This blog chapter is in celebration of the centenary of the Royal Liver Building WT clock installation. Not to mention the timely publication of Colin Reynolds' fascinating record of its construction. These were the largest electrically driven clock dials in the world when installed in 1911. Colin Reynolds' book covers the story of its construction from within the Gent company. With many unique, original illustrations and photographs from the time. Bringing the entire clock installation to life despite the intervening century.
Colin Reynolds' excellent book detailing the construction and installation is available from Formby-clocks or from Reprint.
Books on Church or Turret clocks - Jeffrey Formby Antiques
The Great George Liver Clock : Reprint [No longer available?]
Gent enjoyed considerable, global publicity from the prestige of providing such a record breaking installation. Particularly for their newsworthy meal for 40 dignitaries around one of the completed dials. This led to WTs, for public dials, being sold right around the world. No doubt the sales of their impulse clocks systems increased as a result. WTs could be added to any impulse clock system. Often without the necessity for the special architectural details always needed by weight driven clocks. Not least finding room for the weight chutes.
The WT was a truly revolutionary public clock movement. Providing a compact, reliable and incredibly accurate performance independent of weather conditions. Moreover it did not need arduous, regular winding or bulky weight shafts to house massive weights. Nor was it subject to the wear and breakdowns to which the far more complex, weight driven clocks were prone. Thanks to its relative simplicity a WT did not require a skilled turret clock maker to maintain it. This made it particularly attractive in undeveloped countries. Even haphazard mains electricity supplies were no real hindrance. Because the impulse clock systems and WT movement usually ran on trickle-charged batteries. Allowing the WT system to cope with power cuts.
Royal Liver Building - Wikipedia, the free encyclopedia
These large WT movements were designed and hand built specifically to drive the hands of these enormous dials. Bigger, even, than the dials of the Westminster Clock which strikes the hours on Big Ben. The loads were made worse, on the Liverpool clock dials, by their exposure to Atlantic gales. Loads on exposed clock hands increase as the cube of wind velocity.
No practical mechanical clock could ever cope with such a task. Many unique problems were overcome in the manufacture and supply of the complete clock installation including the dials.
Accuracy, reliability and long life were essential. The WT is renowned for its accuracy under the most appalling weather conditions. Being also, and quite uniquely for a turret clock, as accurate as the master clock which controls it. With enormous reserves of torque to cope with icing and fierce, storm force winds on the giant hands.
Here is a view of just one of the four WT movements and the dial motionwork beyond. They are each mounted in separate, glazed, iron framed cases. These keep the mechanisms clean and avoids accidents to the unwary. The cases also provides unprecedented visibility of the clockwork mechanisms for visitors.
The darker roller assembly can be seen at the centre of the huge dial in the image above. Plain bearings would have had far too much friction and potential corrosion problems over time. Particularly in a maritime environment. While the rollers have provided reliable, low fiction bearings for 100 years.
The many tie rods and turn-buckles can be seen holding the cast framework of the huge dials onto the inner masonry of the tower. Lighting is provided so that the dials can be seen and read from a great distance at night. This stand-off dial design allows the tower to be closed behind the dial. Otherwise a huge hole would have been necessary right through each face of the tower to allow the dials to be evenly lit at night.
The main frame is diagonally braced against twisting. Resisting the reaction forces of the giant wormwheel as it drives the exposed hands. Frame bracing, in depth, is provided for the massive pendulum. A brass, hand setting dial is provided on the free end of the wormwheel shaft. The, long, bright steel, horizontal shaft near the bottom of the movement frame is the worm arbor (or shaft).
The freely pivoted, Hipp toggle (hanging from its bracket at top left) looks no different from that on my own relatively tiny WT. Almost hidden below the Hipp block and contacts are the contact locking electromagnets. Also wrapped in red, protective material. Just like the larger drive electromagnets. The Hipp toggle and its block form a simple, but totally reliable, electro-mechanical switch. Together, these apparently simple components constantly monitor the pendulum arc. Only giving a drive boost (via the large drive electromagnets) if the pendulum arc falls below the set limit.
