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Chuck, the only thing that comes to mind is, go with very thin narrow wheels with ball bearings. I would make them out of plastic with a groove in the outer edge to roll a thin O'ring into to act as a tire. That would help it track better. Other than that maybe a compressed air nozzle to give it a better launch!!??:D:rofl::rofl:
 
Many years since I was embarrassed by helping my son with a pinewood derby car. The first one didn't make it to the bottom of the track. We endured the harrassment, and the next time around we took 3rd in the regionals. Lessons learned. Actually, my son made the car, I provided the work on the things that let it go fast. If you have to stick to kit pieces (that was our rule), about all you can do is make everything as smooth as possible. Also use a forstner bit on the bottom to make places to add weight in strategic spots so the weight is right up at the max allowable (minus a smidge since you don't want to be disqualified because somebody's scale is out of whack). I put the axles in a drill press and smoothed them with steel wool and polishing medium. I also rigged a way to chuck the wheels in the drill press so I could use an abrasive to get them as round and smooth as possible. Can't remember how I did this, but it's also important to install the axles so the wheels are all tracking the same and not fighting each other. Sounds simple, but as I recall it was quite a bit of work. But it paid off. I don't think aerodynamics comes into play with something that small, but don't take my word on that. Maybe we would have done better than 3rd if I'd considered it, but my son had ideas about what he wanted it to look like, and actually it was his car. Good luck with that.

Cheers.
 
Chuck,
I wish I could help out, but we didn't win anything for speed. What I've read and been told breaks down to 1) geometry - wheels/axles square to the body and each other and 2) friction - polished axles and concentric wheels. We only did the basics to get the car down the track.:D:thumb:

Good luck and have fun!

Wes
 
Chuck: my grandson's cub scouts did thiers two weeks ago. We had a blast. We finished 9th outa 11; but we did finish. The other two did not finish. My grandson insisted he build a truck so I cut and glued him a ford pu and he already has said next year it will a fast car.
When this thread is finished I will print it for him as a guide for next year.
Have fun.....
Ray Gerdes
 
Chuck:

It's all in the wheels and axles. My son's troop specifies that you must use the BSA wheels and axles and you cannot modify the wheels other than polishing to remove casting marks. They check that the molded "tread edges" remain.

Like Wes said - it's all in the rolling friction and geometry. I'd be temped to get the wheels perfectly round and fill them SOLID with some material. The wheels would have a higher moment of inertia (if all my physics is being remembered properly) and would/could maintain speed better in the flat.

Good luck -

Jim
 
...As of right now it weights in at 5 oz. That would be the limit for the boys. I have to get mine up to 10oz.:eek:
The last thing to do is add another 5oz to my car but where front, back, top, bottom.
I was also thinking about putting a tin body on it to cover the wheels. But don't know if that would eliminate enough drag to make a difference.

If I remember right (now there's a stretch), I think low weight in the front will help your initial takeoff and help the car track straighter. My dad used to have bullet molding gear, so he'd drill holes in the bottom of my cars and pour molten lead into them to add weight. I have no idea how smart or dangerous this was, but that's how we did mine when I was a kid. Aside from my first car, the other several I did were for school-sponsored (not BSA) contests, so the weight and wheel rules were a bit more open.

Instead of fenders, can you mount one or two horizontal wheels on each side, to run on the side rails of the track (in case your tracking isn't quite right)? Essentially roller bumpers on the sides. :dunno:
 
That's what I remembered as well Vaughn - weight as far forward as possible. BUT, I was informed the weight should be as far BACK as possible. Something to do with the center of mass and having gravity act on that mass as long as possible. Oh, and lead and zinc are now passe - they're using tungsten now because it's denser than lead allowing for more precise placement of the weight.:rolleyes::doh::rofl:

I do remember one of the winning cars had the slots for the axles re-machined accurately on the top (now the bottom) and ignoring the original slots.

