Hi all,
I would like to understand the design of the safety valve housings prevalent on pre-1900 locomotives of the GNR. GNR Stirling single No. 1 is a good example. A similar type was used on the NER Class E1. It may have been open-topped, as evidenced by the Bachmann model.
Here is a diagram taken from The Locomotives of the Great Northern Railway by Geo. Fredk. Bird, publ 1910.
Specifically a class of saddle tank built in 1897:
GNR M6
I am unable to find any information on these housings, and thought one or more members may
be able to answer the following:
1. Was the housing a cover for aesthetic purposes to hide the valve/s?
2. Was it open topped?
3. What is the purpose of the lever which seemed to extend into the cab?
My wife thinks it looks like a Morroccan cooking vessel, but that is not much help
Like most these days no real expertise, just a long time study of early GNR locomotives.
The bright shiny trumpet shape just in front of the cab on all Stirling locos was certainly a decorative cover for the safety valve
which in many of the drawings I hold has two springs of the Salter type safety valve inside, and actually some distance below the top.
Like most I do not have many early photos overhead of Stirling engines with this device, so the only one which can be checked
is No 1, but of course that was rebuilt a couple of times, and may have been modified, either to take it backwards, or allow it to steam.
As for the lever, this is the same as when you look at any other type from the time, in terms of being the pressure relief arm.
Check any LNWR locos you may have in photos and you will see the same on their Ramsbottom valves. It was relating to this
that caused a number of problems on the NER when McDonnell joined them from Ireland, and only lasted about 2 years, before
being replaced initially by the Loco Committee under Tennant. The relevance of that, is that the 1463 class of the NER, Tennant locos
had a very similar design to the Stirling 2-4-0's not least the safety valve cover.
Distant memories tell me that there was a top to the cover, which was not completely open, but its purpose was to allow
the excess steam to escape.
if you have copies of RCTS Locos of the GNR, vol 2 there are photos of Stirling locos as built and as rebuilt by Ivatt with
Ramsbottom safety valves and no covers. How much of the design is due to Stirling not having a dome on his boiler is
difficult to know.
This general style of safety valve cover - rather like the Tagine of Morocco in form - is to be seen on the very earliest locomotives for the GNR, procured from locomotive builders various, and subsequently on those built when Sturrock was locomotive engineer. So it well predated Stirling's time in office, and the fact that independent locomotive builders used it suggests that it was a common fitting in the early UK railway industry.
It's primary functions probably to conceal the unseemly working parts from public gaze, and to make it more difficult for irresponsible enginemen to attempt alteration to safety valve setting in an attempt to increase boiler pressure. It has to be quite substansially vented - at least the cross sectional area of the safety valves at full release, and preferably larger yet - or it will impede the functioning of the safety valves, at least until it is blown off its mountings which may be characterised as a bad thing as it might alarm the horses..
I am not sure I agree with all that Hatfield Shed has put forward. I think we need to remember that the Victorian engineers
spent an awful lot of time thinking about how the complete item would look. You need only to look at the inside of many
Steam Powered Pumping Stations to see how they cared for the look of things. When you study all of the details you
wonder where that skill went?
The shape of the early safety valve covers was very different from that used by Stirling both at the G&SWR and GNR many being
very narrow more like coffee pots. The other thing is the shape and size of so many of the domes on contractor built locos.
Remember that Stirling spent time at Hawthorns' before going to the GSWR and many of the things that became his standard
on the GNR had been evolved by Hawthorns', for instance inside springs on tenders.
When Ivatt arrived at the GNR, he took the valve cover off his rebuilds whilst his own locos started with Ramsbottom valves
not covered, and later after Gresley many had Ross pops as you have seen.
I suppose I should have mentioned that I am modifying one of the cheap and cheerful Hornby J52 engines to "look" like a batch of 5 supplied by Neilson and Co, which were supplied with the Stirling style covers.
From my reading of Bird, H. A Ivatt inherited a couple of pre-destined builds from Patrick Stirling.
These were in 1896 being a couple of domeless 0-6-0, a domed 4-4-0, and a domed 2-4-0 which all retained the "coffee pot" cover.
The Neilson domeless saddle tank (as in my diagram above) also inherited the "coffee pot" cover, whereas other builders' domed versions had the Ivatt cover.
On an unrelated matter, Bird refers to class designations (example LU for the famous 251 class Atlantic) which are no longer in common use.
Did the GNR change class designations sometime between 1910 and 1923?
The whole deal about GNR loco classes is very complex, there are a number of different claims as to class etc.
Tuplin in his book refers to some classes but I think that some of those refer to power classes rather than actual
classes.
Until Ivatt arrived at Doncaster, the classification of loco series was more related to the number of the locos.
Ivatt introduced different load classes as well as loco series types. Gresley cleaned it up, not least to produce
the Pacifics as Class A1 which had been the later title of the Stirling 8ft singles, which by then had been scrapped
except for No 1, which was actually in storage.
As for your comment about "inherited" locos, most were on order by Matthewman, Stirling's accountant during the
period of about 3 months until Ivatt arrived at Doncaster from Ireland, so many of us think that Ivatt was unable
to influence the overall design very much so the "accessories" are like some tenders, known as Interim.
However, Stirling did not design a 4-4-0 that was put into production. yet the first 4-4-0 had a Stirling type cab before the
well known Ivatt cab arrived.
kimballthurlow wrote: ↑Mon Oct 15, 2018 2:10 am
...On an unrelated matter, Bird refers to class designations (example LU for the famous 251 class Atlantic) which are no longer in common use.
Did the GNR change class designations sometime between 1910 and 1923?...
From recollection of a talk given some decades past, the systematic description of GNR loco classes by a wheel arrangement letter followed by a design number (which principle would later be adopted and developed with some alteration by the LNER) seems to have begun in earnest with Ivatt's tenure. However 'on the ground' these descriptions were little used by GNR operating staff; and loco classes were often identified by any - or all! - of the first works order description, the first running number in service, or the nickname, rather than the systematic wheel arrangement/design number description.
