Fast Pinewood Derby Car 2008 Scout Race

His last year racing in Cub Scouts ....................................Now visit .....www.p-d-d-r.com

Category:

Autos & Vehicles

Tags:

• PDDR
• Pinewood Derby
• Fast Cars
• Jewkes Engineering
• The Block
• How to build a fast car

[Symphonitron]

That car with the thin wheels has an unfair advantage (smaller surface area). Normally packs disqualify cars that use these techniques, and even if they don't, the car won't advance to district races. In the 70's the Pinewood Derby wheels were thinner but tended to wobble, so the wheels have gotten wider, but an honest sportsman uses the wheels in the current official kit.

[dannykhoo]

south park brought you here

[GregJoshuaW]

@daleyjem i truly doubt wind resistance has any measurable impact on these races. If so, then the spoiler will be slower. All spoilers do is add down force so that a car won't lift off the track at very high speeds (especially important in Formula racing).

[psilobla]

@bbrownrigg: giving the wheels negative camber does help, but for a different reason than you think. The camber puts extra stress between the axle and the wheel hub, which actually causes extra friction at first, but after many trial runs wears away a tiny amount of hub material, reducing friction at that interface. It's essentially a sneaky way of modifying the wheels (but totally within the rules as far as I know)

[psilobla]

@bbrownrigg: "The less surface area touching the track, the less friction caused at point of contact." This is incorrect, even if it feels right. Static friction (which is what this rolling friction is) = the normal force * k. (k is a constant that depends on the surfaces) This does not depend on any area, only the normal force, shared between the wheels.

Also, "diver doing a flip. They tuck tight to spin faster. That's increasing rotational inertia" -- backwards. It's decreasing.

[bbrownrigg]

@psilobla wrong @ the wheels. The less surface area touching the track, the less friction caused at point of contact. Raising the fourth wheel is common. I also tilt my wheels upward, so less surface area on the track. The skinny wheels still have the same diameter as the fat wheels; any point on the edge of the skinny wheel travels the same distance as a fat wheel with the same diameter.

Think of a diver doing a flip. They tuck tight to spin faster. That's increasing rotational inertia.

[bbrownrigg]

well done on the skinny wheels! If your pack allows it, do it! Ours doesn't, so we're making do with a lot of polishing and balancing.

[DARKSTAR1462]

what ward is this?

[fineitaliandesign]

Of course the car with razor wheels wins...duh. It's unfair to start with and is no surprise. And against the official rules to boot. I can use a CO2 cartridge and blow it away...but is it fair?

[psilobla]

Cutting the wheels has nothing to do with surface area or friction. Cutting them reduces their moment of rotational inertia, and this alone differentiates the car from all others.

Despite how you shape the car, its inertia is proportional to its mass, so you want a SMALL mass. But, force of gravity on the car is ALSO proportional to its mass, so you want a BIG mass. These considerations cancel each other exactly, so in the end all cars are basically the same - until you mess with the wheels.

[jeiger]

Why is everyone crying unfair advantage. He cut the wheels that came with the kit. Is it unfair to cut your block of wood into an aero dynamic car? He did the best with what he had.

[arkadd61]

Nice job dad.