Wes
 
I do remember one trick dunno if it is against the rules now, but we set our cars up so that only three wheels touched the track:rolleyes: the fourth wheel "looked" like it was touching but really was not, three wheels equals less friction ;) :D
 
Hi Chuck

When my son was in cubs and we built these we had to use the "approved kit" which included the block of pine, 4 nails and plastic wheels.

I take it you are outside of these "rules" ?

If not the one thing we did that improved speed was to carefull file down with a small file the burrs on the unerside of the head of the nails. These would snag on the plastic wheels.

Then given all your tools you are in a position to ensure that the slots that the nails (axels)are inserted into are parrallel. We had a number of blocks of wood from kits where the slots were off and causes a wheel alignment issue.

Then we experimented with where to put the weight.

What we did was to buy old lead sinkers and then drill appropriate holes and after having achieved what we thought was a good design for the shape, up the weight by drilling into the base and setting in the lead sinkers with a good whack from a punch and hammer.

This was a fun time for my son and I each year we all tried different things to speed up the "cars"

I always wanted to build my own track to be able to test our cars before the big day. We had to rely on non conventional track to test it did not have the tracking piece in the middle.


Thought some past pictures would be nice touch so here goes.

Best of luck by the way.
 

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I can see lotsa dads with similar experiences. When we did ours for my sons the wheel alignment was a big factor. But hard to change since the kits came with the axle slots already cut, or drilled, I forget which. We used powder graphite as a lubricant. My son recently helped the grands with theirs and he says that current rules allow only the graphite for a lube.

When my sons did theirs, I was Cubmaster at the time. The night we had the races was one of the worst days of my life. The national rules we had to abide by was a single elimination race. Meaning that the second fastest car out of several dozen could be eliminated early and not get any award.
I was not successful in calming down a whole bunch of angry parents and sad kids who (justifiably) felt they were cheated.
Today, I understand it is, at least, a double-elimination, competition. Much fairer.
 
I find this post really interesting, we haven't this sort of competitions here and I'm fascinated how a block of wood and four wheels can drive so many people's attention and the incredible amount of fine tunning them.
And there are kits available even !!

I guess that the goal is that the car that reaches the fartest point is the winner, isn't it. I'm a complete ignorant about that, but I find it a good way of kid doing something together with their parents.:thumb:
 
I find this post really interesting, we haven't this sort of competitions here and I'm fascinated how a block of wood and four wheels can drive so many people's attention and the incredible amount of fine tunning them.
And there are kits available even !!

I guess that the goal is that the car that reaches the fartest point is the winner, isn't it. I'm a complete ignorant about that, but I find it a good way of kid doing something together with their parents.:thumb:

Cars...four wheels....Toni, that is a worldwide obsession we are just starting them young. ;)
Really, it is an old American Cub Scout tradition. And, perhaps the best part, it is a great father-son project.
The kit part is to keep most factors within certain bounds. The obsessive fine tuning is the opportunity to make a winner out of ingenuity and some hard work.
The cars run on a track using gravity, the one to get to the finish line first wins. The tracks have evolved and gotten a lot more sophisticated than when our boys raced more than 30 years ago.
And, it really is fun.
 
Toni - I think this was the after result of the original soap box derby; which was out of reach for our little men.

Speaking of my little man, he was in Barcelona last week end and will be back next Friday. My family is on the NCL Jade this week. Today they visited the pyramids. They were facinated by spanish architecture.

Ray Gerdes------- in beautiful Texas where the beautiful bluebonnets grow.
 
I forgot how much fun it was helping my son build his pinewood derby cars. That was about 10 years ago, and I miss it. I'm hoping my grandson will get into scouts, however his father is a very good woodworker, I may be able to help a little.:thumb:
 
When I made mine with my dad, we used old sheets of lead plumbing parts. We cut 1/2" strips, rolled them up into 1/2" rolls and then drilled holes into the bottom of the car to put them in. I earned quite a few medals and trophies using this method. For the wheels we put them on a finish nail, chucked them in a drill and held sandpaper to them to get rid of casting marks.
 
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