Who has experience building fast PWD cars? I just finished building some cars for my boys but I’m wondering what go-fast tips might be out there besides the usual.
I know the basics:
Get the weight up to 5 oz, put most of the weight over the rear axle
File, sand, and polish the axles to make them as smooth as possible
Lightly sand the wheels with a drill and a wheel turning mandrel thing. (our pack’s rules prohibit any wheel mods besides light sanding)
Lots of graphite lube in the hubs, axles should be smooth and lubed enough so wheels spin for 25-30 seconds.
What other tips do you have that maybe aren’t widely known? I read up on rail riding a bit, but it seems like one of those things that will hurt you more than it helps unless the car is setup perfectly, so I just try to get it aligned so it will roll perfectly straight.
Oh, I also left the axle area unpainted and sanded it and rubbed graphite into the wood.
I think you got it. When I was a kid in the 80’s, I won a few of these and they sold little metal weights that you could break off to get it to the exact weight you needed. We put the weights under the car if they scales at the race weighed it too much, we broke off a little brick.
If your wheels are spinning 25-30 seconds, you are doing pretty well. Graphite is the way to go.
I ended up going on to a district competition, but to protect the gym floor from graphite stains, they banned graphite.
Don’t take this the wrong way (seriously!) but based on your post, it appears that you may have missed the point of the Pinewood Derby. You say that you just finished building some cars for your boys, and you list all of the other things that you have done.
In my son’s Cub Scout pack years ago, we had a Cubmaster who used to make a very good speech. He said (paraphrased) that there are two extremes in building Pinewood Derby cars: (1) the boy builds the car by himself with no assistance, and (2) the father (and it’s always the father) builds the car himself with no input from the boy. Both are undesirable. In the first case, a boy who is 7-10 years old is not really capable of building a car that can compete and will become discouraged if his car comes in last in every heat or is disqualified for rules violations. In the second case, the boy knows he had no part in building the car, which defeats the purpose of the Pinewood Derby, which is to encourage a parent (or other adult) to work with a boy to build the car together.
Anyway, I may be misreading your post (and if so, forgive me), but it just seems that you might be leaning a bit to the second undesirable extreme.
They do still sell the weights. However, in my experience (and depending on the track), you generally cannot put weights underneath the car because the car has to be able to straddle a guide rail.
It’s not over the rear axle that you want the weight necessarily, it’s as far back on the car as you can get it. The advantage comes because the track starts with a ramp and then levels out. You want the weight as far back as possible because it will be on the ramp the longest.
When my kids were Cubs they had a separate competition for the dads. When I was a Cub I made the whole thing myself, but in my kid’s Pack they encouraged us to help our kids, but not to build the whole thing for them.
ETA: We took the cars to the deli to weigh them on the scale there before hand. A post office might do this for you also. We also took a drill driver and drill bit to the event so we could trim the weight if needed.
Do a 4 wheel alignment.
You want the car to roll straight not to rub the rail on the side.
You might have to sand the axle carriers to shim them to be square with the car so it rolls straight.
We do build it together, but yeah I will admit to doing some of the work on my own. My kids designed the cars 100%, drew the lines to cut and then I did the cutting with a manual coping saw and finishing work with a dremel sander. I can barely cut the darn things, my 7 year old and 9 year old wouldn’t have a prayer.
Then we both sanded, they painted, I added the weights, polished the axles and attached the wheels. We did any other decorating (gluing on parts) together.
I’m thinking next time with my older son I’ll leave him more on his own, but part of the fun is having a competitive car on race day and I know other dads are helping with the go-fast portion, so I don’t feel guilty at all for the work I’ve done on it.
One thing I’m not sure how to tell is rear-wheel alignment. How do you test that?
That’s why the Pinewood Derby sucks. The boys at that age simply can’t build their own cars. The dads know that if they don’t do the lion’s share themselves, their kid has no chance to compete.
