GWR four-cylinder arrangement?

Well no, it rather suggests that you have reached the limits of gigantism in steam locos and need to think of diesels or electrics if you want to increase power! The only places which seemed to be able to make giant steam locos work was where coal was cheap. That tells you something.

My wider point is that there seems to be a cult of Chapelonism which is vey partial to quoting selected statistics about locos, without considering the whole picture. So you get magic power outputs from the cylinders, but much less discussion of how the steam was to be supplied, or whether the mechanical structure of the loco could deal with those power outputs. My feeling is that once you get above about 2,500hp with a coal-fired steam loco, you have to start accepting much reduced efficiency, from a machine that is already inefficient. At that point the rationale for moving away from steam starts to become inevitable.

Tom

 

The phenomenon of carryover was and remains a serious issue. It was addressed but needed further development work. It achieved the result of reducing lineside fires and the cost of associated insurance claims which was the leverage to get the ideas applied. Fuel consumption was reduced for a given power output and as an extension of this power output went up which was what the creators of the system wanted to test.

 

25%? It's powered by a small steam engine! You will find that the figure is somewhere between 3 and 5%.

 

Two firemen?

 

It's not the steam to power the stoker that is the issue, it is that large amount of coal disappears straight up the chimney unburnt.

Tom

 

Perhaps you should take a look at the 5,500hp N&W Y6s? They had cast frames and roller bearings throughout. Since they were equipped with roller bearings and automatic lubricators, the amount of time and expense required to maintain a Y6 was akin to diesel locomotives. In 1952, N&W tested its A class and Y6b class locomotives against a four-unit Electro-Motive Division F7 diesel set. The tests indicated that fuel costs and similar items were roughly the same, and the test was considered a tie. The Y6s lasted until 1961, long after most US railroads had given up steam. However, diesels eventually won out for lower maintenance and other operational costs.

 

For some the rationale for moving away from steam is at a very much lower power level. Apart from heritage applications, of course.

 

And the overall financial efficiency of that?

You are falling into the same trap as everyone else, finding ever more elaborate workarounds to enable one technological option while ignoring the total cost of operation.

Tom

 

But where do you get the figure of 25%? Unburnt coal going up the chimney? Char maybe.

 

According to Bill Withuhn in his book American Steam Locomotives Design and Development 1880-1960, the Pennsylvania Railroad ran a series of tests at the Altoona Test Plant on two otherwise identical locomotives. The stoker-fired engine burned about five percent more coal throughout its power range, due to the fact that a stoker grounds up the coal, injecting more of the coal as powder that was lost out of the stack.

So it would appear that 3 to 5% figure does include dust lost to the chimney.

 

Unburnt coal going up the chimney; plain and simple. You need to define what you mean by char but, in my book it is unburnt coal or, more exactly, partially burnt coal which has lost its volatile content but still contains unburnt carbon. That’s the sort of stuff you get in a smokebox and, if there is a leak in the smokebox which allows air to be drawn in, will continue to burn in there, hence the reason locos can get burnt smokeboxes from time to time. Tom will no doubt give chapter and verse but I think the SECR used to collect smokebox char and send it to Ashford for burning in the works boilers.

 

Depends on the circumstances. Picking up a second fireman at Bromsgrove or Tebay would be far cheaper than a banker, if that solution works with the locomotive.

 

No. Even Beattock was only ten miles long and the engine would arrive with a well prepared fire and plenty of steam and, important, water in the boiler, and the preparation would have started at least twenty minutes before the start of the bank. The second fireman is not going to do anything to raise the fire / steaming just by getting on the footplate.

The benefits of compounding would need to manifest themselves over a long proportion of the journey. Even if our engine's 6,000 i.h.p. is not needed for all that time, unless it's delivering 4,000 for most of it then your wasting your time, and you still need a second fireman at that.

 

I'm just considering that there might be a scenario where a steam locomotive with two firemen might be the most economic scenario. If you wanted to run high speed schedules, you could build a suitably powerful 4-8-4 - or something like that, which is too much much for a single fireman. I understand the LNER Garratt was also demanding to fire when it was working hard.

 

But was only for short bursts up the bank, with time between turns to clean the fire and box it up again .

 

So just imagine the logistics for a while.

In the normal scenario, a loaded rain comes to rest at Tebay (for Shap). The banker runs onto the back from a convenient siding; within a few minutes the train is back on its way. The banker drops off at the top of the bank, the main train continues uninterrupted; and the banking loco then gets the next path back down the hill for it next duty.

So now let's consider it your way. It's no good (for the reason given by @LMS2968 ) the second fireman getting on at Tebay. So the train has to stop somewhere well back from there, probably 20 or 30 minutes away, to allow that second fireman to get stuck in assisting in building up the fire. OK, at the point you don't need to stop for a banker (you've still made one stop, just 20 or 30 minutes earlier), but when you get to the top - what then? Somehow the spare fireman has to got to continue on the train until its next stop, then - without his own loco - catch a service train back to his original starting point so he is ready to lend a hand to the next service.

It's a really inefficient use of manpower - in an eight hour shift you might be lucky if you could assist 2 or 3 trains; your spare fireman is doing an hour of productive work in a full day and spending the rest of it unoccupied, or waiting for a train or on the cushions. And meanwhile your loco is too big for 90% of its daily duty, with all the additional capital expense that that entails.

Tom

 

Please note that post WW2 the SNCF bought hundreds of locos from the USA
These were all simple 2 cylinder machines
What they required was high availability and high milage

 

Was it ever proposed to electryfi Shap banking operation?

 

Being unbalanced 141R locomotives were not alowed to run faster than 100kmh.
Their minimum steam consumption was 14.1lbs/ihph at 1975 ihp compared to 11.2 for the french 141P at 2470 ihp.
It interests me to think what 141Rs could have done as two-cylindered compounds with better balancing.

 

No. It was always steam. One of the main functions of the bankers on Shap often wasn't so much to assist the train engine to get the load to the top but to act as a defence against coupling breakage and runaways of unfitted goods trains beyond the capacity of the brake van to control them. I read somewhere that any train with more than nineteen unfitted wagons had to take a banker. Although liberally provided with catch points, clearing up the mess and the closure of this major route while this was done would create havoc.

On the passenger side, the big Pacifics generally declined a banker unless over fourteen coaches over Shap and twelve coaches over Beattock. The engines could physically manage more than that but it was to ease the load on the fireman. By Tebay he would either have come all the way from Euston and would have to continue to Carlisle, or come on at Crewe and would continue to either Glasgow or Perth, both getting on for 300 miles, so this made a hard day a bit easier.