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[Bill]

2.3.3 Rope Guiding Equipment

In the case of circulating monocable ropeways the parts used to guide the rope are the bullwheels and the sheave assemblies. These fulfill the following functions:

1. Guide the rope at a predetermined height and take up the vertical and horizontal forces (dead weight of rope, carrier weight, rope deflections, wind load, variations in line geometry, etc.)

2. Deflect and return the haul rope.

Bullwheels

Bullwheels are rotating rope supports which impart their curvature to the rope. The haul rope is returned or deflected by means of bullwheels in the stations and angle constructions.

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The angle of wrap on return bullwheels is between 45 and 240 degrees. In order to keep the bending stress exerted on the haul rope within acceptable limits (fatigue strength) the diameter of the bullwheel is usually a minimum of 80 times the diameter of the rope.

The area where the rope contacts the bullwheel is covered with a liner (made of rubber) or with liner segments (usually made of plastic).

The choice of bearing system for bullwheels is of major functional significance. In the case of bullwheels which are only supported from below (cantilevered configuration), the design solution must ensure that in the event of bearing failure the bullwheel is prevented from coming off its mounting at least long enough for the damage to be recognized and the lift brought to a standstill.

[Bill]

Sheave Assemblies

A sheave assembly is a group of sheaves arranged one behind the other on a support structure, which is used to deflect and guide a moving rope.

On passenger ropeways the sheaves are fitted with rubber or plastic liners. Lined sheaves have the following advantages over unlined sheaves:

1. Reduced rope wear (lower surface pressure)
2. Higher ride comfort (lower stand-induced vibrations)
3. Less dynamic stress on mechanical parts.
4. Lower noise emission
5. Simpler and cheaper to replace once worn.

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Sheave assemblies are fitted with rope deflectors and rope catching shoes to intercept the haul rope, should it leave the sheave groove and drop off the edge of the side plate. If the rope drops into the rope catching shoe the break fork will snap, thus interrupting the safety circuit and bringing the ropeway to a standstill.

In accordance with the direction in which the load of the rope is exerted of the sheaves, we distinguish between support sheave assemblies and depression sheave assemblies.

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Combination sheave assemblies are special type of sheave assembly used where rope reaction is subject to reversal with varying position and load status of the carriers. In order to ensure reliable rope guidance at the inflection point where rope reaction is reversed, i.e. at zero rope deflection, the contact pressure is maintained either withthe aid of compression springs which press the sheaves against one another, or by a forced deflection of the rope. As well as reducing the number of towers required, combination sheave assemblies bring about an improvement in ride comfort thanks to the smoother passage of grips over towers.

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[Duck]

This is great stuff, Bill. Thanks for taking the time to write all this up!

-Iain