Myles, Going back a few posts, to the davits on top of your tower...... As it is necessary for the davit to pivot on the vertical axis, the davit arms are set into a corresponding vertical pipe "sleeve". For instance, a davit made of formed 3 inch pipe may be fitted down into a 4 inch schedule 80 vertical sleeve. This would reduce the I.D. of the sleeve pipe for a better close tolerance fit with the 3 inch. A collar ring would be at needed length from bottom of the 3 inch to sit on top of the opening of the 4 inch vertical. On larger capacity davits a grease cert would allow for maintenance lubrication of the inner gap between the two sized pipes. Naturally, all was engineered according to the required capacity of the davit, and on occasion an arm was affixed to the davit just above the sleeve pipe to assist with turning of the davit arm. The size and weight of the top PRV and diameter of the column (center line of davit distance to O.D. of column) would most likely be the determining factor for size and capacity of the entire davit arm. Just a few notes to assist with just how prototypical you wish to be in detailing.
Great work and anticipating the final completion, and what end product you plan to be shipping by rail.
Jesse TCA 12-68275
