Not Necessarily Interesting News

Today was my son’s big pinecar derby with the Cub Scouts. Over the past 2 weeks we put a lot of time into his car. He wanted a Ford GT-40. First thing we had to do was make sure the axles were straight. With a micrometer we found the axle slots that came precut were out of straight by about 8 degrees. That won’t do. We borrowed a friend’s drill press and drilled some new axle holes that also give the benefit of lowering the car. When drilling we made sure that the axles have a slight downward droop. This way only the outer rim of the wheels touch the track lowering friction. We also drilled one front axle hole about 1/64″ higher than the rest. This way it rides on 3 wheels instead of 4, again to lower rolling friction. After this I cut out the rough shape and he did most of the sanding. He got to use the electric sander which he thought was cool. Once things were nice and smooth he got to use the spray paint after a lot of begging by him to let him do it. A nice glossy red was the color. Add some Black Widow stickers he picked out and the body was done.

Now came to boring part, sanding and polishing axles. The little nails they give you to attach the wheels have some wicked burrs on the underneath side of the head. Those kill speed. We put the nails in the drill and while he held the trigger I filed them down. After that we used 150 grit sandpaper to knock down any other ridges. We worked our way down to 600 grit. Then it was time for emery powder. We got those axles gleaming. Then it was on to the wheels. Some 600 grit paper to knockdown any imperfections and make sure they were round and square the the axle.

I did some unscientific tests on our axle work. Take a stock axle and wheel and spin it while holding the nail. It’ll spin for about 3 seconds before coming to a stop. After our polishing work it’ll do about 10 seconds. Once graphite is added for lubrication it goes over 20 seconds. That’s a heck of a difference.

Next we ground out a hole in the bottom of the car for adding weight. Luckily we have a fairly accurate scale at home. Research says the best place to put the weight is about 1-1.5″ in front of the rear axle. Too far back and the front of the car can bounce all over robbing speed.We added lead weight to the cutout to bring it up to the 5 ounce max. A test on the kitchen counter showed it rolled arrow straight and the front right wheel just barely touched the ground. Perfect.

On the side I built the pencil car you see for his mother to race in the family/sibling races after the main event.

Today was race day. There were about 55 racers. A lot of them looked like they could be some serious competition for ‘The Widder’. At check-in we weighed 5oz on the nose. No last minute weight adjustments for us. The pit table was a beehive of activity as parents tried to figure out how to add 2 or more ounces to their kids’ very underweight cars.

The races started on time and my son’s car was in the first heat. Only two cars raced at a time. He lost the first heat by about a car length. We were stunned. We know we have a fast car, how could we lose? Luckily it’s a double-elimination event. We’d have another chance to show our speed. We easily won the next 7 races. Some in total blowouts. We came down to the race for 3rd place. The loser gets 3rd place and the winner goes on to the final. It was a dead heat according to the judges. I saw my son winning by a nose but didn’t argue as I don’t want to be seen as the kind of parent that argues every call. They re-ran the race. The finish looked exactly the same but the judges agreed that my son won by a nose. We were in the final. Woot! We then realized that we were going up against the only undefeated car of the day. We’d have to beat him twice to win. I also realized, but didn’t say anything, that the car we were going against was the one we lost against in the first heat. We ended up losing to him again by about a car length. This gave my son second place over all, beating out 53 other cars. Funny thing was, he was disappointed. He wanted the first place trophy. Then after showing him all the cars he did beat he felt better. He ended up with two awards. The second place trophy and also the fastest car in his den which earned him a 1st place ribbon.

After the race I got to take a look at the winner’s car. The wheel motion was a thing of beauty. Smooth as silk.

Next it was time for the sibling/family races. They are open to any relations of the Cub Scouts. Long story short. The Pencil killed every other car in the race taking first place. My wife beat out about 22 cars for first. Normally there are a few adults racing in that race but this year she was the only adult. She felt bad beating the kids, but only for a little while. 🙂

After the races I had several dads ask what the secret was to building such fast cars. I had two wining cars so they knew it wasn’t a fluke. One asked how much my consulting fee would be for next year. I laughed and told them my secrets then said get a hold of me next year and I’ll show you how to do it.

Here’s a list of things to help your pine car go fast:

• Body shape: It means nearly nothing at the speeds and distance the cars travel don’t worry about it. Do whatever you like for the body shape.
• Deburr those nail heads: This is the number one thing you can do.
• Polish the axles: Start with 150 grit, then 300, 600, and finally wet emery powder.
• Don’t use the stock axle slots: They are almost never straight. If you have access to a drill press use that. Drill the holes with a slight up angle into the body. Don’t use a hand drill. You’ll never get the hole square to the body. Place one front wheel slightly higher than the others so you only run on 3 wheels.
• Graphite the axles as you insert them: This guarantees that graphite gets where it’s needed most. Don’t use liquid lube like WD-40 or oil. These can eat the plastic.
• Glue the axles in place: Too many cars have lost races because they lost wheels somewhere during the race. I use rubber cement. It can be removed if I need to take off the axles. Wood glue is also good. use any glue sparingly and make sure it doesn’t squirt out and glue the axle.
• I wax the body where the wheel hub touches the car body. I don’t have enough data to tell if this helps but I don’t see how it could hurt
• Weight: Get your car’s weight as close as possible to the 5 ounce max. I usually try to overweight them just a touch then bring a drill to drill out weight if needed to bring it back under 5oz.
• Weight location: Try to use as dense a weight as possible, like lead, and place it about 1-1.5 inches in front of the rear axle. This keeps the front wheels from bouncing and robbing speed

If any of these tips help, drop me an email and let us know.