Author Topic: Aluminum vs Zinc for mortar balls (Read 939 times)

Double D · « **on:** April 11, 2005, 05:35:22 PM »

I have had my beer can mortar opened up to 6 PDR dimensions. 2.6 in to 3.67 inch. I can buy 6 PDR zinc balls for $10 plus shipping. First does anyone know where I can get them cheaper?

Second, I am considering have a mould made for aluminum 6 pdr. ball.

Does anyone have any experience with aluminum ball or can give me the pros and cons of aluminum versus zinc?

Evil Dog · « **Reply #1 on:** April 11, 2005, 05:56:00 PM »

The main thing that jumps into my mind is the higher temperature required to melt aluminum. Zinc can easily be done on a large propane burner.... well within the range of my home workshop. I'm still climbing the learning curve as far as casting with zinc but it is getting better.

Aluminum would be a lot easier to find locally though and would probably be a bit less expensive. Virgin 97% zinc alloy was $1.25 a pound and I had to drive about 50 miles each way to get it (still cheaper than paying for shipping though).

Then there are the fumes associated with melting zinc... not a good thing. Think ventilation, ventilation, ventilation.

Double D · « **Reply #2 on:** April 11, 2005, 06:49:03 PM »

Thanks Ed for the response.

Perhaps I should have been clearer in posting my question. Is there a difference between shooting zinc versus aluminum?

But you did spark a thought. Could a mould used to cast Aluminum later be used to cast zinc and vice vesa?

I know that zinc in a lead mould is a no no.

GGaskill · « **Reply #3 on:** April 11, 2005, 08:45:11 PM »

Since you should be casting zinc in a steel mould, aluminum would work fine in the same mould. The primary end user difference between aluminum shot and zinc shot would be ballistic coefficient. The zinc shot is maybe three times as dense as an aluminum one and you would get better trajectory from the zinc one at the expense of higher chamber pressure caused by the greater inertia.

Cat Whisperer · « **Reply #4 on:** April 12, 2005, 12:38:53 AM »

Quote from: GGaskill

Since you should be casting zinc in a steel mould, aluminum would work fine in the same mould. The primary end user difference between aluminum shot and zinc shot would be ballistic coefficient. The zinc shot is maybe three times as dense as an aluminum one and you would get better trajectory from the zinc one at the expense of higher chamber pressure caused by the greater inertia.

Since aluminum doesn't go as far (less dense, lower BC) why not go all the way and use a large whiffle ball for back yard mortar games at the bar-b-q ? You wouldn't have to use the neighbor's yards that way.

Double D · « **Reply #5 on:** April 12, 2005, 02:09:39 AM »

George, are you saying that from the point of theory or the point of experience.

I do know that the original mortars used hollow shells and not solid shot and would have had a different densisty also.

But from practical experience using solid zinc or aluminum which works better?

GGaskill · « **Reply #6 on:** April 12, 2005, 06:32:35 AM »

My comments are based on theory as I have only fired lead shot or cement filled beer cans from my pieces. But the theory has much experience so I would be highly surprised if those predictions would not pan out.

Cat Whisperer · « **Reply #7 on:** April 12, 2005, 06:56:43 AM »

In my 4.5" mortar, using 4 lb and 7.5 lb projos made from pvc pipe filled with concrete, the heavier ones go MUCH further. In the same respect, look at the tables of velocity of bullets - the heavier ones (way down range) will hold the velocity, where the lighter ones drop off fast.

Will Bison · « **Reply #8 on:** April 12, 2005, 08:00:50 AM »

Just a few thoughts here. Zinc has been one of the preferred metals used by cannon shooters for many years. Aluminium requires a higher temp to melt as George has indicated. That said, mortars most often fired hollow iron shot with a bursting charge. Aluminium would more closely approximate the weight of a hollow iron shot due to the lower specific density.

At ten bucks a round for zinc shot it would get expensive real quick unless you recover the rounds. Fired over soft ground most should be reusable. If you can recover/reuse them then the price is not out of line.

With either zinc or aluminium, a steel mould is a reqisite.

guardsgunner · « **Reply #9 on:** April 12, 2005, 08:20:05 AM »

DD,
How much do your 3.67 balls weigh for your 6pdr? Cast solid or hollow?

Daveinthebush · « **Reply #10 on:** April 12, 2005, 09:38:50 AM »

Does not inhaling zinc fumes cause brain damage?

GGaskill · « **Reply #11 on:** April 12, 2005, 09:46:17 AM »

Zinc fumes (evaporated zinc atoms) can't be much worse than evaporated lead (it would likely be less exposure due to the higher melting point of zinc.) In either case, you should be melting the metal in a fashion that allows the fumes to be removed from your presence; a fume hood if melting indoors.

