[ARCHIVED THREAD] - Pinewood derby (Page 1 of 2)
Posted: 8/23/2014 7:19:33 AM EDT
| Ok, looking for designs and build tips for my sons first car. Who can help? |
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As heavy as legally possible. Right there it is. Lighter cars slow down faster past the bottom of the hill. Add weight, weight it, add weight, weigh it, etc. We drilled into the body all around the rear axle, dropped in some match bullets to keep the weight all in that area, added wood putty, sanded. |
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Hollow out the bottom and fill with lead to legal weight limit then polish nails for wheels with crocus cloth in a drill to a high polish then coat with graphite. First place winner in my pack around 1972 when I was 10 yo.
 Yeah,my father is a manic with stuff like that, even now at 72 years old he hasn't changed. |
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Right there it is. Lighter cars slow down faster past the bottom of the hill. Add weight, weight it, add weight, weigh it, etc. We drilled into the body all around the rear axle, dropped in some match bullets to keep the weight all in that area, added wood putty, sanded. Quoted:
As heavy as legally possible. Right there it is. Lighter cars slow down faster past the bottom of the hill. Add weight, weight it, add weight, weigh it, etc. We drilled into the body all around the rear axle, dropped in some match bullets to keep the weight all in that area, added wood putty, sanded. Heavy as possible yes. I found keeping the weight as central as possible is best. Evenly distribute the weight over both axles. Concentrating the weight fore or aft will actually slow you down due to excess weight/friction on one axle. Oh, and paint it red or yellow, those are documented to be the two fastest colors known to man. |
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The performance is in the axles and wheels. I bevel the heads of the axle and polish the crap out of it. I bevel the inside of the wheel hub to lessen the contact area and then polish it as well. Here is my son's from last year. He came in second overall.  The Batman car was the overall winner and my daughter's car is directly behind my son's. She probably came in fourth overall.  |
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Sand the wheels tread and axles smooth. read the rules on lube, I used dry teflon spray i think graphite is ok but not sure.
weight to the limit, I used adhesive wheel weights. My Boy cut the shape and painted i. I did the bulk of the sanding. Have Fun with him, You'll look back to that later. |
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So I have to confess, I went a little overboard on a pinewood car one year. I was race chairman and added an adult class to let all the dads build thier own cars so the boys could focus on theirs.
Here are the top tricks: If your pack rules allow these all will really help. Axles and wheels are your biggest friction area. Order a set online that have been cut and polished. The axles should be polished to a mirror shine and several places sell the micro fine sand paper to do this as a kit. If allowed get wheels that have been cut. This removes about 75% of the surface of the wheel so you are not fighting the friction of the track and wheel contact. Mount the axles as wide apart as possible. Forget the pre cut slots. Drill your own holes as close to the ends as possible. Never paint where the wheel may rub the body. Most paints will have a little stickiness to them and will slow your wheel. Leave bare wood. Order some very high end graphite powder and rub the axles, wheels, and wood with it. Spin the wheels in a drill on a cloth with graphite in it to really coat them well. Now onto weight: I mounted my weight high and in the back. I made a false air foil out of bar stock and it gave it plenty of weight. You want to be as close to legal weight as possible. Check out your track. If it has the old style post drop pin gate you can back cut a notch in the front of the car so it will release done as the pin drops down. This can give you up to a 1/2" head start on the other cars. If it is the swing down gate you can cut your car with a high front end so it will release earlier also. Car shape makes almost no difference as long as you can mount the wheels as far apart as possible. I have seen square blocks run faster if you do the wheels and axles right. Google pinewood derby and you will see dozens of store selling the high performance parts. I've got one more son to get through cub scouts and can't wait for the next race in a a few years..... Lol |
Wanna win? This will. Weight should be crossways, though. You want to reduce to a minimum the rotational inertia where the car transitions from pointed down the hill to horizontal. The suspension means that the weight is not being lifted up and over each little bump. It will also absorb energy as the car hits the bottom of the hill and return it to forward momentum. My boy did a car like this for his last year. Wood should be a little thinner, too so it's more springy.
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So I have to confess, I went a little overboard on a pinewood car one year. I was race chairman and added an adult class to let all the dads build thier own cars so the boys could focus on theirs. That is a great idea! We always did the same as the other advice here- drill and insert lead weights, fine polish the axles and lubricate with graphite. Good times. When I was cleaning out my father's shop I found that precious tube of graphite, and that brought back some good memories. 
