Author Topic: I need some help.. (Read 772 times)

halfarod · « **on:** August 05, 2009, 05:07:24 PM »

So i am planning on building my second cannon and i'd like to do it out of brass. Now i don't really know the rule for wall thickness and i'd like to have a 1.75" bore. It's going to be a napoleon style so it'll be tapered and about 30" long. So any impute would helpful.
thanks

dan610324 · « **Reply #1 on:** August 05, 2009, 09:26:06 PM »

I would say minimum 5,25" breach diameter and 3,5" at the smallest diameter close to the muzzle .
but to add 15 - 20 % isnt any bad idea
it all depend on how heavy charges you are going to use .

Cat Whisperer · « **Reply #2 on:** August 06, 2009, 12:21:46 AM »

Where the powder is, the wall thickness should be the same as the inside diameter. This means you can make it a little smaller at the breech if you use a powder chamber. The trade-off is that it's a little harder to load. If it was me, I'd put in a SEAMLESS liner (with the breech plug fitted (shink fit) and welded at the back. Then you can either shrink-fit or glue the liner into the tube.

Double D · « **Reply #3 on:** August 06, 2009, 01:27:01 AM »

A 1.75 inch bore will require a minimum of 5.25 inch diameter of over the bore. I agree with Tim for a bore this large you should have a seamless tube liner with a properly fit breech plugged.

cannonmn · « **Reply #4 on:** August 06, 2009, 03:42:29 AM »

Quote

I agree with Tim for a bore this large you should have a seamless tube liner with a properly fit breech plugged.

Question: If he used, instead of brass, gunmetal bronze, or a tensile-strength-equivalent bronze alloy, wouldn't that be considered sufficiently strong to go without a steel liner?

dan610324 · « **Reply #5 on:** August 06, 2009, 05:56:40 AM »

90/10 bronze is stronger then mild steel
Im not sure but I think the gunmetal 88/8/4 (copper/tin/zink) is even stronger then the 90/10 alloy .

carronader · « **Reply #6 on:** August 06, 2009, 06:08:22 AM »

could be usefull see attached pdf

dan610324 · « **Reply #7 on:** August 06, 2009, 07:55:15 AM »

yes , all info is interesting info .
but personally I dont like the 5% lead they mix into those alloys .
the lead is there to "lubricate" the alloy to get better machinability .

so for cannon and mortar tubes I wouldnt use them
and with a zinc content of 4-6% you loose a lot of the "bronze" color on the casting
'
Im the old fashion foundry man , if they used 90/10 400 years ago it will be good enough for me today.
ok , I got full control of temperature +/- 7-10 degrees celsius
also use filters ( 20 and 30 ppi to remove slag and impurities from the mold ) and degassing .

Ihave seen many small , medium size and also larger foundries , some of them dont degas , some dont check the temperature , some dont Use filters .
a few of them dont do any of the 3 above , AND THEY CALL THEMSELF PROFESSIONALS .
Im just an happy amateure , but still I keep record of every pour statistics to look at if something goes wrong ,
but as we are dealing with cannons for shooting my opinion is that QUALITY WILL ALWAYS COME FIRST
ITS A BIT MORE EXPENSIVE BUT YOU GET THE BEST QUALITY MONEY CAN BUY , EXCEPT FOR VACUUM CASTING

so it aint much more to do to increase the quality if you not are prepared to use vaccun casting ,
but thats heII so expensive, so its not for hobby use ,

Double D · « **Reply #8 on:** August 06, 2009, 08:43:55 AM »

Quote from: cannonmn on August 06, 2009, 03:42:29 AM

Quote
I agree with Tim for a bore this large you should have a seamless tube liner with a properly fit breech plugged.

Question: If he used, instead of brass, gunmetal bronze, or a tensile-strength-equivalent bronze alloy, wouldn't that be considered sufficiently strong to go without a steel liner?

Under the guidlines of the N-SSA which we point to as the safety guidline, No.

cannonmn · « **Reply #9 on:** August 06, 2009, 08:45:36 AM »

Everyone don"t forget that there were a number of requirements that drove the bronze composition used, not only tensile strength. A very important one was hardness, because they were shooting very hard iron balls, which ballotted going down the bore. Unless the bronze was quite hard, the balloting ball would dent up the bore pretty quick and make the gun useless.

