Thanks for all the help.

[FatSebastian]

For the record, I am not creating the ban. It was brought to my attention that all of us who allow Lead(Pb) to be used in a pinewood derby car are breaking the law. Lead(Pb) in toys is very regulated. [...] Please go to the source of the regulations before worrying about a potential conflict of interest.

Having looked at your citation sources, may we ask what legal counsel brought it to your attention "that all of us who allow Lead(Pb) to be used in a pinewood derby car are breaking the law"? The page you cite states that enforcement of the law applies to "manufacturers, importers, distributors, and retailers" of "consumer products intended for children 12" and under. The scope does not really seem to apply to "all of us" then, plus, finished Pinewood Derby cars are not consumer products (perhaps except for eBay cars). Even then, note that "Sellers of used children’s products, such as thrift stores and consignment stores, are not required to certify that those products meet the new lead limits." Homemade Pinewood derby cars are certainly used toys.

Maybe we are just leading the newest rules for a well established event.

Maybe. Or maybe overreacting? Any legal counsel out there that can chime in on whether the Consumer Product Safety Improvement Act of 2008 applies to homemade Pinewood Derby cars? (A little googling suggests that the reduction in lead levels originates from the Consumer Product Safety Improvement Act of 2008, rather than the Lead-Free Toys Act of 2005 and 2007.)

[gpraceman]

OK, guys I think the debate over lead in these cars has gotten rather out of hand. Let's get back on topic. If you guys would like to debate the issue, start a new thread.

[FatSebastian]

If you guys would like to debate the issue, start a new thread.

Done. Sorry Randy and my apologies to Rukkian.

[Rukkian]

No worries, it was an interesting topic. As far as offering free weights to everybody, maybe offering a cheaper weight would be fine, but the bar weights can get pricey, especially for a pack with limited funds (we serve a fairly low-income area). What is the cheapest way to offer weight - Pennies, washers? Are there other weights readily available?

[FatSebastian]

No worries, it was an interesting topic. As far as offering free weights to everybody, maybe offering a cheaper weight would be fine, but the bar weights can get pricey, especially for a pack with limited funds (we serve a fairly low-income area). What is the cheapest way to offer weight - Pennies, washers? Are there other weights readily available?

Steel is easy to find and it is relatively cheap. Brass is denser, but tends to be more expensive per ounce because it contains copper. U.S. dimes and quarters are about as dense as brass because they are mostly copper inside. To make, say, 3.5 ounces of brass ballast, you would need about the same amount of metal that is in eighteen (18) U.S. quarter dollars or forty-four (44) U.S. dimes. Now, pennies made since 1982 are actually 98% zinc. To reach 3.5 ounces, you would need about 32 copper pennies (made before 1982), or 39 zinc pennies (made after 1982).

IMO pennies may be the cheapest form of weight ounce per ounce, but if you collect 39 new pennies (or 44 dimes, or 18 quarters), then ask yourself how you might attach that much metal to an existing car design, you should discover that it may not be very practical to use zinc, steel, brass, or cupro-nickel as ballast on a finished, unweighted car because it can take up a lot of space.

This is why I suggested lead tackle - it takes up half the space of zinc. We are able to get lead fishing weights from the local Walmart. Also, as Darin noted, depending on where you live, scrap lead can usually be found around tire service centers (ugly but free). (Lead tape is also available from golf pro shops, and lead is sometimes sold at hobby stores for ballast in radio-controlled model airplanes and cars, but I agree that this is one of the most expensive ways to obtain lead.)

Material v. Density (oz/in3) (approximate)
Pine Wood ~0.3
Craft Plywood (Baltic Birch) 0.38
Water 0.58
Hot Glue ~0.44
Zinc (Cast) 3.8
Tungsten Putty 4.0-4.6
Steel 4.5
Brass 5.0
Cupro-Nickel Alloy (U.S. Nickels) 5.0
Cupro-Nickel Alloy (U.S. Dimes & Quarters) 5.1
Copper 5.2
Lead 6.6
PWDRacing TundraTM Composite 7.1?
Tungsten 11.2

No worries, it was an interesting topic. ... (we serve a fairly low-income area).

