Electrokinetica The Electro-mechanical Museum

St. Pancras Chambers - Waygood Otis DC goods lift

Introduction

Goods lift well

Goods lift well

The landmark at Kings Cross now known as St. Pancras Chambers opened as the Midland Grand Hotel in 1876, with 300 rooms in a splendid Victorian Gothic building designed by Sir George Gilbert Scott. Although well appointed in its day, it did not keep up with the times and closed as a hotel in 1935, whereafter it served as railway office accommodation for the next five decades. After failing a fire safety inspection in the 1980s it was vacated, without ever having been 'modernised'. As a result of this unusual history the building had many remarkable features and early fittings surviving in context until a major refurbishment began in 2006. Amongst the many interesting electrical items were the 1930's lift machines and controllers in very original condition. The electrical equipment of the two main passenger lifts and one service lift was considered worthy of conservation, and removed from the building intact during the enabling works.

The goods lift

This pre-WW2 installation by Waygood Otis was supplied with DC power for its entire working life, and by the time it was decommissioned in the 1980s this was a very unusual state of affairs. It is typical of the DC practice of its era and has all the essential features required of a basic service lift. As it covered only four floors at moderate speed there was no need for great complexity in the control functions. Floor control is automatic but handles only one call at a time, i.e. when a push is operated the lift will proceed to that floor and ignore all other calls until stopped. This system (equivalent to the operation of a taxi cab) is ideal for goods lifts where it may not be possible to embark any other passengers or loads until the journey underway is completed and the car vacated. The car ran on T-section steel guides inside an existing stairwell serving the lowest three floors of the building and a mezzanine, and was probably reworked or replaced at least once, at which time some extra safety features were installed. In its final implementation it was designated as a goods lift with 10 cwt capacity, but the running gear remained unaltered throughout. The motor room was a wooden-screened compartment built within an ordinary room over the head of the stairwell, and was probably one of the only lift motor rooms ever to contain a fireplace! The electrics are especially interesting due to the early type of controller used, which was a rare breed even during its last working years. Hefty solenoids operating large contact trees, drawing big hot arcs from the contacts, make it interesting to watch in action.

Automatic controller: how it works

6-floor DC controller

6-floor DC controller

A typical lift journey using this controller progresses as follows:

DC controller schematic

DC controller schematic

Two main contactors are employed, one for 'up' and one for 'down'. They are electrically and mechanically interlocked, and carry the motor line contacts and those for both electrodynamic braking and control of the main brake magnet. The actual reversing of the motor is carried out by contacts engaging with the interlocking lever, which move only when the direction is reversed. Pressing a push energises a floor relay, closing its own holding circuit and energising whichever direction contactor is selected via the changeover contacts in the floor selector. The appropriate contactor operates (setting the direction contacts if necessary) and applies power to the brake magnet, motor and accelerator solenoid. The latter raises a wiping contact slowly under control of an oil dashpot, cutting out the starting resistance step by step, finally bypassing the series field and inserting its own cooling resistance. When the correct floor is reached the contactor circuit is broken by the floor selector and all coils are de-energised at once, bringing the car to a rapid stop as the motor armature is short-circuited. The traction machine itself is of very conventional design and simple robust construction. The two-pole compound-wound motor runs at 800 rpm and drives a four-groove sheave with vee-profile grooves via an under-driven worm reduction gear.

Recovery

The recovery was a team effort involving the surveyors and contractors engaged on the refurbishment works, the specialist lift decommissioning contractors and ElectroKinetica. First, a schedule of equipment was made by Dave Cope and Lucien Nunes of ElectroKinetica and submitted for approval by architects RHWL and contractors Laing O'Rourke. The electrical equipment was then documented and photographed and the wiring traced by Lucien and Dave. Lift-Out, the lift removal contractors then made a superb job of dismantling and extracting the heavy plant from an awkward and inaccessible place with the minimum of damage, and Edward Rutter transported it to the workshop with his customary efficiency and precision. Here, Edward and Lucien took the opportunity to put the hoist machine back together immediately, and it was running (with limitations) by the following day. The main unit of the controller was given a quick clean-up and adjustment, a few broken and missing parts were replaced and it too was back in action that afternoon.

Lucien tracing cables

Lucien tracing cables

Assembling the machines

Assembling the machines

Controller awaiting removal

Controller awaiting removal

Modifications

Another panel carrying three contactors and various wirewound resistors was mounted on the wall adjacent to the main controller, providing interlocking functions for the retracting ramp magnet, locks and car gate switches. It appears to be a later addition to the installation, which may correspond to overhaul of the car, as the installation may not have originally used a retracting cam. The original interlock relay on the main controller was taken out of service at the same time. It is hoped that the original configuration can be deduced from comparison of a number of contemporary drawings, however once repairs have been made to this panel it will be put back into operation. The picture of the controller in-situ also shows a rather ugly modification made in 1984 to provide reverse polarity protection as a safety measure. Diodes and fuses were mounted on a piece of laminated sign material projecting from the top of the controller and a modern contactor was added to the panel. The crude arrangement was so obtrusive and out of keeping with the original integrity of the controller that it was decided to remove it from this example. Identical additions were made to both passenger lift controllers from the same site and will be left in place on one of them.

Traction machine on test

Traction machine on test

Floor controller relays

Floor controller relays

Controller on test

Controller on test


Current Status

The few remaining faults on the controller should be easy to remedy, but they are overshadowed by a more serious fault in the motor which showed up during test runs by causing flashovers between commutator bars. Further testing has revealed a short in the armature winding apparently between two coils occupying one slot, which will be more fully investigated with the armature withdrawn from the motor. It may be possible to repair the winding using microsurgery, without damaging its attractive original appearance. If not, it may still be possible to run the motor without further harm at reduced speed and power, by disconnecting one of the affected coils from the commutator and linking the bars. This would seem to be preferable to rewinding, which would be very detrimental to its originality, although it is possible that in time the winding will fail in other ways and leave no option if the motor is to be run. It would be a great pity if this machine could not be enjoyed in working order, as it has the capability to run for many centuries on light 'demonstration duty', and allow interactive operation of the controller. We hope to investigate the armature further within the next few months, and irrespective of the eventual fate of the winding we will true up the commutator and reseat the brushes whilst the motor is dismantled.

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