Duchess of Hamilton specifics

I can't now remember from whom I gleaned this information from, it was certainly a member on here, perhaps Anthony Coulls? Good job I saved it as a word doco...
The steaming of 46229 was tweaked whilst in service, and produced remarkable results as we know... The Coronations originally had trifurcated elements, and apparently 6256 & 6257 had "even better" superheater elements... Also some interesting comments re. 6233...

Richard.


Duchess Of Hamilton & Duchess Of Sutherland specification & modifications

There was a lot of attention paid to things like very accurate valve timing on 46229, at least in the 80's. Some experimentation was involved early on to get the optimum settings which were not as per the drawings. The fellow who did that work had previous experience under Bill Harvey at Norwich with the Britannias. As is quite well known now, Bill Harvey discovered that the Britannia valve settings as specified were rather poor, so he had them modified to the extent that they had to be put back to the drawing every time they went back to Crewe for repair, otherwise enquiries would be made! Unofficial/unapproved modifications were strictly prohibited, although Bill got away with it because he had a degree of autonomy at Norwich. 46229 also has more streamlined cylinders i.e. a later design than 6233. Which is of course not any fault of 6233's owners. It seems from investigations carried out around 1983/4 that both 6229 and 6234 had cylinders cast with better internal streamlining of the ports and passages etc than the earlier engines. Indeed at least five of them had bypass valves. There were also test points for indication etc put in those cylinders, which Hamilton still has. 6234 was used for extensive testing in the late 30's, but not as far as I know 6229, which of course was streamlined at the time. What I don't know is whether the later members of the class had the same cylinders or whether it was just those two. There was a desire at one point to go and take a close look at 46235 in Birmingham, but extensive stripping would have to occur, which they understandably wouldn't entertain. As a matter of interest also is that during the loco exchanges 46229 was the standby engine for 46236, and it was remarked at the time that 46229 should have done the work as it was the better engine of the two.

Anyway as far as 6233 is concerned, the main things I'm aware of apart from the previously mentioned grate, is that they opted for return loop superheater elements rather than the trifurcated ones that the Duchesses were fitted with. The class was considered to suffer somewhat from disappointing superheat temperature. So the trifucated design was used which increased the temperature. 46256/57 for a while had an even better design of element. When the friends were operating 46229 the trifurcated elements were modified in 1983 with streamlined spacers which increased the gas flow through the flues, and the steam temperature was increased by a surprising amount. The engine was fitted with a temperature gauge for about three years, and after the fairly simple modifications it was registering quite high temperatures on the S & C. High superheat doesn't of itself increase performance, but it improves water consumption and efficiency and allows the engine more scope for high end performance. On one occasion (before the elements were streamlined, and the valves and pistons re-ringed) 46229 consumed over 2,500 gallons of water in 25 mins between Appleby and Garsdale, with no visible wastage of water from the injectors. That equates to a very high steaming rate indeed, that hadn't been achieved before in the UK. I was told by an engineer that was at Rugby testing station at the time, that when 46225 was tested there they couldn't manage to get it to run satisfactorily at 50% cut off at 50 mph and maintain steam pressure - which not many classes of engines could do anyway. Whereas 46229 could maintain steam at 60% and well over 50 mph, and even 60.

Another thing that was done to 6233 was that the exhaust injector was converted to live steam only. That may not necessarily be the case now, but anyway at high outputs that makes a lot of difference. Not least because the exaust injector reduces the exhaust back pressure considerably. And of course it increases flow rate and water temperature. I understand also that the driving horn stays were never fitted properly on 6233. They have to be tight otherwise frame defects will develop, so that will obviously discourage working the engine at high outputs. This was the kind of thing that was given a lot of attention on 46229, in order to make it better able to stand up to high performances. One funny thing about all this was that the two people who instigated all this development were both from the Eastern Region originally. Heavily opposed it has to be said by one of the museum staff, also ex-LNER who absolutely hated the engine.

Hope the above provides a little insight.

 

As I understand it, 6229 and 6234, which were built more or less simultaneously, were fitted with a modified design of cylinder to promote easier gas flow and all subsequent class members had this new design. Since the patterns were already available, this would be the sensible thing to do.

The first five engines, 6220-24, had provision for by-pass valves as revealed by the downwards extensions of the streamlined casings, and once these were removed, the valve mountings can be clearly seen (some engines later received new cylinders without the mountings). Some engines later received new cylinders, without provision for the by-pass valves. These were a left over from the Midland Railway and not popular with Stanier or, indeed, Tom Coleman. Although they allowed a freer running engine, they had the problem that, if a valve stuck open, the loco was dead failure with live steam on both sides of the piston. I believe that, although the mountings were there, the valves themselves were never fitted.

 

I'm sure I read somewhere that the Duchesses had too large a clearance volume, I wonder if the redesigned cylinders addressed this.

All water under bridge of course, but as one who experienced 46229 over the S&C in her 'Blue Ribbon' days, I'm rather sad that we can't repeat those fantastic runs today. Needless to say I prefer the non-streamlined look!

Dave