Southern Electric Group 4Cor unit 3142 Preservation Report 2

Car Body Repairs

It had been decided that concentrating on one car (11187) was the most effective way to work rather than spreading effort over several. One car in good condition certainly looks better than several partly restored. An aspect of the car most in need of attention is the external bodywork and it is on this that we have since been concentrating our efforts.

It is probably worthwhile first to describe the basis construction of the vehicle. The Cor bodies were required to be as light as possible to compensate for their reduced power compared to the Pul and Pan units built for the Brighton line. The power cars for the Pul/Pan units were of all steel construction and weighed 57 tons each. (There are also seen quoted as weighing 59 tone, but a Cor DMBSO—with only one power bogie—is recorded as weighing 46½ tons.)

The Cor construction could perhaps be seen as something of a backward step, being built of steel panels on a wooden frame to save weight. The accompanying drawing shows the construction of a typical section of the body side. The lower panels (one under each window) are approximately 6' x 4' with the upper panels a similar height, but about 18" wide to fit between the windows. Finally a thin strip, only some 6" high finishes the sides off above the windows, between them and the cant rail.

The windows are fitted from the outside these overlapping the body panels on the outside and are held in place by wood screws. The frames are of aluminium with the top part carrying the sling opening sections which are made from brass. The aluminium and brass sections are riveted together.

All the body panels overlap each other, the top overlapping the bottom and each bottom panel has one edge raised to overlap the adjacent panel. The panels are again held in place with wood screws and the joints sealed with putty. The screws are countersunk and the holes in the panels are pressed in to a suitable concave recess to take the screw heads. The upright frame members (made of mahogany we think) are slotted into the massive teak main bearers with the joints stiffened by webbed metal brackets as shown. The brackets are screwed by two ³/₈" (10mm) coach bolts into the main bearer with another two securing it to the upright.

Father time has done his worst over 60 years and the structure has suffered some quite severe damage due to rusting, but fortunately almost all the woodwork is free of rot. Rust has given rise to two main problems. Firstly the body panels, which fortunately are all galvanised, have rusted along the edges, especially along the bottom and at the very top under the cantrail. These cars do not have gutters, only a cantrail, which in this case is a strip of wood about 2" wide and less than ½" thick, to overlap the joint between the canvas roof and the steel side panels. Another point where rust has got a hold is around the window frames where water has seeped in. The frames themselves are in good condition, as a result of their aluminium and brass construction.

The second and less immediately obvious problem is in fact the more serious. The steel bolts holding the stiffening brackets to the main bearers have rusted almost completely away in some cases. These bolts were never galvanised. Deterioration of the bolts is not a serious fault in itself as they could be replaced easily enough. However iron expands as it rusts and the inevitable result is that the main bearer splits. Such splits run for some considerable distance along the length of the coach. When this was first explained to me I was particularly worried to see a split several feet long under the guard’s van. It was however, pointed out that this was just the gap at the bottom of the guard’s door. Even so, some splits are two to three feet long.

The tell tale signs of this damage are bulges in the body sides and we have sought advice from other groups who have had to deal with similar problems. We are grateful in particular for advice given by volunteers from the bluebell Railway and from the Isle of Wight Steam Railway. The approach we have adopted is to cut away the outer part of the bearer to a depth well beyond the inside of the split and just outside the steel sole bar, typically to a depth of 2" to 3". A replacement piece is made up, not from teak as this is too expensive, but from iroko which is reasonably priced and, if anything, harder than teak. This piece is affixed with coach screws, glue (Cascamite) and, where possible, coach bolts passing right through the bearer. The shape of the piece is not square, but angled at the edges as shown in the diagram, to help hold the weight of the upright.

The prototype repair was completed some time before the bogie overhaul and all body panels on the rear nearside of the coach were removed beforehand. Since the work on the bogie, three more similar repairs have been carried out on this side.

One of the biggest headaches on these repairs is the removal of the coach bolts, in particular those on the uprights which are less severely rusted. Sometimes they can be driven out, although this tends to split the far side of the upright as the head of the bolt is forced out. Others can be loosened by twisting, but some just break off. Often a new hole has to be drilled and the old bolt left in place. We have also improvised with a core drill—i.e. a hollow drill just wider than the bolt using a piece of an old tenon saw blade. This has not been a great success because of insufficient room to get the drill into position. Experiments are still continuing. One thing we are most unwilling to do is to apply heat, due to the fire risk. Once the patch is in place and the brackets bolted back, the wooden frame is painted in aluminium paint over wood primer. Attention then turns to the body panels.

All the lower panels on the nearside of the body from the trailing end to the guard’s van were considered beyond repair and new replacements have been made. This is expensive as each one costs about £80 and seven were required. These are screwed back into position using new wood screws, slightly longer than the originals and a mastic compound, similar to silicon rubber bath seal, is used to seal the joints. This should remain much more flexible and provide a better long term seal than the original putty.

The upper body panels were in better shape with many needing only simple sanding off and repainting. Some however were rusted away quite badly around the window frames and cantrail. The cost of replacing all of these was daunting, but we were worried that any attempt to weld patches in position would result in the panels buckling. However we figured that as they do manage to do this on motor cards (the automotive variety), one weld was worth trying to see the result.

The approach was to cut a section away from the edge and fit a patch flush with the panel, this being held in place by pop-riveting temporary metal plates on the outside and across the join to make it ready for welding. As none of the team was equipped to carry out welding we took the item to a garage. It was explained that a smooth finish would be required (rather like welding two halves of cars from insurance write offs!) and it seems they appreciated the joke. They did a very good job, running a continuous weld along the back while leaving the front pretty well flat. With a bit a grinding and filling, the result looked perfectly acceptable. About half a dozen panels have now been treaded in this manner with some patches running the full width of the panel. Probably, in the long term, some of the bigger panels may also be patched in this fashion, rather than being replaced.

A further problem with screwing the body panels in place is that some of the old screws break off when removing the original panel. Here the approach of using a hollow (core) drill to get the offending piece out has worked well, with a dowel glued into the resulting hole to take the new screw.