Author Topic: Piece of Bronze shafting... (Read 2876 times)

flagman1776 · « **on:** July 25, 2011, 12:50:47 PM »

bronze shafting 2" Diameter... 3" at full 2" then a 1/4" lathe cut which would give another 1" of length at 1.5" Diameter for 4" Length Over All.

GGaskill · « **Reply #1 on:** July 25, 2011, 01:09:26 PM »

Do you have any short scraps of the same material that could be used for reinforcing bands? They would have to be at least 2.25" in diameter and an inch long.

It's really a little too short for a golf ball Coehorn. If you could find something 1.5" in diameter to use for shot, a 1.5" bore Coehorn would just fit.

keith44 · « **Reply #2 on:** July 26, 2011, 07:56:22 AM »

Wow!! Good eye GGaskill. I was going to say a mini .60 cal Dahlgen.

flagman1776 · « **Reply #3 on:** July 26, 2011, 09:32:33 AM »

I have some scraps of smaller diameter bronze, nothing bigger.

Cat Whisperer · « **Reply #4 on:** July 27, 2011, 01:50:09 AM »

Quote from: flagman1776 on July 26, 2011, 09:32:33 AM

I have some scraps of smaller diameter bronze, nothing bigger.

Candidates for trunnions.

flagman1776 · « **Reply #5 on:** August 05, 2011, 06:41:38 AM »

1.25" caliber.

Double D · « **Reply #6 on:** August 05, 2011, 08:40:38 AM »

Quote from: flagman1776 on August 05, 2011, 06:41:38 AM

I am thinking of 1.25" caliber. Machining the base to start the taper but cleaning up the bottom but leaving the bulk of the material on place... I'm also considering bottom trunions. Either bolting a piece of 1" shafting (flattening one side) on the bottom for the trunions... or drilling through the base. I'm favoring bolt on as it leaves the most material around the chamber.

Dimensions for powder chamber?
How does one attach a "pocket" to hold priming? I'm thinking a hollow bolt touchhole liner with one side cut away.

For the this type shooting just fill the vent with FFFFG. My vent has a countersink that I fill with powder. Works just fine. You don't need a great big trough.

flagman1776 · « **Reply #7 on:** August 05, 2011, 08:57:16 AM »

self delete

keith44 · « **Reply #8 on:** August 05, 2011, 09:37:42 AM »

pictured below is a close up of the flash pan of my .32 cal flintlock. The powder tray groove measures .050" at the max depth, is about .600 inch in length, and .260 inches wide. Something that size would look out of place, but this should give you something to work with.

Double D · « **Reply #9 on:** August 05, 2011, 10:05:37 AM »

Quote from: flagman1776 on August 05, 2011, 08:57:16 AM

That works fine with a cannon... I'm thinking not so much with a mortar. I'm thinking more along the lines of a flintlock flashpan which is pretty shallow & below the touch hole if properly constructed.

Sounds like what you need is quill. Simple to make and work well. We have several post on the subject on how to make them

http://www.gboreloaded.com/forums/index.php/topic,95774.0.html

http://www.gboreloaded.com/forums/index.php/topic,100550.0.html

http://www.gboreloaded.com/forums/index.php/topic,59198.0.html

flagman1776 · « **Reply #10 on:** August 13, 2011, 10:49:12 AM »

I know about quills

GGaskill · « **Reply #11 on:** August 13, 2011, 11:08:06 AM »

DRILL THE BORE FIRST!!!

flagman1776 · « **Reply #12 on:** August 13, 2011, 12:05:28 PM »

2" shafting stock. 4" LOA. 1.25 bore.

Double D · « **Reply #13 on:** August 13, 2011, 01:34:23 PM »

Trunnions should be equal to bore size in cannons.

flagman1776 · « **Reply #14 on:** August 13, 2011, 02:31:26 PM »

Mortar

GGaskill · « **Reply #15 on:** August 13, 2011, 07:17:43 PM »

For the US 24 pounder Coehorn mortar, the bore is 5.82" and the trunnion is 2.75". So the ratio is .4725. Half would be close enough for me.

flagman1776 · « **Reply #16 on:** August 14, 2011, 04:07:25 AM »

I am designing the project around the limitations of my own machines.

