Bluebell Motive Power

The 0-4-4 arrangement beats the others in one respect: there is little restriction on the size and shape of the ashpan - very handy for suburban work I imagine.
Pat

 

The Barry Railway had both 0-4-4T ( G class, 2 in 1892 and 2 in 1895) and 2-4-2T (J class, 3 in 1897, 4 in 1898, 5 in 1899) (standard across almost all Barry classes), but the 2-4-2T was longer and heavier with more coal and water capacity. Both were classified as passenger locomotives with 5'7.5 in driving wheels. Cylinders were apparently the same too, so it seems reasonable to assume that the Barry CME decided he preferred the 2-4-2T.

 

I guess if you start with an 0-6-0 tender engine and want to make a tank engine (so need a bunker) then you have about three options (*):

In one you keep the relative positions of the front two axles and cylinders, and replace the rear axle with an extended frame and bunker supported by a bogie - that gives you an 0-4-4T.

Or you keep all three axles and cylinders, extend the rear frames and add a pony trick, which gives you an 0-6-2T (or, rarely in the UK, an 0-6-4T).

Or you keep the rear two axles, extend the rear frames to give a bunker supported by a pony truck; and replace the leading axle with another carrying set of wheels - that gives you a 2-4-2T.

In each case, the basic arrangement of the driving axle, boiler and cylinders remains basically the same; what changes is how much you change fore and aft.

If you look at that Barry Railways 2-4-2T and compare it with, say, "Birch Grove", then you can see the close relationship between an 0-6-2T and a 2-4-2T: I guess the trade off is between adhesion and the ability to follow curves at speed.

(*) Clearly in reality it is more complex than this when you start considering wheel diameter and weight distribution, amongst other factors ...

Tom

 

I think the Lancashire and Yorkshire 2-4-2 tanks were the most numerous class, 330 in all, 1008 is preserved of course.
Holcroft describes a ride on a Great Western 0-4-4 tank as the worst of his life, "like a terrier shaking a rat". Both this class and the LSWR M7 were involved in accidents, the GWR locomotives subsequently being rebuilt as 4-4-0 tender locomotives and the M7s transferred to London suburban workings, presumably at lower speed. The problem is that the main guidance going round curves comes from the front axle, and any side control on the rear bogie opposes this, whereas if it is given no side control there is no constraint at the back, as experienced by Holcroft.

 

There were indeed Barry 0-6-2Ts with the same boiler, but we're getting rather a long way from the Bluebell...

 

https://m.facebook.com/story.php?st...LjpiQfNovmyJ7GbkF4fJqeE2jl&id=100064682796476



Not sure about the latest draughting design on 73082...

 

At the time of Grouping, the British main-line companies had approximately 980 2-4-2 tanks and 1200 0-4-4 tanks. I don't think there is clear evidence that one option was better than the other; it seems to have been very much down to engineers' personal preferences.

Ahrons ("British Steam Locomotive 1825-1925") identifies the first British 0-4-4T as having been built in 1866 to the design of James Cudworth of the South Eastern Rly. The Southern Rly consituents were among the companies who particularly favoured the 0-4-4T, so it is perhaps fitting that the Bluebell and Swanage railways have preserved examples of the type.

 

....Not to mention Calbourne on the IOWSR.

I guess that givne the current weather, any footplate crews from these three lines who look at your picture of Mr Cudworth's pioneering loco must be grateful for the relative comfort of the enclosed cabs of 30053, 263 and W24!

 

Now that would be worth 'New Building'

 

The LYR started with 0-4-4 tanks, designed by Barton Wright, then changed to 2-4-2 tanks under Aspinall

 

Marsh seemed to dislike passenger locomotives with leading driving axles, and went to the extreme of converting a couple of Terriers into 2-4-0T, with smaller front wheels. (I'm not sure what mechanism he put in place for side control). The currently preserved "Boxhill" is one of those thus converted. He also converted some of the E4 0-6-2Ts into 2-4-2Ts, simply by removing the front sections of the coupling rods, while leaving the leading wheels the same diameter.

