Author Topic: Trunnion Center Line (Read 2452 times)

smokemjoe · « **on:** July 11, 2011, 03:47:38 AM »

I am making another bowling ball mortar, Base will be 30 in. long, Where should the trunnion be place from the center line , My other one is just ahead ahead of the center line, What is correct, Thanks- Joe

gunsonwheels · « **Reply #1 on:** July 11, 2011, 04:32:01 AM »

Maybe some clarification is needed here..?? There's about four center lines there.

Tube CL, Trunnion CL and Bed CL for to aft and bed CL side to side.

Are we to assume you mean the trunnion CL in relationship to the Bed's front to aft CL?

GOW

Double D · « **Reply #2 on:** July 11, 2011, 06:20:51 AM »

I just checked 4 different drawings.

Model 1841 8 inch siege mortar, trunnion on center front to back
24 PDR Coehorn, 1 inch to rear of center
10 inch Seacoast mortar, 1/2 inch to rear of center
Confederate 24 PDR, 1/4 inch to rear of center.

cannonmn · « **Reply #3 on:** July 11, 2011, 06:43:10 AM »

Quote

24 PDR Coehorn, 1 inch to rear of center
10 inch Seacoast mortar, 1/2 inch to rear of center

Maybe I'm not awake yet but unless those are scaled drawings, I can't make sense out of those numbers when I'm thinking in terms of full-sized pieces.

Double D · « **Reply #4 on:** July 11, 2011, 07:05:44 AM »

Quote from: Double D on July 11, 2011, 06:20:51 AM

I just checked 4 different drawings.

Model 1841 8 inch siege mortar, trunnion on center front to back
24 PDR Coehorn, 1 inch to rear of center
10 inch Seacoast mortar, 1/2 inch to rear of center
Confederate 24 PDR, 1/4 inch to rear of center.

We are talking about where to locate the trunnion in the mortar base, front to rear.

Model 1841 8 inch siege mortar, trunnion on center front to back
24 PDR Coehorn, Trunnion center 1 inch to rear of center of base
10 inch Seacoast mortar, Trunnion center 1/2 inch to rear of center of base
Confederate 24 PDR, trunnion center 1/4 inch to rear of center of base

Those numbers are from full scale drawings

gunsonwheels · « **Reply #5 on:** July 11, 2011, 07:45:25 AM »

The bowling ball mortar I am doing is a variant of the 1841 8" mortar. As bowling balls are 8.5" to 8.595" in diameter the dimensions for the 8" 1841 are probably most appropriate for you. I am mounting the trunnions in the middle of the bed or on the for-to-aft centerline of the bed. My bed is 40.5" in total length so the trunnions are at 20.25" from either end.

Good luck... I have an aquaintance who destroyed his bed while reaching for a long distance shot... so build the bed stout... it sometimes takes a real beating.

Double D · « **Reply #6 on:** July 11, 2011, 08:12:21 AM »

A bowling ball gun with proper windage would need a minimum bore of 8.815 inch.
Circumference of a bowling ball. Max 27.002 inches. 27.002 xi .31831 = 8.595 maximum diameter of a bowling . (8.595/39)x40= 8.815 inches http://www.topendsports.com/sport/tenpin/dimensions.htm

gunsonwheels · « **Reply #7 on:** July 11, 2011, 09:59:49 AM »

dd:

Quote

A bowling ball gun with proper windage would need a minimum bore of 8.815 inch.
Circumference of a bowling ball. Max 27.002 inches. 27.002 xi .31831 = 8.595 maximum diameter of a bowling . (8.595/39)x40= 8.815 inches

And please DO NOT try to use a reduction in the windage if you are doing one of those BB mortars made from a HP cylinder end. They, especially, need to be combustion chamber effect only.

keith44 · « **Reply #8 on:** July 11, 2011, 03:51:23 PM »

Quote from: gunsonwheels on July 11, 2011, 09:59:49 AM

dd:
Quote

A bowling ball gun with proper windage would need a minimum bore of 8.815 inch.
Circumference of a bowling ball. Max 27.002 inches. 27.002 xi .31831 = 8.595 maximum diameter of a bowling . (8.595/39)x40= 8.815 inches

And please DO NOT try to use a reduction in the windage if you are doing one of those BB mortars made from a HP cylinder end. They, especially, need to be combustion chamber effect only.

