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Author Topic: Mortar Trunnions - a Question  (Read 767 times)

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Offline Musketeer

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Mortar Trunnions - a Question
« on: August 21, 2007, 07:36:21 PM »
From what I understand from various comments on this forum, some mortars are built with a fixed angle of 45 degrees,  the distance is varied by the amount of powder behind the shot.   Then why do these mortars have trunnions ?   What purpose do they serve?
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Offline GGaskill

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Re: Mortar Trunnions - a Question
« Reply #1 on: August 21, 2007, 08:25:15 PM »
I can't answer the question from original documents, however, the trunnion of a Coehorn-style mortar would spread out the recoil force over a wider area, its inletting would be a relatively simple machine-performed process which would provide a better fit, it would prevent the tube from turning in the mount and it provides points of purchase to retain the tube in the mount.  Maybe even more things I can't think of right now.

And maybe it was just tradition.
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GG
“If you're not a liberal at 20, you have no heart; if you're not a conservative at 40, you have no brain.”--Winston Churchill

Offline Cat Whisperer

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Re: Mortar Trunnions - a Question
« Reply #2 on: August 22, 2007, 12:57:46 AM »
The forces from firing are in line with the axis of the bore pressing down on the base.  Upon firing the impact causes a bit of a bounce - the trunnion caps keep the tube and the base together. 

I have one ~3" mortar that the trunnion caps are nothing more than sheet metal.  Crude, but they do the job. Traveling and moving the rig often produces more forces to separate the two pieces, hence a thicker (iron/brass) plate works well.

AND, WELCOME to the board Musceteer!

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Tim K                 www.GBOCANNONS.COM
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Offline Artilleryman

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Re: Mortar Trunnions - a Question
« Reply #3 on: August 22, 2007, 01:51:48 PM »
Maybe the best answer would be another question.  How would you attach the barrel to the base without trunnions?
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Norm Gibson, 1st SC Vol., ACWSA

Offline GGaskill

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Re: Mortar Trunnions - a Question
« Reply #4 on: August 22, 2007, 03:05:55 PM »
How would you attach the barrel to the base without trunnions?

A threaded stud on the back of the barrel that would fit through the base and be secured with a nut on the rear?   ;D
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GG
“If you're not a liberal at 20, you have no heart; if you're not a conservative at 40, you have no brain.”--Winston Churchill

Offline lance

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Re: Mortar Trunnions - a Question
« Reply #5 on: August 22, 2007, 03:12:53 PM »
Quote from: GGaskill on August 22, 2007, 03:05:55 PM
How would you attach the barrel to the base without trunnions?

A threaded stud on the back of the barrel that would fit through the base and be secured with a nut on the rear?   ;D
how about, since the trunnions are done away with, get rid of the base too. then everybody could run around with just the tube, and dig a quick hole when they want to fire it...........forgive us Musketeer, and welcome to the board. ;D
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PALADIN had a gun.....I have guns, mortars, and cannons!

Offline Tropico

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Re: Mortar Trunnions - a Question
« Reply #6 on: August 22, 2007, 03:24:43 PM »
I've got mine and I am ready ! ! !    Its the only thing I have without a trunnion.,(By the way trunnions are delicious)

I eat trunnions for breakfast.
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Offline lance

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Re: Mortar Trunnions - a Question
« Reply #7 on: August 22, 2007, 04:20:48 PM »
Rich, i keep telling you , we need to market TROPICO'S BREAKFAST TRUNNION BARS. i know lot's of artillerymen that need to start their day off right ;D ;D ;D
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PALADIN had a gun.....I have guns, mortars, and cannons!

Offline Cannonball

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Re: Mortar Trunnions - a Question
« Reply #8 on: August 22, 2007, 05:07:09 PM »
Snap, crackle, POW!
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Offline Terry C.

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Re: Mortar Trunnions - a Question
« Reply #9 on: August 22, 2007, 05:20:44 PM »
I like my trunnions sauteed in butter and served over a grilled ribeye...
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Offline Cannonball

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Re: Mortar Trunnions - a Question
« Reply #10 on: August 22, 2007, 05:28:29 PM »
I'm too lazy to cook in the morning. A bowl of grapeshot and raisin cereal and a hot cup of Fg cocoa. Caution: add Fg after removing from microwave!
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Offline copdoc

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Re: Mortar Trunnions - a Question
« Reply #11 on: August 22, 2007, 05:42:46 PM »
Nice thunder mug Tropico.  where did you get it?

I also think the trunnions being perpendicular to the grain would spread the recoil and keep the sled from splitting  You need a sled and a wooden platform if you shoot a 24 pounder with a pound of powder (which of course I would not).  You get one heck of a recoil and it will drive the sled in the ground.  Most of the live fire shoots use only a few oz of powder. When they were used these in combat I have read that they also made a timber bed to keep the mortar from driving itself in the ground.  They put the grain of the bed perpendicular to the grain of the sled.  Anyone ever shot a pound of powder in a 24 pounder with a 17 lb projectile?   ;D 
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Offline Tropico

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Re: Mortar Trunnions - a Question
« Reply #12 on: August 22, 2007, 06:17:01 PM »
Breakfast Bars
Snap Crackle POW !
All sounds good to me ......., but for dinner thats a new twist I like it"Rib-Eye and Sauteed Trunnions" definitely would be a class act at a fyne restaurant for sure.   

The Thunder-Mug came from Ebay ., speaking of Ebay I just won an auction again last night I hope to show off soon ..., and Dominick sent me another Swivel Yoke for a project I am doing...., the-the-the-this-ha-ha-has to st-st-st-stop  the addiction is consuming me *Wicked-Wicked-Gold-Toothed-Grin" 

Quote
Anyone ever shot a pound of powder in a 24 pounder with a 17 lb projectile?
Back to the topic .., this sounds like trunnion hammering event.
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Offline GGaskill

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Re: Mortar Trunnions - a Question
« Reply #13 on: August 22, 2007, 09:09:17 PM »
Anyone ever shot a pound of powder in a 24 pounder with a 17 lb projectile?

The official max load for a 24 pounder Coehorn was 1/2 pound of powder.  The mortars were supposed to be fired from a wooden platform, not the ground.
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GG
“If you're not a liberal at 20, you have no heart; if you're not a conservative at 40, you have no brain.”--Winston Churchill

Offline copdoc

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Re: Mortar Trunnions - a Question
« Reply #14 on: August 23, 2007, 01:39:00 AM »
Sorry, I meant to say half pound.  That would be quite a load.  Setting up even a 24 pounder would have been quite a chore, making the platform and hauling in enough ammo for the siege.  I have read when they fired them without that wood platform that they had to dig them out of the ground after a few shots.  I guess it would depend on the terrain.

Tropico what is the bore diameter of your mug?
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Offline Tropico

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Re: Mortar Trunnions - a Question
« Reply #15 on: August 23, 2007, 04:57:40 AM »
1"
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