It takes 50 minutes to cook a full stack of 300 metal in a stone forge.

A 3x3x3 metal box costs 11.1 stacks of metal ore.

Vault = 3.33 stacks

Heavy turret = 5.4 stacks

Cryofridge + 17 pods (ASA) = 1 stack

Indy forge = 16.66 stacks

Motorboat = 8 stacks

Hope this helps!