Thread: lead for ballast

I didn't catch the episode, but I doubt it was 900 deg C.

The show is produced in America. "Normal" reporting of temperature here is in Fahrenheit degrees. 900 deg F makes more sense - 621 for pure lead, plus a few more for alloys and casting flow.

Still hot enough to strip to bones.

And FWIW, high-temperature silicone caulking (for sealing stove pipes) can be used for flexible molds for lead casting. Expensive, though.

Cheers,
Joe

Correct, it was actually 850degF which is only about 450 degC

Here is a cut version of the episode.

[ame=http://www.youtube.com/watch?v=UZio0f7fP04]YouTube - Myth Busters (Molten Lead)[/ame]

Car batteries aren't a good source for lead. Separating the plastic from the lead is very problematic.

Lead pours in small quantities are fairly easy. Once you get over say 300 kilo, you'll want to have some experience with it.

Yes, the lead has to be poured all at once. Yes, a wooden form works great, though you do NOT want a softwood, but a fairly dense hardwood, like oak. A centerboard slot is easy to mold as the lead will shrink way from the mold as it cools, making withdrawing the casting fairly easy. Most old school designers will account for shrinkage of the ballast on the plans, but the latest generations of designers are more likely to have good computer skills, then actual experience pouring lead castings. If you post the dimensions of the casting, I can tell you how much shrinkage to expect.

Foundries charge a lot of money for casting ballast. You can save a good bit if you provide the mold or a male plug they can use in a sand cast.

You have to account for the weight of the lead, which is substantial. One of the easiest methods and one I use is to bury the mold in the ground and tamp down the soil good. I'll pour about 1,100 kilo in the near future and have starting giving the mold some thought. It'll have a 50 mm thick base plate of hardwood, with a 57 mm stack of oak up the centerline, to form the centerboard slot. The sides will be plywood, with 50 x 90 supports every 300 mm or so down the side, on the outside to hold the casting in shape as the weight increases. The ends of the female mold will be more thick oak and the pivot pin and lanyard holes will be accommodated by oak dowels, screwed in place, inside the mold. It'll be cast upside down, because the bottom edge is flat and I can pour to "level" inside the mold.

The hard part of this type of work isn't the dangers, as you can prepare for them, it's the weight. Hoisting a ton of hot lead around isn't for the squeamish. It takes a surprisingly long time for lead to cool and it'll likely remain in the ground for a week, before I try to hoist it free. My land is all sand (welcome to the tropics) and moving heavy items in sand, is like trying to push a big pile of marbles uphill. I'll probably use the engine hoist, which has a fairly long boom. I'll bolt the hoist in the back of the pickup and then use it's 4 wheel drive the move it over to the building cradle. I also have a gantry I can use, but it'll be tied up with the boat, as it'll have just been flipped.

In short, if you have buddy that's fooled around with this sort of thing, then go for it. On small castings, it's not a big deal, but when things get heavy enough that you need serious equipment just to drag it around the yard, then maybe getting beat up by a foundry isn't bad a thing.

Thanks for the info PAR. I'm setting myself up to start making lead muffins ( on YouTube ) as a practice to get the hang of what lead does etc? I 'm actually looking forward to casting the keel myself as I enjoy a challenge. BTW if you can would you be able to video your job? It would be great to see. My casting only has a centreboard slot but no pivot etc ( they are up inside the boat I think). It looks like afterwards I will have to drill keel bolt holes but I dont think that should be too hard. Mine is flat on top with a couple of steps at the ends ( for why i'm not sure ) and a slight curve on the bottom to suit the rocker of the keel line. I have only a small diagram that was printed in Woodenboat, but when I get the plans I'll take you up on the offfer of advice on mould sizes etc taking into account shrinkage.

A further response to Boatmik and Joe Greiner.
I hear what you are both are saying but I reckon a foundry would see me coming and charge accordingly ( still cant hurt to ask I spose so i can see how much I MAY be saving) . The dimensions of the casting are approximately 9 ft long, about 5 inches wide and varies from a max of 7&1/2 inches depth for most of its length to about 2 or 3 inches at the ends where it steps down in height. The centreboard slot is 1 inch wide and about 5 feet long roughly in the middle length-wise. As for weight - 1150 lb which equals 522 kilo's.
I have a trolley jack and vaious other weight shifting tools.
I also drive quite a lot for work so dropping in to tyre places is no hassle.
There have been other buiders of this boat ( Iain Oughtred -Grey Seal ) who've done it, so here I am learning as much as I can.
Somebody mentioned clay to line the mould. this sounds like a lot of work to me, getting it smooth as well getting it dry after. Spose the hot lead would dry it pretty quick !!!

No offence is intended by the above.

Andrew

Well, oak is softer than lead. I was concerned with drilling it out vs. drilling the lead.

