Thermodynamics, DBHP and related technical matters

The Smith compounding system certainly makes it difficult to deliver a really high powered locomotive within the British loading gauge without seriously pushing the boiler pressure, since the big outside cylinders limit you very quickly. In France this wasn't such a problem, although it was adopted very late for Chapelon's 242A1 primarily to allow for a properly beefy crank axle.

The two classes that I consider the pinnacle of French four cylinder compounding, the 240P and 141P, had 16.5" and 16.1" outside cylinders respectively, so loading gauge is not immediately obvious as an inherent problem (admittedly both were at 280+psi). Both those classes would shame any British pacific for sustained high power output; I think the 240P record is 3200 dbhp for 20 miles or so, although they have a corresponding reputation for mechanical trouble in some circles. I've long intended to scheme out a rough equivalent to the 240P, with the Lord Nelson/Duchess cylinder layout (still a compound though), something like a stretched King firebox and a Bulleid style underside-tapered barrel, just to see whether I could make a reasonably comparable machine fit within the British loading gauge. Oh, the what ifs....

 

When I do this game I usually end up with a 9F derivative.
The german version of mr Cox was mr Witte and his statements to boilers were that no narrow fireboxes would be used for newbuilds.
It is much easier to attend leaking or broken stays on wide fireboxes over driving wheels.
Riddles and his mery men could have made much better standards by only accepting wide fireboxes over five feet wheels.
For higher speeds than five rev per second it shall have three cylinders and a boggie or Krauss Helmholtz up front.
And get rid of that ugly Belpaire firebox habit.

 

All very well, but it does tend to limit you to something like a 9F within the British load gauge.

 

Could be lovely

Diameter of SNCF 4-8-0 boiler was more or less like 9F

Cinderella Starboard by Hermod posted Jul 6, 2018 at 10:16 AM

 

What advantage does that have over a 9F? Just looks like you have lost some adhesion and not gained much?

Tom

 

With three or four cylinder compound at least 8% more power and better balance.
If the outside cylinders sits 37 inch from center they can go where no Kings can.
9Fs would not have been allowed running 90 mph anywhere else than UK

 

So what's needed is to get Frankie's compounding system working properly with uniflow cylinders, install it in bogies and bung 'em under a boiler at one end, fuel and water tanks at t'other, with a decent firebox dangling between the bogies, which means you could have a cab at each end and ...... Ooh! ....... that's a nice white coat ....... yes, it does look like good quality canvas ...... is it for me?..... it's arms look very long ...... a present from all the people named in my will, you say? ...... what a nice quiet room ...... that quilted wallpaper looks like it's made of rubber and so does the bed ...... Hey! I can't move my arms ..... Just a minute ..... there's no handle on on this side of the door ..... hello? ...... Anyone..... ?

 

The 9Fs were so well balanced that they could run at 90 mph. If they were not, it is highly unlikely that loco crews would have driven them at anything like that speed. They weren't nicknamed 'Spaceships' for nothing!

 

Wasn`t the nickname 'Spaceships' caused to the gap between the frames and boiler barrel?

 

Point of order ...... You didn't mention DeCaso's superb and very nicely proportioned 232U1.

So they're miniatures, but I like this clip .... and since hitting 'play' isn't compulsory ....

 

The 9Fs were a very good riding loco, better than many a coach, which tended drivers underestimate the speed they were actually making. But balancing a two cylinder loco to give smooth riding and lack of axlebox knock will have its effect on the vertical forces, and hammerblow follows. This is why reciprocating masses were only partially balanced, never 100%.

 

All true ..... but I gather BR management's objections to high speed runs was based on the bearing surfaces being designed for hauling heavy freight rather than attempts on the sound barrier.

The 9F performance which impressed me most was 92203's preservation era startup of a 2198 tonne train at Foster Yeoman.

Not the best quality clip, but it was back in 1982!:

 

9F at 8.4 rev/sec/90mph hammerblows plus-minus 19 tons 8.4 times a second.
Permanent way people must have loved them.

 

Thanks for posting this clip 30854!

By the way, here they are in scale 1:1



kind regards,
Knut

 

Super clip Knut. The SNCF's early use of CWR is very evident in some scenes. Several of those electric locos I remember in service (especially the 2D2's .... which always seemed to be in a grotty medium brown), but I missed the 141R's by a couple of years .... dammit! Interesting to note the French expresses were mentioned as weighing in at 600t (rather heavier than what the Bulleid's MN's were designed to haul from London to the channel ports) .... which must explain why a fourth driving axle sometimes found favour.

What was it with cinematic newsreels and 'received pronunciation'? They nearly always souded like Arrfa Mullard (a onetime well known cock-er-nee) torkin posh .... It was the same here and in the US ..... very odd .... and that 'music' ..... was it compulsory? .... Ugh! Then .... and Ugh! Now.

 

Accents change over time. Its an interesting exercise to compare the Queen's accent in say 1957 and 2017 christmas broadcasts.

 

Anyone going to Mulhouse to see 232U1, do have a close look around the cylinders where chunks of steel have been welded to the frames and cylinders to stop the latter moving...........

 

"RP" (or BBC English) was real enough. They tried it with me, though it didn't quite take ...... and anyhoo ..... there are only three things which are a constant over time .... death, taxes and data loss!

Never mind HM's voice ..... compare the eyes over the years. I wouldn't wish that job on anyone .... even with holidays long enough to make teachers green with envy! She has to be nice to Trump ..... I don't. I'd chalk that up as a win!

The similarity in just about every way between British and French newsreels of the period was quite striking and the documentary style took me right back more years than I care to admit, to those afternoons when games was rained off ..... though I'd have given anything to see that SNCF film instead of 'Adaptation to the Environment' for the Nth bloody time!

 

You missed a fourth eternal certainty - that whenever two people gather in West Somerset, within an hour they will have split into three distinct factions and ended up arguing about four different things ...

Tom