Tuesday, July 14, 2009

A winning pinewood derby car through continous improvement: Part 3

Wheels: Take the burrs off the tire surface from the stamping process...we used a 1500 grit sandpaper to smooth the wheels as much as possible. Be very careful or you can create damage to the wheels. We tested the smoothness with the 'close eye-touch finger-spin wheel' test to feel any bumps or leftover irregularities on the surface as we sanded it to measure our progress. Also, we had an additional regulation pinewood derby kit and we picked out the best looking and straightest wheels. Not all pinewood parts are created equal.

Next, we waxed the wheel surfaces with car wax several times for a smooth uniform surfaces. I guess my son did it at least 10 times to build up a nice coat of smooth wax. It was smooth and good looking to boot. We used Johnson Car wax that I had for my car. We even tried waxing the inside the wheel where the axle goes...apparently, it didn't hurt. Lastly, test your wheels and axle out and true them up as best you can. I used a small level and checked to see if everything was trued up and straight with the wheels on. Also, leave a space the width of the pinewood cardboard stock thickness between the wheel and the car body. Friction against the body is bad and will slow performance.

Axles: There is a ton of information about the axle prep on the net-read it and follow it. It's better explained with pictures so do your homework. Here's my two cents-have your son polish, polish, and polish some more til he is sick of it. Then it will be ready. Here's my order of abrasives (that I had around my workshop) for axle polishing :

40 grit sandpaper
60 grit sandpaper
100 grit sandpaper
140 grit sandpaper
500 grit sandpaper
1500 grit sandpaper
00 steel wool
000 steel wool
0000 steel wool

By the time you are done, those axles should be shiny and bright. Be sure to do the same on the underside of the nail head too-it has burrs there that will slow down your car. We used a high speed Dremel like tool for the polishing which improved the process over the 3/8" variable speed drill I used in previous years.

For the axle lubricant, it's graphite all the way. I tried the white teflon stuff for several years and graphite made his car go fast. Another tip: Buy your graphite a month in advance-the day of the derby, the store I went to get it at was sold out...fortunately, a kind soul at the derby let me have some. I believe that the greatest improvement for me was to apply the graphite just before the car was weight certified and impounded until race time. We waited until the last possible moment before "graphiting up" the wheels and attaching the axles in a just in time fashion to improve lubricant retention. Several of the other cars had been finished a few days before and it was very difficult to add more lubricant because the axles were glued on or the car was impounded and moved and jostled around in the competition setup. In our "flow", we planned to have the car completely assembled and ready just minutes before the tournament started and it seems that helped as well. One piece flow is a lean concept...so google it.

Paint - Our cars was painted and sat in front of a fan for 3.5 days before the race. The local derby master had told past participants that vehicle paint should be dry at least 24-48 hours before the race to reduce friction. Fresh paint reduces speed-remember that one! There are some really fancy paint jobs and cool looking cars...but if not planned for, it can hurt the speed at racing time.

The results? My son entered his call in a field of 32 competitors and he finished first! Even racing against the adults, there was only one adult car that beat his by a whisker. My older son's best showing was 7th and he was on hand to watch his younger sibling win it all. As for me, we tried several kaizens that seems to work but the greatest joy was watching my boy beam with pride knowing that he had contributed a large part to the win. Victory is sweet.

What have you improved today?