Hand Elevator And Dumbwaiter Question

The wheel diameters give a 1:2 reduction, as does the gear teeth combo. Multiplying, the total reduction is 1:4.

The handwheel could be mounted on a screw so that any force on the wheel lifts a brake pad, and letting go of the wheel reapplies the brake. To lower a load, you would have to lift it slightly at first to disengage the brake.

If you have a chain hoist handy you could demonstrate....the 10 to 1 or whatever ratio will hold the weight once suspended with no effort, it's because of the extreme ratio,,,,now if you want to move faster, more distance per pull, then you can add a counter weight separately attached and go to say a 5 to 1 ratio, or even more counter weight all the way till you are at 1 to 1 ratio....the reversible ratchet locks the pulley, and a governor to limit pulley speed....

Nope the high gear ratio dosen't hold the load it has something to do with a screw like the other poster said, but I can't see how it works.

That's a shame....

Well, the brake is easy if I remember correctly. The box is hung from the cable by a leaf spring articulated at each end. The center of the spring is the attachment point for the cable and the articulations are attached to the edges of the box. Mounted on the very ends of the leaf spring itself are the break shoes. When the cable pulls up, the articulations allow the leaf spring ends to pull in, releasing the shoes from the walls. But if the cable breaks, then the leaf spring straightens out and presses the shoes against the wall, slowing and hopefully stopping the decent.

Worm ans wheel gearing tends to self locking so the worm will drive the wheel but the wheel won't drive the worm.
Del

Metal to metal slopes have a slipping angle. If I remember correctly, steel on steel is 5 - 6 degrees angle. Above, they all slip, below that all have traction and lock.

The worm to gear setup works two ways.:

1,. You move the worm and the gear follows. You overcome friction and the necessary work done. No problem, only inefficient. Inherently safe.

2,. Gear to worm. The gear pushes against the worm. But the effective transfer angle is under the 5 degrees, and it locks. Both the gear tooth angle and the worm's end bearing friction needs to be regarded, as both experience the same thrust, hence produce the same breaking force.

This is simply the long winded, catty version of the physics.