I tried to use metal stamps on an original gun one time just to put tiny initials in it for ID purposes-Dang that bronze was hard-took many strikes with good sized hammer and a sharp letter stamp to get any impression at all! I suspect 90/10 comes in very high in hardness among the various bronze alloys.

cannonmn · « **Reply #10 on:** August 06, 2009, 08:48:34 AM »

Quote

Under the guidlines of the N-SSA which we point to as the safety guidline, No.

That must be a rule only for repro guns, since all the original guns that shoot there don't have any liners. They all have to pass inspection of course.

Double D · « **Reply #11 on:** August 06, 2009, 09:00:44 AM »

That's right applies to repro or new made guns. Original's that fail inspection me be required to have a liner.

dan610324 · « **Reply #12 on:** August 06, 2009, 11:44:46 AM »

the more tin added to molten copper the harder the bronze will be .

tin content in most cannons is between 6 and 12 % , some more some less .
the most common from late 1500 until mid 1800 is around 10 %
common bronze have probably always been around 90/10 .
I read about an archeoligic finding , it was a viking era ship , it had 900 kilo copper and 100 kilo tin on it when it sunk .
so I guess that show us that even 1100 years ago they used pretty much the same alloy .

church bell bronze can have up to 30 % tin in it
but such an alloy would be much to hard and fragile to be used in cannons .
the more tin in a bell the brighter tone (higher frequenzy)
but to much and they will easy crack .

halfarod · « **Reply #13 on:** August 08, 2009, 09:58:07 AM »

So if I were to put a steel liner in what are the rules for thickness of that? I'm sorry if i sound lame or anything but i'm not familiar with doing this. thanks for all the information!!

KABAR2 · « **Reply #14 on:** August 08, 2009, 10:07:57 AM »

Quote from: dan610324 on August 06, 2009, 11:44:46 AM

the more tin added to molten copper the harder the bronze will be .

tin content in most cannons is between 6 and 12 % , some more some less .
the most common from late 1500 until mid 1800 is around 10 %
common bronze have probably always been around 90/10 .
I read about an archeoligic finding , it was a viking era ship , it had 900 kilo copper and 100 kilo tin on it when it sunk .
so I guess that show us that even 1100 years ago they used pretty much the same alloy .

church bell bronze can have up to 30 % tin in it
but such an alloy would be much to hard and fragile to be used in cannons .
the more tin in a bell the brighter tone (higher frequenzy)
but to much and they will easy crack .

Dan,

You mean like this?

KABAR2 · « **Reply #15 on:** August 08, 2009, 10:08:43 AM »

Sorry seemed to have made a double post.....

dan610324 · « **Reply #16 on:** August 08, 2009, 11:01:57 AM »

yeah thats exactly what can happened with too much tin in a bronze alloy

Im just a bit curious about the nssa rules

must ALL repro cannons have a liner ??

how about a barrel turned from a solid bar ??

Double D · « **Reply #17 on:** August 08, 2009, 06:23:25 PM »

Quote from: halfarod on August 08, 2009, 09:58:07 AM

So if I were to put a steel liner in what are the rules for thickness of that? I'm sorry if i sound lame or anything but i'm not familiar with doing this. thanks for all the information!!

The rule stands, Wall thickness should be the same as chamber diameter.

Dan if a guns was turned from solid steel bar stock made to the standard described in NSSA rules for liners , it would meet or exceed the rule.

GGaskill · « **Reply #18 on:** August 08, 2009, 06:54:04 PM »

... andIi'd like to do it out of brass.

Have you checked the price of the piece of brass you would need for this?

I would recommend building it from mild steel (1018) and getting it brass plated. Much stronger, no liner required and less expensive.

Victor3 · « **Reply #19 on:** August 08, 2009, 10:57:44 PM »

Quote from: halfarod on August 08, 2009, 09:58:07 AM

So if I were to put a steel liner in what are the rules for thickness of that? I'm sorry if i sound lame or anything but i'm not familiar with doing this. thanks for all the information!!

No, it's a valid question.

N-SSA rule for liners calls for a 3/8" wall seamless steel tube with heat-shrunk and welded plug. You can get more details on liners by going to the N-SSA website and opening the .pdf file of their rules.