Usually I give a more specific title to my posts, but the problem is I don't even know the name of what I'm looking for. So I'm going to have to describe it...
Summary: I am looking for a small device which can "quickly" move a weight (about 1/4 kg) back and forth along a short distance (about 3 to
5 cm).Imagine that you have a steel rod hanging from a ceiling. It's not a very big rod, only about 18cm (7") long and at most twice as thick as that part that contains the ink in ball point pens. At the other end of this rod (pendulum) is a weight (about 1/4 kilo) that can slide up down the rod, only I want to anchor this weight to behave as follows:
When the rod moves through the vertical position (ie. vertical from the ceiling), the weight should move closer to the ceiling by about 3 to 5 cm. When the rod has reached a high point in its path (and is therefore no longer in motion), the weight should retract to its starting position (see diagram, below).
The question is where can I find (and how is it even called) a device that will be able to move the weight as I described? The exact times when the weight movements happen may vary (ie. I am not concerned about the measurement portion of this problem. We can assume that there is a signal to the transducer that says 'extend' or 'retract'. But (1) the rising should be "quick" even though it may be acting against up to 5g (due strictly to the swinging) (2) the weight has to be able to maintain that 'risen' position until it gets the signal to retract (3) the retraction is never against more than 1g (if you imagine that the pendulum can rise above the level of the ceiling).
Apologies if I have not adequately described what I am looking for. In that case, please ask for clarification and I will provide it.
Thanks for any tips, Csaba Gabor from Vienna
Ceiling | | | | | weight (rises as it swings through) | | -
Ceiling \ \ \ \ \ \ \ weight (retracts to end at high point) -