mklotz
Well-Known Member
I built Elmer Verburg's Rope Drive engine as my first "large scale" engine back when I was just starting out in this intriguing hobby. I thought I would never finish but, with the make-every-part-a-project-in-itself approach, I mustered through and, after a whole summer, managed to get it done - this was back when I had a full time job - designing in-orbit interception algorithms, not that it matters.
It's a very satisfying model to make though I wouldn't recommend it as your starting project. It certainly gets people's attention at exhibitions, though.
Some remarks...
The flyball governor actually works - a linkage (not easily seen in video) links it to the main steam valve. It has an adjustment screw for setting the engine speed.
The "rope" is a continuous loop of three-ply thread. Weaving the ends together and sewing them into place will test your patience but it's straightforward if you make a fixture to hold everything in position while the work is done.
Rope has the unfortunate property of changing length with changes in atmospheric humidity. Ropes would slacken and slip on the pulleys. This problem was solved by having the rope pass through an idler pulley. A weight acted via another section of rope on this idler to provide constant tension on the drive rope, thus taking up the slack as it developed. As can be seen, this mechanism is faithfully reproduced in Elmer's model.
Everyone seems to think that the rope grooves in the flywheel and jackshaft pulley must be thread-like in form, i.e., a continuous spiral. They aren't. The grooves are separate and parallel. I don't know how this misconception arises but it's a persistent one. I had one guy, standing in front of the running engine, tell me it couldn't possibly work if the grooves weren't thread-like.
[ame]http://www.youtube.com/watch?v=jlW3sv9ZKxs[/ame]
It's a very satisfying model to make though I wouldn't recommend it as your starting project. It certainly gets people's attention at exhibitions, though.
Some remarks...
The flyball governor actually works - a linkage (not easily seen in video) links it to the main steam valve. It has an adjustment screw for setting the engine speed.
The "rope" is a continuous loop of three-ply thread. Weaving the ends together and sewing them into place will test your patience but it's straightforward if you make a fixture to hold everything in position while the work is done.
Rope has the unfortunate property of changing length with changes in atmospheric humidity. Ropes would slacken and slip on the pulleys. This problem was solved by having the rope pass through an idler pulley. A weight acted via another section of rope on this idler to provide constant tension on the drive rope, thus taking up the slack as it developed. As can be seen, this mechanism is faithfully reproduced in Elmer's model.
Everyone seems to think that the rope grooves in the flywheel and jackshaft pulley must be thread-like in form, i.e., a continuous spiral. They aren't. The grooves are separate and parallel. I don't know how this misconception arises but it's a persistent one. I had one guy, standing in front of the running engine, tell me it couldn't possibly work if the grooves weren't thread-like.
[ame]http://www.youtube.com/watch?v=jlW3sv9ZKxs[/ame]
