Author Topic: Who's got Pinewood Derby tips for speed (Read 8834 times)

GammaFlat · « **on:** November 12, 2009, 09:26:16 AM »

My son is a cub scout. The Pinewood derby is coming up soon and I need help in making sure our car is fast. Anyone got good recommendations for going fast.

I remember what my dad and I did but it appears the game is quite different (cars and rules are different now). For example, we cut the wheels down to reduce the contact patch but modifying wheels that way now is verboten.

Anyone got anything for me? Does this belong in the "High Performance and Racing Forum"?

mystic_1 · « **Reply #1 on:** November 12, 2009, 09:40:35 AM »

Reduce the rolling resistance of the wheels by polishing the contact surfaces between the wheels and the axles.

mystic_1

mgbgt89 · « **Reply #2 on:** November 12, 2009, 09:44:34 AM »

Keep the weight as much to the back as possible. When i was in cub scouts our winning cars always had a COG bearly in front of the rear axle. The wedge shaped cars almost always win. Keep the wood thin as possible, then fill the back of the car with lead. Always get them to the maximum allowable weight. I had to sand the paint off 2 of my cars to get them bearly under weight at the tech inspection.

Buy multiple kits. Choose the best parts from each of them. Dont use the stock axle slots, they are never straight. We cut ours on a CNC.. lol.

We polished axles on a drill press, polished the wheels, and had them set up so that only one front wheel touched the ground. With perfectly straight axle slots, this worked very well. TONS of graphite. My cars were always filthy by the end of the heats from all the graphite flying off.

How is your track set up? On the pack track we used, it was two straight boards joined in the middle by a very short transition. On tracks like this, the cars with rear COG's just shot off the transition. The district track was a smooth curve, and it didn't have as much of an effect, but it was still faster.

I miss pinewood derby...

333 · « **Reply #3 on:** November 12, 2009, 11:23:21 AM »

Who's competing? Parent or child?

kirkn · « **Reply #4 on:** November 12, 2009, 11:26:02 AM »

...and that's what it's all about - beating the other 11 year olds 'cause you have a CNC machine or lathe or willingness to buy 17 kits and use the best parts of each.

Sheesh - let the kid make his own car, and have FUN with it.

And that's what both of MY sons did for the 3 years they competed... And at 18 years old, my oldest son STILL has his self-designed, self-built car on the display shelf in his room.

mlinder · « **Reply #5 on:** November 12, 2009, 11:42:52 AM »

Car battery and properly geared electric window motor should give you a clear, silent advantage.

GammaFlat · « **Reply #6 on:** November 12, 2009, 12:00:47 PM »

Thanks guys. I'll be taking the suggestions to heart. I wish I had a cnc

My dad and I did a "city champion (Chicago)" car in 1969-ish. I think I have about 10 trophies (and at 48 years old, my trophies are still on my shelf - just kidding). My dad was all over this stuff and I'm kind of glad.

I understand kirkn and 333's point but building the car with my dad so deeply involved, I learned a lot. In our pack, the car that was most obviously built solely by a kid usually got an award. I have to say I'm torn on the topic a bit. To give a child a taste of victory early on does something and maybe not all positive - but a life experience none-the-less. It's a bit like helping your kid through their homework. My daughter is getting all A's (holy cow - that's different than my story) and I don't think she would if it weren't for the amount of time my wife and I spend with her every night on her homework and test prep. Oddly, I think the teacher recognizes the fact that we help and treats our daughter differently (better). The same goes in sports and other activities. When there's a support mechanism behind a kid, it's completely game-changing. I experienced it first hand as a kid (mostly negatively - long story).

My son at 6 years old, would not be able to construct a car that would make it to the end of the track, let alone paint it. I believe it's fully expected that a parent will be involved. What I'd really like to get out of this with him is the understanding that hard work can pay off - we work hard on the car and it's more likely to win. Advantages that can be gained through whatever reasonable means are a lesson in life.

If my son wasn't so big on blue, I think I'd make the car Antares Red like my K6

I don't think I'll make any headway there.

myhondas · « **Reply #7 on:** November 12, 2009, 12:17:37 PM »

Having done the pinewood derby many times and currently on the board of directors of the GCC Eagle Scout Association, my suggestion to you is this. Let your son do most of the work building the car with you helping him where he needs it. Try (as hard as it is) to verbally help instead of hands-on help. The more he does to make the car himself, the more he will appreciate the outcome. Your involvement with him in making the car will also last a lifetime in his mind. If you take over the project (like some dads do) he will have a car that his dad build with him rather that a car that he built with his dad. Winning is good! But the path to get there is more important and the success is always sweeter when it is accomplished by doing it oneself.

