# Pinewood derby weight distribution questions **URL:** \ **Category:** Factual Questions\ **Created:** [January 13, 2011, 5:46pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481 "2011-01-13T17:46:26Z")\ **Posts on this page:** 15\ **Page:** 4
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [January 15, 2011, 12:50am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/61 "2011-01-15T00:50:12Z")
> [@CurtC](#): > > I thought all Pinewood races required you to use the same wheelbase, which is determined by the slots that are pre-cut into your block of wood. I’ve heard of that restriction before, but in our Council they specifically state that the wheelbase can indeed vary, and that you do not have to use the pre-cut slots. My son and I never bothered, though. To change the wheelbase, you either have to cut new slots, or drill holes with a drill press. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 15, 2011, 1:11am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/62 "2011-01-15T01:11:06Z")
> [@CurtC](#): > > I thought all Pinewood races required you to use the same wheelbase, which is determined by the slots that are pre-cut into your block of wood. > > I really like that system. I’m the “racemaster” of my son’s pack, and our pack’s track has six lanes, but it only indicates the finish order - first, second, third, etc. No time measurement, so you can’t compare across races. > > Before I took over, the pack had a system that involved racing each car once in each lane, and with all the coordination that had to go into each race, the whole thing lasted three or four hours and the kids all lost interest. I changed it to a system based on double-elimination, where the fastest three cars advance in each race and the slowest three drop. I give each kid a ticket at the end of a race that indicates his next race number, so they’re aware of when they need to race next, and they’re ready. We can knock the whole thing out in about an hour. The downsides are that there’s no compensating for one of the lanes possibly being slower, and that some of the kids are eliminated after only two races. But at least the race is over before their attention span is, and that’s a really big factor IMHO. My son’s Pack has an aluminum track that has a laser eye at the start and at the finish. The entire rig is hooked up to a laptop that in turn is hooked up to a projector which projects the laptop’s desktop onto a movie screen. Not only are the orders of finish displayed, but the times for each car as well, and the computer calculates your average time over the course of all your heats, etc. Its pretty high tech for a pinewood derby! Which reminds me…I need to get cracking on my son’s car! We only are in the idea stage at this point, and the race is next Saturday! :eek: ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [January 15, 2011, 3:35am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/63 "2011-01-15T03:35:25Z")
Well my son took first tonight but it was somewhat disappointing. Only 2 kids showed up at his level. Next up is the regional competition. So we’ll see how fast the car is for real. ---
**Author:** ![Raguleader](https://avatars.discourse-cdn.com/v4/letter/r/258eb7/32.png) [@Raguleader](https://boards.straightdope.com/u/Raguleader)\ **Post date:** [January 15, 2011, 4:37am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/64 "2011-01-15T04:37:38Z")
> [@billfish678](#): > > What if the Derby car is on a treadmill? Doesn’t matter, the wheels are free-spinning, so the car will take off regardless of what the treadmill does. What if we set the car on fire? Would that affect the speed any? ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [January 15, 2011, 4:59am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/65 "2011-01-15T04:59:29Z")
> [@cornflakes](#): > > No matter what your rules say, you can find a custom wheel that will be allowed and will run truer than anything that most of us can make. > [@robby](#): > > This was illegal in our local Boy Scout council. All Scout were required to use the official BSA pinewood debery materials sold in the kits. Substitute wheels were strictly prohibited, and would get a car disqualified if discovered. It was also considered to be cheating. Sorry. I had the impression that virtually all councils required BSA parts but that there was a lot of variation regarding the level of modification that could be done. I assume that everyone turns and polishes the axles, that most fathers and sons deburr the wheels and some taper the area where the wheel touches the body. These mods were fairly standard in my district. There is also a lot of random variation in these cars. Some of the fastest cars at our last race were from kids from poorer schools, most of whom built their cars with no parental involvement. The axles may have been polished and we told them to glue washers to the backs of the cars to bring them to five ounces, but that was all that was done to make the cars faster. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 15, 2011, 6:38am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/66 "2011-01-15T06:38:54Z")
> [@](#): > > Sorry. I had the impression that virtually all councils required BSA parts but that there was a lot of variation regarding the level of modification that could be done. I assume that everyone turns and polishes the axles, that most fathers and sons deburr the wheels and some taper the area where the wheel touches the body. These mods were fairly standard in my district. Oh, if by “custom parts” you mean that someone buys up official kits, picks out the best wheels and so on, polishes and lubes them, and then re-sells them, I imagine that that would be allowed. I was interpreting you to mean parts that weren’t ultimately from the official kits, and those would be considered cheating. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [January 15, 2011, 12:54pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/67 "2011-01-15T12:54:18Z")
