Tim, you really have a great idea there. What a wonderful way of winnowing out worthless whiners! Mike and I want to be the first to sign up for a group price. Getting a little older as we are, lighter mortars seem like a good idea. Years ago a friend had a soda-can mortar and it went off with a lot of authority! Mike and I studied this mortar's design and excellent photos of it in "Wikipedia", found by entering "Siege Artillery in the Civil War", yesterday after work, and believe we can put your scale 10" Seacoast Mortar on a diet that will shed as much as 1/3 of that 250 Lbs without changing materials or altering the original shape. After you find those photos, look at the one featuring a pair mounted on Morris Island by Federal troops in order to bombard Fort Sumter. This very high resolution photo can be enlarged several times until you can see that the cheeks of it's bed are hollow, just like the ones on our 1/2 scale 1797, 8" U.S. Land Service Siege Mortar.
George is correct, 105 pounds will be the scale tube weight. Add the windage factor, 1/40th, to the can diameter,(2.60+.065), then divide the original bore diameter,10.00", by that amount, (10.00/2.665=3.752) to get the scale factor. Cube this amount, (3.752 x 3.752 x 3.752= 52.82 ) to get the divisor. Divide the original tube weight by your divisor to get your scale tube's weight, (5,575lbs/52.82=105.55lbs.). See, George and the seacoast guys saved you 85 lbs already! Just kidding, the real weight savings comes from the fact that the cheeks are hollowed out on the inside, so while the flange all the way around the cheek may be as wide as 5", the actual thickness of the load bearing web is probably only 3/4". Without a drawing of the bed, it is difficult to know for sure, but we are betting that the inside of the cheek is a flat surface and that the protrusion visible on the outside, middle surface, is an increase in cheek thickness to about 1.5" in the area under and around the trunnions to take the shock of firing. Figuring the scale thicknesses and calculating the weights for all the sections, we figure each cheek will weigh approx. 30 lbs. or 60 for the pair. Add this to the 105lb. tube and you get 165lbs. To this, add about 5 lbs of hardware and 10 lbs. of oak or maple transoms and you get approx 180lbs total. It will be quite a bit easier to move this than a 250 pounder! We speak from experience; our 1/2 scale 1797 mortar with it's 200 lb. tube weighs 275lbs and is a beast to move any distance! This is our best guesstimate; actual casting results could be a bit different.
Regards,
Mike and Tracy
