11-25-2012, 05:37 PM
Robert,
Using your comments about the bent beams as inspiration, I've started working on a revised drawing of a DeReffye type onager. Hopefully I will have more time to work on it tonight. It seems a reasonable assumption that they would have used either a log specially selected for it's natural bend, or possibly steam bent one to fit rather than carving the curvature into it. Doing so would violate the grain and invite splitting under pressure.
One other thing I plan to incorporate is a winch drum that starts out thicker at the outer ends and tapers gradually towards the middle. If the rope is anchored near the
ends it will start out winding quickly when the draw weight is less and the winch will gain mechanical advantage, and the rope's angle will improve, as the arm is pulled further back and the tension increases.
Using your comments about the bent beams as inspiration, I've started working on a revised drawing of a DeReffye type onager. Hopefully I will have more time to work on it tonight. It seems a reasonable assumption that they would have used either a log specially selected for it's natural bend, or possibly steam bent one to fit rather than carving the curvature into it. Doing so would violate the grain and invite splitting under pressure.
One other thing I plan to incorporate is a winch drum that starts out thicker at the outer ends and tapers gradually towards the middle. If the rope is anchored near the
ends it will start out winding quickly when the draw weight is less and the winch will gain mechanical advantage, and the rope's angle will improve, as the arm is pulled further back and the tension increases.
P. Clodius Secundus (Randi Richert), Legio III Cyrenaica
"Caesar\'s Conquerors"
"Caesar\'s Conquerors"
