David Shepherd (RIP) and his locomotives.

That's more or less it. In theory, the tractive effort is a variable over a revolution but the average tractive effort can be derived from the mean effective force over the length of the piston movement. Because no steam engine admits steam for 100% of the stroke the mean effective pressure is never 100% of boiler pressure. Most locomotives have a maximum cut off of about 75-76% because that ensures a two cylinder loco always has one cylinder open to steam. With such a cut-off the M.E.P. is of the order of 85% of the admitted steam pressure. A shorter max cut-off would theoretically require a lower percentage value.
I have asked this question during M.I.C.'s and the usual answer I get is to allow for the fact that the actual boiler pressure is rarely at the red line. Not so.
As Tom says, the 85% figure became standardised by the ARLE but it was for good reason, not an arbitrary figure.

 

As a figure for what would be available from cold - cylinder cocks open and neither superheater nor cylinders warmed up - as a worst
case starting its not unreasonable to make some reduction.
(Though with a bit of thought one can think of all sorts of things: safety valve blowing off light, green fire not lit through........)

Seriously, the first use of a tractive effort figure is by de Pambour in the 1840s but it did not immediately come into general use.
I think, like the Whyte notation for wheel arrangements - 4-4-0, 4-6-0 etc - it probably came to be widespread here from American
influence about the end of the nineteenth century. The obvious occasion one can point to is the quick delivery orders for American style 2-6-0s that were got for the Great Central, Great Northern and Midland railways which must surely have been talked about between different railways but there were also Goss's publications based on early detailed dynometer testing. The elder Ivatt was certainly involved and ran trials with one from Baldwins on GNR suburban trains involving acceleration from stops - to which t.e. would be apposite.
Using a high percentage of boiler pressure definitely seems to be from the USA. The American Locomotive Company produced
a "LOCOMOTIVE-HANDBOOK"giving all the likeliest calculations and the 1917 edition states it is 85% and then
" in Europe as low as 60% is used".

 

Err - Yankee Moguls on the GCR, GNR and MR? First I've heard of this! When were they withdrawn?

 

https://en.wikipedia.org/wiki/Midland_Railway_2501_and_2511_Class_locomotives

 

Modern outside cylinder Moguls all scrapped by Grouping, but they were still building 4Fs up to WW2... got to love Derby logic.

 

The American locos were not very successful by all accounts. A design produced for long straight runs across the prairies probably wouldn't take to well to the rough and tumble of British short haul unfitted freights.

 

That's a bit of a false stereotype, though. Not many flat straight prairie lines in Pennsylvania or Maine...

 

Perhaps the build quality was as bad as the cars they turn out today!

 

They certainly weren't well thought of; their sole purpose was to fill a gap which the British builders couldn't fill, being somewhat over-committed at the time. Once they were able to fulfil the orders, the Yanks had completed their function.

Their problems wouldn't just be a matter of spare parts availability; these engines were built to totally different principles to those in Britain. They were on bar frames for a start, and I doubt they would have fitted easily into British maintenance routines or overhaul systems. As far as the comparison with Midland engines goes, the Derby engines were ideal for the Midland; it was only when foisted on to the rest of the LMS that issues arose. And inside cylinder 0-6-0s still had a long life ahead of them: a certain very modern and progressive Southern CME produced a new design of such in the 1940s!

By the way, I don't think David Shepherd was ever tempted to buy one!

 

It's doubtful whether the Q1 would have been built had (a) Maunsell not ordered the materials for more goods 0-6-0s or (b) WW2 not broken out...

Another false stereotype... seen the inside of a modern Cadillac or Corvette, or the new Ford Mustang, or Dodge Charger? Better-screwed-together than a lot of European stuff, and with nicer seats.

 

Yes I have and I can see why Caddys and Cheverolets are not imported to the UK anymore. I did a self employed driving job for a number of year after I retired and one of the contracts was the GM demonstration fleet. I never had a Mustang but did once have a Corvette which did my back in with its horse and cart rear suspension technology and as for the Caddy of which I drove a few, what can I say. I know a lot of modern cars have a lot of cheap plastic but They felt like cheap imitation plastic.

 

It's more because GM are still struggling to shake off preconceptions dating back to the 90s and beyond. The improvement in their quality over the last decade has been enormous - and the Caddy ATS is fully the equal of the BMW 3-series in handling. Cadillac pioneered the magnetorheological adjustable dampers which now underpin all Ferraris and a lot else besides. BTW, the Corvette has never had a live rear axle - it has always been fully independent, with a transverse composite leaf spring (as also used extensively by Volvo, Triumph, Mercedes-Benz, Fiat and others). The Mustang is now officially imported to the UK and Europe, and guess what? Ford is struggling to make enough to meet the huge demand.

The Americans have been way ahead of Britain in locomotive engineering for a long time - look at the Pennsy K4 Pacific brought out while Gresley was faffing about with enlarged Ivatt Atlantics. Totally transformed his thinking on his own Pacific design. The K4's instantaneous success also makes the failure of Churchward's Great Bear at the same time look a bit pathetic. They ended up outlasting everything that PRR tried to replace them with (e.g. the woeful T1 6-4-4-6 - why they're trying to build a new one of those...), lasting right up to dieselisation (which also went a lot more smoothly than here - no chronically unreliable crap blowing up all over the country!).

 

I think you've got your PRR locos a bit confused.
Undoubtedly, the K4s was one of the very greatest of all locomotives, and none of the below is intended to detract from that.
The 6-4-4-6 was the S1 test locomotive, not the T1. It wasn't useable in real service, but did (sort of) demonstrate that the Duplex concept was workable. The ride was exceptionally smooth, and much kinder on the track than a big two-cylinder 4-8-4, which was the mainstream concept.
The T1 was the service loco, and they were 4-4-4-4. They were very powerful and very fast and handled the PRRs heaviest expresses with ease. But they did have slipping problems (although these can be exaggerated, as with Webb and Drummond double-singles: a good driver could handle then fine). You can see a video of them here:
It has to be remembered that the PRR was heavily investing in electrification at the time. The Duplex locos were an attempt to build a steam loco for their Western lines with the smooth ride and power of their GG1 electrics.
The T1 had some adhesion problems: this is not uncommon with express passenger locos including many of our favourite 4-4-2 and 4-6-2 types.
The K4s did outlast the T1: again, but not in front line express service. As in many parts of the world, medium power and smaller locos survive better than frontline express types as they can be used for other services - in the K4s case, e.g. suburban service.

 

Now there's the prototype for the next cut-&-shut austerity!

 

My daughter has a V8 Mustang California Special. It is a nice car, well equipped and very well made. It's comfortable, even in the back seats.

But as @LMS2968 says, I'm not aware of David Shepherd being tempted to buy one of these either.

Dave

 

Id actually like to see one. I understand they were withdrawn because a standard Midland boiler couldn't be made to fit. A few railways did import locos from the USA at that time, One, or more, of the South Wales companies had some 0-6-2 tanks, there were the Midland/GN/GC 2-6-0s and the 2-4-2 tank on the Lynton & Barnstaple, which was the longest lasting of them all.

Wonder if there are any of the same type of 2-6-0 still in existence anywhere else?

 

Actually that would make perfect sense. I have long been intrigued by how long they lasted and probably it was until some considerable boiler work was necessary: because of the thickness of the bar frames you would have needed a special boiler with a reduced width firebox to go in between them.








ac

 

Sadly it has been announced that David has passed away following a short illness. Condolences to his family and thanks david for having the gumption to buy 92203 and 75029

https://davidshepherd.org/news/david-shepherd-cbe-1931-2017

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