I don't quite understand the lead shrinking away from the centerboard form. Shrinkage usually is overall, including the hole, and would (I think) tend to pinch the insert.

The old-school way of accommodating shrinkage is simply to use distorted measuring instruments for construction of the formwork, or of the pattern for conventional founding. Different distortions for different metals. Distortion is on the order of about 2%, but it can vary with the shape of the casting and rigidity of the formwork/mold, as well as differential cooling.

From the dimensions you give, it appears the middle portion will be 2 slabs of lead about 2" thick bounding the 1" slot. You might incorporate draft in the slot form by using two boards milled with a lengthwise taper, say 1/4" at one edge and 3/4" at the other, assembled anti-symmetric to create a constant 1" thickness. Slope the ends of each board corresponding to its own taper, so that one can be pulled from above and the other from below, using screw eyes into the wood's thick edge after casting, and/or by driving from its thin edge. The ends of the slot will be irregular, but I don't think that would affect its function.

Please don't rely on molten lead for drying, unless you crave excitement.

Cheers,
Joe

Howdy Andrew,

No problem with any of that. But most foundries I know of are pretty competitive. Just send them the info and see what they say. These days most people are hungry for work and don't charge too much if it fits within their work schedule OK.

After all you have a back up plan.

But like I said, there's nothing wrong with self improvement!!!

Best wishes
Michael Storer

Please don't rely on molten lead for drying, unless you crave excitement.

Ah yes, the excitement of splattering the roof of your house, your neighbours' houses and some of the cars out in the street with molten lead. I remember it well.

Had a go at making lead muffins the other day. Not too hard, but with a camping stove and small saucepan its real slow work. Guess its a visit to get a serious burner and bigger pot. Weights melt ok but at first I couldnt figure out why some didnt melt until I looked and noticed Zn stamped on them.
Spose I could take em back and ask for my money back
Apart from that went ok, except for what looked like air pockets on bottom and sides of finished muffins. May try pouring lead slower into muffin pan and see what happens, but its a toss up between lead solidifying and pourability.
My aim is about 500 (so far got 4 !!! ) muffins to get clean lead ingots for the big melt, otherwise I'll have too big a guess at weight if leave them dirty as wheel weights.
Fumes are the other problem, fan nearby blows the heat away as well so gas fume filters on a mask are definately the go. Makes the shed stink too.
Fun times ahead, what with lead, epoxy and wood dust this boat building is a toxic business. No wonder blokes dont live as long as women. Better than watching Master Chef Kids though

Hi Andrew
you might want to think about your neighbours as you do this.
If one of them has young kids arround or is female and pregnant, she'll be real impressed (not) that you're playing with large quanties of molten lead and blowing the fumes around.

If you're finding the casting is a toss-up between pourability and solidifying, you don't have the melt hot enough

oh, and don't forget to make sure you're really clean before you eat -- from memory diaorea is one of the early signs of lead poisioning

The best thing for avoiding the fumes is to have a box fan and stand up wind of the suction side. This way the fan isn't trying to blow down your fire and clean, fresh air is coming to you from behind, which is good for you and the fire.

Heat is the key and if doing large amounts of lead you'll need a camp fire type of burner, the ones designed to boil a 5 gallon bucket of water. These are gas operated and make big heat. Also vibration will help tremendously in removing the air pockets in the mold. As you pour, have a jitter bug or other tool, like a reciprocating saw, banging away on the sides of the mold. This will help the molten lead settle and fill the nooks and crannies.

If casting "muffins" then think about a long tray the height and width of the muffin, but several feet long. You can cut them to length after you pop it out of the mold. I cast bricks this way. I cast a trapezoidal shape so they stack and interlock neatly in the bilge. 10 to 15 pound bricks are ideal, but if you have to place a ton of these, then 5 pounders would be the better way, as lifting 10 to 15 pounders into the (or out of) the boat can wear you down pretty fast. I have a 40' powerboat that has 2,200 pounds of lead bricks, each 5 pounds. Yes, that's 440 bricks and it takes about an hour for me to drag them out of the bilge and load them into a few carts or on the dock as I clean the bilge. If they were 15 pounders, then I'd only need 147 of them, but I wouldn't have the strength to put them back, let alone clean the bilge after moving them. Now, you're thinking, "I'll never have to take them out again", but you'd be wrong, as they are the greatest dirt and crap catchers a bilge has ever known. They get clogged up with all sorts of crap and the bilge starts to smell like my ex-wife's undies, so they have to come out. I usually just hit them with a pressure washer (wish I could have done this to the ex-wife). While there out I clean the bilge too, usually stumbling on that damn adjustable wrench, I haven't been able to find for the last few years. A clean bilge is a happy bilge and you also get up close and personal with the planking and other elements of the boat that you probably haven't seen since the last time you cleaned the bilge.

