Brainstorming the hand/winch operations

When I last left this blog, I was beginning the brainstorming process for the design of a stage elevator based on certain specifications.  The main concern when operating this lift is safety, for both the operator and anyone (or thing) being lifted.  If the desire is to have the ability to operate the lift both by hand or using a standard endless loop electric winch, my first thought was to couple the system in a manner that would allow operation of the winch by hand if the electric winch ever failed.  The transition between hand and winch operation should be quick and easy, with the ability to switch in low lighting and relatively intuitive.  What if a circuit breaker blows?  What if the winch dies suddenly?  Of the many things that could cause winch failure, I wanted a system that would allow a stagehand to quickly switch to ‘hand’ mode and complete the lifting move (or lower to safety!).

The weight lifted should be counterbalanced using an arbor system.  I’ve sketched out a quick rendition of what my original thoughts were, and it involved a wheel and a ‘power’ drum around which lifting, lowering and winch wires would be attached.  When you wanted to operate the lift using the winch, everything was already in place: winch connected to power drum, drum connected to counterweights, counterweights connected to lifting platform.  Torque applied by the winch would transfer through to drum which then would raise or lower the counterweights and thus the platform itself.

If hand operation was necessary, the changeover would be simple.  Disengage the winch via a to-be-designed clutch (after brakes have been applied to stabilize the lift platform) and insert a wheel/hand crank into the end of the power drum.  Release the brakes with a foot-operated brake override and crank away, either up or down.

Here’s a sketch of the idea:

The interesting thing about this idea is that the wheel/crank is removable, so during winch operation the wheel can be tucked safely away from the action and is certain not to injure anyone passing by.  One of the main issues initially seems to be the fleet angle (ie. the angle of the wire from the power drum to a block…as the wire wraps around the drum this angle will change) and the clutch system.  Also, when the platform has been fully lifted, what holds it in place?  Are the brakes engaged?  Do you leave the winch on, providing a torque?  How about a solenoid-activated bolt system that locks the platform in place at stage height?  These are all questions that I am keeping in mind as I move forward…

A second idea is a modification in the manner the lift is hand operated.  Instead of a crank, the operator pulls a loop of rope directly attached to the counterweights.  Something like this:

However, this is just a rough draft.  More to come!!

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