Normally the toggle rattles freely back and forth across its block. Only when the pendulum swing drops low enough will the toggle catch in the block on the return swing. The toggle then depresses the block and firmly closes the attached electrical contacts. Electricity flows through the large drive electromagnets. Giving the pendulum a really strong push.
Note the heavy thrust bearings to resist the severe end-loads on the worm. The worm not only drives its wormwheel against the loads on the giant clock hands outside the building. It also locks the hands safely against any unwanted movement. Perhaps due to ice imbalances, flocks of birds on the clock hands or wind loading. Backlash would be very undesirable because it would show timekeeping inaccuracies on the minute hands of each separate dial.
Interestingly, it was the inability to limit variations between dials which excluded the use of four separate weight driven, turret clock movements. Gents were able to offer a guarantee that all the dials would show the same time thanks to their master clock control. The contract to build the Liver Clock installation stipulated 2 seconds per week accuracy. Few turret clocks can manage this.
On smaller WTs a hand wheel is provided, just here, to allow random rotation of the ball races. Presumably the friction would be too great in a WT of this massive scale to turn a knob by hand. The Gent engineers have cleverly provide auto-rotation. So nobody needs to worry about forgetting to turn the knob at intervals.
Pendulum top and bearing assembly from the other side. The cylindrical, black-painted counterweight of the gathering pawl and the pawl bearing can be seen centre right. The black bar hanging almost against the main frame is the pendulum crutch. Oiler caps can be seen on the pendulum bearings. The fine ratchet wheel (bearing rotator) is well seen here. The bearing shaft, ratchet pawl is rocked between adjustable stops by the swinging pendulum.
This incredibly simple mechanism, is used in a design of pure electro-mechanical genius. It forces the giant hands of the dial to follow the master clock exactly. Maintaining an accuracy to within a couple of seconds per week. The pendulum becomes a powerful and totally reliable electric motor. The WT mechanism harnesses this enormous power to keep perfect time.
Driven by the gathering pawl, the L-shaped lever lifts until it has been locked by a step in the relay electromagnet's armature. Now the gathering pawl can no longer reach the teeth of the wheel. A forward projecting pin, on the pawl, slides freely back and forth on top of the L-shaped lever. (without the pawl able to gather more teeth on the ratchet wheel)
The Gents' Waiting Train mechanism now seems almost blindingly obvious. Until its invention there was no way to synchronise a large and powerful public clock with a precision master clock. The greatest acts of mechanical genius often seem incredibly simple with our perfect hindsight. Yet, before its invention the problem was seemingly insurmountable.
The brilliant Gent engineer, A.E.J. Ball, was the genius who provided the solution. One which totally revolutionised public timekeeping. Clock dials, driven by WT movements, could now be easily fitted into slender war memorials and industrial chimneys alike. There was no longer any need to provide easy access to clock winders and minders.
Only the arrival of the Warren synchronous electric motor finally beat the WT for compactness. The synchronous motor driven, public clock dial was several decades away when the Liver building clock system was installed in 1911.
The motionwork provides the usual 12:1 ratio between the minute and hour hands. Normally the motionwork is fitted just behind the dial. In this case the loads on the giant hands are so high that an inboard motionwork is provided for each dial. The motionwork supports the inner end of the hour pipe on solid masonry. The cantilever bracket, behind the dial, supports the outer end. The great length between the bearings provides extra stability and distributes the loads more evenly. A closer view of the dial motionwork. The 12:1 reduction is provided by two reduction pairs of gears. Only two gear wheels and two pinions are required. Albeit unusually large ones in this case. Only the sheer scale of the wheels and supporting castings gives an impression of the huge size of the hands and dials involved.
The minute hand counterweight rotates once per hour on the arm between the cases housing the WT movement and its motionwork.
I am most grateful to Colin Reynolds, author and ex-managing director of Gents for sharing this information. He was also able to confirm the presence of two D-shaped, lifting pins and even provided a diagram of the electromagnetic locking of the extended impulse mechanism. Original images of the WT can be found in his book shown at the top of this page.