Inigo Montoya · « **Reply #8 on:** November 12, 2009, 12:27:46 PM »

There is a lot you can do BUT you must follow the rules set forth. You have to use the wheels and axles(nails) in the kits. If this is a scout race, I think they only allow boy scout approved kits. The biggest thing is to work on teh wheels. body shape can help but a wedge is not always best. The winner in my area last year(A girl scout btw) Got a scale speed of over 235 mph. My daughters car got up to 227. You do this by using powdered graphite. You put the axle in a drill with the wheel on, get the whole thing spinning and start squirting graphite into the wheel. Keep it going like this until you got a good coating inside the area for the axle. Do not polish off the axle, all this does is remove the graphite and your car WILL run more than 1 race. Also, you can't narrow the wheels BUT you can sand them to remove burrs and edges just a little and make the wheel smoother. Fine sandpaper on a hard, flat surface is all you need. Lightly sand the wheel. Do not take too much off, a larger wheel is going to spin slower on the axle and wear off less graphite than a smaller wheel will.
the idea is to not be THE fastest but to stay fast longer for a duration of races.
Weight placement, I am not sure on. I am not sure if it really makes that big of difference. My daughters car had a open cockpit cutout and I mounted the weight there. It all pretty much fit in the cut out. I would worry more about putting the weight on the bottom. If you cut out and area there, make it deep, not wide. A wide slot might catch on the guide rails.
Also, make sure you take graphite with you. Put a bit on before the weigh in and spin the wheels some. You also get to relube 1 time if I remember right. Do not just put in graphite, It must be spun to break down otherwise it will slow you down.
last year was my first year but my father in law helped and he has active in scouts for years with his sons.
My daughters car(mostly mine but then she was 5 and in daisy scouts)was overall 4th fastest once averaged.
this year I was thinking of making temp hubcap and filling them with graph and spin them to see if that helps.
Just what I was shown last year but it seems to work very well.

And yes, the girl scouts raced the buys. Why not. I suppose if you were in the boys and got beat by the girls 2 year running(both years they raced each other incidentally)you might feel different. But I think it is a good thing.

JohnCurW · « **Reply #9 on:** November 12, 2009, 12:45:52 PM »

One thing that seemed to work pretty well for me when I was in cub scouts (I think that was about four or five years ago) was to cut the body of the car in the shape of an airfoil. Slight amount of lift=less friction on the wheels=go fast. That being said it sometimes worked a little too well and would pass the finish line with a slight lead but not trigger the switch on the track so 2nd place car regestered as a winner.

Or mount a small rocket engine from a model rocket to the back of it...

Tretnine · « **Reply #10 on:** November 12, 2009, 12:59:12 PM »

Well, (huffs on fingernails, then rubs them on chest)

Having won a couple of pinewood derbies myself, (3rd, 1st, and 3rd in regionals) I'd have to say that while my cars were never the most beautiful. (mostly shaped like a wedge, with a little flair built in) All we really did was polish up the axles, put graphite on them fill them up with lead so they hit the exact maximum weight. Did you know you can melt lead in a coffee can with a blowtorch? Careful, though, the coffee cans tend to melt through... That was pretty much it. Maybe today's competition is a bit stiffer.

Brady

mystic_1 · « **Reply #11 on:** November 12, 2009, 01:29:08 PM »

Paint flames on the body and detail it with chrome paint, that should be good for at least 10 scale MPH

mystic_1

Jerry Rxman Griffin aka MuthaF'er · « **Reply #12 on:** November 12, 2009, 01:37:08 PM »

CHEAT!! by all means...............

I agree with the responses about giving him your fatherly guidance. Show him how to do things but let him do it.

mgbgt89 · « **Reply #13 on:** November 13, 2009, 07:26:46 AM »

Quote from: kirkn on November 12, 2009, 11:26:02 AM

...and that's what it's all about - beating the other 11 year olds 'cause you have a CNC machine or lathe or willingness to buy 17 kits and use the best parts of each.

Sheesh - let the kid make his own car, and have FUN with it.

And that's what both of MY sons did for the 3 years they competed... And at 18 years old, my oldest son STILL has his self-designed, self-built car on the display shelf in his room.

Haha.. i was the kid. I did the majority of the work on the car. Obviously not the CNC work. One year i did design my own car on cadkey, which my grandpa then cut on the CNC. That was pretty cool. I got to use a FARO arm to digitize a model car i had, then modified the demensions in cad. I learned way more about cad programs than any 11 year old should know.

That car looked like a 1930's indycar. It wasnt a winning car, but it sure did look cool. My grandpa ended up scaling up my car and selling the design to the company he bought his CNC from, they use it as a demo at trade shows, and hand them out to potential customers.

