Sweet mods for pinewood Derby cars?

For anyone with or had cub scouts what did you find works best.

My findings from last year:

clean off axle burs
hone and ruff spots on wheel OD and ID
get axles in straight (not that easy)
use graphite

most inportant I think mount the weight so center of gravity is as far to the back of car(higher up) without causing the car to lift the front end. Our packs track is a long sloped hill with flat bottom run. Seems like the farther the weight is back the farther is falls and thus has more potential energy. It seemed to be like a extra "push" at the end, little extra power. Seemed to work but I had to toe in one of the front wheels so my sons car didn't make everyones eleses car look like a civic. Still almost went too fast.

Back in the 80's the eng dept I worked in designed & built one for a single mother. We cut the block down to 1/8" above the axle slots & tapered the front down to a flat point. It kind of looked like the old STP indy car they called the races wedge. Also hollowed out the bottom between the axles to add lead to bring it up to max. weight. We were told that it did very well winning all races till the kid forgot to clean the wheels between races.

I just painted my whole block of wood red and called it a fire engine.

lost every time.

Angle the wheels so that you are running on just the very edge of them. I done this and won a lot. Now my cousin is doing this and winning a lot doing it.

Polished the axles, polished the hubs, make axles perpendicular to centerline of car, lowered car as much as possible, take the weight to the max allowable, aero shape. Came in third out of 223:drivin:

If the front end lifts too much it will leave the lane which is a DQ....

I was a cub scout back in the 1960's..... We used molten lead for weight end embedded it into the car at various points by carving out where we wanted it to go and pouting it right into the wood. Lead has a very low flash point. Polish and smooth the nails (axles), and polish the actual wheels as well, inside and especially outside to reduce rolling resistance as much as possible. Definitely make the car as aerodynamic as possible. The old (mid 1970's Wedge dragster of Don Prudhomme would be the perfect example of the correct aerodynamics. The reason the Wedge design was abandoned in top fuel was because of too much weight, not the aero properties, and in Pinewood the maximun weight is what you want, especially over the rear if you have a decent flat at the end of the race. If the flat is shorter you want the weight more central or toward the front for the quicker start. The location of weight placement is a tactic based on the actual design of the course. Short runouts want it close to the front and longer runouts want it toward the rear.

I do not remember the details of the rules, but if you go in a fraction "heavy" becasue we used lead we could shave it off with a pocket knife to get the maximum allowed because the the scale used at the event will be different than the one you check it on at home. Weight will be more important on a longer track than on a short track.

If the rules allow a sliding weight, then you can use smoothed and rounded BB's and enclose them inside the vehicle with a hatch and arrange them on a long trough the entire length of the vehicle. Start them at the rear of the car. As the car decends down the hill the BB's will roll forward until they stop at the front of the car and will provide a boost going into the flat just like someone giving the car a slight kick at the base of the hill. If this is legal and if you elect to do it, each BB must be perfectly smooth and round, and you want the trough perfectly smooth and "rubbed" with graphite.

Otherwise have fun with paint and decals and do not install anything that creates air drag.

The more perfect the axles, the more perfect the wheels, the better the car will perform. Every bit of drag hurts performance dramatically. There is no such thing as "too perfect" when dealing with gravity.

Also, you want the axles to be perfectly stiff. No flex at all. The track is smooth and perfectly stiff is much better than having flex.

Quote:

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Originally Posted by tnthub

If the rules allow a sliding weight, then you can use smoothed and rounded BB's and enclose them inside the vehicle with a hatch and arrange them on a long trough the entire length of the vehicle. Start them at the rear of the car. As the car decends down the hill the BB's will roll forward until they stop at the front of the car and will provide a boost going into the flat just like someone giving the car a slight kick at the base of the hill. If this is legal and if you elect to do it, each BB must be perfectly smooth and round, and you want the trough perfectly smooth and "rubbed" with graphite

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:yup: