H2, H7 , J5 etc Clerestory roof appendages

[Oil-burner]

A technical question rather than a modelling question on this occasion, even though it was prompted by a set of Bettabitz H7 etches recently on eBay.

 

Can anyone please shed any light on the purpose of the additional sloping glazed sides to the clerestory roof of the J5 diner and the H2/H7 diners (there may be more)? For those who haven't spotted them they are visible on the gently rotting H7 Composite diner 9520 at Didcot and the restored J5 Sleeping car 9038.

 

Initially I had assumed that they were constructed instead of the normal vertical glazed panels but interior views show the verticals to still be present. Second thought was that it was for ventilation, however in pictures of the interior of the converted cafe cars 9502 (Harris page 56) and 9516 (Semmens ‘History of the GWR vol 2 The Thirties’ page 72) the internal verticals had by that point been blanked off though the external portions remain. 

 

On an allied point, looking at the exterior view of 9502 as a Refreshment Car in Russell Volume 1 page 129 fig.121 is anyone aware if the beading on the coach sides was removed, or maybe plated over, in the conversion process, or is it just a trick of the slight over exposure?

 

Ken...

[Miss Prism]

I had assumed the internal vertical bits had sufficient strength but with large apertures to let in the extra light given by the sloping glazing. 

[Oil-burner]

Thanks for that suggestion about the strength of the verticals being sufficient. Having shown the various internal and external pictures to a colleague in the heating and ventilating trade he pointed out that, on the dining cars, 2 of every 3 glazed elements is able to open inwards at the top. This combined with the apparent gap at the bottom of the sloping glazing could, in his opinion, give a ventilation effect when the train was in motion without the need for fans.  I shall have to take a trip to the WSR museum and have a look at the sleeping car roof sometime (assuming it has been restored as per original build) but, for now, my curiosity is satisfied.