The real risk with zinc is zinc oxide fumes from excessively heating the metal. Look at the other zinc subjects in the forum for the report on metal fume fever. Metal Fume Fever (about half way down).

Shells weigh about 3/4 of the corresponding solid shot (a 24 pounder shell weighs about 17 pounds, I think) so the density difference between zinc/cast iron and aluminum (about 3:1) is too great. I am not aware of any commonly available (and cheap) metal with a density that would fit that requirement.

Cat Whisperer · « **Reply #12 on:** April 12, 2005, 12:04:18 PM »

Quote from: Daveinthebush

Does not inhaling zinc fumes cause brain damage?

It doesn't take much zinc fumes to make one seriously ill within a few minutes or hours of inhaling. Lead, on the other hand accumulates over time. Neither is good. Casting lead bullets isn't as dangerous because the lead doesn't get hot enough to put the really nasty stuff in the air in the same way that zinc does - especially when someone gets around someone with a cutting tourch cutting up galvanized steel.

I think both of these would warrent accumulating a few references and posting a health-related resource at the top of our forum (and perhaps some of the other forums that deal with casting and swaging bullets).

Double D · « **Reply #13 on:** April 12, 2005, 12:36:46 PM »

I can guarnentee you aluminum or zinc, one the tools in my tool box will be a shovel.

My only concern about the difference between zinc and aluminum is the down range performance.

Since no one is forth coming about using aluminum, that must mean nobody is using them.

I will be retired in couple of year and sitting out on the Montana prairie, ventilation won't be an issue.

A couple of miles down the road is a custom aluminum foundry. I may take the mould over there and get some balls cast up. I can test them and see how they work.

In my research I did see a reference to aluminum balls in flat trajectory cannons and they were not desirable as they tended to bounce to much.

Cat Whisperer · « **Reply #14 on:** April 12, 2005, 12:41:16 PM »

I do recall one conversation (ok - this is identified as 2nd hand information) with a fellow who used both, the comment was that aluminum would break easier.

But then with aluminum you won't have to walk as far to go find them!

guardsgunner · « **Reply #15 on:** April 12, 2005, 03:20:39 PM »

DD,
If your going to play the closest to the pin type games, the zink will not bounce as much. The zink balls can be re-shot many times as long as you are not landing on anything hard. like another ball.
The balls for my 24pdr. were cast hollow so as to approximate the weight of the shell.
GGaskill touch on where I was going with the question about the weight of your pre-cast 6 pdr. balls.Original mortars shot shells which weighed about 2/3 of the pounder designation. An 8" (90lb.) shell weighs 54Lb.
24prd. 17lb. and the 12pdr, is near 8 lb.
As many of these mortars are somewhat patterned after the smaller mortars; with welded or bolt on trunnions, maybe it would be a good idea to use 2/3 of the pdr. (or there abouts) as a rule of thumb to figure out the proper weight of projectiles that we should be firing.
Just my thought's to help keep pressures down and give a guideline for those that are new to such things.
You can rough guess the pdr. rating by multiplying.....
dia.3 (cube)x .13268 X.66(2/3)= aprox. shell weight.

Double D · « **Reply #16 on:** April 13, 2005, 01:32:43 AM »

Well none of you gave me the answer thought I wanted to hear, instead you gave me the answers I needed to hear. Thanks gent , every one of you , I do appreciated it.

So here is going to be my course of action.

First, I am going to order the mould.

The I am going to send my wife yard saling to find a turkey roaster burner and pot.

When the mould gets here I am going to take it to the Aluminum foundry and get some aluminum balls.

When I get to Montana, then I am going to cast zinc balls as needed.

George, I am going to add the link to the Zinc supplier to the resource list

GGaskill · « **Reply #17 on:** April 13, 2005, 09:40:05 AM »

I think we should try to come up with sources scattered about the country because shipping the stuff any distance is not going to be cheap.

Semco Enterprises, 475 Wilson Way, City of Industry, CA 91744 (626) 333-2237

(I think this is the place; Evil Dog actually made the pickup.)

Evil Dog · « **Reply #18 on:** April 13, 2005, 02:24:42 PM »

Yes, that was the place.... right friendly folk over at SEMCO too. If you are within driving distance of LA and need more than just a few pounds it would be well worth the trip.

One thing to keep in mind though, if you have to pay for shipping also and the total comes to more than $1.84 a pound you might as well melt pennies... it would be cheaper. Just be sure to check the dates on them though.... copper ones don't melt worth a darn. Don't ask me how I know that.