Monday, January 19, 2015

Pinewood Derby - Rebuilding the Perfect Beast

Pinewood Derby - Rebuilding the Perfect Beast

Last spring the boy took first place in in the Pinewood Derby for his Troop. This year we needed to build a new car that will be just as competitive as the old car. Here are the previous posts.

2014 Pinewood Derby Results Mea Culpa
2014 Pinewood Derby - The Boy Isn't Going to Win...

Planning - Blue Steel Part Deux

We wanted to use a simple shape - to reduce the amount of time in the shop. The troop was really lucky to have access to a workshop with everything needed to convert a block of wood into a racing machine.

Our plan was to go to the preparation event with the full design in hand, run the block through the band saw, do a bit of drill work to manage weight placement, sand lightly and walk away.

Mistake #1

When transferring the design to the side of the pine block, I rotated the block to get a better angle for tracing a pencil line down the edge. We went to the preparation event, did our cut-out, light sanding, weighed in, then walked out. According to plan. 

At home, we were dry-fitting the weights when we discovered that the large weight would be slightly behind the rear axle. This would not be the optimum placement since the car might pop a wheelie at the bottom of the ramp. On further examination, I had reversed the wheelbase when drawing the line for the cut. 

OK, so we had to go to the make up session. 

Lesson #1

In order to counter-sink our weights, we used a drill press with a bit that the same diameter as a quarter. Three drill holes on the back of the car, a bit of work with a chisel, and we could slide in a second layer of weights. Based on the preliminary weight-in, it looked like two (2) quarters would do the trick. I do want to build a car and call it 50-cent, but the boy doesn't get the joke.

Make Up Session

For the make up session we double (triple, quadruple) checked the layout and the wheel-base. We cut the simple form, and then went back to the drill press. Our first build required some chisel work to get the groove size correct - we wanted to skip that additional work. We reset the bit-depth so that the drill would not penetrate all the way through the vehicle then used a bit just slightly larger than a quarter.

This round was much easier - squaring out the round corners with a chisel, then flattening the bottom of the groove where the tip of the bit counter-sunk into the pine. Finally, we went over to the belt sander and worked out all of the rough spots.

It's amazing how fast you can get all of this done when you know what you are doing.

Non-Make Up Session

Last year we used Krylon primer and metallic blue paint with silver glitter. This year the boy wants to go au-natural - with no paint at all. Pine and lead... nice.

Formal Weight-In and Turn In

Next week is the formal weight in session. We will have to hand-over the car until after the races are complete.

Fingers crossed that we do as well as last year.


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