[LT] Portcullises

[Bruno]

Originally Posted by Figleaf23

Eight men to operate a mechanism for lifting a 900lb grate is only slightly less off that 8 men to operate a mechanism for lifting a 450 lb grate.

I'm finding that a rather extreme statement, but then folks basing calculations off of maximum lift or maximum carry are also striking me as presuming rather extreme levels of resistance.

If my soldiers can only go around the winch/drag the rope at about a yard a second (which is what maximum encumbrance gets us) that gate isn't going up very fast at all - if there's any benefit from pully ratios, the gate is going up in something like 1/4 the rate of land-based travel (Depending on the ratio) - a 10' gate going up at 1/4 yard per second with some guy standing over the men with a whip and yelling HEAVE is not how I envision this sort of mechanism working. That's hauling an extremely large seige engine, not lifting up your own dang portcullis. :/

Shooting for a felt weight-per-man in the ~60 lbs range (like the usual cited maximum military marching load) seems like a far more sensible target - they can slog along at a reasonable clip and won't be exhausted at the end of it.

The mechanism has to lift the gate and the weight of the cables/ropes. A reasonably simple pulley mechanism is pretty efficient but requires significantly longer ropes (more weight and much more room to work in) or a winch, which introduces more significant mechanical efficiency problems if I've got this right.

I'm not an engineer, and the only one I can easily reach is an electrical engineer, but I'll see if I can dig up someone who can eyeball it.