Melting Lead

[ohiofitter]

In the past I've always use the stick tape lead weights. But this car I would like to melt in the lead. I'm a pipe fitter by trade. So I have heard older fitters talk about leading pipe joints. Went down to the local tire place and got a handful of 2 oz. used weights. But once I have the melted how big of an area should 1 of the weights take up. And is there any thing special I need to do with the wood..Like put a flux on or not...I've seen guys use solder as ballast But they ended up with a pretty big clump of solder. I was think if I had a form lets say 1/2 tubing by lets say 4 inches long would all 2 ozs. fit

[Pinewood Daddy]

Lead is .41 lbs/cu in.

[knavekid]

Once you know how much weight you need to add, you can take the density of the lead and subtract the density of the wood to get an approximation of how much weight will be added by replacing wood with lead.

Start by determining the density of your wood. It is best to weigh the block before you start to get a good number. Taking the basic block dimensions of 7" x 1.25" x 1.75", you get a volume of 15.3125 cu. in. The standard blocks should weigh between 2.5 oz and 4.5 oz. Calculate the wood density by dividing the weight by the volume. For a 3.5 oz block, the density is:

3.5 / 15.3125 = 0.2286 oz / cubic inch

The density of lead is 11.34 grams / cubic centimeter or 6.555 oz / cu in.

For the 3.5 oz block example, replacing the wood with lead will add:

(6.555 - 0.2286) oz / cu in = 6.3264 oz / cu in

For this example, if you need to add 1.5 oz to your car, you must replace (1.5 / 6.3264) cu in = 0.2371 cu in of wood with lead.

Once you know the volume of wood that must be replaced by lead, you can calculate the hole size you need. For a needed volume (V) and a drill diameter (d), you can calculate the depth (h) as follows:

h = (V x 4) / (pi x d x d)

For the example above and a 1/2" drill, you would calculate a hole depth of (0.2371 x 4)/(pi x 0.5 x 0.5) = 1.21".

Drill the hole and then pour in the molten lead. This will get you very close to your desired weight. If you are slightly heavy, you can drill out some of the lead.

[Stan Pope]

There is a handy "calculator" on my web page at http://members.aol.com/standcmr/cmcomput.htm to help with CM and ballast planning. It does things like compute sizes and locations.

Generally, it supplies the missing data because almost all of the fields can be used for either input or output!

I don't personally like pouring hot lead into a wood car body. Part of the reason is that I don't like the smell of burning pine wood. The other is that the owner/driver doesn't get to do it. But, I have done it in the past and the lead does end up fitting the hole pretty well! On the other hand, I like the idea of being able to put the car sans ballast on a pair of scales and move the weight around to see where it fits well and provides the weight distribution that I want to end up with.

[Dad of 3]

Pouring hot lead into your car can burn the wood, you also only get 1 shot at it. In some cases you have no choice. If you can simulate the hole in a 2x4 or 4x4 and pour the lead there you won't destroy your car if you make a mistake.

[Teeeman]

We found drilling some holes in a 2X4 works… it makes rough slugs of lead… we had to bandsaw out our lead (they don’t necessarily just “fall out of the wood”).

We have even found it necessary for longer, thin drilled holes (in attempt to make long thin round rod for last minute weight tuning)… to get the lead to fill the holes, we had to cross drill a bleeder hole… as you pour the lead in, you’ll lose some out the hole usually… just keep pouring ‘til the lower lead cools and the mold is full… if the vent hole is too short and the molten lead can’t freeze in it… it may not work quite as planned.

We found it kinda fun to work with molten lead but it is very, very dangerous (mostly for sake of burns)… but you really don’t want to breathe the lead…

and we always found touch up work necessary on the lead parts… bandsawing or sanding lead produces a lot of fine lead dust… again, DO NOT BREATHE this stuff…

it is not a kid friendly thing you are undertaking.

BTW… the rough finish on the lead slugs allows them to press fit nicely into drilled holes in the car so you don’t have to worry about burning the car’s body.

And if a lead slug is slightly too small for a hole … squeeze it with pliars and create an out of round spot… this will anchor it nicely as a press fit.

I wish lead weren’t toxic… it was fun to play with but we gave it up… now, if I could give up the rest of my bad habits…

-Terry

(p.s. our smelter was a Chunky soup can with wire and a piece of threaded rod to serve as a handle… the pour spout was made by using pliars… we sat the can right in the fire in the hot rocks of our gas grill and it would melt up nicely… just had to be very, very careful not to spill any!... and WEAR HEAVY LEATHER GLOVES (or welders’ gloves))

[nodakindy]

Personally I don't use lead, mostly because I am not comfortable with my
grandkids who I help, handling it. This means I have to do more for them and I just feel like there are other good options.

However, If I were to use it and wanted to custom fit it to a car I would use a lost wax method much as you do with making jewelry.

For this I would line area in wood that I wanted to fill with cling like food
wrap. This would protect wood from excess wax or residue. Cover the whole car and the kids can do this part if you like. Then melt wax and and
pour into cavity and let cool.