Whatever the intended effect, they were converted back to conventional form in short order by his successor.

For his own design of passenger tank engine, he preferred the 4-4-2T, probably drawing on his experience of Ivatt 4-4-2Ts on the GNR (LNER class C12).



Tom

 

Interesting stuff. Why were 2-6-0 tanks hardly ever used? I can only think of one on the Garstang and Knott End Railway which was named Blackpool and ended up on the LMS as 11680 I think. The only other ones I know of were some narrow gauge ones in Ireland on the Tralee and Dingle Railway.

 

I think with an inside cylinder loco (as was the norm for most British locos before World War 1) it is very awkward to arrange. If the middle axle is the crank axle, it has to sit considerably in front of the bottom of the firebox to allow the crank throw. You then end up with either a very long wheel spacing to the rear axle if the rear axle is behind the back of the firebox; or a steeply sloped grate and restricted ashpan if it lies above the rear axle; or a very short firebox (= small grate area); or a very high-pitched, small-diameter boiler; or a very long overhang at the back to support the bunker; or some combination of all those. Essentially you end up compromising the boiler and probably ending up with a loco that is under-powered relative to the nice amount of adhesion you have given it!

By contrast, laying things out with carrying wheels at the back avoids those problems. The logical tank engine development of a 2-6-0 tender engine is a 2-6-2T or 2-6-4T, not a 2-6-0T.

Looking at the loco you reference, it seems at first glance to have a boiler that is small diameter and pitched quite high; plus it is outside cylinder (but looks like inside motion) which does buy you a little bit of length relative to having an inside crank axle (i.e. the middle axle can go a bit closer to the front of the firebox).

https://transportsofdelight.smugmug...OMPANIES/GARSTANG-KNOTT-END-RAILWAY/i-zQdJ2XW

Tom

 

Thanks Tom. The GKER was the smallest constituent of the LMS, it's engines were not numbered, they just had names, Blackpool, Knott End, Farmers Friend, Jubilee Queen and New Century.

another railway unrepresented in preservation!

 

The Ballymena & Larne and Castlederg & Victoria Bridge both had single examples of 2-6-0 tanks as well as the Hunslet and Kerr Stuart designed locos on the T&D

Sent from my SM-A105FN using Tapatalk

 

Ivatt had introduced the 4-4-2T on the GS&WR(I), prior to building a further class for the GNR:

https://en.wikipedia.org/wiki/GS&WR_Class_37

But just as Marsh was removing front coupling rods from some LBSC 0-6-2 tanks, Ivatt was himself adopting the 0-6-2T as the GNR's new standard suburban type (Class N1)!

That explanation seems logical. You could take the power drive onto the front coupled axle, but such an arrangement may also have seemed awkward.
The outside-cylinder 2-6-0T was common in some countries. Possibly the most numerous were the Prussian T11 (saturated) and T12 (superheated). Similar in size and function to the Bluebell's LBSC E4 0-6-2T.

https://en.wikipedia.org/wiki/Prussian_T_11
https://en.wikipedia.org/wiki/Prussian_T_12

 

I think that's understandable. Its something that occurred to me when I was trying to think through the GWR 15xx in a past thread. If you have inside cylinders then the cylinders can be between leading coupled wheels with the crank on the second axle. If you have outside cylinders then they must be in front of the leading coupled wheels, and weight distribution may be difficult, so a carrying wheel deals with it.

 

It kinda feels like a lot of the last few pages probably should be on their own thread rather than this one, no?

 

Getting back to Bluebell matters, is the plan still to move Beachy Head out of Atlantic house this month and into the workshop for the final works to commission the loco.

 

I think it's been said that Normandy and the Adams Radial are due to move into Atlantic House in next month (I'm sure I've seen February as the month they go in anyway), so presumably 32424 will come out and into the main works around the same time.