type of weight options

[plhiatt]

Am I missing something or is using tungsten really not necessary unless you get thinner than 5/8 or so?
I started working on new "thinner for me" pinewood derby prototype car for our 2nd season in the scouts. I have set of scales etc...using cut lead (45/70 gov. bullets) into cylinders.
Just using this as weight I can get a COG in front of the rear wheels at 1/2" with a less than 5/8 thick car. I am still cutting it close to a "car style" and not a true plank of wedge style yet.
I guess once you start getting under 1/2" it makes using tungsten necessary, but with around -5/8 or a little less I actually have to move some weight a bit forward to get around 3/4" COG.

 

[TedBull]

Tungsten is the only way to go regardless of body type or thickness. 1/4 tungsten cubes to be exact. It's all about getting the most weight packed around that rear axle. I stick with right around a 1" com or slightly less.

 

[Crash Enburn]

Basically, you want your weight to be as densely located as possible. Tungsten is 80% denser than lead, so you can put the same amount of weight into an area that is 55% as large as with lead.

But, it is definitely much more expensive. I got ~5lbs of used tire weights from my tire guy for free.

That is a great price.

That being said, my cars (scout races and AGP -- I have not entered a race here yet) are typically 1/4" - 3/8" thick and filled with molten lead. With the rear wheels all they way back (drilled 5/8" from the end of the block), my COM measurements are usually 3/4 - 1". Good enough for scouts.

 

[Kinser Racing]

Tungsten will allow you to get the car thinner. 5/8" is really thick. My cars are about 5/16" or less with tungsten.

 

[IAE Racing]

It is possible to get a sub 1" COM with a 5/16 to 3/8 body thickness. If you make weight pockets as described in several different threads. If your drilling at 5/8 you would need to remove some between the axles as 5 kids described. If you have a lead pot make a form from a 2/4 roughly the same size or slightly bigger than your rear weight pocket. Make another form smaller for the front weight. Pour lead into form. EDIT Be careful if you pour hot lead into thin car. let cool. pop out. use hammer to finish shaping lead to fit. glue in. The lead is very maluable. if you need to trim some off, just use your knife and shave some off. Be sure to use safe lead handling techniques! Lead has been known to cause cancer if you live in California!

If you don't have lead pot. your slugs could still be easily shaped as needed. With your weight glued in to bottom, it's a lot easier to reduce the height of your car. If your doing a dozen cars a year for the kids tungsten = very expensive, knowing tire guy (that's where I get mine) = Free!

 

[plhiatt]

These are sort of shaped like cars-thin in front and thicker in back, but when I use the lead I can get at least a 1/2 COG in front of the rear wheels which is really a little unstable without a lot of steer.
But I have to use the standard wheel base.
So I guess my question is how would tungsten be better with a thick car like this?
I guess I am wondering because I really can not put any more weight behind the rear axle or the COG will be 1/2 or less?
Am I missing something?
For most of the kids cars that would get expensive.
I am planning to do a 1/4 plank style with the tungsten cubes as well.
Thanks

 

[IAE Racing]

Here's a pic of my form block. Notice the black. That's why you don't pour hot lead in a paper thin body. No actually never tried it

 

[Kinser Racing]

It is possible to get a sub 1" COM with a 5/16 to 3/8 body thickness. If you make weight pockets as described in several different threads. If your drilling at 5/8 you would need to remove some between the axles as 5 kids described. If you have a lead pot make a form from a 2/4 roughly the same size or slightly bigger than your rear weight pocket. Make another form smaller for the front weight. Pour lead into form. DONT POUR HOT LEAD INTO THIN CAR. let cool. pop out. use hammer to finish shaping lead to fit. glue in. The lead is very maluable. if you need to trim some off, just use your knife and shave some off. Be sure to use safe lead handling techniques! Lead has been known to cause cancer if you live in California!

If you don't have lead pot. your slugs could still be easily shaped as needed. With your weight glued in to bottom, it's a lot easier to reduce the height of your car. If your doing a dozen cars a year for the kids tungsten = very expensive, knowing tire guy (that's where I get mine) = Free!

I've poured hot lead into several cars with no problems. It will burn the wood a bit but that's all. That's how we used to do it before tungsten was readily available, I'm sure many builders here have. It's pretty easy too. I also never used a lead pot. A large stainless steel spoon and a blow torch will do the trick. /images/boards/smilies/smile.gif

 

[IAE Racing]

My rear weight pockets are open, so I have no form to hold it. Also, didn't want to advise someone to torch their car.

 

[down4derby]

Concentrated weight is usually faster. Also tungsten allows the weight to sit lower in the car for better stability.

 

[IAE Racing]

These are sort of shaped like cars-thin in front and thicker in back, but when I use the lead I can get at least a 1/2 COG in front of the rear wheels which is really a little unstable without a lot of steer.
But I have to use the standard wheel base.
So I guess my question is how would tungsten be better with a thick car like this?
I guess I am wondering because I really can not put any more weight behind the rear axle or the COG will be 1/2 or less?
Am I missing something?
For most of the kids cars that would get expensive.
I am planning to do a 1/4 plank style with the tungsten cubes as well.

My lead blocks for the rear are roughly 5/8 x1/4 x 1 1/2 and weight about two ozs. my front weights are smaller. If your looking for a longer COM, move the front weight forward in the front pocket.

 

[DerbyDad4Hire]

TO answer your question, if you are going to have cars that thick then there is no reason to use tungsten except for health concerns. You will be fine in the scout races with lead.

 

[txchemist]

edited

 

[Vitamin K]

super low cost for Cubs- weights in just the 6 or 7 back holes, other holes to drop weight of body. Easy to move CG with moving a nickle or two. No problem to get a 5/8 to 3/4" CG

How it is done- need a forstner bit for nickles. Drill for 3 nickles deep. Typical Cub car needs 18-22 nickles

(Sorry to be posting in an old thread like this)

Wish I'd seen this earlier. For my two year old's car, I decided to ballast it with pennies, because lead (my usual choice of weight) is not cool for something I'm going to let a two year old play with. The car's about done, and it has a CG of about 1".

I like the nickels idea, though. Looks like two nickels, side by side, pretty much exactly fit in the standard car width. Thus, it would seem they're slightly better at pennies for efficient use of space (they're about the same density.)

I may suggest parents bring nickels to our Pack workshop, if they don't want to use lead or spring for tungsten.