GWR four-cylinder arrangement?

Around twenty years ago I was on the footplate of Evening Star exhibited alongsite a Star/Castle or King thing in Swindon museum.
I also went under the 4-6-0 and found it complicated but it was before mobile phone cameras and light was to low for silver iodid photograhy.
My dream before sleep is to modify a Manor into a two cylinder compound by scrapping one outside cylinder and put a new big low-pressure cylinder where King etc have two simple inside cylinders.
Can I be guided to a decent drawing or photo of GWR four-cylinder ,frames,stay and cross-head fixation?
If not ,then the three cylinder LMS/BR arrangement can also show how to do it.
Or the LNER footballers.B17

 

That makes Francis Webb's three-cylinder compound system seem quite sensible! It's basically the same but with one less High pressure cylinder.

 

I would stick with the day job!

 

It is tempting to think Webb Three cylinder compound system on the many simple three and four cylinder locomotives that followed on UK and German rails.
The smaller outside high pressure cylinders makes placement within UK loading gauge easy.They can be very well insulated.They can be steam jacketed.
The low pressure low temperature inside cylinder is a solid rock for rest of locomotive.
Newest german three cylinder Pacific 03 was compared to a norwegian designed 2-8-4 fourcylinder compound in 1941 and used 18% more steam at high speed and power.
The total mass of steel and coal wasted in Germany and UK by not compounding is alarming.

 

Not so the second driving axle having to deal with offset torque and massive torsional stresses.

Not a huge problem in a country like Britain sitting on massive reserves of cheap coal, so the building and maintenance costs became the dominant financial factors.[/QUOTE]

 

I have tried to show the consequence of putting Webb on P2 compared to what was not working.
The two small outside high pressure cylinders can be spread wider and allow a Krauss-Helmholtz or Zara truck arrangement

Webb P2 by Hermod posted Jun 23, 2026 at 9:30 PM

 

I'm reminded of Adams' trial of the Wordsell-von Borries system (a two cylinder compound) on one of his 4-4-0s. It worked OK, and saved a small amount of coal, but that was more than outweighed by the additional lubrication demands, such that it was overall more expensive to run.

British engineers were not stupid, (and I don't suppose Norwegian ones were either). If there had been a saving to be had with compounding in this country, the CMEs would have used it. Most railways tried it towards the end of the 19th century, and most reverted to simple propulsion - that tells you something about the total costs, not just coal and steel. By contrast, the rapid uptake of superheating and improved valve events for express locos in the early years of the twentieth century shows you that if there was a genuine improvement to be had, the major CMEs were perfectly willing to adopt it. But you have to judge their work against the economic and social restraints of the era in which they were working, not of today.

Tom

 

[/QUOTE]

Locomotives can be 18% cheaper in first cost and boiler maintenance is also 18% less?

Webb P2 by Hermod posted Jun 23, 2026 at 9:30 PM

Webb cylinders versus Gresley on P2
High pressure could have sat farther out so that a Krauss-Helmholts or Zara could guide locomotive

 

The first thing to point out is that reduced coal costs bring costs elsewhere

Secondly the UK loading gauge is much more restricted than the European making it easier to fit the larger cylinders a compound requires.

Finally as the UK had large indigenous coal resources fuel economy was not the priority it was in Europe.