Any last minute Pinwood Derby tips?

[89911]

My son has a Pinwood derby event for Saturday. Of course I'm "helping" him, (he is 8). Last year his car finished in the top 1/2. I've searched the internet for some more tips, but the same ones seem to be repeated which I've done. And no, I'm not looking to buy Big Bob's Pinewood Derby Secrects and spend an entire week working on the wheels and polishing the nails. I'm just wondering how the same 2-3 kids keep winning every year. Any tips? I'll post the results.

[cstreit]

General principles of speed
Your car goes down the track from the pull of gravity. Your car is slowed down from friction. Friction is the enemy of speed. Reduce friction and your car will go faster. Here are some ways to reduce friction and increase speed…

Axles
You want to make your axles as smooth as possible. Be absolutely sure that the burr under the nail head is filed or sanded off. Once that is sanded off, polish the nail head to a mirror like finish.

Gravity / weight
This one is simple. Be sure your car weighs as close to 5 oz as possible. The heavier your car, the faster it will go. Find someone with a scale, purchase an inexpensive scale or weigh your car at the post office. Add weights until the car with the wheels and axles is up to 5 oz. Don’t wait until race night to get this right.

Making the car go straight
This can be tricky. Roll your car along the kitchen floor. If it veers to the right or left too much, the axles are crooked. Just like steering a car, you need to adjust the steering on your Pinewood Derby Car. To do this, you must adjust one or more of the axles so the car rolls straight. You can do this by re-drilling the axle holes and re-inserting the axles.

Lubrication
This is essential. Purchase a tube of graphite and sprinkle a little on the axles near the wheel. Spin the wheel so the graphite works in. You will notice a significant improvement in the speed of the wheel as it turns.

To win the race, you’ll need to learn the speed secrets from the experts. If you are serious about speed, spend a few dollars to download one of the products from the experts or start the process of trial and error like I did. Either way, have fun and happy racing.

[72 four door]

From what ive heard putting the weight in the back helps also if you remove alot of wood replace that wood with weight good luck

[cstreit]

http://www.pinewood.schoolreference.com/pinewood-derby-car-weights.html

[RickM]

Did you install an ERam?

Actually, there was a thread on this last year. Perhaps you can find....Good luck!

Here's three: pinewood derby

Pinewood derby car - where to start?

Pinwood Derby

[89911]

Thanks so far. Yes, I've done all that you mentioned. I'm actually going to use graphite on the axles and then seal them with stick on paper hub caps to hold the stuff in there. One thing I noticed is the car seemed slower and slower with each event, using up what little dry lubricant was there. This way I'll (I mean my son ) will have an ever lasting supply around the axle head to fead it lubrication. I've checked and it is legal to cover the wheels.

[304065]

OK, whoever wrote the gravity/weight thing needs a refresher course in Newton's Laws.

And you smartie pants out there, I KNOW that the gravitational attraction between two bodies varies with the distance between the centers of mass. And for a pinewood derby race, that don't matter.

I say, go as LIGHT as possible, you will accelerate to top speed faster.

Everything about friction good, don't let the wheels rub on the car.

One last point: CHEAT YOUR ASS OFF!

[David]

What Chris said. I also check the wheels for wobble and pick the best ones. Then I put them on a mandral in a lathe and turn the OD just a hair to get them concentric. After a few years you'll have a few sets of wheels you can reuse.

I make the wheel base as long as I can to help it go straighter.

You do want the car as heavy as possible. The heavier it is the less affect the friction has on slowing the car down as it accelerates.

I also put the weight in the back so it falls farther and I use tungsten since it's over twice the density of lead so I can get it farther back. Don't put all the weight behind the axle or it will do wheelies down the track and be slow (don't ask how I know this).

[bell]

i just built one for our company owners kid (yes on company time LOL) it weighed 4.9 oz (had to be between 4-5oz).
he came in third and got a ribbon....he was happy.
i simply carved out a car looking shape on a mounted belt sander, carved out as much material from the underside as possible with a dremel, made a little wing then melted some lead (fishing weiights) in the nose until it was in spec.
the body alone weighed 1.1oz, with wheels it was something like 1.7, the rest was lead in the nose.
it sat on 3 wheels with a little camber so it rode on the edges and used graphite dust on the axles.
imo the setup on the wheels is more important than where the weight is, but having the weight in the nose keeps that 4th back wheel in the air no matter what.
wish i would've took pics.....looked kinda cool

[David]

I forgot about the 3 wheels, bell. I have only one front wheel touching, just make sure it's low enough to stay over the center guide.

I also sharpen the inside of the wheel's hub where it touches the body so there's only a small contact area and I chamfer the inside of the nail heads so there's less contact with the wheel.