Last year my (then) second-grader completely designed his car himself. I used a band saw and drill press to make the cuts, then he did all the sanding, painting and gluing. I also did the soldering.
He had an amazing design - he started with the skull and hands of a plastic skeleton model he had. Then he had me drill out the eye sockets. He took two flickering yellow LEDs (from little battery powered tea candles) and stuck them into the eyeholes, then I soldered the wires to the battery holder/switch (from the candles). He had me drill a hole to bury the battery holder in. Then he painted the whole thing black and cut out a little tombstone from foamcore, which he colored and decorated to say ‘RIP.’ He spread glue on the top and covered it with modeler’s ground foam to look like grass which covered the wires and battery case except for the switch, then he glued the skull in front of the tombstone with the hands kind of clawing out of the ground. Finally he used the computer to print “DEATH CAR” in dripping red letters on a black background which he cut out and glued to the sides.
I also helped get the wheels lubed with graphite and nailed on straight.
In terms of speed he was in the middle of the pack but he won the grand prize for Best Design.
ETA: BTW, our pack also has a separate competition for Dads and other family members. It helps to discourage the Dads from ‘helping’ the boys too much.
They might have changed the rules, but in my day that would have been illegal: You had to use the wheels and axles provided in the kit. Though you might be able to modify them in some way to reduce wobble.
Another possible tip would be to cut out sections of the wheels, since rotating weight is parasitic on your energy budget. But I don’t know if you could take out enough to matter, while still maintaining enough strength.
EDIT: Oh, and Skammer, that sounds amazing. Got any pics?
Very cool! When I was a scout, I thought the design category was loads more fun (in part because nobody in my family was an engineer, but my mom was an artist). I won one year with a car dressed up like a monster, complete with feather antennae. The feathers didn’t exactly make it aerodynamic, but it was awesome looking. I didn’t quite win the next year with my eRacer car painted up like a cap eraser, but I still thought it was fun. The winning cars always looked like some sort of Formula 1 anorexic numbers and were clearly designed by helicopter dads.
When I was a cub scout 35 years ago, I had much more fun designing ‘funny’ cars than trying to win with fast ones. One year I use two foam balls (tennis- and billiard- sized) stacked and covered with yellow feathers, googley eyes, a foam beak and pipe-cleaner legs to create Big Bird sitting down on an uncarved wooden block. Very un-aerodynamic.
What my old pack used to do is give trophies to the fastest cars and the best design, and then a special trophy for the slowest car that still crossed the finish line. My Big Bird won that one and I still have the trophy - I bring it out every year to show the boys in my den. A trophy dated “1979” is like a ancient artifact to them.
I couldn’t agree more. I’m a Scout leader myself, and our Pack has gotten out of hand with this. 90% of the kids have their father build the whole thing, some even buy their cars. The few that do it themselves have no shot at winning. I wish we’d either just get rid of the event, or find some way to keep this nonsense from happening, because a lot of time and effort goes into planning the event and so few of the kids get much out of it at all. A lot of the kids don’t seem to care that they had nothing to do with the car, they just want to brag that they won. I’m only a Den leader though, and, while I’ve voiced my concern to the others, a lot of them are guilty of the very thing I’m complaining about so there doesn’t seem to be much interest in changing things.
Yup, that is what my pack does so the handful of adults who really care can play too. There is also a siblings division - my daughter came in second with her Brownie Mobile, complete with Girl Scout pin.
It can get even worse. There’s a troop where I used to live that boasts that 100% of their members make Eagle. A former boss of mine had been in that troop, and his son was at the time I worked for him. Almost all the members came from the wealthiest families in town, and the dads pretty much held their hands the whole way through, to the point of doing the work for their merit badges if the boys couldn’t do it themselves (or even if they could but the dads wanted to make sure). It was pretty well known that most of them didn’t earn their Eagle, their dads bought them for them.
My boss bragged that the boys weren’t even allowed to touch their Pinewood Derby cars except to put them on the track at the races.
