OT: Pine Derby Car building help

[Michael Cody]

I am assisting my nephew to make his first (and mine) pine derby car...anyone have tips to make descent one?

They can only use the nail type axle and the approved nails are much smaller than the wheel holes which is causing some wobble...anyone have a good fix for this? I am planning on building it up a bit with thin CA but not sure if that is a good idea or not.

Planning on using graphite powder lube...is there better choice?

Thanks!

Make sure you know your pack's rules. My pack rules stated you had to use the wheels & nails that came with the kit, you couldn't modify them. Only graphite dry lube was allowed. Additionally you had to fit the size (we have a size box the car must fit in.. and we were at the 5 oz. limit. If the rules let you, route out the slots for the nails and replace with a piece of hardwood that has nail holes drilled square and accurate. The slots often are not square with each other in the kits.

Best cars I've run in the dad's race and based on 10+ years experience with my sons ... is the old lead sled... basically cut the body down to about 1/2-3/4 inch thick -- just a flat piece of wood with the wheels mounted as straight, square & even as possible. You want the sucker to track straight. Then hang all the weight as far back a possible ... center of gravity should be at or behind the rear wheels. Based on the kits we got, we actually always built the cars backwards as the rear overhang we more than the front. So we put reversed the body to get the most overhang on the front. We were allowed to take any flash off the wheel outsides .. and we always polished the nails -- just put them in a drill and polish till they shine.

Lastly the old lead sled can look good too. My youngest son's last car was the sled with a toilet paper wrapper on top with a nose cone ... it said ACME ROCKET on the side and had a small Wyle E. Coyote cutout on the top of the rocket. Came in 2nd. One of my scouts built a sled the looked like a hersey's candy bar, another built a piano keyboard. The last 5 years I was in cubs (my oldest is an Eagle scout now and in college, his younger brother is still in scouts @ 1st class) .. my den finished 2-3 boys in the top 5 each year... including the winner in 2 of them.

[Tom Henry]

You have to go online and get the best axles and wheels...That is the key...

[Dan Mages]

Wow... I remember building many, many pine cars as a kid. Everything from the General Lee to a hershey bar. I might still have one sitting in my parent's basement. The key is to let the kid have fun. You can also use this as an educational opportunity to teach your kid the basics of physics and aerodynamics.

Have fun and good luck.

[David Epperson]

You have to go online and get the best axles and wheels...That is the key...

But illegal in some councels. So know your rules.

Make sure you know your pack's rules. My pack rules stated you had to use the wheels & nails that came with the kit, you couldn't modify them. Only graphite dry lube was allowed. Additionally you had to fit the size (we have a size box the car must fit in.. and we were at the 5 oz. limit. If the rules let you, route out the slots for the nails and replace with a piece of hardwood that has nail holes drilled square and accurate. The slots often are not square with each other in the kits.

We usually sanded the bottom of the car so that the slots were mearly a suggestion as to where the axles went and drilled the holes directly above the slot locations. Axles were between .070 and .085 inches in diameter so a drill slightly larger than 1/16 worked best - real snug, but not enough to split the wood.

Best cars I've run in the dad's race and based on 10+ years experience with my sons ... is the old lead sled... basically cut the body down to about 1/2-3/4 inch thick -- just a flat piece of wood with the wheels mounted as straight, square & even as possible. You want the sucker to track straight. Then hang all the weight as far back a possible ...

All true, till this part

center of gravity should be at or behind the rear wheels.

If the CG is behind the rear wheels the front wheels will be levered up off of the track. I found that right around 3/4" to 7/8" in front of the rear wheels worked best for our set up - long overhang to the front of car and wheelbase/axle locations as in the supplied kit. Any farther back and the front end would lose stability and develope too much side to side wobble, which bleeds speed. I always was of the opinion that the extended wheelbase philosophy was counter to the spirit of the rules and purpose of the game...Just my opinion. But with with several pack championship cars, a district champ car and a councle wide champ car built by my instruction by my boys over a 15 year span of building and teaching, I think I know a bit about it. But if you rules and concience allow it, do it your way.

Based on the kits we got, we actually always built the cars backwards as the rear overhang we more than the front. So we put reversed the body to get the most overhang on the front. We were allowed to take any flash off the wheel outsides .. and we always polished the nails -- just put them in a drill and polish till they shine.

We agree on body direction. I used a benchtop drill press as a lathe and taught the boys to use a needle file to take off the worst of the flash, followed by an inexpensive whetstone to take the humps out, followed by a high speed spin with Flitz or Simichrome polish. One other item, when removing the flash I had the boys put an ever so slight (5 to 10°) bevel on the inside of the nail head - just to reduce the amount of area in possible contact with the wheel hub. No disc brakes, more speed.

Lastly the old lead sled can look good too. My youngest son's last car was the sled with a toilet paper wrapper on top with a nose cone ... it said ACME ROCKET on the side and had a small Wyle E. Coyote cutout on the top of the rocket. Came in 2nd. One of my scouts built a sled the looked like a hersey's candy bar, another built a piano keyboard. The last 5 years I was in cubs (my oldest is an Eagle scout now and in college, his younger brother is still in scouts @ 1st class) .. my den finished 2-3 boys in the top 5 each year... including the winner in 2 of them.

Good Job Dad!

[Dario Octaviano]

All the info and advise are great and appreciated.

Thank you very much guys!!!