The modern tendency in disk clutches, however, is away from those of few plates requiring a very high spring pressure - since the friction area is necessarily limited - toward the multiple-disk variety, in which a very large area is obtained. This allows of a very light spring pressure, and consequently is easier to engage and disengage and, for this reason, it is becoming more popular with owners and drivers than the variety requiring the extra-heavy effort. The construction of the three-plate disk clutch does not differ radically from one maker to another. Three fingers are used to clutch and declutch generally, the amount of movement being adjustable. A single spring of large diameter and large-sized wire is generally used, and sheet steel is used for one-half the clutch plates. Between the three-plate and multiple-disk are many gradations.
Fig. 53. Lanchester (English) Disk Clutch and Disk Brake.
In the true multiple-plate clutch, there are three general varieties met with in practice: the metal-to-metal with straight faces; the metal-to-metal with angular or other shaped faces, designed to increase the holding power; and the straight-face kind in which metal does not contact with metal, one member being either lined with a removable lining or else fitted with cork inserts.
A most unusual combination of clutch and brake is to be found in the English Lanchester cars. In this, as shown in Fig. 53, the multiple-disk clutch is placed at the forward end of the shaft, and consists of 12 external or driven disks and 11 internal or driving disks. These are comparatively small in size, and are stamped from flat pieces of steel, the external members having a square shape, with a projecting key at each corner, while the round internal members have six projecting keys.
The latter fit onto a splined shaft on which the keys correspond with the spaces inside the driving disks, while the keyways correspond with the projections or keys in the disks. In this way, all the driving disks are driven by the shaft, carr times. Be is an exterr have their in the corr driven slee.
When gether by the oil in mally is between disks slow of each dri latter are carried around with them. These must take the casing with them, because they are keyed into it,consequently when the oil is entirely squeezed out and the disks grip, the whole clutch revolves as a unit.
The brake, which is shown directly back of the clutch, but which is operated by a separate pedal, is constructed in exactly the same manner and is similarly operated. There is this exception, however, in that the external rings - the driven members in the case of the clutch - are in this case entirely stationary, being held by keys on the casing, which cannot turn. That being the case, as the pressure is applied through the medium of the foot pedal, and as the oil is squeezed from between the nine external and eight internal plates, the power is gradually absorbed, and the car slows down or stops according to the amount of force applied and other conditions. The two sets of plates are identical, and except for their number, are interchangeable. As has been stated, all these run in oil, and to make sure of a copious and continuous circulation, an oil pump is placed in the bottom of the rear end of the casing, being driven off the main shaft. To facilitate its use, the bottom of the case forms an oil well.
Fig. 64. Panhard Disk Clutch with Spring Fully Enclosed.
Fig. 55. Multiple-Disk Clutch and Transmission of Winton Cars Courtesy of Winton Motor Car Company, Cleveland, Ohio.