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This ugly SOB was mine, way back in the early 80s. All the work was done by me, with my Mom supervising to make sure I didn't hurt myself. She also gave the suggestions to use graphite lube on the wheel/axle area, and to melt some solder into a cavity I bored out in it, and the last thing we did was take it to the base post office to weigh it. Damn near perfect weight, at the end. And it won. Yeah, that ugly wedge shaped car won, and I was damn proud of her. I will always remember, years later, when my Dad found out I still had it, and he said "Son, always keep that. Some day, you may be married or have a girlfriend, and she may want to throw away that old thing, but never, ever let her." |
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So I have to confess, I went a little overboard on a pinewood car one year. I was race chairman and added an adult class to let all the dads build thier own cars so the boys could focus on theirs. We added a dad's unlimited class the last year. Only limits were 10oz and length. Oh, and no power. I'll try to get a picture of my entry when I get home. .06" wide delrin wheels on abec6 bearings. Lead shot in a container suspended by a .01 leaf spring for the weight. Body was HDPE about .08 thick.
It wasn't very fair, really. You know the friction ramps at the finish that are supposed to stop your car? Yeah, I had to squat down there like Johnny Bench to catch my car as it ramped off the end.  
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| I was cheated in my cub scout days. The pack leaders were a couple of old women. There was no pinewood derby. So of course there would be no campouts either. All they had the boys do was cutting out construction paper to make posters. I think I am emotionally scarred because of this. |
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Wanna win? This will. Weight should be crossways, though. You want to reduce to a minimum the rotational inertia where the car transitions from pointed down the hill to horizontal. The suspension means that the weight is not being lifted up and over each little bump. It will also absorb energy as the car hits the bottom of the hill and return it to forward momentum. My boy did a car like this for his last year. Wood should be a little thinner, too so it's more springy. http://www.maximum-velocity.com/customerflex.jpg interesting design and execution from a cub scout. |
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Suspend your graphite densely in rubbing alcohol and apply it with something like a tiny turkey baster. In this way one is sure to get the graphite inside the hubs.
Beware of getting the center of gravity too far to the rear; it'll make the car 'shimmy' in the transition from ramp to the flat of the track. Make its profile (height) as low as practicable. Polish to remove the die flashing (the two tiny ridges) from the axle's and remove as little of the axle's diameter as possible. I think casting the hubs with graphite suspended in a bonding agent that dries leaving something like solid graphite is cheating, but it would return faster times and not likely to be detected unless it does exceptionally well. The benefit of a smooth surface-finish should not be overlooked. Good luck. |
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I think casting the hubs with graphite suspended in a bonding agent that dries leaving something like solid graphite is cheating, but it would return faster times and not likely to be detected unless it does exceptionally well. . a pencil lead from one of those big carpenter's pencils could be jammed in the hub and drilled for the nail. But seriously, you've got to step back and ask yourself: "is this something a cub scout would think of and be able to do?" |
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Very common cheat is to only have 3 wheels touch the track. Please on wheel a little higher.
You can buy very good axels and wheels online or Polish the axles and remove all burrs. Bevel the head of the nail. Also cut groves into the nail so less contact with the wheel. Polish the wheels. Use a lathe and thin the wheels as much as you can. Remove The lettering which will cause friction against the track. Bevel the wheel where it Touches the car. Polish the inside of the wheel with a pipe cleaner and rouge. Coat The wheels in graphite. The car. As heavy as legal. Cut the body away from the wheels so the body Does not touch the wheels except at the axle. There is a lot of arguements on where to weight the car. |
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interesting design and execution from a cub scout. Quoted:
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Wanna win? This will. Weight should be crossways, though. You want to reduce to a minimum the rotational inertia where the car transitions from pointed down the hill to horizontal. The suspension means that the weight is not being lifted up and over each little bump. It will also absorb energy as the car hits the bottom of the hill and return it to forward momentum. My boy did a car like this for his last year. Wood should be a little thinner, too so it's more springy. http://www.maximum-velocity.com/customerflex.jpg interesting design and execution from a cub scout. Jakes wasn't that nice but it was effective. I doubt the one in the picture was completed by a lone scout. 
