Re: Need speed switch for DIY funicular/hillside elevator

["B Fuhrmann" <b-fuhrmann-usenet@xxxxxxxxxxxxxxxxxxxxxxxxx>]

<astutesolutions> wrote...
> Yes, something like this might work.  The spring/lock cable grap could
> be held in the open mode almost like a mousetrap with a little force
> that is easily triggered provided it could be done so that no jostling
> or sharp inpact would force it to snap.
>
> Another thought along a similar lines is to have two brake pads pushing
> on the cable with a spring applying the force (like an emergency brake
> on car?).  A fulcrum weight could hold the tension off of the spring
> keeping open and something like that centrifugal governor could lift up
> on the weight at higher speeds.  Cool.  Thanks!


The problem with the second solution is that a mechanical failure causes the
brake to release.
There is a chance of this with version 1 but fewer.

A second item that should be considered is that a fault should shut off the
drive motor and not allow it to be restarted by the standard controls at the
ends.  This is similar to automated machinery controls.

Since you have controls at each end, there should be wires in the circuit
that can be opened to shut down the system.
The mousetrap (I like that analogy better) opens the circuit until it is
mechanically reset.
Your control switches should be wired so that they have to be pressed AFTER
the mouse trap is reset before the car can move again.
DO NOT reset the mouse trap until after the cable is back on the capstan
and/or have a way to lock out the power to the circuits at the capstan end.
If this was an industrial control, the lock out would be mandatory.  At home
it depends on where the mouse trap is and how safe you want to be.  I
recommend having it.

Another part of the circuit should be a timer that shuts off the system if
the motor is running past the time the car should be at the other end.  This
will shut down the system if the cable comes loose at a time when anything
prevents the car from making the trip or a limit switch at the end fails.
This control should also not be overridden by the normal start buttons.

Bill Fuhrmann