Best thing for avoiding the fumes is not to heat lead more than 500°c and depending on what elements are in the mix.

"Car batteries aren't a good source for lead. Separating the plastic from the lead is very problematic."

Going to a recycling place like ARA and asking for a car battery is like going to a car wrecking yard asking to buy a whole car... doesnt happen not in this country legally.


Is it possible to just pack an area with the lead(just like using your lead muffins!) using battery lead sheeting packed/hammered into a form/mould would work just as well as a casted lead ballast, then you would have no need to heat the lead.

In 16yrs of casting lead for a living I have never seen it casted without some sort of pitting in the lower half of the "pig", even using CMS die coat or preheating the mould it still pits, metallurgist reckons its to do with gases releasing.
I'll see if I can find the photo at work of the famous Lexan winged keel that we supplied(the lead not the casting of it) I think we recycled it too.

Interesting thread..... As an Engineering Pattermaker by trade (who learnt to mould & worked in foundries), and as someone who spent quite a few years building boats (and casting a couple of keels) I'll add my thoughts...

A foundry will usually prefer a pattern - they'll mould & cast it on the floor (not IN the floor anymore - none of them have dirt floors to dig in any more!). They'll pack sand - greensand or CO2 cured resin sand - around it & pour away. Any non-ferrous foundry will do it & it will be much cheaper of you source cheap scrap lead - if the foundry gets it, they'll simply order it at a commercial price. Most non-ferrous foundries will have to clean out their furnace before & after & their cost may well reflect this - mostly they will be used to melting aluminium & zinc alloys, rather than lead. If you need a core - think centerboard slot - you will need to either make a corebox (a mould that can be used to make a sand core in the reverse of your slot), or a hardwood plug - either method will need a way of accurately locating it within the finnished mould.

The couple I have done (neither huge - maybe ~700kg from memory?) have been done in the following manner, set up on a dirt floor under an open carport roof:

A mould made from 3/4" plywood, 2" thick bottom, extra hardwood batten around the upper edge, with plywood core for the centreboard slot, and some hardwood dowels (turned with 1deg taper) set vertically in place for through-bolting. Plain roofing silicone will seal the joins & withstand the heat long enough for a one-off. Whole lot painted in refractory paint (from a foundry suppliers, normally used to coat sand moulds), reduces scorching of the mould.

Mould buried in ground, with a few bricks or concrete pavers pushed up against the top edge, to prevent movement - tamp the ground down well.

Get an old steel / iron bath - hard rubbish special - and set it up inline with the mould - set it up on a STRONG & WELDED steel frame, off the ground by maybe 500-600mm - enough to get your gas rings underneath. Place the legs of your frame on concrete pavers so they don't sink into the ground. The frame needs to be strong enough to support the lead - it seems obvious, but people forget how much it weighs.....

The plug hole in the bath should be over the mould, but not right at one end - maybe 1/4 of the way along if possible. Screw in some galvanised steel water pipe to the thread in the bath & terminate it 30-50mm above the finnished height of the casting. have a tapered steel plug made up to suit the hole in the bath, with a long rod / handle wended on.

Set up 2-4 gas rings - the big cast iron ones you buy at disposals stores on bricks, etc, under your bath. HAVE PLENTY OF GAS BOTTLES ON HAND - if you run out, you don't want it cooling down, so as they run out, simply screw another on & keep heating.

If possible, build an insulating lid for the bath out of a light steel frame & some foil-backed glass blanket - wrap the bath in some too, if you can - this will reduce heating time & gas useage, and can mean the difference between achieving pouring tempreture or not.

The rest is fairly obvious..... start heating nice & early, as it will take some time. When she's ready to pour, get somone to start heating the pouring shute (galp pipe) with an oxy set or propane torch, then gently & slowly lever your plug out - don't open it up in one go or you may get splashing - try to control the flow. Needless to say, long trousers & leather gaiters area good idea.

Last but not least - leave the beer until the mould is full. To many accidents are caused by too much social cheer on the big day....

As PAR has mentioned - the biggest problem is moving the completed item...... For those people who will find it too hard to move a keel, consider casting lead shot mixed with epoxy into the bilge / keel of a boat - works just as well for very little extra bulk......

Have fun!

Thanks for that reply Wombat200. Just a couple of questions.
Why is it necessary to have a two inch thick bottom on the mould if its in the ground, my keel is only about 7 inches deep and bolted to the bottom of the deadwood.
Will one of those old thin metal/enamel baths do, I'm a bit worried about the enamel coming off in the heat?
Do you allow for shrinkage?

Hey PAR enough about the ex, I'm going to have bad dreams now and you've just ruined my -site viewing