We thought the design was very interesting and it performed as planned. He didn't actually win because his car broke due to a part he'd made too thin. Missed out on the winning heat so he got third. While I'm talking cars: There was always a "siblings" class. And I made Annie's cars for her. The last one was a rabbit. It was so slow it barely made it to the end of the track. One of the other kids was giving the girl some crap about her slow car. She said," It's supposed to be slow so everyone has more time to watch it go down the track".  It was hilarious. Took the wind right out of the other kid's sails.
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I can see how dad's can get pretty carried away. I like the idea of dad's having their own class, that's great!
I'm not a dad yet but now I want to build one just to see how good I could do knowing the things I know now. Haha I came in 3rd for my area. I thought it was great. I admit, my dad had to explain to me why I should do most all of these suggestion like with the weight and polishing. But he let me do all the work, unless it was unsafe. In high school I came in 1st for a rocket powered car competition. |
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Quoted: I enjoyed it when I was a kid. But the real question is http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg" target="_blank">http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg I felt sorry for the kid. This year I am going to run a work shop for the kids and parents. |
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No. Obviously they waited until the last minute to put it together though. I felt sorry for the kid. This year I am going to run a work shop for the kids and parents. Quoted:
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I enjoyed it when I was a kid. But the real question is http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg" target="_blank">http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg I felt sorry for the kid. This year I am going to run a work shop for the kids and parents. That's cool, but remember no good deed goes unpunished. I'd be worried about other people, especially kids, around my power tools. I hate to sound like that, but that's the way it is. |
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Let your kid design it and build it. EVERYONE can tell when a car was dad-built and it doesn't make you or your kid look good Yeah well I wasn't going to let my 7 yr old son chop his fingers off in my saws or sanders.  I did build both of my sons cars and none of us cared what other adults thought, since the kids were as proud of them as if they built them themselves.
I think 95% of the cars were parent built in our district and they were not shy about telling you either since we were competing against each others work while the kids just wanted to race.
I will say this though I did let them pick the style/shape and they painted them, but I did the cutting and sanding and assembly. |
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Quoted: Axles ... it's all in the axles and wheels. Let the kid design and build, but you take are of those axles wheels.. My oldest son passed down his winning axles and wheels to my youngest son ..... both had First Place cars. . |
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I enjoyed it when I was a kid. But the real question is http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg" target="_blank">http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg</a> No. When my son was in scouts one of the other boys had a car like that. It won. Both his parents were there. He Built It Himself. Quite frankly, I think most of the cars are built mostly by the parent not the scout. Roy |
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Quoted: Did he get his "Trollin', they hatin'" badge? Quoted: Quoted: The guy who won when I did it as a cub scout literally just left the block of wood as it was and then put the axles/wheels on. |
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Did you buy the winning axels and tires or fix the ones in the kit? Quoted:
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Axles ... it's all in the axles and wheels. Let the kid design and build, but you take are of those axles wheels.. My oldest son passed down his winning axles and wheels to my youngest son ..... both had First Place cars. . By the rules .... used the ones in the kit. If you put up one with purchased axles .... your car was disqualified. |
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Lots of tips here!
Get David's book and follow the tips and your son will have a very competitive car.
You don;t have to be a Rocket Scientist but having an understanding of Physics can be an advantage. 
My son is a Life Scout now but from Tigers through Webelos 2 he never lost a race at the Pack or District level.
We had some people try to say he was using the same car at his 2nd District race and accused him of cheating. They enjoyed a nice serving of crow when we got his 1st car out of the "tool box" and it still had the last years stickers from District on it.
BigDozer66 |
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He deserved it that's for sure. Lots of pissed off people over it. Quoted:
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The guy who won when I did it as a cub scout literally just left the block of wood as it was and then put the axles/wheels on.
There must have been some pitiful cars if that won.
BigDozer66 |
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No. Obviously they waited until the last minute to put it together though. I felt sorry for the kid. This year I am going to run a work shop for the kids and parents. Quoted:
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I enjoyed it when I was a kid. But the real question is http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg" target="_blank">http://imagizer.imageshack.us/v2/800x600q90/674/AKT4Tr.jpg I felt sorry for the kid. This year I am going to run a work shop for the kids and parents. In my son's 2nd year of Cub Scouts I was took over as CubMaster and one of the things I started was helping other Scouts with their cars. Some had parents that could/would and did help but there were some kids (single moms) that brought their sons up for the clinics and their sons had much better cars than they did the year before.
There is nothing more heartbreaking as a leader than having a kid show up with a car that wouldn't make it to the end of the track. 
Our Pack had very competitive cars at District. BigDozer66 |