The 10A Allocation

As I say that’s quoted from David Smith that 4767 can do 75mph in the latest Trackside

 

Is that a typo for 65 mph?

RSSB RIS 4472 states the following:
G D 1.6 The steam speeds formula takes into account:
a) Wheel diameter rotational speed of 6 revs per second.
b) Piston stroke and oscillation speed of 1600 ft per minute.
c) Number of cylinders (see G D.1.8 b)).
d) Presence of leading pony truck or bogie to add steering and derailment resistance.
e) Age of original design (see G D.1.8 a)).
G D.1.7 Derivation and application of the steam speeds formula is overseen by RSSB, to whom requests for access may be addressed.
G D.1.8 The following general criteria have been applied to the speeds derived:
a) The cut-off for age of design (by which a lower speed is allocated) is 1923. This date is suggested partly because it is the date of the post WWI ‘grouping’ (that created the London, Midland and Scottish Railway (LMS), London and North Eastern Railway (LNER), Great Western Railway (GWR) and Southern Railway (SR) ‘big 4’) but also due to the landmark bridge stress committee work, begun in 1923 and reported in 1928. The output of this work, including the determination of the hammer blow effect, influenced locomotive design philosophy thereafter in a manner beneficial to track force considerations.
b) 2-cylinder locomotives are those most prone to display the ‘hammer blow’ effect as there is no natural balancing to the effect, with piston sequence at 90 degrees. By contrast, 3-cylinder (120 degrees) and 4-cylinder (180 degrees) locomotives are naturally better balanced and exhibit a less pronounced effect.
c) The additional rear wheelset on the 4-6-2 pacific types, although adopted mainly to spread axle load, generally offered additional benefit in ride quality; conversely, certain 4-6-0 types displayed deterioration in ride quality as speed increased. This has therefore been taken into account in setting speeds for the two generic design types.
d) A marginal increase in maximum speed (75 > 80mph) has been allocated to certain pacific types with 6' 8''driving wheels or greater, on the basis that this is a significant increase over 6' 2'' (the basis for the previous maximum limit for 75 mph when operating on the GB mainline railway). One consequence of this is the requirement for fixed rather than portable headlights, as set out in 3.7 where operations are proposed at that speed.

 

I don't believe so Steve, I've heard it said a few times that 75mph will be permitted. Perhaps the owners have had discussions with their vehicle acceptance certification body and made out a technical case as to why 4767 can be treated differently to the other LMS 5s? There was clearly a case made for 45305 20 years or so ago, as a test run was carried out. Presumably WC was the operator of 45305 in 2005 at the time of the 75mph trial?

 

44767 was given permission for 75MPH as the loco was proved under testing to give less hammer blow than a standard black 5.

Coupled with roller bearings it had 75MPH classification in its last mainline stint

 

7802 Bradley Manor was also passed for 75MPH running to allow it work the Torbay Express trains and that has 5' 8" driving wheels

 

Can't remember precisesly but guessing that 44767 was last on the mainline best part of 25 years ago, maybe longer, so the testing was probably under BR auspices and pre 'VAB' regime?

 

A close guess, 18th Feb 1998 was its last run!

 

All true but perhaps the latest owner of 44767 is less concerned about conservation or not too worried about the costs of maintenance due to having full workshop facilities 'in-house'?

 

Good grief, where does that time go? I remember it came in to ELR around that time via a railtour (Pilkington set!).
So it would have been certified around 1991 and the 75mph testing presumably assessed by Brian Penney?

 

Couple of Shots of 44767 ,Banavie 09.09 .1984,with Ben Nevis in the background, and passing 15A Wellingboro Round house. Still standing in 2026 ,listed I think,on a St Pancras to Stockport train ./03/1995

 

I’m sure this’ll have come up somewhere else, but what was the rationale for 4767 being built with Stephensons in the first place? It seems a pretty unusual outlier if there wasn’t anything wrong with walschaerts in the first place!


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The story is that the GWR men told George Ivatt that he had a good engine in the Black Five, but it was a shame it couldn't be fitted fitted with Stephenson's gear like the GWR Hall class, which, they reckoned, would improve it. Ivatt was known to have a strange sense of humour and ordered the Drawing Office to look into it, 4767 was the result. And she turned out to be one of the best of the 842 Fives built.

 

Presumably the as built double chimney wasn't deemed to improve performance though?

 

I'm not sure how many Fives retained the double chimney but 4767 certainly didn't. Nor do I know how effective it was on a Black 'un; they were good steamers in single chimney form anyway.

 

Probably 4767 simply had a replacement boiler at first heavy general which was single chimney.
Am I right in thinking aside from 4767, the only other remaining Fairburn/Ivatt variant boiler is now on 5491, albeit the smokebox is standard length compared to 4767s extended due to the frames being longer to accommodate the rollers?

 

44686. 44687, 44755, 44756, 44757, 44765, 44766 and 44767 were all built with double chimneys. 44765 reverted to a single chimney in 1950 during tests at Rugby testing station, but the double chimney was put back during these tests. . 44767 received its single chimney in 1953 following problems with drifting exhaust.

 

This is one of the misunderstood parts of steam loco overhaul procedures, but when an engine received a replacement boiler, the smokebox, chimney, etc. stayed with the engine, it didn't go with the boiler. For the boiler to be repaired, the smokebox had to be removed anyway so they wouldn't be kept together. The most notable aspect of this was the streamlined / non-streamlined Pacifics. When the streamlining was removed from 1945 the original smokebox with the depressed top to fit below was retained until it eventually wore out and was replaced by a conventional circular item. The last to be changed was 6246 in 1960, but others appeared much earlier. Boilers would be changed on the Pacifics at anything from two to five year intervals and the boilers were fully interchangeable but there is not a single case of an engine built without streamlining being fitted with a modified smokebox.

The matter of Black Five boiler fitting is that there were basically two types: vertical throatplate and sloping throatplate. They could not be interchanged without work to a frame cross stretcher, but once done, they would all go together. After that, domeless / domed and position of the top feed was just a matter of pipework. The English works tended to keep the same type of boiler as the engine came in with but St Rollox was a law unto itself and an engine could emerge in any configuration.

 

Correct, West Coast operated all VT trains at the time.

 

One possible explanation for 75 mph limit for 4767 contrasted to 65 mph for other black fives can be different reprocicatory balance.
LNER B1 had originally ca 35% balance.To be able to test it on rollers in Rugby it was upped to 60% without much ado.And locomotive was much nicer to serve on.
If we can have pictures of driving wheel of 4767 and the normal black five variants it should be possible to judge any balancing differences.