V2s and Bowden cables

[drmditch]

While volunteering at NRM Shildon last week (I do this sometimes, and it can be sometimes be interesting) and manning the cab footplate of ‘Green Arrow’, I noticed something I hadn’t noticed before.

On the RH side of the firebox there is a strange oval aperture, with a surrounding plate.

A close up shows that there is (apparently) a pipe or tube between the cladding and the firebox plates.

As far as I can interpret, this tube contains the Bowden cable leading from the cylinder-cock lever on the fireman’s side of the cab:-

Through the firebox cladding

[drmditch]

Leading through a hole in the underside of the footplate just behind the driving wheel splasher.

And presumably connecting to the mechanism under the cylinder just visible in this rather poor mobile-phone photograph here.

So, several questions arise:-

I know that the A4s used Bowden cable to connect to the cylinder-cocks because the streamline cladding made a ‘normal’ linkage difficult. Presumably, the V2s being developed after the A4s used a similar mechanism.

(I’m not sure if I have seen this commented on before, but will have to re-check my library.)

It appears to be from the original design, because it shows on the picture of 4771 on page 6 of Yeadon Volume 4, dated 3rd June 1936.

But, what is the oval hole for?

If for ventilation it seems a bit small considering the position.
If for introducing lubricant why not do the job further forward, or in the cab.

Perhaps a suitable Christmas Mystery?

[61962]

There are greasing points at intervals along the cables(there are two, one for open and one for shut) and the two points on the firebox side are the only ones that cannot be directly accessed, hence the hole. The A4s had the same although they had a little sliding door on them.

Eddie

[drmditch]

Thank you Eddie

I've checked through my library, and the aperture shape(s) in the cover plate seems to vary over time.
You can see the two cable runs clearly in my fourth and fifth photographs.

I'm still slightly mystified by the placing of a a greasing point so close to the cab linkage and where the cables emerge from the cladding, in what must have been a very hot position.

Fig 68 in RCTS Part 6c shows 4844 under construction with a gap in the firebox insulation apparently being left for these cable runs. (It's in the right place anyway.)

[61962]

Its actually very difficult to grease the cables from the ends, the best you can do is to squirt some oil on the exposed cable which is not very effective. The section at the side of the firebox does need a bit more attention because of the temperature and those grease points are there to do that, and properly used will lubricate the cable right back to the cab end.

Eddie

[drmditch]

Thank you again Eddie for your insights.

I was looking through other pictures this morning and the same feature appears on the Fireman's side of some of the A3s in the later 1930s.
Those I have found have the 'double oval' aperture.

I had understood that the use of Bowden cable was introduced on the A4s (I will try to find the reference; it's not in the Green Books), so does this illustrate the practice of gradual improvement that was followed by the great engineering works?

[61962]

I've just had a look in Yeadon's and there's lots of pics of A1s and A3s prewar with the cable greasing point on the firebox side. The earliest looks to be 4472 dated 1935 (greenglade please note). It was overhauled in May 1935 so it possibly had the bowden cable to operate the drains fitted then, which pre-dates the A4s, so you could well be right that it was part of the continuous development of the pacifics. There is a large photo of the firebox side of 2743 dated March 1938 which shows the cover plate with two holes each with a grease point visible.

Eddie