Thanks for your understanding. Low-income situations is exactly why I questioned whether councils should be in the business of regulating ballast materials without adequate justification; a competitive builder usually must spend ~$20+ per car on tungsten or tungsten-based lead substitute.

[Stan Pope]

What is the cheapest way to offer weight - Pennies, washers? Are there other weights readily available?

Great question!

Here is a short review.

"Density" is a major factor, since it affects the minimum volume needed, and volume affects car design choices and their aerodynamics.

"Effective density" is a factor in choice. Effective density is the density of the convex volume occupied by several samples of the item when "packed." Effective density for a given base material depends on the shape of each sample and on the manner in which the samples are packed. Pennies, for example have an effective density nearly equal to the individual sample density when they are "stacked", because there is little air space between stacked pennies. A roll of pennies is almost "all penny"! On the other hand, if pennies are packed edge to edge, the effective density goes down because of the air space between them.

Packing is stongly affected by the volume that is to be filled. A low, flat volume rewards packing of rectanguloids where as a longer cylindrical volume rewards stacked cylinders!

Washers have large hole inside which may be difficult to fill with material of equal (or greater) density, depending on the packing need of the volume to be filled. Edge to edge packing would not be efficient, for example, but face to face packing, combined with a length of mating bolt would be much more efficient.

Cost is a factor ... pennies cost about $1.60 per pound which is just a bit less (if memory serves) that typical steel washers purchased in bulk. And, when packing options are included, may be more dense.

Not too many "bulk" materials are available in small, handy rectanguloid shapes. But some, such as used tungsten carbide inserts have shapes that pack efficientlly. A list of such products would be useful. (Well, I see that FatSabastian has started just such a list ... if readily available shapes were included!)

[FatSebastian]

But some, such as used tungsten carbide inserts have shapes that pack efficientlly.

My understanding was that carbide inserts usually have a big hole in the middle of them, which reduces their effective density. (When we use fishing line weights as ballast, we usually fill the hole with a steel nail or copper wire of proper gauge.)

"Density" is a major factor, since it affects the minimum volume needed, and volume affects car design choices and their aerodynamics.

The points Stan raises about effective density are right on.

I might guess that the folks showing up to a derby with an unweighted car aren't going to be very particular about the efficiency of the weight available (or the appearance, for that matter). But as far as performance weighting is concerned, it may not be enough to simply drive up the total weight, but to drive up the ratio of weight with respect to cross-sectional area. One can add lower density ballast (say, gobs of hot glue) to the outside of a car to get it exactly 5.0 ounces, but the car will almost certainly be slower to accelerate due to an increase in aerodynamic drag. Likewise, gluing a couple of coins to the outside of a car to bring it close to 5.0 ounces generally won't provide any significant speed advantage for the same reason.

Solid lead (Pb) is the only cheap material that is almost guaranteed to increase the total mass car faster than the cross-sectional area being added. IMO the goal in the pit environment should be to to push up the weight as fast as possible - which implies attaching dense weight to the top of the car using as few pieces as possible.

[Stan Pope]

Thanks, FS! Good points.

I stand corrected on cost of pennies per pound ... my memory was playing tricks on me again ... more like $1.30.

Perhaps as organizers we are approaching the problem incorrectly ... perhaps the specifications (rules) should be altered to 2 ounce weight limit. (This is NOT a serious suggestion ... I know that this would, in fact, increase the total cost because even more builders would be moving to tungsten and offsetting the reduction in purchase volume of the present users.)

[Darin McGrew]

On another forum, another CSB leader suggested buying lead-free shot in bulk from a gun shop. Apparently, it's available in 25# bags for less than $1/pound. I haven't checked any of the local gun shops to confirm availability though.

[FatSebastian]

On another forum, another CSB leader suggested buying lead-free shot in bulk from a gun shop.

Shot, and many other spherical ballast materials, can have a fairly low effective density.

