car on an edge, to find the Cg? It seems like you could verify the Cg along the wheelbase measurement this way, but the other 2 would be hard to measure to the accuracy you calculated. It also seems like you...

we bounced a few sets of wheels for excessive rounding What's that? How do you determine how much rounding is excessive? I assume you mean sanding the outside tread to remove the seam. Removing too much material would give you an advantage. Did you measure wheel diameter with calipers, or was it a ...