Home made big mortar, how did they do it??

[entsminger]

In my searches for manufactures of full sized 8 and 10 inch 1861 style mortars I found a short mention of at least one family out in Wisconsin that has essentially made their own mortar. They sculpted the barrel from wood and took it to a foundry and had them cast it for them and then they took the iron casting to their machine shop where they work and machined the trunions and the rest to an exact replica of a 1861 10 inch mortar! I find this fasinating and incredable that someone can actually do this!! I can weld and make things all the time but I never untill now thought someone could actually make a real mortar especially considering the 10 incher weights close to 4,000 pounds! It must take huge lathes and huge equipment?
   I would really like to learn more about how building a big mortar as such could actually be done, so if there is anyone out there who has done so and will share your thoughts with me please tell me about the process and how it's done or how you did it.
   Thanks
  Scott    sdakss@aol.com

[GGaskill]

I only have plans for the 8" mortar so I will discuss making one of them.  A 10" is substantially (about 50%) larger.
 
The basic dimensions for an 8" M1861 siege mortar are 16" barrel diameter, 22" overall length (actually plus the elevation notches, maybe another 1/2" or so), 22.9" across the trunnion ends and an extra 3" for the lifting lug.  The trunnion centers are 10" from the muzzle.  The trunnions are 10" in diameter and 3.25" wide, the rimbases are 11.5" in diameter and the diagonal across the trunnion corners is 24.9".
 
If I were to cast one, the only machining I would do on it is (1) drill the bore and touch hole, (2) drill the lifting lug, (3) face the muzzle, and (4) machine the trunnions.  All of that could be done on a large vertical mill with a heavy duty rotary table.  Drilling the bore on a lathe would require at least a 25" swing to clear the corners of the trunnions.  
 
The greatest difficulty would be holding the casting to drill and face because there is no cylindrical portion on the rear to hold.  I might make the casting with integral lugs for holding which would be ground off after the machining processes requiring them were completed.
 
Actually, since I am more interested in launching bowling balls than 8" or 10" shell, I would fabricate one from thick-wall tubing and round stock and not worry too much about the deviations from the actual 1861 pattern.

[Cat Whisperer]

entsminger -

It makes fascinating reading - doing research on the methods.  I'd look at the Watervliet Arsenal (still operational in NY) and the old Tredigar Iron Works (CW period in Richmond, VA).  You will find a few references to them in the References sticky and others in some of the other museums and other links.

[CU_Cannon]

1861 8 inch Civil War Siege Mortar

I too have looked long at this mortar.  I wish that they had more info on the actual construction.  It doesn't look like the pattern would be too hard to build.  It would be a job to machine though.  The weight alone would make it difficult for many machine shops.

[GGaskill]

Making the pattern would not be all that difficult as it is made from wood so the weight wouldn't be all that great, at least compared with cast iron.  

What one does is glue together enough flat boards to make up the bulk, then turn the wood on a lathe to the proper shape and size (with allowances for shrinkage and machining, if any external machining is intended.)  Then the various pieces (barrel, trunnions, lifting lug, elevation rack) are glued together and the corners filleted and flaws repaired to give a smooth surface so the pattern can be removed from the sand mould without damaging the cavity.  Take a look at the http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?p=353390" target="_blank">One of my half scale mountain howitzers thread for more info on casting.

Unless you have a foundry, you take the pattern to a foundry and they make a mould and cast it.  You get your pattern back along with a 1000 lb chunk of cast iron in the general shape of your pattern.  

If you have a copy of the South Bend Replicas catalog, they have a few pictures showing some of the processes of pattern making.

I would try contacting these people and see if they could have a casting made for you since they already have the pattern.  Or even making the whole thing since they have a machine shop, too.

[Freddy]

It is indeed a task to build both the 10 and the eight seige mortars. The metal thickness at configurations are not standard materials. I have built both from the ground up including the patterns. The barrels where truned on a 56 inch vertical lathe.

Freddy

[entsminger]

Freddy I really would like to talk to you sometime. I'm hearing differing accounts about how folks have made these big mortars. Hearn Iron works seems to indicate they do very little machineing to their 8 inch mortar barrel other than some minor grinding of joint seams and others say they literally bore out the barrrel and mill the trunnions etc etc.. Are the $$savings really worth it to make your own mortar or is it around the same cost that they can be bought for?$10,500. I really would like to talk personally with somone who has made one of these mortars and I would appreciate it if you would call me collect sometime  ( or I could call you if I had your number?)so we can chat. My phone number is 703 528 1548 and I live in Virginia.

  Scott Springston