Meaning do not reduce the windage for velocity / pressure increases, or do not live fire?

gunsonwheels · « **Reply #9 on:** July 11, 2011, 06:06:33 PM »

"A"... i.e. do not reduce the windage to try and use the BP pressure in the area of the bore/tank... depend getting your range ONLY from the pressure of the reduced bore, thick walled powder chamber so when that ball starts to rise the pressure dissapates very rapidly... I wouldn't even start to trust those tank walls with BP pressures... but I've heard the scream of flying fragemts overhead more than once...

Double D · « **Reply #10 on:** July 11, 2011, 06:52:58 PM »

I think what he is trying to say is to use a powder chamber in these tanks. Don't use the tank as a chamber. The tank should be nothing more than a ball holder and expansion chamber.

keith44 · « **Reply #11 on:** July 14, 2011, 10:54:34 AM »

Yet again sound advice from experienced voices! I am glad there is a consistant safety stance from all who are here. I've been watching youtube and can say without hesitation that there are some real idiots out there.

Zulu · « **Reply #12 on:** July 14, 2011, 11:07:00 AM »

Quote from: keith44 on July 14, 2011, 10:54:34 AM

Yet again sound advice from experienced voices! I am glad there is a consistant safety stance from all who are here. I've been watching youtube and can say without hesitation that there are some real idiots out there.

Nothing is foolproof to a sufficiently talented fool.

Zulu

smokemjoe · « **Reply #13 on:** July 14, 2011, 03:57:40 PM »

To clear things up on the safety side is , The powder chamber is 6x6 in., 1018 bored 2 in.x2 1/2 in. deep hole, bottom cut with a 2 in. radius ball mill, and will be welded up inside of the 3AA2400 tank, A trunnion 2 in. X 16 in. welded the end of the chamber and to the end of the tank.
My other one is made of the same materials but the chamber is weld the the end of the tank onthe outside,
The base is made of Hickory , The trunnion is 1 in. behine the center line and gives no trouble.Just want to make this one right. Thanks for the help.

Double D · « **Reply #14 on:** July 14, 2011, 08:02:13 PM »

I would think that a 2 inch trunnion is a bit small for a bowling ball mortar.

Co. Batguano · « **Reply #15 on:** July 15, 2011, 09:18:12 AM »

Where will you get your bowling balls to shoot? How much do they cost (you) and for the averave "cannoneer on the street"?? Been thinking about a BB mortar, but that question is a daunting one.

Double D · « **Reply #16 on:** July 15, 2011, 10:02:10 AM »

Go to any bowling alley and ask if the have any bowling balls to get rid of. They will.

GGaskill · « **Reply #17 on:** July 15, 2011, 12:03:16 PM »

I have gotten two batches of bowling balls. One was from a bowling center that was replacing their house balls; I paid him what I charged for hauling them away. Could have had hundreds but at 16 lbs a piece, the weight builds up faster than you think. The other batch came from a trade-ins to a bowling pro shop that closed. Those were free also.

smokemjoe · « **Reply #18 on:** July 15, 2011, 05:29:59 PM »

I get most of mine at the Salvation Army store, I went in there this week and didnt want anymore balls as I must have over 130 now and the house is ready to roll down the hill, Walked in and said they were glade to see me, had 10 more balls at $1.00 ea, Last week I found 5 in my drive way, Then a lady gave me 3 and a friend gave me 5 more. Its getting out of hand. Need a placed of my own to shoot. Joe
DD: I have shot some good loads on my other BB mortar with a 2 in. trunnion and still straight as a string. The base is made out of Hickory and heavy.

Double D · « **Reply #19 on:** July 15, 2011, 06:47:45 PM »

May be straight as string....now, but it is still to small. Rule of thumb is trunnion should be the same diameter as bore.

Now if you were shooting an 8.5 inch mortar using George's round ball calculator http://gunneyg.info/html/ShotWeight.htm we find a an 8.5 inch solid iron ball would weigh 81 lbs and you would definitely need a 8.5 inch trunnion. But the bowling ball projectile is only around 16 lbs so you don't need a trunnion that big.

