Best Speed Secrets: Pinewood Derby

You want to taste victory in the winners circle with your son (or now, daughter)? This gives you the secrets broken down using physics, and shows you how to pull off a legally outstandingly fast pinewood derby car!

[@jacksond.hardcastle3422]

I don't have any kids, but that was some very interesting aerodynamics.

[@rufus2894]

Kid: "Dad can I help?" Dad: "Uh, you can hand me the 3750 grit sandpaper."

[@HelicoolsHelipad]

...and that is why we had an "open" division for the adults to play. Nothing wrong with making wheels and axles that are race ready, so long as Jr. is assembling.

[@dkturner10]

Use a USB scope and you can see metal fibers coming off the shaft.. once you remove those then your wobbling stops.

[@HelicoolsHelipad]

Every little bit helps, right?

[@justmike57]

Interesting on what it takes to build.

[@thanethebrain]

How did you do? I definitely like your tool to shave the wheels! You ever thought of using 3 wheels and rail riding?

[@HelicoolsHelipad]

I have thought about using only three wheels, but getting the balancing from left to right along the long axis of the car was problematic. I suggest if you want to go this route, drill either the left or right front tire axle point about a 1/16 inch higher on the car body. This will lift the tire off the ground which will eliminate friction on that wheel. Personally, I never was a fan of this, since the cars had a hard time tracking true.

[@thanethebrain]

I'm definitely a fan. That's why I was asking. Check out my videos on pinewood derbys. Search from my channel with "Five Tips for Fastest Pinewood Derby." How did this car do in the race?

[@HelicoolsHelipad]

If I remember correctly, Alex won his division along with the overall title. His little brother got second in his division and third overall. The adults have an "open division" that they compete against each other. In that division, you can have a "potential energy" devise... such as a mouse trap, rubber band with propeller, etc.. It keeps the "big" kids a little more out of the "little" kids race. I do my kids wheels, and advise them on the rest, but it is up to them to do much of the work on their cars (with the exception of using power tools).

[@monsterhobbies]

...such a tiny scale! :D

[@HelicoolsHelipad]

Harbor Freight... works great, lasts long time.

[@monsterhobbies]

@@HelicoolsHelipad Sounds good!

[@buildingracingvideos4714]

You were so serious about aerodynamics but you totally overlooked skin drag. With that much surface area a cone on the rear is pointless. By that point the boundary layer has gotten thick enough to cause turbulence. Your efforts would serve you better to use that area for weight placement

[@HelicoolsHelipad]

Building/Racing videos if the vehicles were going fast enough for parasite drag to have much affect, I’d have covered it as well. I also tried to race a car with short “fur” on the surface to test small objects and boundary layer effects, such the hairs on a bumble bee. It was negligible. I flew helicopters for a living, and have done a lot of research... the majority of drag for a pinewood derby car is profile drag. Parasite drag is negligible. And, if you can reduce induced drag (drag from lift, as in an airfoil shaped car), that’s about all you can hope for. Did you watch the entire video?

[@buildingracingvideos4714]

@@HelicoolsHelipad yeah I watched your whole video. I've done this with 2 kids 4 years each and the 3rd is on his 3rd year I've studied this a lot. I'm also an amateur drag bike racer on the weekends. You say negligible but one thing I've learned in racing is 2 negligible things = .01 second. But you're probably talking to the wrong guy, I port cylinder heads and know a ton about air flow and the affects of skin drag

[@HelicoolsHelipad]

Building/Racing videos one thing you might consider... high speed, like a main rotor blade moving through the air has a boundary layer about as thick as a playing card. Low speed, like a pinewood derby car, parasite drag is negligible, since the speeds are such that airflow gently moves and does not become “sticky” enough to have much effect. My boys are both Eagle Scouts. Good on you for getting your kids involved with a great program. I wish you great success in raising the future leaders of this great country.

[@markmiller3954]

I can appreciate the technology and engineering you possess --- the "Spirit" of this project for Dads and kids was founded on the principles for elementary technology/engineering and child-like ideas and participation with mentoring from adults. I was only allowed to use a pocket knife and sandpaper for my design with nominal imput from an adult. I even agree, that may be "too much" of low technology for the present day --- but the "Spirit" of the project was still achieved. There should be two competitions: (1). Children Only participation and (2). "No holds barred" competition for Adults who can use all of their technology/engineering skills to defeat, humiliate and crush their opponents --- As Tim the Tool Man used to say: "UUUEEGGHH?!?!"

[@bruceyhead8327]

AmI supposed to be confused? is it because I'm a kid? Probably.

[@HelicoolsHelipad]

Brucey head if you need help, ask me. I’ll get back to you.

[@bruceyhead8327]

I already made it but Thank You.