Gent's Fig.C271 restoration. [Pt.2]


It was found that the movement's paint best responded to a dry rag. Oil from previous lubrication tended to remove the silver paint on the motor plates and required special care. Oil does have the advantage of being a gentle cleaner on most surfaces. While not allowing further rust to form. It also provides a more acceptable finish. Particularly where there is considerable paint damage.
The exposed steel shafts were cleaned of rust. The motor's armature shaft bearings were replaced. The bronze gearbox bearing bushes were removed, cleaned and refitted. Interestingly, the bearings were not interchangeable. Suggesting that the entire movement was handmade. This was certainly true of the Waiting Trains. Each WT was made to order, or in small batches, from the basic castings.

Here is the final drive shaft with sturdy gear wheel, hand setting clutch (and its locking/unlocking wheel) and a universal-expansion joint.

By loosening the large wheel the clutch is freed and the clock hands can be turned to the correct time. The wheel is then tightened and the drive to the hands continues. A simple but foolproof system which may offer security against damage should the clock hands become locked by ice or some obstruction. The clutch plate can be seen separated and tightened against the gear wheel in this image.

The knurling on the edge of the clutch's friction wheel allows a good hand grip under all conditions. Yet is deliberately made too large, smooth and inaccessible for the application of ordinary tools.

It was not unknown for some workers to apply huge torques where only finger tight will do. They reasoned(?) that if tight is good then really tight must surely be better. Even if it requires a long bar or pipe on the spanner and the nut or bolt will never (ever) come undone again. The force applied may even destroy the thread. By the simple means of providing a hand wheel such cases of operator idiocy are largely avoided.

Here are the cast base plate and gearbox after considerable but careful work to clean and restore the mechanical details to fully functional.

The brass item near top centre, with two protruding pins, is a typical universal joint starting the lead-off work to the clock hands. The pins will drive a similar plate which has two matching slots. Thus allowing for variations in temperature and building movement without causing binding. Such simple details have been part of turret clock installations for centuries.

It was the standard to drive the rods to the dials at one revolution per hour. (Or minute hand speed) The hour hands were driven via a simple 12:1 reduction gearing from the minute hands just behind the clock dial.

Most turret clock hands were balanced to reduce backlash and stress on the whole system. Otherwise the hands would try to run downhill and struggle to climb back up again.

Temperatures can soar to scorching hot and plunge well below freezing in roof spaces and unheated towers. The great length of some connecting rods, between the clock movement and distant dial, would cause them to grow and shrink considerably with the constantly changing temperatures.

Timber in buildings is also subject to movement with changing temperature and humidity. These sliding universal joints allow for linear, thermal expansion, building settlement and small changes in drive direction. Large changes of direction would normally utilize pairs of bevel wheels.

Though contrate gear wheels were not unknown. These used a gear wheel with raised teeth around the edge like a king's crown. Sometimes driving a lantern rather than a solid pinion. This gearing practice was copied from windmills. It should be remembered that lantern pinions never drive. They are always driven by another gear.

Click on any image for an enlargement.

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