Rick, have you given any thought to the type of iron you want in your 8” Mortar? We do not know anything about Hern Iron Works. You should find out what type of cast iron they use before you send them or Anyone a check for $2,600. Does this foundry offer a good solid warrantee on their cannons designed for shooting? Also, most important, do you know what type of cast iron they use in the 8” mortars they sell? Are you going to use your big, bad, 8”, fire breathing, mortar for strictly “decorative” purposes, to fire blanks or to launch 50 Lb. shells? Remarkably different pressures associated with each use!
from their website:
“Hern Iron Works makes no Warrantee whatsoever concerning its cannons. They are sold for decorative purposes only and we do not imply that they are good for anything else.”
Buyer accepts all responsibility for all use or misuse of the cannon. However, if at any time you are unhappy with a Hern cannon, you may return it, postpaid, to the foundry for replacement or refund.
Mike and I studied cast iron quite a bit before we chose 4150 Ordnance steel with which to make our cannons. There are four types of cast iron. For critical, read stressful applications, Grey Iron is the worst. It is extremely brittle. White Iron is very nearly as bad. Ductile Iron is better, but lacks the strength of Malleable Cast Iron which is what La Pans Foundry used to make the 4” Cannonballs we use in the 1797 Mortar.
Gray cast iron is by far the oldest and most common form of cast iron. As a
result, it is assumed by many to be the only form of cast iron and the terms "cast iron" and "gray iron" are used interchangeably. Unfortunately the only commonly known property of gray iron- brittleness- is also assigned to "cast iron" and hence to all cast irons. Gray iron, named because its fracture has a gray appearance. It contains carbon in the form of flake graphite in a matrix which consists of ferrite, pearlite or a mixture of the two.
The flake-like shape of graphite in Gray iron exerts a dominant influence on its mechanical properties. The graphite flakes act as stress raisers which may prematurely cause localized plastic flow at low stresses, and initiate fracture in the matrix at higher stresses. As a result, Gray iron exhibits no elastic behavior and fails in tension without significant plastic deformation.
The disadvantages of Grey Cast Iron are that it is Brittle (low impact strength) which severely limits use for critical applications.
Within Grey Iron, Graphite acts as a void and reduces strength. Maximum recommended design stress is 1/4 of the ultimate tensile strength. Maximum fatigue loading limit is 1/3 of fatigue strength.
Malleable Cast Iron, by contrast, is tough, strong and suitable for high strength applications and has a modulus of elasticity which far exceeds that of Grey Iron.
Several people Mike and I know have purchased Cannons from Hern and are pleased with them, however none of these people are shooting anything but blanks. Does the 8” mortar have a steel liner?
We know you are anxious, Rick, but before you stand next to that big mortar, with a friction primer in it’s vent, do a bit of research and get some answers.
Two cautious cannon makers,
Mike and Tracy
