If you have a 100W electrical load and you drive 100W plus efficiency losses, say 110W, into the generator, things will be in a state of equilibrium, with 100W being converted from mechanical input power into electricity, and the other 10W of mechanical input power being eaten up by losses.
Now suddenly put 1kW of mechanical power into the machine; at that instant, before the rotational speed can change, the 100W electrical load will continue to present the same mechanical load to the prime mover. Things will not be in equilibrium, and the machine's rotational speed will accelerate. Depending on circumstances, this may or may not increase the electrical load. Certainly the generated voltage will go up, and any simple resistive load will therefor absorb more power, but maybe you have some regulation such that the load continues to draw exactly 100W.
So assume the load continues to draw exactly 100W. Where does the extra 900W of mechanical power go then? The machine's speed must increase until the losses equal the mechanical driving power; so it ends up turning extremely fast, the increased power going into increases in friction in the bearings, windage loss due to the rotating parts, eddy currents in the magnetics (and doubtless a couple of other things I forget at the moment), none of which are desirable.
You would find that, without exceeding the machine's electrical rating, you would quickly exceed its mechanical ratings, i.e., probably long before you got to 1000W, the rotation speed would be several times the suggested speed, and catastrophic failure would likely result. Note you can do this with no electrical load on the generator at all.
You are likely to get some good ideas here - all images connect to a related webpage.
Something like these adapters would allow you to connect two threaded studs together which should meet your need.
This arrangement is similar - tube with both ends threaded.
Something like this can have the cable from above entering from the opposite end to the stud (black as shown here, but with an end that is wider than the exit hole so it cannot escape. The stud is screwed in from the other and and tightens against the broad end of the cable.
Items like these and like these are not suitable directly but may give ideas.
Best Answer
Look at piezo linear actuators. They work at relatively low energy rate, slow speed, low torgue, accurate movement in range of few mm. With correct driver the motor will consume very low power