Once it is cool you would remove using plastic food wrap to pull
it out. Then you have wax block which represents what you want in lead.

The next step would be to set wax block into receptacle of some kind, preferably something that is easy to tear apart that is not water soluble. A dixie cup or small box lined with plastic, paper milk carton, etc.

Fill container with plaster. Dry wall mud, plaster of paris, anything like that will work for this. It might be a good idea to use a couple of tooth picks, straws or whatever to attach to top of wax block to keep it from sinking into plaster.

Once plaster was set and hardened, perhaps allowing an hour, you can remove wax by softening with a little hot water and removing with knife. You can even use boiling water poured over it to flush out. You could use torch as well, but do so carefully as plaster will crack with to much sudden heat.
It might even be a good idea to dry your mold in the oven for a bit, to eliminate moisture which could cause it to crack. This is easily done by putting in cold kitchen oven and running it up to a temp below 200 for about a half an hour then move it up to 250 for another half of an hour.
Once your mold is set your ready to pour your lead.

Once lead is set and cool, just tap mold with hammer to break it out. Clean off excess plaster with water and tooth brush.

Lead should fit well now into cavity without any worry of burning wood.

A couple of suggestions regarding the wax going into your car.
If there are undercuts into wood from gouging out unevenly or whatever you may want to line sides with relief prior to putting layer of plastic wrap. Paper, tape or anything will work and keep wax block from getting stuck. This also would allow relief for epoxy or whatever adhesive you might want to use.

You could also pick up hardware, nuts, bolts, pins, whatever in the wax block, just as long as they protrude so that plaster holds them in place between wax elimination and pouring lead.

Regards,
Nodakindy

[Stan Pope]

Some great ideas, Nodakindy!

Question when casting lead into plaster of paris, etc. I've heard that moisture in a mold is extremely dangerous. The cause is that the moisture almost explosively vaporizes and blows molten lead out of the mold. How much drying do you have to do to avoid this problem?

When I have cast lead, it has been into dry steel 2-part molds and no problems with moisture there. But with more porous plasters???

[nodakindy]

The problem is steam, so get it dry. The plaster will dry somewhat from exothermic reaction while bench setting but still will have a considerable amount of moisture. the two step process I detailed earlier should work ok, but you will be able to tell if mold isn't dry. Leaving in oven at higher temp in second stage won't hurt anything either.

Unless mold is very large an hour of drying in oven should be sufficient. However is mold is 200 grams or more you may want to allow additional oven time. The mold only need to be big enough for what your casting with no more then a half of an inch larger area or thickness then your piece for strength. Less is more as it takes longer to dry. If going very large you might want to consider getting high heat investment from a jewelers supply.

Regards,
Nodakindy

[psycaz]

Would putting that same wax block into something like sand then pouring the lead into the sand work.

I have a friend who used lead into sand a couple years ago, said it worked fine. But He wasn't going for an exact size. He wanted a rounded shape, used a light bulb, and placed weight on the top portion of the car.

[nodakindy]

You could use sand, but not sure why you would. Sand will leave a lot of texture and may be rough, and need adjusting, unless you want that texture for some reason. Wax will leave a very smooth impression in plaster mold, hence needing less adjustment or smoothing.

Another nice thing about using the wax method is being able to calculate the weight of the lead going into a given space by weighing the wax. Much easier to shape and trim down wax you want to duplicate than lead.

Regards,
Nodakindy

[Darin McGrew]

At our workshops, we use a crucible with a spigot like this one. We heat the lead (actually, recycled tire weights, so who knows what alloy we end up with) just until it melts and pours, and we haven't had problems with burning the wood. It does darken a little in places, but not enough to be a problem. The main problem is with thin cars that have already been painted: the paint blisters.

[derbster]

After the car was shaped, we determined where the weight was to be postioned and took the measurements (ie 1.25in x 0.875in x 0.625"). Then we simply made a form out of 5 small wood blocks (bottom and 4 sides) cut to size and held together w/ drywall screws. Poured the lead in, scraped the top off flat and let cool. If the blocks are cut square then the form comes out relatively square too!! And, given it was held together w/ screws, it was resuable.

[emptyd]

Pouring hot lead into your car can burn the wood, you also only get 1 shot at it. In some cases you have no choice. If you can simulate the hole in a 2x4 or 4x4 and pour the lead there you won't destroy your car if you make a mistake.

Not true for us. We pour into the cars all the time. In the simpler designs (like wedge) we over weight by pouring in a bit too much, then use a drill to remove the excess.

In more advanced designs, we pour into an open cavity and as the lead cools, it shrinks - so it pops right out if you need to try again with more or less lead. Once you like the pour, us a bit of glue to hold it in.

The wood does scorch a bit, but we've never had any "damage" from it. If you have to pour it too many times I'm sure their might be a problem - but that hasn't happened to us.

[scoutfrog]

above are 2 pictures of before and after a lead pour of my 1.7pound outlaw car from 2007 [/img]