Quote:
Originally Posted by audietron
To clarify on what Eric has said, a 3/4" aluminum rod is propelled forward by surgical tubing. The whole set is pulled back by a winch with a dog gear, when the dog gear is released the rod is launched at the ball.
here is exactly what they describe. http://simbotics.org/first/2008#robot |
Does a pulley spin free on a shaft when dog gear is released?
If so, this lowers peak velocity of ram, since rotating winch pulley/drum stores energy as unwinding cord spins it up to peak rpm.
A better system, when triggered to shoot, will have the contracting surgical tubing be accelerating only the ram itself and whatever low mass tension element(s) are attached to the ram.
Plus, what happens to the winch cord as pulley/drum spins free when ram fires? Does it reverse wrap, such that the next wind gets done continuing in the reversed wrap direction. If the ram travel is small, not so many turns of winch will be needed, so less chance of cord getting tangled up during free spin.
If variable power shot is desired, reversing the rotation for alternating shots is useful, for when a multi-turn potentiometer is used to control cutoff point for desired amount of wind, since the pot only has a limited number of turns over its full range. Winding opposite ways for alternating shots keeps the pot from hitting its end of range.
-Dick Ledford