(This relates to the arm idea shown in the September 11, 2013 10:47AM post. That's the post I clicked "reply" in!)
I don't think this 2-joint arm scheme works as-is, because the string headed for the second joint will float off the left-hand bolt when the first joint bends a bit to the left.
I assume you can't stand a full wrap around the bolt, to keep the string in position, because the friction would be too great.
You could use a pulley instead of the bolt to reduce friction, but when the string goes more than one turn the incoming and outgoing are going to rub and likely cause some erratic behavior.
Perhaps some guides to keep in and out apart could do the trick. The bolt pulley could be just a flat roller, and little guide pulleys could force the string to follow a very slight spiral to avoid interference between in and out strings.
What you'd really like is some frictionless guide to get the string past that first joint. Bicycle brake cable...
I don't think this 2-joint arm scheme works as-is, because the string headed for the second joint will float off the left-hand bolt when the first joint bends a bit to the left.
I assume you can't stand a full wrap around the bolt, to keep the string in position, because the friction would be too great.
You could use a pulley instead of the bolt to reduce friction, but when the string goes more than one turn the incoming and outgoing are going to rub and likely cause some erratic behavior.
Perhaps some guides to keep in and out apart could do the trick. The bolt pulley could be just a flat roller, and little guide pulleys could force the string to follow a very slight spiral to avoid interference between in and out strings.
What you'd really like is some frictionless guide to get the string past that first joint. Bicycle brake cable...