[dad911]

Originally posted by john_cramer
OK, whoever wrote the gravity/weight thing needs a refresher course in Newton's Laws.

And you smartie pants out there, I KNOW that the gravitational attraction between two bodies varies with the distance between the centers of mass. And for a pinewood derby race, that don't matter.

I say, go as LIGHT as possible, you will accelerate to top speed faster.

Everything about friction good, don't let the wheels rub on the car.

One last point: CHEAT YOUR ASS OFF!

Weight absolutely matters. Make it as heavy as possible. Potential Energy =MASS * Height * Force of Gravity. Some light cars don't make the finish line. I make it a llittle heavy on my home scale, and bring a drill to the weigh-in to lighten the car. Put the weight towards the rear, but in between the axles (not behind the rear axle.

Three wheel car. Wheels need to be smooth & round, I trued some up on a lathe a few years back, and have kept the best to use each year. I drill the axles holes straight in the block of wood with a drill press. You could also make the wheelbase a little longer to go straighter. Rub some graphite on the car where the wheels rub on the block of wood. Rub graphite inside the wheels hubs with a small paintbrush. Polish the axles until they look like mirrors.......

[araine901]

Now understand that this is cheating, so do with it what you will. As a former cubmaster I agree the camber on the fatty wheels coupled with the bicycle effect by misaligning axles is the fastest way. I only fell for that my first year though. so if you have a seasoned cubmaster your gonna get pegged.

(the bicycle effect is the above mentiond three wheel set up done properly. It will balance on two wheels when done right)

[911pcars]

Is that enough detail for your 8 year old to digest? My best wishes to him (ahem, and you).

What I'm trying to say is that I've been overzealous at my son's PW Derby entry too. I did some of the tricks mentioned above and did pretty good. Even made one that looked like an F1-type body with a front nose wing out of aluminum sheet for effect, then sealed, primered, painted, color-sanded and rubbed it out. I guess we're kids for a long time.

Make sure your son has enough sweat equity in this to feel good about the project. If you do it all, he'll be happy he won, but he won't get as much out of it. It doesn't matter if it's butt ugly. It's his creation. You as Dad can "fine tune" it.

Have fun,
Sherwood

[304065]

Potential Energy =MASS * Height * Force of Gravity

. . . only matters if you plan to smash the pinewood car through a brick wall at the end. F=MA, great, but your Porsche doesn't go faster if you make it heavier, only if you increase the acceleration factor. Which, in the terrestrial realm, is a constant, 9.8 m/s^2.

I hadn't thought about the greater mass overcoming friction . . .have to think about that. . .

[Tim Walsh]

years and years ago(ok only about 15) I came in 4th in the district and my secret was mostly what's been mentioned (4.99oz, graphic, polished axles etc). One thing I didn't seem mentioned was to place the weight towards the back to increase your energy potential. The problem is that this can disrupt the balance of the car so it wobbles down the track, so you have to balance the increase in gravitational potential to stability.

Above all though let your kid do as much work as possible to give him that sense of pride that it's his project, not yours.

[azasadny]

We drilled a hole through the middle of the car, then added shot from a shotgun shell until we were at the maximum allowable weight, then sealed the hole with candle wax and we did very well, although we didn't win. We should have polished the axles (nails) more and used more Moly lubricant to help the wheels spin better.

[dad911]

My son shapes & paints the car. Dad 'just' puts on the wheels & weight. John, I'll argue weight all day long. The 'light' cars do poorly. Less than an ounce below max and the car won't make the top 10 in our pack.

I don't think shape matters as much as some say. One year my son painted the block red, called it a fire engine, and still did well.

It's all in the weight & wheel alignment.

[911pcars]

Weight (and size, in some areas) matters. Gravity is the same for all in PW derby unless you have a stealthy electromotive force within the pine body and a heavier car will win every time (all other things being equal). That's why they have a weight limit.

When I first started cycling, I coasted down a hill on my lightweight bike but was soon passed by my slightly heavier friend in his 30 lb. bike. Despite the skinny high pressure tires and the low friction bearings I had, the 50 lbs. of add'l weight he was carrying did the job. Of course in cycling, for every downhill there is an uphill.

Sherwood

[304065]

Alan, I'm not arguing with you about weight. I'm arguing with you about physics, and the reason why a heavier car wins.

Can someone explain the relationship between higher weight and "overcoming friction?" What is the relationship between the mass of the object and its coefficient of friction with the wheel? I don't see why it makes any difference.

I'm not suggesting that heavier cars don't win. I'm suggesting that the reason people think they win isn't the real reason, and I'm wondering what the real reason is. Does that make sense? I dunno.

[Tim Walsh]

I belive the reason that the heavier cars win is because they have the extra momentum at the end of the bottom of the hill to carry them to the finnish line faster. The course is not just downhill, about half the course is flat.