【正文】 t center and so alleviate rope fleeting angle problem, even with sheave wheels at closer centres [11]. The rope safety factor The graphs in Fig. 5 illustrate the endload advantage with reducing static rope safety factors. While serving their purpose very well over the years, the static safety factor itself must now be questioned. Static safety factors, while specifically relating to the static load in the rope were in fact established to take account of: a. Dynamic rope loads applied during the normal winding cycle, particularly during loading, pullaway, acceleration, retardation and stopping, b. Dynamic rope loads during emergency braking, c. Rope deterioration in service particularly where this is of an unexpected or unforeseen nature. If peak loads on the rope can be reduced so that the peak remains equal to or less than that experienced by the rope when using current hoisting practices with normal static rope safety factor, the use of a reduced static rope safety factor can be justified. The true rope safety factor is not reduced at all. This is particularly of importance during emergency braking which normally imposes the highest dynamic load on the rope. Generally, the dynamic loads imposed during the skip loading, cyclic speed changes and tipping will be lower than for emergency braking but their reduction will of course improve the rope life at the reduced static rope safety factor. The means, justification and safeguards associated with a reduced static safety factor are discussed in [4,7,9,12]. Based on the static rope safety factor of 4, the rope endload of 12843 kg per rope can be achieved. With twin ropes, this amounts to an endload of 25686 kg. With a conveyance based on 40 % of payload of 18347 kg with a conveyance of 7339 kg. There are hoisting ropes of steel wires strength up to Rm = 2300 MPa (Rm up to 2600 MPa [6] is foreseen) used in deep shafts. There are also uniform strength hoisting ropes projected [2,8]. Conveyances The winding machines made from a light alloy are used in hoisting installations in deep shafts. The skip factor (S) has been defined as the ratio of empty mass of the skip (including ancillary equipment such as rope attachments, guide rollers, etc) to the payload mass. If the rope end load is kept constant, a lower skip factor implies a larger payload – in other words, a more efficient skip from a functional point of view. However, the higher the payload for the same rope end load, the larger the outofbalance load – implying a more winder power going hand in hand with the higher hoisting capacity. If, on the other hand, the payload is fixed, a lower skip factor implies a lower end load and a smaller ropebreaking load requirement. Under these conditions, an outofbalance load attributable to the payload would remain the same, but that due to the rope would reduce slightly. The sensitivity of depth of wind and hoisting capacity to skip the factor is illustrated in Fig. 6 and 7. A reduction of skip factor from 0,5 to 0,4 results in a depth gain of about 40 m for Blair winders and 50 m for singlerope winders. The increase of hoisting capacity for a reduction of skip factor by about 0,1 is about 10 %. Typical values for the “skip factor” are about 0,6 for skips and about 0,75 for cages for men and material hoisting. Reducing skip factors to say about 0,5 is a tough design brief and the tradeoffs between lightweight skips and maintainability and reliability soon bee evident in service. The weight can be readily reduced by omitting (or reducing in thickness) skip liner plates but this could reduce skip life by wear of structural plate leading to the high maintenance cost or more frequent maintenance to replace thinner liner plates. Similarly, if the structural mass is saved by reducing section sizes or changing the material from steel to aluminium for example, the structural reliability is generally reduced and the fatigue cracking bees more efficient. Some success has been achieved in operating large capacity all – aluminium skips with low skip factors but the capital cost is high and a very real hoisting capacity constrain must exist before the additional cost is warranted. It would appear that the depth and hoisting capacity improvements are better made by reducing the rope factor of safety and increasing the winding speed. The philosoph