I need help using a servo as a pulley

I'm currently making a battle bot for year 10 assignment and i had an idea to have the handle of the axe attached to an axle and a servo with a pulley on the end so it can pull the axe down on a spring or something, the idea was to somehow release the tension on the pulley so the spring pushes the axe, but I don't know if this idea is possible mainly because I don't know how i could make the pulley just release smoothly then retract the axe.

Here is an idea: have the servo drive a cam to force the axe downward and a coil spring to pull the axe back up.

The thing is i'm not sure if the servo will move fast enough or have enough force to actually do any damage, I do like the idea though.

Or, have the servo pull the hammer up, and the spring pull it down when the cam releases. Then it can accelerate freely.

This was the original idea, do you know if you could make the servo release freely without have to cut the rope, because it will need to retract. If not i think i will start looking into your idea

Well I would use a "clutch". Engage to lift, stop to hold, release the clutch to lower the hammer. The clutch could be a friction plate or pin.

What if i made the servo spin a gear that had a triangle cut out of it so it stops spinning the pulley and it lets the axe swing from the spring?

Kind of looks like a cam, doesn't it?

You see, the way you are doing it looks like only a one shot. I'm talking about using a servo to wind up the spring. The cam could have a spiral profile to wind up the hammer, and a "cliff" back to the center, to release the hammer.

Actually you might not need a spring with sufficient weight in the hammer.

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