Here's an experiment. Fill a container (e.g., drinking glass) with spherical objects (shot, bb's, marbles, etc.). Add water until the top of the ballast material is just covered. Now pour out the water into another glass - that's how much unused volume was taken up by the spherical ballast.

[Darin McGrew]

On another forum, another CSB leader suggested buying lead-free shot in bulk from a gun shop.

Shot, and many other spherical ballast materials, can have a fairly low effective density.

Actually, the suggestion was to melt the lead-free shot, not to use it "as is". Basically, it's a cheap source of lead-free metal with a low melting point. (Assuming you don't buy steel shot, of course...)

[FatSebastian]

Actually, the suggestion was to melt the lead-free shot, not to use it "as is". Basically, it's a cheap source of lead-free metal with a low melting point.

If you find out more information, let us know. I would be especially curious as to its density and whether its melting point is at or below that of lead.

[Kenny]

We moved it to Saturday, and provided lunch after checkin so we could get the schedules ready to go. Overall everything went fine, except for one thing - We had 3 scouts (2 from the same family) that came in with absolutely no weight on their cars. One was a tiger and it is understood, but the others were Bears that were in their 3rd races. We had brought some weights to help out if somebody came in a little light, so we could help tweak, but these scouts basically wiped us out, so we had to use other weights to help the scouts that simply needed minor tweaking.

I would like to know how others handle this type of thing, we like to be able to help scouts out as much as possible to get better competition, but do you draw a line (IE: only give out up to .5 oz). Also, what do you think of the way I put the dens together, is this fair to them?

Again thanks to all for the help.

Our Pack is quite a bit larger, and with open races, several hundred cars run requiring most of Sat starting at 8 am.
We separate ranks and the pack generally provides tables with Dremel, Glasses, assorted weights (much of it donated by folks scavenging for it), graphite, and some hot glue guns. We expressly forbid any other glues. It always surprises me how many take advantage of this "pit" area. We always have kids with too little weight and usually someone is there to help them. But we're talking a half dozen so no big deal.

We have lots of WEBELOS and many Boy Scouts (whose troop is selling breakfast and lunch items for fund raising) to assist in addition to informed parents and leaders. Track is setup and everything is laid out on Friday night, Races all day Sat, then tear down and into storage by late afternoon. We use a School cafeteria/Assy room for our event.

There is a Pack level workshop which is well attended. We provide templates, and lots of assistance. Dads bring their band saws, sanders, etc. Not very many people are far enough along by this night to weigh their cars but there are a few. The highly skilled, or very competitive just show up to help others. In our Pack speed is a big deal, but so is design. We have about half and half and it's fairly competitive. I would say the design side of the competition has been the fastest growing and most competitive however. Winning 1st place design is every bit as coveted as 1st place speed, if not more so, over the past few years.

SIDEBAR:
This year we had a Bear Scout turn down a race trophy to remain eligible for design (cannot win both in our Pack) - He won 1st Place Design by a landslide Scouts pick the design champions in our Pack.

Anyway, it sounds like you're doing great with what you have. The computer timing and race management software is huge for us. We require advance registration so that we don't have to futz with entering people into the computer on race day. We just weigh, inspect, and impound. 45 mins later we race em 6 heats each. top 2 speed are held for pack championship but all trophies are given as soon as the boys vote. Ribbons and certs to all participants. We also have a turtle award that has become quite popular too (lowest avg time for 6 completed heats). Many people actually build to win the turtle now! Apparently there's an art form to going slow on a 40 foot tract

Hope this helps you a little. If there's anything else let me know and I'll share what works and what doesn't for us.

Bottom-line communicate well, spread the load and enjoy it as it goes by so quickly...

[Darin McGrew]

We separate ranks and the pack generally provides tables with Dremel, Glasses, assorted weights (much of it donated by folks scavenging for it), graphite, and some hot glue guns. We expressly forbid any other glues.

Just out of curiosity, why would you forbid other glues? Hot glue isn't a very good glue for many of the materials used to build derby cars.

[FatSebastian]

Hot glue isn't a very good glue for many of the materials used to build derby cars.

And burns when you drip it on your skin.