Working on the design of my bowling ball mortar I had no idea how to figure out how big a trunnion I needed. So I winged it and applied rationalization to come up with a number.

The rule of thumb says trunnions should be one caliber in diameter. Since the weight of the solid shot provides how we identify the caliber, I used the bowling ball weight to do a reverse engineering rationalization and George's round ball calculator to come up with a 16 pdr bore was 4.943 or 5 inch, And that is how big my trunnion will be on my bowling ball mortar.

GGaskill · « **Reply #20 on:** July 15, 2011, 06:52:34 PM »

... 5 inch. And that is how big my trunnion will be on my bowling ball mortar.

And combined with the rest of the steel, it will be honkin' heavy.

Double D · « **Reply #21 on:** July 15, 2011, 06:59:26 PM »

Quote from: GGaskill on July 15, 2011, 06:52:34 PM

... 5 inch. And that is how big my trunnion will be on my bowling ball mortar.

And combined with the rest of the steel, it will be honkin' heavy.

yes and stable also!

GGaskill · « **Reply #22 on:** July 15, 2011, 07:05:10 PM »

yes and stable also!

Just don't deploy it if it has rained a lot in the last 24 hours.

Double D · « **Reply #23 on:** July 15, 2011, 08:08:42 PM »

Quote from: GGaskill on July 15, 2011, 07:05:10 PM

yes and stable also!

Just don't deploy it if it has rained a lot in the last 24 hours.

In Montana 24 hour after a rain we have dust!!!

Ex 49'er · « **Reply #24 on:** July 15, 2011, 09:25:28 PM »

Quote from: Double D on July 15, 2011, 06:47:45 PM

The rule of thumb says trunnions should be one caliber in diameter. Since the weight of the solid shot provides how we identify the caliber, I used the bowling ball weight to do a reverse engineering rationalization and George's round ball calculator to come up with a 16 pdr bore was 4.943 or 5 inch, And that is how big my trunnion will be on my bowling ball mortar.

I guess you're gonna have to wait until the circus comes to town and borrow their elephants to help you move the heavy beast. Or will you tip it forward and slip it onto a cart? Or use an engine hoist?

Zulu · « **Reply #25 on:** July 16, 2011, 03:21:11 AM »

Quote from: Double D on July 15, 2011, 08:08:42 PM

Quote from: GGaskill on July 15, 2011, 07:05:10 PM
yes and stable also!

Just don't deploy it if it has rained a lot in the last 24 hours.

In Montana 24 hour after a rain we have dust!!!

Rain? Rain? What's rain? $:-\$
Zulu

SLEEPY BEEPER · « **Reply #26 on:** July 16, 2011, 07:24:00 AM »

A 2 inch trunnion will work if a heavy timber or steel piece supports it full length. But it is minimum. Don't try supporting it just on the ends. My trunnion warped when welded in. Do to all the welding on one side. Don't know how to prevent this. But it still works fine. A lot of people will tell you to build a mortar heavy. But having a bowling ball mortar that 2 people can lift into a pickup truck is a big benefit. And with a good base. I'm still very competitive at mortar shoots.

dan610324 · « **Reply #27 on:** July 21, 2011, 02:36:37 AM »

DD , do you really think that 5 inch trunnions is neccesary on a bowling ball mortar ??
as it has a subchamber I mean
3 inch solid steel can take a lot of punishment before it bend, especially if its supported correctly

Double D · « **Reply #28 on:** July 21, 2011, 03:49:21 AM »

Quote from: dan610324 on July 21, 2011, 02:36:37 AM

DD , do you really think that 5 inch trunnions is neccesary on a bowling ball mortar ??
as it has a subchamber I mean
3 inch solid steel can take a lot of punishment before it bend, especially if its supported correctly

Yes and No I was rationalizing.

Mine will have a five inch trunnion, but it also will have an adult size powder chamber.

quaker4u · « **Reply #29 on:** July 21, 2011, 08:54:25 AM »

Hi
My mortar has a 3" trunnion and I send a 16# ball 500 yd with 3/OZ charge
and no problems weighs 255lbs. "that is the chamber capacity"
Don't see any reason for anything larger for an 18" barrel.
Quaker