Southern standardisation (follow-on from the 94xx thread)

In the evening the 33+TC worked a |Kenny Belle" to Clapham Junction then collected an EMU (usually a 4-VEP) to run ecs to Waterloo then a peak hour service in reverse of the morning working.

In response to thread drift note this was a "Southern working" hence worthy of comment in this thread IMHO.

 

There was a similar working on the down on weekday evenings .
From memory 1810 Waterloo to Yeovil Jn and Southampton. All was well unless the 8 EMU was late and the 33 and TC had been let into the platform at Waterloo first!

Cheers, Neil

 

Not really, I like electric engines, 73's, 86's, 87's etc, just not units, personal preference.

But back to Southern Standardisation, pretty sure the only differences between Maunsells U's and U1's/N and N1's were U's/U1's were 2 cylinders while N's/N1's were 3.

Also U1's/N1's had Western style cylinder designs, just like the W tanks.

 

I'm tempted to say that every day's a school day, but prhaps not in this case

Peter

 

Already knew that, oh well.

Reading up about the North Downs some years back suprised to see alot of U's and N's deployed on the trains, although I still don't know why Restriction 0 coaches were used on those services.

 

Not quite. I'm afraid I was taking the micky there, sorry.

You have your differences a bit mixed up. The Us and Ns are the 2 cylinder locos while the U1s and N1s are the 3 cylinder ones. The difference between the U Classes and the N Classes is that the former are basically mixed traffic locos with 6ft diameter driving wheels while the latter are really freight locos with 5ft 6in diameter wheels.

I doubt that there is much similarity with Western design as far as cylinders go. Like the U1s and N1s the W class tanks were also 3 cylinder locos, an arrangement the Western never followed as far as I know.

Hope this explanation is helpful

Peter

 

Yes it is, thank you.
I was referring to the shape of the outside cylinder, looked a bit Western.

 

What you call "Western" style cylinders had nothing to do with the GWR. The valve chests were inset to allow the conjugation levers for the three cylinder valve gear to clear the valve chests:



On a three-cylinder Maunsell design, the conjugation levers were driven from the back of the valve spindles. That avoided taking the weight of the conjugation levers on the front valve spindle guide, but meant you had a problem of how to get the motion past the cylinders, which was achieved by inclining them inwards.

They are fundamentally different to GWR cylinders on two-cylinder locos, in that on the SR design, both the cylinder and the valve chest are outside the frame even though they slope; whereas on a GWR design, the cylinder is outside but the valve chest is inside the frame.

The W class tanks were built without the conjugation gear, replaced with independent sets of valve gear, but the cylinder design remained for reasons. ... remind me again about the thread ... oh yeah, standardisation. No point designing entirely new cylinders which would require new patterns and a complete new frame arrangement (because the two of the cylinders were cast as a pair).

The Z class 0-8-0T shunters also used the same cylinders.

There is a lot of Churchward concept in a Maunsell mogul, but not, I don't think, a lot of detail design.

Tom

 

Nice.

 

The valve chest isn't really inside the frame on a Churchward standard Tom - see this extract from a GWR drawing. I suppose if one were being really pedantic one could say the cylinders were in front of the frames as they were mounted on the extension frames. I suppose with the valve gear inside and the movement transferrred laterally by the rockers it made sense to have the valve spindles as close to the frame as practical without interfering with the driving wheels on the 2cyl classes.

It occurs to my inexpert understanding that with outside Walschaerts the valve spindles are forced to be further from the centre line in order to align with the rest of the gear, and this presumably comes with a weight penalty for a larger casting. Looking at the drawing in locomotive adventure I think I see that Holcroft arranged to offset the spindles inward with what he calls a pendulum lever as part of the arrangement to drive the extension rods that run past the cylinders. Clever man that. Of course he had the best mentor [grin].

It does seem to be an issue with any kind of conjugated gear that the fundamentally simple concept gets more and more complicated as one fits it into a real locomotive. By contrast the layout on the GWR 4 cylinder classes seems to dodge any number of gotchas on the design side.

Посмотреть вложение 64112

 

It does seem to be very common on outside-cylinder locos for the cylinder block to be slanted so that the top (the steam-chest/piston valve bit) is wider than the bottom, i.e. slanting the opposite way to that on GWR engines. Of course, the loading gauge on British lines typically widens above platform edge height, so there is often more space permitted at the top of the cylinder block than at the bottom.

On the SR N-class, with horizontal cylinders set quite low, the cylinder block must have been a tight fit for the restricted SECR loading gauge, and possibly exceeded it. But I don't know of any specific routes where they were banned on width grounds, apart from Tonbridge to Hastings.

 

On the GNRI 3-cyl 4-4-0 Class VS (an updated 'simple' version of preserved compound, No.85 Merlin), the (outside) piston valves' centre lines were pitched outside that of the cylinders. Built as late as 1948, these five fine locos had all too short a life.

The reason the GNRI persisted with 4-4-0s was disarmingly practical .... Dundalk Works simply couldn't cope with anything larger, even then needing to remove buffers on many classes before they entered the shops!

 

I think that's common on a lot of engine types, just less obvious than on the VS class. See attached view of an Ivatt 2MT 2-6-0:

 

I'm a bit mystified by the VS layout, as the Irish loading gauge isn't that much more generous than here.

 

I think you have to consider alignment. I'm not a steam locomotive designer, so this is me guessing and feel free to disagree/correct/tell me I'm an idiot (the latter politely please!). If you look at the driving wheel from above you have, starting at the frame and working outwards, wheel, coupling rods, connecting rod, return crank, eccentric rod, so the component that drives the valves is a long way outboard of the one that's driven by the piston. OK by the time the motion gets to the valve spindle its been through a fair few joints, but my guess is the ideal is to have every part aligned with the minimum of offsets. So my marginally informed guess is that the valve rods tend to be further out than the piston rods because that's how everything lines up, and the exceptions tend to be where something tricksy is going on like inside gear driving outside valves, or Holcroft's conjugation.. The GWR 15xx for instance, has the valve spindles further outboard than the piston rods.

 

To which I’d add: if you’ve got (say) 20” diameter pistons and 10” diameter valves, then the valves can be offset by 5” outboard from the piston without incurring any width penalty.

Tom

 

If you look at a lot of loco valve gears you'll find that many of the components aren't exactly straight and have offsets to allow things to line up. There's a lot more to it than that in positioning the valve centreline, including the portways in the cylinder casting. Steam loco design is nearly always a compromise to make it work.

 

So what would you call those cylinders then?

 

Erm ... cylinders?

Tom

 

Rephrase: Style of cylinders.