> [@Raguleader](#): > > Doesn’t matter, the wheels are free-spinning, so the car will take off regardless of what the treadmill does. > > What if we set the car on fire? Would that affect the speed any? In that case the moral thing to do is shoot the Cub Scout dead. And maybe the father too just to be sure. Avoids any needless pain and suffering. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [January 16, 2011, 1:06pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/68 "2011-01-16T13:06:17Z")
> [@Chronos](#): > > Oh, if by “custom parts” you mean that someone buys up official kits, picks out the best wheels and so on, polishes and lubes them, and then re-sells them, I imagine that that would be allowed. I’m not sure how it would be enforced, but any modification to the official parts or work on the kits performed by anyone other than the Scout (though assistance is allowed, of course) is strictly prohibited in our Council. So the Scout (with the help of his parent) can polish the axles, etc., but is not allowed to purchase polished axles from a third party. This is because the whole point is for the Scout to do the work. Similarly, it is strictly prohibited to purchase pre-built or partially pre-built cars. The Scout must start with the raw, unmodified official parts. However, there is nothing prohibiting someone from buying several official kits and picking out the best wood, best wheels, axles, etc., so long as any modifications to the official parts are done by the Scout themselves. In fact, the official BSA Scout store sells smaller official kits that contain five extra wheels and axles (but no wood) for someone really wanting to pick out the best possible. > [@Chronos](#): > > I was interpreting you to mean parts that weren’t ultimately from the official kits, and those would be considered cheating. Exactly–the main parts (wood, wheels, and axles) must come from the official kits. However, any add-ons (like weights or detailing) need not come from the official kits. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [January 16, 2011, 3:02pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/69 "2011-01-16T15:02:12Z")
Many people don’t own the kind of tools you’ve described (lathe. drill press, band saw, etc). So what arrangement is made for those people? ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [January 16, 2011, 3:23pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/70 "2011-01-16T15:23:26Z")
> [@Dewey\_Finn](#): > > Many people don’t own the kind of tools you’ve described (lathe. drill press, band saw, etc). So what arrangement is made for those people? My son’s pack solved this by having the meeting one week at the home of one kid whose parents had a pretty substantial shop. This really helped some of the parents who seemed to have no shop experience in that there was always someone who could help if they had any questions. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [January 16, 2011, 3:31pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/71 "2011-01-16T15:31:21Z")
> [@Dewey\_Finn](#): > > Many people don’t own the kind of tools you’ve described (lathe. drill press, band saw, etc). So what arrangement is made for those people? Actually in many cases parents with tools invite the others over. In earlier years this is how my son’s den worked. This last year though nothing, but only two boys in his den participated in the end. A lathe and drill press is not needed. Any drill will do the job fine. Many saws will work fine including a good manual miter saw. A Band or Scroll saw does make it easier but a $20-$30 jigsaw can do the job. As \*\*Robby \*\*mentioned most troops all require official kits be used. So the most important tools are sandpaper, some sort of saw to cut the angles and a drill might be needed for the weights but many designs do not even need a drill. My son strictly uses sanding blocks. Just small pieces of 2x4 with sand paper stapled on.I set him up with 4 grits of paper to shape the car. Note: My son doesn’t like using palm sanders thus the blocks. The sanding still takes no more than an hour for a simple wedge design. The saw is probably the one big time saver. I really don’t think any other tool is needed. We have had weights on top of the car, many have weights under the cars but the last 3 years we went with a simple wedge and drum weights in the rear of the car. This has worked well for us. This did need a power drill but not a drill press. (Which I have) ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [January 17, 2011, 1:42am UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/72 "2011-01-17T01:42:32Z")
My son always used the pre-cut slots for the axles, so we didn’t need a drill press. (To ensure the axles didn’t come loose, we filled the slots with wood putty after tapping in the nails.) The first year my son just used a hand [coping saw](http://en.wikipedia.org/wiki/Coping_saw) for the basic car shape. His second year, one of the fathers with an elaborate wood shop, including a band saw, let Scouts and parents come over to his shop and use his tools. (He did the actual cutting with the band saw per the shape drawn by the Scouts.) His third year, we just made a straight cut on the back to produce his square Spongebob car. And his fourth year, we used a power miter saw to make a straight cut to produce a simple wedge shape. Interestingly enough, the fancy car produced in the wood shop for his third year (which also had internal lead weights) was his slowest car of the four. He got a 2nd, 3rd, and 1st place trophy for his age group for the other three cars (in his first, second, and fourth years, respectively). ---