Double D · « **Reply #17 on:** August 14, 2011, 04:13:22 AM »

I looked at the drawings of the three mortars. They all had Gomer chambers. All the trunnions were were larger than the small end-bottom of the chamber, and smaller than the mouth of the chamber. I didn't do the math, but I believe there is a relationship between trunnion size and powder chamber.

flagman1776 · « **Reply #18 on:** August 14, 2011, 06:56:29 AM »

I'm not happy with the trunion situation (or my lack of a mill to do it better). I'm going to put off that part & see if I can find someone with a mill.

Max Caliber · « **Reply #19 on:** August 14, 2011, 08:05:46 AM »

You could forget the conventional trunnions and turn the breech end of your barrel to a standard drill size like 1.5 inches then drill and tap the breech end to something like 3/8X18tpi. Drill a block of wood for your bed at a 45 degree angle with a Forstner bit to fit the barrel then bolt the barrel to the bed from the underside of the bed. I have always wondered why mortars that are not adjustible for elevation have trunnions anyway.

GGaskill · « **Reply #20 on:** August 14, 2011, 10:45:06 AM »

I have always wondered why mortars that are not adjustible for elevation have trunnions anyway.

Convention, probably. And it spreads the recoil over a wider area.

Double D · « **Reply #21 on:** August 14, 2011, 11:31:55 AM »

Quote from: Max Caliber on August 14, 2011, 08:05:46 AM

... I have always wondered why mortars that are not adjustible for elevation have trunnions anyway.

To have some method to attach the barrel to a base; to absorb recoil and to minimize side to side rotation on firing.

THat'smy best guess.

I checked Muller to see if there is a rule thumb on trunnion. He says:

"Of all the parts of Artillery, the construction of Mortars is the most variable and uncertain; almost every artillerist has some favorite notion or other concerning their figure."

So what ever we come up with may be good..

Max Caliber · « **Reply #22 on:** August 14, 2011, 12:13:09 PM »

They did build mortars without trunnions like the one shown below. The small block at the bottom of the breech end is not a part of the mortar. More interesting than a mortar without trunnions is the fact that this mortar has it's complete firing lock still attached after 177 years.

Double D · « **Reply #23 on:** August 14, 2011, 12:45:47 PM »

Quote from: Max Caliber on August 14, 2011, 12:13:09 PM

They did build mortars without trunnions like the one shown below. The small block at the bottom of the breech end is not a part of the mortar. More interesting than a mortar without trunnions is the fact that this mortar has it's complete firing lock still attached after 177 years.

Give us some history on this mortar.

flagman1776 · « **Reply #24 on:** August 14, 2011, 01:24:33 PM »

Interesting

Max Caliber · « **Reply #25 on:** August 14, 2011, 01:49:55 PM »

Quote from: Double D on August 14, 2011, 12:45:47 PM

Quote from: Max Caliber on August 14, 2011, 12:13:09 PM
They did build mortars without trunnions like the one shown below. The small block at the bottom of the breech end is not a part of the mortar. More interesting than a mortar without trunnions is the fact that this mortar has it's complete firing lock still attached after 177 years.

Give us some history on this mortar.

The mortar is located at the Army Museum in Brussels, Belgium. It was cast in Liege, Belgium in 1834 and weighs 8120 kilograms or approximately 17900 pounds. It would be interesting to know how the mortar was mounted.

flagman1776 · « **Reply #26 on:** August 15, 2011, 05:27:43 AM »

grinding a new cutter

flagman1776 · « **Reply #27 on:** August 17, 2011, 11:25:06 AM »

I have the bore 1.252"

gulfcoastblackpowder · « **Reply #28 on:** August 17, 2011, 01:55:43 PM »

Should be roughly 1.282 to account for the 39/40 windage. Correct me if I'm wrong, guys.

Double D · « **Reply #29 on:** August 17, 2011, 03:23:56 PM »

If you bore is 1.25 then the windage is 1.25 /40 = 0.03125. So your projectile should be 0.03125 x39=1.21875

If you projectiles 1.25 the windage is 1.25/39= 0.0320512820512821. (hey that's what calculator widget said) Your bore for the is projectile should be 0.0320512820512821 x 40=1.282051282051282....okay okay 1.282