NDR- Pinewood Derby - no rules

Mark W

Mark W

Well-known member
I thought I would ask here as there are so many talented people. My 14 year old daughter came home last night with a school project to make and race a pinewood derby car. This in and of itself is not a big deal as my son and I have done many of these before. What makes this one different is that there is only one rule according to my daughter and that is the total width of the car can not change from what the car + the wheels are out of the box.

So I'm thinking heavier is better. I was thinking of drilling out the whole thing and filling with the smallest lead shot I can find. I'd love to melt the lead and pour it in but I'm thinking that is a bit too much.

Any other thoughts? I know all the tricks with the wheels, axels, cutting a slot in the front etc.... Just looking for other thoughts.

Mark W
 
I thought I would ask here as there are so many talented people. My 14 year old daughter came home last night with a school project to make and race a pinewood derby car. This in and of itself is not a big deal as my son and I have done many of these before. What makes this one different is that there is only one rule according to my daughter and that is the total width of the car can not change from what the car + the wheels are out of the box.

So I'm thinking heavier is better. I was thinking of drilling out the whole thing and filling with the smallest lead shot I can find. I'd love to melt the lead and pour it in but I'm thinking that is a bit too much.

Any other thoughts? I know all the tricks with the wheels, axels, cutting a slot in the front etc.... Just looking for other thoughts.

Mark W
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Weight can be a curse and a blessing...depends upon the slope. The heavier it is.......the more momentum it will carry. Also, the heavier it is.....the tougher it is to get it going to begin with. It can be a double edged sword. Test it on a "track" of your own.
The best thing to do is eliminate as much friction as possible. I've drilled out and inserted tubing to use as bushings and lubricated this with graphite. Make the tires as skinny as possible. My son built 4 of these and I built 4 of my own along with him. This allowed me to be involved but keep my hands off his car. :) Lou
 
In my old boy scout days we did a `grown up class unlimited ` pine wood derby cars these were super fast. the one thing i remember was all seemed a little bit longer "ie altered wheel base" and i think since you are stuck with the same weight as the original pine wood derby car id try too reposition as much weight ahead of the front axle and concentrated towards the front of the car as possible. Kinda think of it like an arrow lots of weight at trhe tip helping kenetic energy or in your case speed.
 
Yeah, for the whole boy scout/cub scout etc.... we also had an adult class and I always made fun models of F1 race cars. I'm only doing to power tool part of my daughter's car as I do not want her to handle a jig/band saw nor a power drill or other tool to drill out the car. The rest is hers. We are just discussing what she wants her car to be. Ugle but very fast (ie heavy) or cute and not worry about speed. She wants fast and she decided that with her limited physics knowledge that heavier would be better. Heavier and ugly it is.

I'm not following you Lou on the bushings comment. We were thinking of ways to limit friction between the wheel hub and the side of the car and were just thinking of putting some teflon tape or a teflon washer and glue it to the side of the car.

Mark W
 
Pound of feathers falls as fast as a pound of lead. Watched a movie about this and it was hillarious..Ben Stiller was in it and I laughed till my side hurt. I think friction is gonna be the biggest enemy. Never built one though.
 
How about a spar that protrudes about 8" or so in front of the car, position off'center so that it doesn't catch on the starting mechanism? In any close race your daughter would win, but she wouldn't be very popular. People would accuse her of cheating even though she wasn't breaking any rules.

I agree with Lou on the weight. You wouldn't want it too much heavier than the Cub Scout rules allow for. But you could position the axles about 1/4" from the front and rear of the car and then place most of the weight toward the front axle.

Rick
 
How about a spar that protrudes about 8" or so in front of the car, position off'center so that it doesn't catch on the starting mechanism? In any close race your daughter would win, but she wouldn't be very popular. People would accuse her of cheating even though she wasn't breaking any rules.

I agree with Lou on the weight. You wouldn't want it too much heavier than the Cub Scout rules allow for. But you could position the axles about 1/4" from the front and rear of the car and then place most of the weight toward the front axle.

