Author Topic: Brass Mortar (Read 1772 times)

IvarForkbeard · « **on:** October 12, 2011, 01:29:00 PM »

So I ended up with a piece of brass wide enough for a can mortar, but not long enough, so I designated it as a tennis ball/short can mortar. I am able to get 8 oz cans of soda, they will be filled with concrete.

BoomLover · « **Reply #1 on:** October 12, 2011, 03:16:50 PM »

Looks pretty interesting to me... Like to see shots of it firing, and what your range is with those concrete filled 8 oz cans...BoomLover

IvarForkbeard · « **Reply #2 on:** October 12, 2011, 03:43:20 PM »

It has a smallish, by my standard, powder chamber. Only 3/4" X 1 1/4" so I imagine using FFFg probably about 100 yards, plus or minus....but tennis balls, another story ENTIRELY, will keep you posted.

Double D · « **Reply #3 on:** October 12, 2011, 04:47:44 PM »

The bore walls look on the thin side to me, even in a mortar

flagman1776 · « **Reply #4 on:** October 12, 2011, 04:58:23 PM »

IvarForkbeard · « **Reply #5 on:** October 12, 2011, 05:02:33 PM »

Walls are 7/16 thick, almost 2/3 the thickness of the DOT AA2400 cylinders for bowling ball mortars. I am pretty sure that the powder chamber, being 1" from the bottom, 3/4 inches X 1 1/4 inches in a 3.5 inch piece will tolerate the pressures it will generate.

Double D · « **Reply #6 on:** October 12, 2011, 05:30:04 PM »

DOT cylinders are steel, this is brass. Powder chamber looks just fine. I am concerned about the pressure as the gases expand behind the can in front off the chamber. Take some diameter measurements on the out side of the barrel directly in front the chamber. Shoot a few shot and remeasure.

You can do a a couple proof shoots and see what happens. A proof load is one that generates 125% of average mean pressure...

IvarForkbeard · « **Reply #7 on:** October 12, 2011, 05:37:11 PM »

Some are not unschooled in the art of safety, having 13 years in the ordnance field, I DO understand what safety is. I regularly proof to 200% of AMP.

Double D · « **Reply #8 on:** October 13, 2011, 06:34:28 AM »

200% goes into destructive test. Industry standard for proof is 125%. Also might be pretty hard to get a 125%, let alone a 200% load in blackpowder in the small a chamber.

dominick · « **Reply #9 on:** October 13, 2011, 07:40:36 AM »

I don't know a lot about brass but if I'm correct, brass has a very low yield and will show a bulge if it's at it's limit. Measuring the OD after a proof is a good idea.

"Or" you can make one out of cardboard.

Personally, I don't advocate the construction of cardboard cannons, but it surprised me to see how well it has held up. Don't try this at home.

elad5173 · « **Reply #10 on:** October 13, 2011, 08:41:12 AM »

Sure surprised me that it did'nt come apart!!

RocklockI · « **Reply #11 on:** October 13, 2011, 11:21:00 AM »

Well many cardboard tubes are used in fireworks displays but I think they are a one time deal .

Hold that brass mortar hold by one trunion and tap the tube with a hard object . I bet it will sing Bingnnnnnnnneeee...

Gary

IvarForkbeard · « **Reply #12 on:** October 13, 2011, 12:27:50 PM »

Quote from: RocklockI on October 13, 2011, 11:21:00 AM

Well many cardboard tubes are used in fireworks displays but I think they are a one time deal .

Hold that brass mortar hold by one trunion and tap the tube with a hard object . I bet it will sing Bingnnnnnnnneeee...

Gary

Like a bell

GGaskill · « **Reply #13 on:** October 13, 2011, 05:48:41 PM »

Well, tennis balls really don't weigh very much so I wouldn't think it has to resist much pressure but almost anything will hang together for one or two shots. I have some cardboard cores from rolled copier paper that I (275 lbs) can stand on sideways and not crush so I would think they could work for a while as a mortar tube. Although I am in no rush to see how long one would last.

