OT: Pine Derby Car building help

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Dario

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I am assisting my nephew to make his first pine derby car...anyone have tips to make descent one?

My main question is where is the ideal center of gravity located on the length of the car? I know it should be as low as possible but not sure if the CG should be nearer the rear or the front. I read that it should be 1/3 from the rear but not sure if that is good advise.

They can only use the nail type axle and the approved nails are much smaller than the wheel holes which is causing some wobble...anyone have a good fix for this? I am planning on building it up a bit with thin CA :D but not sure if that is a good idea or not.

Planning on using graphite powder lube...is there better choice?

Thanks!
 
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Let's see if I can remember some stuff from my younger days . . .

Graphite powder is good but be sure to wear it in good before the race by applying it multiple times and spinning the wheels a bunch before race day.

take off as much of the top as you are allowed and make it as heavy as you can, weighted on the bottom.

You might see if you can make some shims for the wheels maybe out of delrin, drilled to fit the nail, then mounted on the nail on the lathe and turned to fit inside the existing hole in the wheel or drill it larger to make it easier to turn.

You may also put some very thin washers between the wheel and the car and between the wheel and the head of the nail. This should cut down some of the friction that could happen there.

I'm not sure on the weight distribution, but I think about in the middle between the axles, maybe slightly toward the rear would be best. you might want to make it adjustable front to back and test it to see where it works best.

Obviously smoother is better and present the lowest profile possible in the front.

You may also want to make sure the wheels are square to the car so it won't veer to the side of the track and rub on the way down.

Sorry this was so long, hope it helps.
 
If they had the NASCAR tech inspectors for the derby cars, half would be disqualified [:D] Our Lions club did a soap box derby race about 20 years ago. After a couple of cars crashed threw the hay bales, we noticed kids were putting huge rocks into their cars to weigh them down [:0]
 
It's been at least 15 years since I ran pinewood derby but here's what I can remember.

We used a car with a very basic wedge shape that tapered from about 1/8" at the front to about 1/2" at the rear. We didn't use the standard axle locations, opting to extend the wheelbase by moving all 4 wheels closer to the front rear by 1/4" or so. My father was a jeweler and had access to a mini lathe of some kind so he sanded the axles perfectly smooth and if I remember correctly he also turned the inside of the wheels down to reduce the surface area in contact with the axle. We used powdered graphite for lubrication, going so far as to paste a paper hubcap over the outside of the wheel after filling the cavity with powderer graphite.

The weight was as close to the rear of the vehicle as possible, probably centered over the rear axle (theorizing that the wieght had further to drop and that would increase speed over the same distance). We drilled 3 holes in from the side and filled with molten lead. Adjusting the weight was easy, just drill out excess lead little by little until the weight in the ballpark but still just a bit heavy. Additional weight removal could take place at the race site using the official weigh in scale provided. Every scale is different and it was easier to remove a few grams with a small drill than try to tape pennies or fishing weights to the top of the car as many other racers did.

Two last tricks we always used to have one of the front wheels off the ground at all times. This was supposed to reduce friction with the track. The other was to make sure the car was centered on the track at the beginning of each race. You don't want your car rubbing the center guide and slowing your start.

The last year I ran pinewood derby I wanted to do something different. I opted to go for the most creative trophy, using a small piece of handrail that was tapered to point on one end, I created a crayon car, we made a Crayloa label and everything. It was surprisingly fast and appeared to get faster after each race. I think I still ended up taking 2nd or 3rd with my younger brother and his "speed" car taking 1st.

Jason
 
Awana Clubs International has a similiar event called the Awana Grand Prix. We are avid participants!! I don't know how the rules compare, but here's some tips. (I'll give 'em to you since we probably won't ever race you. [;)])

The center of gravity should be just ahead of the rear axle.
All your weight should be in the BACK.
We use hot glue in our wheel axles, you also have the option extending your wheelbase and drilling your own holes.

Polish your axles (Brasso), sand and polish your wheels (more Brasso).
You should be able to get a tool for doing the wheels at a hobby store, Lowes, etc.

Graphite is a good choice for lubricant. Make sure your axles aren't too tight against the body of the car, resulting in poor spin for your wheels.

G2G, I'll write more later.
 
Ah! Pinewood derby days. It's been awhile...my son just had hs 29th birthday. I still have a track we built for the cub pack. I really should see if I could give it to a pack somewhere here in town.

