Where to find write up on O2 Tank Cannon

[Cannon salute]

I would go with a 3" stock at minimum, that would leave you with a 1" bore diameter I would bore it 1.5" deep. 

[BoomLover]

So, that would be 3" X 4.5" Stock , actually that sounds about the right dimensions for a 1" X 1 1/2"chamber. Then, as far as the Trunnion, I think 3" would be way too big, probably looking at closer to 2", or 1 3/4"? Length of trunnion should be....how far past the sides of the walls of the Mortar?  With 6.5 I.D., and 1/4" wall thickness, that totals 7" O.D.. Any and all suggestions gladly accepted! BoomLover

[Double D]

Before you go to far, take a piece of wood and drill a hole in it to the powder chamber dimensions.  Fill the hole with Fg and weigh it to see if your hole is to big or to small for the recommended charge for diameter.

Rule of thumb for cannon  trunnion is diameter and length equal to bore diameter...mortars are different.  I haven't seen a rule of thumb anywhere.  But I have never seen a drawing where the trunnion on a mortar is less than the powder chamber diameter.  Unlike a cannon which dissipates some the recoil energy through free recoil of gun and carriage, the mortar recoil energy is transmitted through the trunnions to the base and is resisted by the ground.  The greater the surface area of the trunnion the more the recoil energy is spread out through base, the less likely you are to break a base and or bend a trunnion...

And yes you can break a base.

Use a larger trunnion, and it will  look a lot better also.

[BoomLover]

  Thanks, Double D...and also Cannon Salute, for all the helpful info...I got the idea, and that is something I never thought of, regarding the trunnion size of Mortar's vs Cannons. I know your busy, Double D, but a dimensional drawing sized to fit this one will help a lot! I need to know where to cut the neck off, and how long to leave the barrel, (I know 2 calibers for a Mortar), however, how far down the neck? If you can picture the Folgers Coffee Can, 6 1/2" diameter, plus 2 X lenght...also, will the sled base such as you drew back on page 2 of this thread, work for this also, just scaled for proper perspective and size? Just full of questions! Thanks, in advance! BoomLover

[GGaskill]

Trunnion length is a function of the width of the base and the width of the tube.  The mount cheeks, assuming you are not going with a Coehorn-style solid base, need to be wide enough to resist sinking into the ground from the recoil.

The trunnion on the M1841 10" mortar is 30" versus 20.5" diameter of the tube(68.3%).  The 24 pounder Coehorn numbers are 12.5" and 8.65" diameter (69.2%).  Not exactly the same proportion but pretty close.

[Double D]

So, that would be 3" X 4.5" Stock , actually that sounds about the right dimensions for a 1" X 1 1/2"chamber. Then, as far as the Trunnion, I think 3" would be way too big, probably looking at closer to 2", or 1 3/4"? Length of trunnion should be....how far past the sides of the walls of the Mortar?  With 6.5 I.D., and 1/4" wall thickness, that totals 7" O.D.. Any and all suggestions gladly accepted! BoomLover

Listen you guys, I am retired.  In order to make these drawings for you I have give up my nap time...so to make it simple for me, you have to be real clear for me.

The chamber you are describing? 3" diameter by 4.5" long, with a powder chamber 1" diameter x 1 1/2" deep.  How much powder will that chamber hold?

Would it be better to make the 1" x 1 1/2"chamber  in piece of 3" diameter stock 2 1/2" long?

I have a foil wrap max charge for my 1" cannon here and it is 2" long.

Gotta run time for coffee.

[BoomLover]

Let's see if I got this...You both are recommending a longer and fatter trunnion for this size Mortar...if I'm reading right, with what I have for the tube, I should be looking at a minimum of 2" diameter, and approximately 11 inch length, if not slightly more to each dimension...up to 2 1/2 diameter and up to 12 inch length? I got it that the size of the trunnion helps dissipate the recoil, now another question....assuming I can cut the cheek mounts as Double D drew out on page 2, how wide (thick?) should they be? I'm thinking possibly 2 inches? Or more?...Thanks, everybody for all your assistance! BoomLover

[Double D]

Well I missed my nap and now I am grumpy.  When I get grumpy the dogs  growl at me,  and now the  Mods are probably going to growl a me for drifting this topic from  Bowling balls to coffee cans...hey topic o2 tanks and a SCUBA tanks is well with in topic---where is the thumb your nose at the Mods smiley?


Here is what I came up with for a SCUBA tank coffee can mortar.

[GGaskill]

I have no trouble with topic drift; normal conversation works the same way.  These are not learned discourses of subjects of little interest as we get from the academic industries.

Looking at DD's drawing above, a 9" long trunnion on a hemispherical breech would have rimbases about half way between the max dia of the tube and the contact point between tube and trunnion.  I would estimate that would be about 2.5" from the ends but it would be better to draw and measure than just guessing.

So having said, "Draw it," I did and it works out at exactly 2".  Now I would put a wider foot on the bottom of the mount cheeks for more ground contact.

[Cannon salute]

Looking for the thread that has the rules for building powder chambers, i.e. 1:3 chamber to wall, breech thickness all of that good stuff. Anyone have the link?

[GGaskill]

Check out Reply #4 near the top of this thread.