IvarForkbeard · « **Reply #14 on:** October 16, 2011, 04:22:47 PM »

OK maybe you convinced me, Ammo change may be in order.

What do you think of cutting a 1/2" hole into the tennis balls and filling them with expanding foam?

Double D · « **Reply #15 on:** October 16, 2011, 04:32:42 PM »

Why note shoot a couple of pop can filled with cement and take measurements...I mean what can happen, blow up, nothing, you get a bulge

IvarForkbeard · « **Reply #16 on:** October 16, 2011, 04:55:56 PM »

Quote from: Double D on October 16, 2011, 04:32:42 PM

Why note shoot a couple of pop can filled with cement and take measurements...I mean what can happen, blow up, nothing, you get a bulge

Have you priced brass lately? A bit expensive for an unemployed blacksmith. And at max powder charge of 100 grains, tennis balls will go a lot further.

Victor3 · « **Reply #17 on:** October 19, 2011, 01:22:17 AM »

I'd feel completely safe shooting the short cans filled with cement out of that one, even with the chamber full to the top with FG.

If you're concerned about pressure, maybe just fill the can 1/2 way(?) They make a nice whistling sound thataway. I've never been very impressed shooting tennis balls but I've never tried filling them with anything.

jamesbeat · « **Reply #18 on:** October 19, 2011, 06:11:30 AM »

Whenever I think about safety issues, it always makes me think about blackpowder smallarms.

I certainly don't want to sound like I'm not a cautious person, but if you look at the chamber wall thicknesses on black powder muskets and pistols, including those with brass barrels, they don't even approach the 1/3 rule.
Now, I understand that pressures increase exponentially with volume, so the bigger the gun, the beefier the construction has to be, but for something this small, I'd be happy with a careful measurement before and after a proof load.

One thing that I've often wondered about is compression of tennis balls.
In my mind's eye, I see the ball being distorted by the force of the charge behind it, and being rubber, deforming enough to expand and grip the sides of the barrel, causing a pressure spike.

Is this just a lack of understanding on my part, or could this be something to take into consideration when designing a tennis ball mortar?

JeffG · « **Reply #19 on:** October 19, 2011, 07:29:52 AM »

Quote

The bore walls look on the thin side to me, even in a mortar

First and foremost....nice work, great finish and proportions!!
For me I like thicker walls. Light charges and tennis balls would be my preference. Aaaaand..... regular micrometer measurements of the barrel. Just my 2 cents.

Victor3 · « **Reply #20 on:** October 19, 2011, 11:38:30 PM »

Quote from: jamesbeat on October 19, 2011, 06:11:30 AM

One thing that I've often wondered about is compression of tennis balls.
In my mind's eye, I see the ball being distorted by the force of the charge behind it, and being rubber, deforming enough to expand and grip the sides of the barrel, causing a pressure spike.

Is this just a lack of understanding on my part, or could this be something to take into consideration when designing a tennis ball mortar?

James,

We've had more than one discussion here about a projectile/wad becomming a bore obstruction so yes, it is something to consider.

One item that's been said should never be used for a wad over powder for a blank is wet newpaper, as it can compress upon firing and hold tight in the bore.

I wouldn't think that a hollow tennis ball could present much of a problem. Even if it stuck for an instant it should collapse and blow out without much extra force required. I've shot some with hefty charges that partially stripped the cover off.

quaker4u · « **Reply #21 on:** October 24, 2011, 01:17:23 PM »

Hi I have shot tennis balls out of my mortar with a heavy powder charge and they blow apart
when they exit the bore but I have a heavy brass mortar #250 lbs. and I have filled them with
bird shot and had good luck for several shots before they came apart weight about 1-1/4 lbs.
then I tried plaster Paris and that works well. but now I just use dog balls from the dollar store.

Quaker