Southern Electric Group 4Cor unit 3142 Preservation Report 6

4 COR Preservation Report Spring/Summer 2000

Work has been continuing on several different fronts during the last few months, both in body work and on the electrical side. The rear (train end) panelling of the motor coach 11187 is now all replaced, but the brake gear and junction boxes are still to be refitted.

One area of progress has been the windows. Figure 1 consists of a section through a window frame showing how the glass is held in to the lower part of a saloon window. The aluminium frames were presumably cast in the Southern Railways own works as the letters SR are stamped on the inside. The glass is sandwiched between this frame and an inner wooden frame about one inch wide running right round the edge of the window. This inner frame is held in place by about three dozen 2 BA countersunk screws with long round nuts embedded in the wood placed six inches or so apart. The heads of these screws are filled so as to give a smooth finish on the outside. In the original windows conventional putty was used as a seal.

Dismantling of one of these windows is quite a time consuming operation, the screws and nuts are mostly made of steel, inevitably the two tend to be rusted almost solidly together after sixty years or so, however after a good soak with WD40 and gentle rocking back and forwards about half of them will undo. Repeating this process every day or so will surprisingly free a few more but shearing some screws completely is unavoidable. Some of the screws are brass which you would expect to undo more easily, but in practice these are softer and more ready to break. In the end you will probably have about ten or so broken off by the time it is possible to remove the wooden frame and lift out the remains of the glass. The next line of attack on the broken screws is to clear out the their heads and unscrew them from the frame, this sounds easy enough but the screws tend to be set solid in the frames even tighter than the nuts to the screws. Probably some locking compound was added during the construction to prevent the screws turning when the nuts were tightened.

For some of the screws there is no alternative but to do what the railways used to do when the units were in service i.e. to re drill new holes just to the side of the broken screw. It is virtually impossible to drill out the broken stump because the drill "walks" out of the hard screw into the soft aluminium.

Having replaced the screws we can now turn our attention to the wooden frame. On some of the windows the original can be replaced, requiring only cleaning and re varnishing. However some have to be completely replaced, luckily we have some replacements in stock but not enough to replace them all. This has meant that for some we have had to replace just one or two of the edges, the frame obviously consisting of four edge pieces like a picture frame. Here again we have been fortunate in that we have a stock of replacement pieces for some of the other windows on the trailer cars. These can be cut down or spliced together to make the right size parts for our saloon windows.

The frame then has all the old paint removed and thoroughly cleaned and coated in red oxide primer, ready for the new glass to be fitted. The original window construction made use of putty as described above but we are refitting the new glass using "arbo seal" which is a black non setting compound like a cross between rubber and tar. This comes in a reel with waxed paper backing. This is pressed into the frame then (after the glass is put in place) wrapped round the edge of the glass before the wooden frame is screwed back in place. Thus forming a complete seal right round the edge. The round nuts incidentally have a slot in the top requiring a slotted screw driver to tighten them up. As the nuts are tightened the arbo seal oozes out and the surplus is cut off with a craft knife. This is not quite the end because it continues to ooze for a day or so later and so requires further trimming.

Finally the completed window is screwed to the side of the body with mastic under the edge as for the overlapping body panels.

The sliding top lights may then be refitted. The top part of the window is made of brass, presumably aluminium is too soft to stand up to the sliding action. The aluminium and brass sections are riveted together, the layout of the top windows is shown in Figures 2 and 3. Reassembly of the top part begins with screwing the top runner into place (in fact two runners side by side). These are held by wood screws which pass through the top edge of the window frame into the wooden framework underneath. The two windows can then be slotted into place from the outside on top of the runners cast into the sill. The three "L" section retaining pieces are then added to the sill to keep the windows in place.

We now have three windows on the blind side replaced with original glass. Three more are close to being finished, again using the original standard glass. One of these is the half width window of the coupe seating bay, at the guards end of the saloon. The glass for this was broken but luckily one of the larger windows had glass broken at one end only, and this was cut down to fit the smaller window.

One further area of work that we have undertaken recently is rewiring of the lighting circuit for the entire coach. The wiring of a typical seating bay is shown in Figure. 4. It may be seen that the four lights are in general switched individually. The lights on one side are backed up by the 70 volt emergency lighting battery, so remaining on even during a mains failure. The other two are powered from the motor generator only, also at 70 volts. The wiring to the light fittings and switches is looped through from one fitting to the next to avoid having to make joints in the centre, the wiring down each side of the carriage being separate. This method does however have the disadvantage of using more wire. Not all the bays are the same one or two lights on the side with battery back up are not switched to ensure some emergency light at all times. The wiring consists of single core cables, running in a duct along the centre of the ceiling. and looping off to the light fittings and switches. The ends of the wires have spills crimped on to prevent having to make screw connections directly onto the wire.

The first part of the rewiring is to remove the centre ceiling panel over the wiring channel. This is a strip only six inches or so wide but quite difficult to remove with the screw heads buried under many layers of paint. Wiring from this centre channel to the light fittings could be effected by using the old wire to pull the new one through. However the wiring down to the switches was less easy. The switches are set in behind the plywood panelling, so this must be removed, but before this can be done the seat backs must be taken out also. The same approach may now be used to renew the switch wiring as was used for that to the lighting, i.e. using the old to pull through the new. This worked well in most bays but on one or two the old wire gave up the ghost and broke. At first this looked as if the ceiling panel would then have to be removed, but it turned out after a few attempts that the new wire could be pushed behind the main ceiling panel and then picked up at the other side quite successfully. Both saloons were thus completely rewired without having to remove any ceiling panels.

The complete ceiling has subsequently been repainted in white. I must say I never realised that this was the original colour, ceilings always appear to be cream, I suppose that this is the effect of smoking. The new paint work certainly brightens up the interior, all we need now is for the lights to work. The light switches were not, in general, in very good condition, many of them having weak springs. Luckily some replacements were found and although these were not the same shape as the originals this is unimportant as they are hidden behind the panelling as shown in Figure 5.

All of this wiring leads nicely into the next phase of the electrical restoration, namely supplying an input to the motor generator (MG) to provide 70 volts for the lighting and control circuits. To provide the power input we are intending to use a rectified 3 phase supply which can give about 540 volts. The layout of the proposed scheme is shown in Figure 6. It was not clear to us at first that the output from the 3 phase rectifier is 270 or so volts not the 0 and 540 volts that we want. The EPB preservation group who are using a similar technique to charge batteries on their MLV discovered this problem first, when the rectifier negative output is connected to the MG negative input i.e. train chassis, the circuit breaker in the rectifier trips out straight away. The remedy that they have found for this is to isolate the MG negative input from the carriage body. We are indebted to their pioneering work, and in due course must make the same modifications to our power car. At present we have run a 3 phase cable to a point close to the car. We will keep you informed of progress of this very interesting phase of bringing the train actually into life.

One other topic that I mentioned last time was the repair to the edge of the plating over the top of the power bogie (under the guards door on the blind side). We now have a way forward on this, and are making good progress, but I will save this also for a later article. Suffice it to say that when this part is repaired we will be able to refit all of the remaining body panels. We are still making good progress but also still a long way to go. Working in the summer months is always easier and more pleasant than in the winter. We believe however that it will be a while yet to get this one car restored.