Good luck Dario....it is great fun.

free info: http://members.aol.com/randywoo/pine/

http://www.pinewoodprofessor.com/

http://entertainment.howstuffworks.com/question169.htm

http://home.simplyweb.net/bosworth/

http://www.pinewoodpro.com/
Do a good turn daily1
Don
 
between the wheels and the car apply a piece of slippery tape from Lee Valley. Greatly reduces friction. Then again you could always just buff the ends of the axel with the beall system. That carnuba wax would work wonders.
 
As a Scout's parent, and former Cubmaster, I have seen, used, and/or tried all of the above. Two years ago, a scout put the wheels on the block of wood that came in the kit, painted it red, named it the "Flying Brick". He came in 1st.[:D]
So after all is said and done, if the kid has a good time, you did it right.
 
I have to agree with Ron. It more important that the child enjoys his car than winning the thing. I've organized and ran our Packs Pinewood Derby for the last 8 years (only 2 more to go) and we've gone from one rickety three lane track to two four lane tracks with electronic timers. In all those years I've tried all the techniques mentioned and then some but none of my sons have ever won the event. I have tried very hard to instill in them that winning the derby isn't the biggest thing but having pride in your car is (we do give out a number of awards for car appearance - shiniest, most realistic, most patriotic, etc...). With this my sons have won numerous awards and are just as happy as winning the races.
I also build a car each year that usually a little off the wall but shows lots of creativity and care. I've built them to look like a tube of toothpaste and toothbrush, Sponge Bob Squarepants, and have even turned one to look like a pine tree. If your pack doesn't do appearance awards I'd suggest that you mention it as it spread the wealth out farther. Bob I.
 
Lots of good advice here, Dario, but make absolutely sure you understand the rules for YOUR race. Many of the things being suggested here are totally illegal in our Pack's Derby. For example, no hubs of paper, tape, etc. No bushings on the axles...only the supplied wheels and axles with no add-ons. Be sure you're within your local rules...a DQ would be horrible!

My son won not only our Pack last year, but went on to win the District Derby...by a big margin. We did the basic wedge design, lengthened the wheelbase, and raised 1 front wheel off the ground. The most important thing is preparing the axles. You can go to Hobby Lobby, Hobbytown, AC Moore, Michaels, etc (they're all carrying Pinecar stuff) and buy the "Speed Pack", I think it's called. We mounted each axle in a Dremel tool that was clamped in a Workmate bench. Spin the axle at high rpm and use the wet-dry polishing cloth, then buff with the pumice till the axle really shines. Don't do what one guy in our Pack did...he thought the pumice was graphite...bad thing.

Speaking of graphite, I always see 2 kinds for sale. Get the plain old black graphite. The other kind is white and says "with Teflon". Myself and several other Dads in our Pack have had terrible experience with that Teflon stuff. I used it on one of my Leader cars that I thought I did a good job on, and the thing barely made it across the finish line...quite embarassing!

Oh, and speaking of axle prep...look closely at the inside surface of the hub and you'll see a small burr from the molding process. With a steady hand and a grinding wheel on your Dremel, you can knock that burr off for a much smoother surface (before you do the polishing/buffing). And the plastic wheels...they're snapped off a plastic "tree" in the molding process. Take an Xacto knife and scrape that little burr off, too, so the wheels don't "bounce" when they roll. Also, when all else is done, make sure your car rolls straight. If it bounces back and forth off the center rail very much, you lose.

As for weights, I'm a firm believer in placing the weight on the bottom of the car, at and in front of the rear axle. If you have more weight behind the rear axle and your car starts bouncing off the center rail, the weight seems to make it worse if it's pushing.

OK, I admit it...I take this stuff way too seriously![:D]

The most important thing is to have fun!
 
Yes, double check your rules. Our rules state that all 4 wheels must be on the ground - no raised wheels allowed.

My son won the pack race last year, but didn't do too hot at the district. His car fell getting into the car to go to the race, and though I tried to straighten the wheels, I still didn't realize they weren't straight and were rubbing badly.

Still trying to work out a design for this year - not much time left! He wants an Oscar-Meyer Weinermobile!
 
When the car is completed do not play with it. The axels are fairly fragile and bend easily. My son kept his car on a raised platform with the wheels hanging freely. He won 1st place in every race he was in.
 
Last year, out of my 3 boys, the best shape as mentioned was the wedge with a lot of weight in the dead middle (it was the Cheese Car) [:D] Great advice here, wheels is the most important thing. How about chucking them on the lathe and running the tires up thru your MM?? [}:)] (again, check your rules) but if you can turn a light taper to the tread so that you have a crown you can reduce the surface contact by 2/3 rd's [;)]
 
I remember a kid whose machinest dad drilled the down the center of the axels and across the axel to create a graphite resevoir. The rest of us hardly used sand paper and our cars looked like they were shaped with an adze. Needless to say his car was perfect and he was way out in front at the finish line.
 
