CAD drawings for 12 or 24 pound Coehorn Mortar

[mac_hunter]

Does anyone out there in cyberland have any drawings of a 12 or 24 pound Coehorn Mortar in CAD format?

Also, does anyone know if the Rebs simply scaled down the dimensions of the 24 pdr to make the 12 pdr or was it a design all their own?

I know that the Union forces did not deploy mortars smaller then the 24 pdr but that the Rebs did and that they made them in Southern foundrys. That leads me to believe that there has to be drawings or plans out there somewhere for a 12 pound mortar.

Again fellas, great forum. Thanks again, in advance, for any help. 

[CU_Cannon]

I have the union 24 pdr and a scaled version in 12 pdr in cad.  The 12 pdr is scaled to be machined from 7" dia. steel.  What version autocad are you using?

[mac_hunter]

It's a freeware version of CadStd from Apperson.

[Double D]

I have cad drawings that have been transfered to JPEG format of the both Confederate mortars.  Drop me a PM if you are interested.  27 drawings

[mac_hunter]

Here is my first attempt at posting a drawing I made of a 24 pound Coehorn Mortar based off what dimensions Gibbon provide in the chart at the back of his book. Some of the dimensions I had to guess at since they were not published (like the dimensions for the length of the reinforcing bands and their depth, O.D. of tube, etc.). From what I can tell, I believe that I'm pretty close though. Anyone got any comments; good, bad or indifferent?

[Michael Az]

Nice drawing. While I am new to this cannon building, I probably don't know what I'm talking about but there is only 1/2" of material between the trunnion and the powder chamber. Is this enough for a big mortar? That's about what I have for my golf ball mortars. Also, shouldn't dimension F be .710?
Michael

[mac_hunter]

I have never built one. From what I know of them through reading, they were cast of bronze with trunnions and rimbase moulded in and then bored out down the center, thus the drawing is distorting the fact that there is solid metal clear back to the larger radius behind the trunnion.

[Michael Az]

Yes, you are correct in that cast there would be plenty of material there. I noticed you replied to my post while I was altering my reply. Go back and read the last sentence in my reply.
Michael

[mac_hunter]

To be honest, I have no clue. That is one of those dimensions that is not stated in the chart at the back of Gibbon's book, which is where I got the key dimensions from.

[Michael Az]

OK, look at it this way. The large diameter of the barrel is 7.5 . The diameter of the small turned area of the barrel is 7.000 as dimension C is .25 per side. So if you subtract 7.5 from .5 you get 7. Now subtract dimension L, the bore, which is 5.58 from 7 and we have 1.42 . Now divide 1.42 by 2 because the drawing is showing the dimension of one side and not the diameter so it would be .710 
I'm not saying this will build a proper cannon, but just saying when you make a drawing be sure all the dimensions add up correctly to prevent building mistakes.  Also, I know you would have caught it but in the list of dimensions there is two D's and no B.
Michael

[Double D]

Okay guys hang in there, I am uploading my drawings to my photo hosting sight. I will post a link to them when down in this thread.

[GGaskill]

Check this link for a 52% drawing of the US 24 pounder Coehorn.  Multiply the dimensions by 1.923 for full scale.

[mac_hunter]

Thanks Y'all for your inputs. You truely are gentlemen and are amazing with the amount of info that you have collected.

[CU_Cannon]

Here are my drawings for those interested in a union style 12pdr. 

12 pdr corhorn 1
12 pdr corhorn 2
12 pdr corhorn 3