Recently, there was a great deal of interest in an article I wrote about the resurrection of a DC motor. This reminded me of a much more interesting recovery and refurbishment of a DC motor.
Let me start with a bit of history
In the 19th century a French engineer and eccentric, Thomé de Gamond spent nearly 40 years and his personal fortune trying to promote the building of a tunnel beneath the English channel, connecting England with France. The two governments thought that politically and economically it was best to keep the two countries apart, politically quite relevant today. Thomé de Gamond died penniless in 1876. One hundred and ten years after his death in 1986, the then British Prime Minister Margret Thatcher and her French counterpart François Mitterrand, signed the Channel Tunnel Treaty. Both governments had decided it would be economically advantageous to build the tunnel.
This wasn’t though the first attempt the built the tunnel. On the 18th June 1922, the Channel Tunnel Company Ltd. started up a Whittaker tunnel boring machine and dug 128 meters of channel tunnel, a task it was never to complete. Again, political objections made any further progress futile. There was always hope that the machine would complete its task and so the boring machine was stored in a shed. Interestingly, the design of the Whittaker machine was the same as those used only a handful of years earlier in The Great War to try and brake the stalemate of trench warfare. The Whittaker machine was designed by engineer Douglas Whitaker of Leicester, and built in Leeds at a cost of £7,150 to the Channel Tunnel Company Ltd. Three boring machines (two Stanley Bros, of Nuneaton machines and one Whitaker) were used to dig tunnels deep beneath German lines which were packed with explosives. All three of these machines are still buried deep beneath Flanders fields today. Many years after the Whittaker machine was stored, a land slide at some time during World War II buried the shed and boring machine and there it remained.
Buried, only part of the Whittaker machine is visible
It was only in 1990 the machine was recovered, and the main contractor Fairclough decided to restore it to full working order and so the motor repair story begins. From down on the English south coast the boring machine was transported to Fairclough’s depot in Swynnerton, Staffordshire. The motor was removed from the machine and we were asked for our help to refurbish it. Commercially the motor was beyond repair however we took this challenge as an invaluable training project for our apprentice school.
How the motor was received in our apprentice school
As with any repair, the initial stage is to assess the damage. Now 70 years partially buried in a hillside we expected erosion of parts, what we didn’t expect was the vandalism afforded to the motor by metal looters. The top half of an end-shield was missing, the exposed armature coils had been crudely removed, the brass sleeve bearings were missing along with the oil rings.
Armature coils crudely removed by metal looters
There was no nameplate and even today the manufacturer of the motor remains unknown. We did reveal after investigation the motor is a 90 Kw (120Hp), 500 volt, 6 pole, separately excited DC shunt motor.
If we were repairing this motor today and quoting a customer for the work required, the list would look like this :-
Rewind work – 6 shunt field coils, 6 interpole coils, 84 double evolute armature coils, 1 equaliser ring.
Parts to be manufactured – DE end-shield top, 1 terminal box, 1 internal cooling fan, 6 brush arms, 1 sleeve bearing, 2 oil rings, 1 oil retainer ring, 2 inspection handles.
Reclamation work – Reclaim shaft journals, Shot blast casing, Remove extensive rusting, dismantle and re-insulate the commutator.
The original commutator, once refurbished, was reused
Restoration work started on 15th November 1990 with every nut and bolt being identified and every part identified and marked. The winding of the 6 shunt coils was carried out, 2000 turns of 0.95 mm diameter copper wire. The interpole coils were bar wound and we were able to repair the damage and re-insulate these with glass tape. By far the biggest task for the apprentices was the rewinding of the armature. This was the the first time they had ever rewound an armature. 84 double evolute coils of 3 turns using 3 bars in parallel, the tops and bottoms were terminated in the 252 segment commutator.
The rewound armature in the banding lathe – original shaft, lamination pack and commutator
One carbon brush was salvaged from the motor and this was identified and a complete set of brush boxes and brushes were fitted. In February 1991 the motor was beginning to take shape. All rewinding work had been complete, with modern (1990’s) materials we were able to rewind the machine to a much higher specification than the original. Following full electrical tests the 3 tonne motor was returned to the Fairclough site on 20th March 1991 and it was re-fitted to the fully restored Whittaker machine.
Ownership of the of the entire machine was passed over to the Science Museum and it became the star attraction at the 1991 tunnelling exhibition.
Proudly refurbished to full working order, the Whittaker machine alongside its 1,100 tonne successor
At the Euro Tunnel Exhibition Centre, the 30 tonne Whittaker machine was displayed next to one of the German built 1,100 tonne tunnel boring machines which dug the tunnel we know today. The exhibition centre closed in 1994 and I must admit to not knowing where the machine is now. If any of you have seen it or know what happened to this incredibly historic machine, please let me know as for sentimental reasons I’d like to see it again.
120 years after his death, Thomé de Gamond’s vision of a tunnel linking England and France became a reality. I’m pretty sure the memory of this repair will stick with those who restored it, after all how many motors do we see day-in-day-out with such a rich history?
The restoration of this machine is a testament to the skill, hard work and dedication of all who contributed, remember, they were all apprentices.