It seems that the Pressed Steel built DMUs have one besetting sin, and that is more or less wholesale failure of the guttering. It appears that the roof is made from one sheet of steel, whilst the bodyside panel is made of another. Over the joint is rivetted the extruded aluminium gutter. The gutter is additionally sealed to the roof and bodyside by a mastic sealer, and it is this sealer which, when it breaks down, is the source of trouble. Trouble will generally be slight so long as the gutters are clear, but leaves and other detritus (and particularly paint flaking off the roof) will allow water to collect and store along the gutter, and seep in behind the damaged mastic. It can then get INSIDE the bodyside panel from whence all the troubles spring.

Very soon after the unit arrived I largely cleared the gutters, but additionally cut a series of slots along the gutter in order to help drain pooled water. This helped enormously, and I was heartened after I had done it, by seeing a picture of a Bletchley 117 which appeared to have had the same treatment. It seems that some attempts had been made to re-mastic the joint, but since the top of the joint is hidden down behind the front of the gutter, it is very difficult to reach, and there was a tendency for excess mastic to simply block the gutter. There HAD to be a better solution.

The answer came in the form of a specially wide type of 'Flashband'' (or some equivalent) - you know the sort of thing, a layer of bitumin with a thin lead (or plastic that looks and feels like lead) sheet bonded to it. The open face is covered with a greaseproof type thin plastic / paper covering. The type ordered was 150mm (six inches) wide. I suffered from one or two false starts until I mastered a reasonable technique, and since I suspect that others will have suffered from this problem with 117s and similar units, I have explained the techniques that I have uncovered in a blow-by-blow fashion. The diagram below shows the main details:

The first step is to clear the gutter of rubbish, and to take any necessary steps to ensure that the problem does not simply reappear as the result of the roof flaking. Clear out as much excess mastic as is possible, finally blowing out the gutter with an airline. The next stage is to roll out the full 10 metre length with the backing paper upwards, and cut through the backing paper with a Stanley knife about an inch from one side along the 10 m length. This is to allow a 1 inch strip of backing paper to be removed whilst leaving a five inch strip behind. Roll the 10 m length back onto its cardboard tube. Now make a special bobbin on which to support the roll. Mine was made from a plastic flower pot saucer through which a piece of stiff steel wire (eg an old coathanger) was threaded. Thread the wire through the roll and turn the top over to form a hook, ensuring that the inch strip is at the bottom of the bobbin. This amazing piece of kit will allow you to hang the roll from the gutter as work progresses!

Now catch your unit! Ascend the ladder at one end of the car and present the bottom of the roll to the OUTSIDE edge of the gutter. Be sure that the attitude of the roll and the direction of working will allow the side covered with backing paper to present itself to the outside face of the gutter. A 10 m roll will cover about half of one car. Peel off, say, 2 m (ie as much as you can stretch to ,either way, from the top of the ladder) of the backing paper and stick to the outside of the gutter,about an inch from the top of the gutter, and unroll a further 2m from the bobbin. Right then! Fall off ladder, move ladder along, climb up again and repeat till the entire roll is consumed. At the end of this stage the entire length will be sticking up five inches vertically from the edge or it will have flopped over, over all or part of its length. No matter.

Now this Flashband tackle has one rather unfortunate habit. It will stick to most things well, but is particularly attracted, narcissistically, to itself, and careless handling whilst the five inch backing is removed is a recipe for disaster. The solution is to make the bituminous material non-sticky. I found that this could be done with white spirit, which, temporarily, renders the sticky surface slimy, until the surface layer of spirit has dissolved into the bitumin when the surface will regain its sticky habits.

Anyway, first get a 2 inch or so THIN paintbrush (the sort where you get five for a quid in the Poundstore). It will need to be thin enough to slip easily into the gutter, right down to the bottom. Climb up the ladder again where you started applying the Flashband and pull back about 2 m of the 5 inch reaning backing paper. Immediately paint the exposed bitumin, the inside the gutter and about six inches up the roof from the gutter. Now nead and form the Flashband into the gutter. The thin paintbrush will now provide a useful tool for pressing the Flashband right to the bottom of the gutter. You may have to come back to do final adjustments, especially toward the boundary with the unpeeled part of the Flashband, it will have a mind of its own. Again, repeat every 2 m or so until the flashband is completely used up. Then go back to the start again and make final adjustments, by this time the white spirit should be absorbed and the Flashband exhibiting close to maximum stickiness.

The work is best done when the roof is not too hot from the sun, nor is it too windy otherwise the white spirit will evaporate annoyingly quickly. For the second roll make sure that there is a generous overlap (say two inches) to ensure that the rain cannot sneak through. You should try not to scratch through the 'lead' layer, though the Flashband will remain waterproof even if you do. The advantage of this technique is that the upper edge of the flashband is well above the level of the gutter and is thus get-attable. When painted over, any failure at the joint can easily be seen and fixed. However, the gutters are now even narrower than they were before so a continuous watching brief must become part of the maintenance schedule if problems are not to re-occur. So there you are, that's what I've done. Now only time and the Blaenavon weather will tell!