Rick
Click to expand...

From a physics standpoint, you're best to center the weight. That balances the weight over each axle and gives you the least amount of friction. If you forward weight the car, you've now added that extra weight-vector to the axle. More weight on the axle translates to more friction on that axle.
Hmmmmmmmmmmmmm.......we need more engineers. :0
Lou
 
I'm not following you Lou on the bushings comment. We were thinking of ways to limit friction between the wheel hub and the side of the car and were just thinking of putting some teflon tape or a teflon washer and glue it to the side of the car.

What I did was use a straight axle and drilled the body all the way through and pressed in a brass tube to use as a bushing. Also polished the axle and curved the wheels (crowned them) on the drill press so that the least amount of wheel was touching the ground.
Lou
 
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The car on the bottom and left is the last one I did....Mahogany, bushed...etc. My son's last car is in the middle of the track. Tons of fun.
Typically, I'd let Patrick do the design and we'd both build to that design.
Lou

Cars01.jpg
Cars01.jpg
 
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Now Lou, since you were trying to decrease the drag / friction why have all the aerodynamics applying downforce, do you have corners on your tracks???hehehehehehehehe
 
A few other tricks for ya. If you don't use a solid axle ( we couldn't when I was a racer) raise one wheel just enough so that is doesn't touch the track, this creates less friction. Our rules didn't allow radiusing the wheels but if it is legal make those puppies skinny! I always used a strip of mylar between the body and the wheels similar to the teflon idea. Clock oil on the axles seemed to work better than powdered graphite, just don't get is dusty. My dad made a car for the adult class that was in the shape of a "U". It had a whole car length head start, not just a notch in the front. We always centered the weight ( drilled the body and poured lead) and then drilled the lead out to the exact legal wieght. We polished the axles with toothpaste, spun the axle in the drill press. The classic wedge shape seemed to always do the good but the fastest on I ever made was only 3/4" thick with a rounded front and back. I don't know if wind resistance is a factor or not but I always made sure to make mine aerodynamic just in case. Be sure to fill us in on the results. We tried to stretch the wheel base as much as possible and still meet spec, without rules I would really stretch it out.

Fred
 
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Now Lou, since you were trying to decrease the drag / friction why have all the aerodynamics applying downforce, do you have corners on your tracks???hehehehehehehehe

Too funny. At those speeds, I never believed in the aerodynamics anyhow. :) That was Patrick's design so that's how I built it. Just too much fun.
Lou
 
A friend of mine had two son's who won almost every year the were in scouts. He was an engineer in our tech center and he said to remove the flash on the OD and polish the wheels and axles, locate the weight high and to the rear(at max weight)and use Pledge with lemon for axle lube. For a scout legal car those are the winning ingredients!!
Worker for them.
John
 
Lou,
I've noticed you have posted several times about weight , drag , aerodynamics, even managed to show a pic of the cars you and your son built....................................not a single mention of who won =)
We all know you raced. Its time to fess up !
 
Lou,
I've noticed you have posted several times about weight , drag , aerodynamics, even managed to show a pic of the cars you and your son built....................................not a single mention of who won =)
We all know you raced. Its time to fess up !

Good observation. I did time mine and it made great time but I never ran it against the kids....on purpose. Unfortunately, none of the other Dads did a car so I had NO competition. So....I came in First......and...........Last. :0 Fortunately, I did it to spend time with my son, not to beat the other Dads. Patrick did well but he never came in first. The first year we did it, the guys running it didn't organize it well and Pat's car almost self destructed when it hit the board at the end of the runway. He outdistanced all the other cars by several lengths. He would have won but his car was trashed and wouldn't run well after that. I was talking with the fella running it and complaining about how they didn't have any soft landing for these cars. He got pissy and said, ".........you think you can do it better"...I, of course answered in the positive and ran if for the next 3 years. :) Must be one of those control things.
Lou
 
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