How long did it take to build various siege engines? I understand this can vary widely based on the size of the engine etc., but I'd be interested in somehowsomewhat average values. Let's say a stationary trebuchet, a normal siege tower and a ballista. What would be the time (man-hours or something) to build each of these?
I'm primarily interested in the (early) middle ages, but ancient time or renaissance answers are also welcome.
