Exposed clock hands not only have to keep accurate time but are subjected to gales, icing, wind blown debris and everything else the elements can throw at them. Resistance to rusting is a serious matter over very long periods of exposure without easy access.
Sealing the motionwork within a closed container provides the rare chance [with clockwork] to apply a long-lived lubricant. Without the risk of contamination from the often-dirty environment. Motion work is often housed in poorly sealed roofs and towers. There is the risk of falling whitewash in stone and brick buildings. With the added risk of woodworm dust and birds nests in all others. Larger birds can fill a tower with decaying twigs and nesting debris over time unless the open louvers are wire mesh screened.
While a securing, spring washer, with locking screw, is provided for the hour hand. The hour hand fits onto its machined square on the pipe first. Then the square hole in the washer is fitted over the pipe. Rotating the washer by 45 degrees brings the sides of the square aperture into the slots provided by the hour pipe. The screw stops the washer from rotating away from the locked position. A very simple, but robust and reliable, fixing. The spring washer is likely to be made of phosphor bronze for very long life.
A screw-threaded barrel has large screwed rings to fix the assembly firmly onto the dial board and allow some linear adjustment. In this case the length of the barrel suggests a dial board or wall about 3-4" [70-100mm] thick. Longer and shorter threaded barrels would be specified for various dial and wall thicknesses at the time of ordering and later installation.
Here a sealed motionwork is housed in a cast, protective cylindrical can or case. A short lead-off rod, with typical universal joints at each end, is seen fitted between the WT output shaft and the motionwork housing. The universal joints provide for thermal expansion and misalignment without binding. The outer screws [with washers] are not tightened but merely avoid dislocation of the forked and pinned joint arrangement. Some of Gents' universal joint designs have a thickened centre section to the pinned half to ensure the joints remain safely together. But still allow the pins to slide freely in the slots without friction.
The sealed gearing arrangement is identical to open motionwork. Using combinations of different metals ensures that the minute shaft does not wear rapidly against the inside of the hour pipe. Nor will they rust fast together over time. As would a steel minute shaft in an iron hour pipe. The combination of dissimilar metals runs together with low friction without the galling expected of using similar metals.[Steel on steel is usually a bad choice, for example] Gents' were early user of stainless steel and hard chrome plating to ensure maximum longevity. The minute shaft [minute arbor in clock-speak] is probably made out of stainless steel.
For the clock enthusiast finding original components like these is all part of the pleasure of owning a WT turret 'clock' movement. Very often demolition crews will see the value in saving the clock movement from a long-disused factory or office block. Since it can be so easily turned into cash. However they will usually ignore the motionwork and lead-off work as being too insignificant to be worth the trouble of dismantling it. Nor is there much metal scrap value to be had. Access to exterior clock hands is very likely to remain difficult to impossible on old, industrial buildings. So all these vital parts are usually lost to the collector.
There must be original WT installations still in use. Though maintaining them must be very difficult without skilled help. Or the continued employment of trained, existing staff. Not that long term employees are likely to be found in our modern, ephemeral world. It is so much easier [and cheaper] these days to simply replace everything mechanical with a compact electric motor. Fitted just behind the dial, switched on and usually forgotten. Modern clock installations will often have a computerized "box of tricks" to ensure automatic summer time changes. Thus, has turret clock practice changed to match the latest technology, yet again.