I'm 20 now and still remember having fun with my grandpa and his tool shop.

We never did build a test track like we had talked about though

mgbgt89 · « **Reply #14 on:** November 13, 2009, 07:32:35 AM »

Quote from: Inigo Montoya on November 12, 2009, 12:27:46 PM

Weight placement, I am not sure on. I am not sure if it really makes that big of difference. My daughters car had a open cockpit cutout and I mounted the weight there. It all pretty much fit in the cut out. I would worry more about putting the weight on the bottom. If you cut out and area there, make it deep, not wide. A wide slot might catch on the guide rails.

I think weight placement is fairly critical on a track with 2 flat sections and a transistion between them. If the mass is farther towards the back, it travels downward for longer, before it starts moving forward. More downward time, more acceleration.

On the track we had, you could tell the cars with rearward weights because they would just rocket past the other cars after the track got flat. Less friction wins on the downhill, rearward weight wins it on the flat section.

The_Crippler · « **Reply #15 on:** November 13, 2009, 08:07:09 AM »

Jesus...I didn't think PWD was that long ago for me, but it musta been. Sensors on tracks? CNC? Sheee-it, all we did was carve a block of wood, graphite the wheels, drill some screws and washers into the bottom for weight and drop 'em down a track.

I specifically remember one year, this kid just put the wheels on the block of wood and raced that. *^$%# won, too.

Inigo Montoya · « **Reply #16 on:** November 13, 2009, 08:30:41 AM »

Quote

I think weight placement is fairly critical on a track with 2 flat sections and a transistion between them. If the mass is farther towards the back, it travels downward for longer, before it starts moving forward. More downward time, more acceleration.

On the track we had, you could tell the cars with rearward weights because they would just rocket past the other cars after the track got flat. Less friction wins on the downhill, rearward weight wins it on the flat section.

I do not know what tracks you have seen the the only BSA tracks I have seen are all straight. You have the slope and then it is all straight. The track is in sections of course for transporting but I can tell you the winning cars did not have weights all at the back. My daughter's car had them in front of the rear axle too.

less friction wins through the whole thing though. weight will not matter if the wheels have a lot of friction. Just saying what I have seen and what I have been told by my in law who was a pack leader.

mgbgt89 · « **Reply #17 on:** November 13, 2009, 09:01:10 AM »

I have seen about 3 tracks, The one i raced on most was 2 straight boards joined by about 8 inches of curve in the middle. That track, weight placement made a huge difference. Say the cars are 8 inches long, Car A has a center of mass directly in the middle, Car B has it an inch and a half from the rear of the car. Car B's mass then would be traveling downward an extra 1.77 inches over car A, if the track was at a 45 degree angle, if my math works out right..

The other tracks were a steady curve the whole way down, like a skateboard ramp. These tracks, the weight placement didn't seem to make as much of an obvious difference to the naked eye. The short transistion of the other track made the difference in weight placement clear.

Rocking-M · « **Reply #18 on:** November 13, 2009, 09:38:00 AM »

you know I wish I better remember my PWD days. I grew up without a Dad and I'm sure some of the
other fathers gave me advice. I do remember putting the weight in the front (I think) and oh yea,
I was the winner at our local Pack.

That's as far as I went in the PWD world of racing.

myhondas · « **Reply #19 on:** November 13, 2009, 10:09:59 AM »

most tracks are straight...haven't seen a curved on yet... this is the type they use in our council

Inigo Montoya · « **Reply #20 on:** November 13, 2009, 12:10:39 PM »

Yep that is the track. If I remember the bsa rules, the track is always straight.

mgbgt89 · « **Reply #21 on:** November 13, 2009, 12:22:08 PM »

I'm sorry.. I meant the way the track is sloped.

One was shaped with a varied slope, like a skateboard ramp.

The one i used most was exactly like this:
http://www.allpar.com/photos/shows/MiM/pinewood.jpg

Straight board with a constant slope, then a transition, then flat at the bottom.

Inigo Montoya · « **Reply #22 on:** November 13, 2009, 12:37:47 PM »

Link does not work now.
Anyways, what myhondas put up is all I have ever seen.

mystic_1 · « **Reply #23 on:** November 13, 2009, 02:09:57 PM »

Here's the pic that mgbgt89 was trying to post.

mystic_1

Rocking-M · « **Reply #24 on:** November 13, 2009, 02:20:13 PM »

Quote from: mystic_1 on November 13, 2009, 02:09:57 PM

Here's the pic that mgbgt89 was trying to post.

mystic_1

looks like the cars would need shocks for that big dip at the transition.
Can you mount a set of miniature Konis on that thang.

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Author Topic: Who's got Pinewood Derby tips for speed (Read 8834 times)

Rocking-M

Rocking-M