Electrical restoration of 50030: what we've done, how we've done it and what's still to do

This article came about after a discussion between myself and Dom Jackson, and is intended to give an idea of the difficulties and problems faced during rebuilding of the electrical cubicle in 50030 Repulse.

When we acquired The Twins, I had already discussed with our original Chairman Paul Taylor where my skills and interests lay, and as such, at the first work party in November 2002, he asked me to go through both locos to see which had the most complete electrical system, which would give him an idea which locomotive would be the most viable to begin work on.  Having never been inside a 50 before, I didn't really have any idea what to expect, but I was shocked at how little remained of the electrical systems of both locomotives. After inspections by various people, the consensus was Repulse was in better overall condition, and so it was decided she was to be restored first.

The electrical cubicles of both locomotives were totally stripped, with the exception of nine of the 18 NR28 relays left in Renown, and I soon realised these had only survived because they were at the far end of the Thin Man's passage, in the most difficult compartment to get at. Both locomotives had various terminal bars missing, and there were cables hanging and lying everywhere.

Paul asked me to be his electrical officer, but I remember telling him that unless he could obtain detailed wiring manuals, there would be little chance of me being able to rewire the cubicle as I knew little about 50s at the time. He assured me he was getting copies of the manuals, so I gave him the benefit of the doubt and agreed to come to the next few work parties to start clearing the debris from in and around the cubicle.

One of the first tasks was to install fluorescent lighting in both locomotives so we could see what we were doing, and a few weeks later Paul made good on his promise and presented Mark Tinker and myself with copies of the wiring manuals, and I duly accepted the role of electrical officer. Mark Tinker was actually a qualified electrician, but decided the formal post of electrical officer wasn’t for him. One of the manuals showed the positions of the various electrical items in the cubicle, and the other gave details about what each piece of equipment was connected to, and with what cables.  There then followed several weeks of poring over these manuals, and I began to have an inkling of what went where, though at that time we had no electrical equipment, so I didn't know what most of the items looked like.  Mark and I began by trying to read and identify those cables that still had readable markers on them, adding our own labels written on masking tape. We were helped somewhat by many of the cables still being tied in bunches, so we were able to start placing them in approximately their correct positions.

We visited MoD Bicester to see the work Paul Spracklen was doing on 50026, and he agreed to sell us some of his spare electrical equipment. However, once I was able to examine it in more detail back at Rowsley, it quickly became apparent most of it was really only useful for spare parts. It was heavily corroded, with many missing or broken parts. We had also by then managed to obtain a quantity of NR28 control relays, so I decided to start cleaning and installing them. Shortly after this I found a supplier in Birmingham for the correct BR-spec cables. The actual manufacturer was still Brandrex, the distributor now is Anixter. Fortunately, all the cable sizes we needed are still used in the railway industry so, whilst expensive, they were readily available. To date I've installed just over 900 metres of control cabling into the electrical cubicle in 50030.  A short while after this, we managed to obtain much of the electrical equipment we needed when the owner of 50023 Howe decided to sell up. This time the equipment was in much better condition, and after stripping and cleaning, was ready to be installed. I attached all the control cables from each piece of equipment as it was fitted, and laid them in to their approximate destinations, carefully marking each cable with masking tape. In this way, by the time the last piece of equipment was fitted, all it's control cables were already there. On the occasions when Mark was not there, Neil Favell gave me much appreciated help.

Cable lengths vary from less than a metre, to six or seven metres depending on how far apart the items to be connected are, and the route you have to take through the cubicle. This means that on the days I had help, we were often able to install up to 20 cables, whereas on days when I was on my own, I'd be lucky to do half that.

A further visit to where 50026 was based after it left MoD Bicester revealed their spare electrical cubicle retained all the compressor, exhauster, earthing and neutral cabling, and many of the required insulators. A deal was struck and we purchased the cubicle frame, which I stripped of all the cables and insulators and fitted them into Repulse.

Part of the haul from Howe gave us the missing cubicle terminal bars which, after cleaning, were fitted into Repulse. This allowed many of the original control cables that we had identified to be reconnected, and all of them have now been done. Refitting and reconnecting these terminal bars however in the Thin Man's passage, takes a terrible toll on the knees, with the combination of very restricted space and the chequerplate flooring.

Wiring the NR28 relays with the new cabling also presented its difficulties at the far end of the Thin Man's, as the compartment is small, dark, at shoulder height, and the relays are quite close together. In contrast, the other nine NR28s behind the cubicle switch door are much easier to get at, as the floor level is higher and there is a much wider passage to work in.

The cubicle switch door we obtained from Paul Spracklen was missing all four of the rotary switches, and only retained the ammeter, fuel priming and local start push buttons. I enquired with several 50 owning groups, but they either had no spares or were unwilling to part with any spares they had, which was quite understandable. Fortunately, one elec manual showed the manufacturers of each electrical item, and I saw the rotary switches had been made by a company called Santon, who I was already familiar with from when I worked for an industrial electrical manufacturer, as they were the Midlands distributor for Santon. And yes, it's the same company that makes electric showers!

I contacted Santon and asked if there were modern equivalents for the four we needed, and to my surprise, when I gave them the part numbers, they told me all were still current stock items! Just goes to show that if you have a good robust design, why change it?

These four switches were not cheap by any standards, the largest one costing almost £200 itself, but we needed them so their purchase was agreed and they duly arrived. After fitting them I laid in all the cables from them, no less than 57 separate cables.