Make sure the car isn't over the weight limit.
It would be a shame getting the car all dialed in and then finding out at the last minute its over the limit.
Being able to make last minute adjustments is helpful as mentioned before.
A postal scale should help in checking the weight.
I think 5 oz is the weight max.
Again like others have said do check your packs rules and regulations.
They do vary from pack to pack.
 
Dario,

It can't be emphasized enough....know the rules for your race. Many races have weight restrictions. It is easier to add weight to cars (when I did this, we had a slot on the bottom that we added melted lead to)than to remove it.

As far as graphite is concerned, I think there are better lubricants, but check the rules to see what is allowed. Lube One, made by Slick 50, won my son the trophy one year.

jeff
 
I have a friendly suggestion for the Cub Scouts of America ...... my recommendation would be that they start a whole other pine derby car race division ... for Dad's Only. The requirement would be that ONLY the Dad can build the pine derby car while his Cub Scout son watches.
 
To give the hyper-competitive dads an outlet, we run an adult division in our annual Grand Prix. The wheels are the key. Proper preparation of the axles and wheels and a hard car wax on the body of the car where the wheels rub make the difference between a competitive car and a winner. We use trumpet valve oil as the lubricant because it has a better cling time than graphite (you are not able to re-lubricate your car once it is weighed and turned in at the beginning of the race). I've won the adult division the last 3 years and 4 of the last 5 (don't know what happened that one time [:(!]), and look forward to defending my title in May [:D][:D]. Oh yeah, my kids' cars usually do pretty well, too [:eek:)][;)].
 
Dario,

Didn't check to see if this was previously mentioned, but there is one more thing. Chuck the axles into your drill press and sand them to around 600 or 800 grit. Helps them run a little smoother.

jeff
 
Jeff,

I already did that...actually run them through my MM too [:D]

Thinking now if I should use Renwax or TSW before the graphite [:p]
 
Originally posted by DocStram
<br />You guys are way too into this. Now that I think about it ... I wonder if I could "adopt" a Cub Scout for the day.
Click to expand...
I bet you wuold be amazed at the reception you got if you offered your services to your local scout pack. We had several boys who for 1 reason or another did not have anyone to help them with their cars. The other dads try to help, but 1 on 1 is usually better for the boys, as they learn more, and its not just a "lets get this thing done quick"
 
Originally posted by RonSchmitt
<br />
Originally posted by DocStram
<br />You guys are way too into this. Now that I think about it ... I wonder if I could "adopt" a Cub Scout for the day.
Click to expand...
I bet you wuold be amazed at the reception you got if you offered your services to your local scout pack. We had several boys who for 1 reason or another did not have anyone to help them with their cars. The other dads try to help, but 1 on 1 is usually better for the boys, as they learn more, and its not just a "lets get this thing done quick"
Click to expand...

I heartily second the other Ron's suggestion. The biggest help most of the boys need is with the basic shape of their car. If you have a bandsaw (or scroll saw) and a belt/disc sander, you would be a hero to a bunch of boys (and most of their parents).

But you'll probably be surprised at 2 things. First, how much a 4th grader can do for himself. For example, last year, I showed my son how to do all the axle prep I described in my earlier post. I showed him on 1 axle and he did the other 3. Everything I did I found through Google...didn't come up with anything new myself. The other thing you'll be surprised at is how little a 1st grader can do for himself. It's a challenge for those younger boys just to "stay in the lines" with a crayon. And you think they don't need a bunch of help building a model car?

So yes, Al, by all means...please go volunteer your time to help. I'll be glad to help you get in touch with a Pack in your community. I guarantee you'll be richly rewarded!
 
Dario: I just ran across this yesterday. It may be too late to be of use this year; but maybe you can salt it away for future reference??

http://www.amazon.com/s/ref=sr_pg_1...ewood derby&rh=n:1000,k:pinewood derby&page=1

Who would of thought?? 16 titled books on building Pinewood Derby cars and many others with some information. Never realized it was such a big deal.....and I was a Soutmaster for a number of years!!
 
Dario: The advice to check your current local rules is excellent. Not having any first-hand experience with the derby. I looked at some of the postings on the Internet and find that many of the suggestions posted in this thread would be illegal under today's commonly accepted rules.

Have a good time. This project sounds like it will be as much fun as turning pens!![^]
 
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