Sled for BB Mortar

[smokemjoe]

 What size should I make the sled for my BB Mortar, I am thinking 12 in. wide x 6 in. high, and 30 In. long made of Oak- 1 1/2 thick, bolted and glued, The tunnion is 2 in. rd. and 12 in. long, Wt. of chamber 36 lbs.with a 20 in. barrel and tunnion is 90 lbs. Total, With 2 oz. max load will I get much recoil, And what else should I do . Any pics. Thanks- Joe

[GGaskill]

What's the mortar tube look like?

[smokemjoe]

The mortar tube  is the top of a 3AA2400 Argon  tank, 6 in. cut off the valve end and a 6 in. by 5 in. piece of 1018 for the safety chamber welded to it with the 2 in.by 12 in long tunnion weld to bottom  of safety chamber , Making the save  and legal way. Could a piece of 12 in. channel iron with a place for the tunnions to rest in be used  to test fire it. Thanks- Joe

[Double D]

This seems to be the most adaptable to your design. Lots of people have built this design.  It's a good



I know you loosely based yours on the Florida mortar.  That mortar has problems flipping on it back because the trunnion were mounted to low down and to far to the rear of the bases.  The trunnions nee to be mounted around the center line.

Here's another design with an 8 inch mortar.

[GGaskill]

I would go with something similar to the M1844 mount about the same overall width as the length of the trunnions.  One thing you can't see from DD's drawing is that the cheeks on that model (besides being cast iron) have a wide spot in the middle where the trunnion bears.  So I would go with 2" thick cheeks with an extra piece under the trunnions with the grain going the same way as the cheek and going all the way down to the ground so the force is transmitted through the extra piece into the ground rather than to the cheek.  And make it the same length as the central area on the drawing.

I would glue and lag screw from the inside the cheek and reinforcement together but I would not glue the transoms to the cheeks as the mount will have a tendency to twist if not fired on hard, flat ground and the twisting will probably break the joints.  Use through bolts in the places shown that go through the transoms and the cheeks.  And make sure they are tight when you fire.  They have a tendency to get loose from transportation vibration and humidity changes.

[smokemjoe]

If I make my sled 30 in. long, 12 in. wide and  6 in. deep, will that be big enought.

[GGaskill]

If I make my sled 30 in. long, 12 in. wide and  6 in. deep, will that be big enough?

The M1844 carriage is approximately 3 units long, one unit high at the trunnions and 1 1/4 units high at the front.  That would be 30 inches long, 10 inches at the trunnions and 12 1/2 inches in front.  You want significant depth to prevent breaking the cheeks from recoil if the area under the trunnions is not sitting squarely on the ground.

Have the trunnions a little in front of the center line, maybe 16 inches from the rear.  The centerline of the bore must pass through the bottom of the cheeks to prevent overturning.

[little seacoast]

DD, That's a great mutherin hunk of old mortar, Boer by any chance? Having just about completed a 24 pound coehorn with base, I'm beginning to understand the attraction of wheels and a trail on one.  LS

[Double D]

DD, That's a great mutherin hunk of old mortar, Boer by any chance? Having just about completed a 24 pound coehorn with base, I'm beginning to understand the attraction of wheels and a trail on one.  LS

British 8 inch ML LS mortar on a traveling base.   This one is a Boer mortar called Seeppot, Afrikaans for Soup pot--see Carronader was right...haggis pot, soup pot...

[dan610324]

dd , please dont say that again .
he might hear you