By the time it came to fit the compressor and radiator fan contactors, the larger cabling we had obtained from 50026 was already there and just needed connecting up. Obtaining the large curly ballast resistors on top of the cubicle took some time, and when we finally got them, it took both Mark and I with our heads up against the roof to fit them and connect the cables.

In front of the large field divert resistors on top of the cubicle are the 18 smaller green resistors which are mostly to operate the various cab warning lights. These lights are always on dimly, and glow bright if a fault occurs. This also ensures that if a fault light is not lit at all, the lamp has blown and needs changing. After we obtained these green resistors I then had to attach all 76 cables to them which, as with the rotary switches, took several work parties

When we went to fit the first of the three main field divert contactors, it wouldn't fit through the front of the cubicle frame however we tried to manoeuvre it. In the end I had to take off the small metal block where the air pipes are connected and re-attach it after fitting the contactor. I then had to repeat this for the other two.

Attaching the auxiliary control wiring to the front of these contactors was relatively easy. However, when it came time to install the 12 large cables on the rear of these boards, it was a different matter. We had purchased these cables from Paul Spracklen and they had lain in storage for some time. As we were fitting them in the middle of winter, not only were they stiff from the cold, they had become accustomed to their prone positions and were very difficult to get into place. In the end it took both Ian Kemp and Chris Thorn to help me get them installed, and again took multiple work parties.

Fitting the traction motor contactors was equally difficult as they are large and heavy. In one case, I had to drill out the mounting holes in the cubicle frame to a larger size, as they didn't line up with the mounting holes on the contactor itself! These six contactors have large 'Faraday-cage' type arc chutes, of which we initially had none. We did subsequently manage to obtain several, and a large box of parts from which Steve Tripp and I were able to make several more. Putting them together was somewhat difficult, as you need multiple hands, and one slip and it all falls apart and you have to start all over again. Wiring the auxiliaries on these contactors requires you to lie down in front of them as they are located very low down in the cubicle frame, almost at floor level, as trying to do it by kneeling and reaching down almost cripples you.

 

On the board that houses the fuses and circuit breakers, the rotary Motor Control Switch was missing. This enables pairs of traction motors to be switched out in the event of a motor failure. We obtained one as part of the haul from Howe, but some of the contacts at the rear were found to be broken, so it was wrapped up and laid aside. A couple years later during a discussion with Steve Tripp, he decided to see if there was any way the broken contacts could be repaired. As we had just been fitting motor contactors, he realised what I hadn't; that the contact blocks were the same kind as the motor contactors used. We were therefore able to take parts from a spare contact block and repair the switch, which was subsequently fitted and wired. On the fuseboard itself, all the fuses were missing, but all the MCB's were present. We have since obtained all the fuses that we need for Repulse, and have a few spares. Re-connecting the cables on the back of the fuseboard was not particularly difficult, as that is one of the few areas where there is plenty of space.

The two large main starting contactors were obtained as part of the Howe equipment, and they were relatively easy to fit and wire. However, we have no spares or any for future use in Renown. These differ from the other contactors in the cubicle in that they have much bigger coils than any of the others and have connections for the large power cables from the batteries.

 

Of the boards that go in the Thin Man's passage, one is very heavy, having seven contactors on it, and it took both Mark and I to fit it. Once fitted, the contactors are very close to each other, and wiring them was very fiddly as access is very limited. The other four were relatively easy to fit and wire. The board that fits behind the fuseboard was somewhat difficult to connect up, as it's difficult to connect the cables when the board is actually bolted in place. Mark had to hold the board at an angle in front of its position, while I reached over to connect the cables, then it could be mounted on the bolts and fixed in place.  On the board that houses the field divert relay, there is a long green resistor mounted above it. We didn't have one, but the 50021 Loco Association kindly gave me one of their spares. However, this turned out to be open circuit, and I was not able to source one from anywhere else. We did have various other similar resistors we had got from 37s at Booths, so my father suggested I make what is known as a 'ladder network' of smaller ones that come to the same total value. I did this and mounted it on a board in the redundant space next to the start contactors.

 

A couple of years ago we were fortunate in obtaining a spare electrical cubicle from the 50021 group, which had some equipment and much of the larger exhauster and compressor cabling still in it. It has all been removed and stored for possible future use in Renown.  We also obtained a genuine 50 reverser from the owner of Howe, but by that time we had temporarily fitted an ex-37 example, so I could get the six large cables from the divert contactors, three from motor contactors 1, 2 and 3, one from the field divert relay and one from one of the start contactors, into their proper positions. While the main cam mechanism is identical, the auxiliary contacts are completely different on a 37, and were incompatible. Chris Thorn offered to make a second set of auxiliary contacts, copied from the original, for future use in Renown, so we left the 37 reverser in Repulse until he had done this. As a result, the 'proper' one was only fitted into Repulse and connected up in 2014. However, these reversers are large and very heavy, and it took four of us to remove the 37 one and fit the proper one. We have two spare reversers in total, one of which now has the duplicate set of correct aux contacts Chris made.

I am at present re-installing the plastic control air pipes between various equipment in the cubicle. As soon as I started it became very clear I should have done it before much of the wiring was installed, as I'm now having to work in very restricted spaces around and in-between bunches of cables, and trying to get spanners in is extremely difficult.  I have also set about identifying the remaining severed cables under the floor around the electrical cubicle and generator room of 50030.  The second part of this article will describe our work in sourcing the electronic control units used in a Class 50, as well as the remaining work required to complete 50030 in electrical terms.