**Author:** ![anson2995](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@anson2995](https://boards.straightdope.com/u/anson2995)\ **Post date:** [January 17, 2011, 3:14pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/73 "2011-01-17T15:14:05Z")
> [@robby](#): > > Instead, parents and Scouts should work together as a team. Scouts should be encouraged to do as much of the actual work as they can. Also, remember that Cub Scouts are not allowed to use power tools." Bravo. The first year my son was in scouts he was 7. He designed the car, and we worked together to make it, and he finished dead last in every heat. He was crushed. I noticed that the other 6 or 7 boys in his pack had very similar designs, and figured the other dads must have gotten them together to work on them. Then several months later when I was at the local hobby store, I saw that you could buy pinewood derby cars, with the wood cut into the shape of an IndyCar, with just the right amount of weights. All that was left for the kid was to paint it. The whole idea of the pinewood derby (and most of the things cub scouts do) is to expose kids to new activities, and give them projects they can do with their dads. A lot of the dads in our group didn’t seem to get that. What kind of 30-year old man gets a thrill from beating my kid’s car? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [January 17, 2011, 4:52pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/74 "2011-01-17T16:52:18Z")
Buying a pre-made car certainly destroys the point of the activity. But in some cases Dads are just being Dads (i.e boys). Maybe the competition should be changed from individual to Den level, with lots of adult help so individual ability and advantages don’t become such a factor. There are going to be kids without Dads, or Dads that aren’t tool guys or engineers who might not get a fair chance anyway. And for a lot of the younger kids, they’re just not ready for a competitive environment. ---
**Author:** ![Shadowfyre](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shadowfyre/32/9972_2.png) [@Shadowfyre](https://boards.straightdope.com/u/Shadowfyre)\ **Post date:** [January 18, 2011, 6:14pm UTC](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481/75 "2011-01-18T18:14:11Z")
Both of my boys are in Cub Scouts and have been since they were Tiger Scouts (6 years old). My oldest is bridging into Boy Scouts in March and my youngest is a Bear Scout (8 years old). I’ve done a lot of Pinewood Derbies. When they both started out, I did all the cutting on my bandsaw but they designed the cars. Now they both use the bandsaw with me looking over their shoulders. That was about the age I learned to use power tools and I still have all my fingers. I also have a drill press where we polish the axles using a combo of a rasp and fine grit sandpaper. But you have to be sure to get the burr off the head of the nail as well as the shaft. Our pack rules say that the wheelbase must be the same as the pre cut axle slots, but we can re-drill them. I have the boys re-drill them with a 1/16th drill bit a little forward of the slots. I’ve read that some the slots are not parallel and it allows us to get more weight behind the back wheels. I’ve also taught the boys to drill one front wheel higher than the others, this is supposed to cut down on friction. We super glue pennies in the car for weight. The boys use the drill press to drill the holes on the bottom before cutting the car and the pennies are cheaper than any other weight system I’ve been able to find. I’m really surprised that no one has brought physics into the discussion about weight. Physics teaches us that Potential Energy (PE) is mass (m) times gravity (g) times height (h) PE = m x g x h So to gain the most PE, you want to maximize the mass and height. So get as close to the 5oz. weight limit as possible and get it as high as possible. The Conservation of Energy law says all the PE will convert to other forms of energy, such as heat, friction and Kinetic Energy (KE). Doing everything you can to mitigate friction and wind resistance (if you believe wind resistance is an issue - I’ve got no dog in that fight), all you’re left with is KE. The formula for KE is mass times the velocity squared, or: KE = m x v^2 (I don’t know how to superscripts) Simplifying (ignoring friction and/or wind resistance): PE = KE mgh = mv^2 gh = v^2 v = sqrt(gh) Since g is constant, you need to maximize height to maximize velocity. For those who have never seen a pinewood derby or haven’t seen one in a long time, the wheels of the car straddle a thin but wide piece of wood. That way the inside of the wheels hit the wood to keep it from interfering with other cars in the track. You need to keep the wheels parallel with each other so that the car travels straight down its lane without dragging a wheel along that piece of wood. When we raise one wheel, it is only by about 1/16th of an inch so it will still grab that piece of wood and keep the car in its own lane should it start to veer. [Previous page](https://boards.straightdope.com/t/pinewood-derby-weight-distribution-questions/567481.md?page=3)