GWR four-cylinder arrangement?

Call it what you like but it's not going to be much bigger than coal dust. The Pennsylvania Railroad, for one, calculated the extra coal consumption used by the stoker as 5% which includes that used by the stoker and the material going up the chimney. The 25% sounds like a finger in the air.

 

If you’ve ever emptied a smokebox you’ll know that what gets through the tubes and into there is certainly more than dust. A loco working hard will certainly end up with particles as big as 1/2”. Locos fitted with spark arrestors have fine mesh grids in the smokebox to stop large particles from being ejected up the chimney.
I can believe 25% as the small coal used in stokers will soon be burnt to a size where the exhaust will lift it and the steam jets used to place the coal help keep it off the firebed. However, I’ve no factual evidence to support it as I’m on holiday. I’m sure the stoker fitted 9F’s were tested and, if so, someone will have the report.

 

It seems to me that ......

The loco needs to be suitable to do the job required - hence the failure if the P2, sounds like a great loco BUT the rolling stock could not handle the force it could produce in the drawgear etc. Ditto the proposed Garret for the Southern would have no doubt have done an excellent job just not what was needed.

Then of course as you move into 'high performance' steam loco's you get the steam equivalent of a Deltic with manner of interesting issues living in an environment full of abrasive dirt and men with big hammers...........

 

Yes, I have emptied many a GWR smokebox, always without screens. I have never seen anything approaching 1/2". I would refer to it as char, fine, partially burnt coal particles.

 

Is this view not a little parochial? In the UK, there wasn't much requirement for anything above about 2,000hp. In France, the speed limit for express passenger at the time was 120kmh. Timetables had to be maintained and high hp was required, particularly on the undulating routes in eastern France. I don't think that anybody with any knowledge of the subject would describe the 240As, 240Ps and 242A1 as inefficient in comparison with other steam classes. Not only were they they more powerful than comparable classes but were also more economical in the use of coal and water. Maybe a little research would be advantageous? In the USA, the use of 5,000hp articulated locomotives would have been more economic than 2 x 2,500hp locomotives, which would probably have had stokers anyway. Stokers were fitted to most heavy locomotives by the mid-1920s and would later become a legal requirement, on safety grounds.

 

And the 5000 hp articulated locomotives in America were killed off by 1500 hp diesels lashed up in multiple.

 

The real issue of course is that a steam loco doesnt have a transmition.

As a result while a diesel or electric loco can produce full power across the speed range a steam loco cant hence the slogging uphill at close to walking pace

 

Erm . .. have you ever tried driving a heavily loaded diesel up a steep gradient?

 

I’ve seen the monster trains in the USA and in spite of the number and size of the locos on them, they don't go very fast up the grades.

 

Challenger 3985 slogging up the 1 in 100 of Archer Hill at “walking pace”.

 

What’s wrong with the first post? Within the limitation of adhesion, a diesel locomotive is a constant horsepower machine whereas a steam locomotive is a constant tractive effort machine within the limitations of its boiler.

 

What's wrong with it is that it suggests, even if it doesn't state, that whereas a steam engine struggles against gradients a diesel will fly up it with ease, which isn't the case. The power output of any internal combustion engine varies with the r.p.m.; there is a maximum power output at a given engine speed and the power reduces either side of that, and the engine won't necessarily reach the optimum r.p.m. at low road speed due to internal resistance within the motors and the load required by the main generator. The next problem is that, whatever the power output of the engine, the traction motors have to be able to cope with it and the wise driver, rather than pulling the controller over to the highest notch, moves it one notch at a time keeping the amps just below the red line. If you go over that the engine is going to throttle itself back and you're starting again and possibly having to reset the trips. But as speed, and therefore traction motor speed, rise the amps fall so you can apply another notch to bring the amps back up for more power to the rails. I was on a Class 85 electric leaving Preston southbound on a damp rail. Three of the ammeters were just below the red line but the leading one was much lower. This axle was slipping so not delivering power and drawing little current, but it cleaned the rails ahead of the others. Applying sand immediately brought the leading axle's amps level with the others, but it would fall again as soon as the sanders button was released.

Getting a heavy train moving with a diesel requires skill, and keeping one moving at speed also requires skill. They aren't the simply 'push-the-buttons' steam fans tend to dismiss them as. The drivers still needed skills with a heavy train, just different skills to driving steam. And they don't fly up gradients with heavy trains; they just don't need a fireman shovelling diesel fuel into the injectors.

 

Thank you for the point about traction current. In effect that limits the tractive effort at low speeds, if the adhesion limit isn't reached first. But can diesel not produce a more nearly constant power at the rail than a steam loco over a range of speeds?

 

Yes it can, but there are still limits as to the power which can be generated and then delivered; diesels (and electrics) do not have super powers when it comes to climbing gradients. There are still limits.

There are advantages and disadvantages to both traction types. If a diesel is rated at, say, 2000hp at flywheel and somewhere about 1600hp at the rail depending on speed, a steam engine is not necessarily so limited and can, for short period, produce power outputs well above its nominal capacity. The process is known as 'mortgaging the boiler', basically allowing the water level to fall to maintain a high pressure. This is obviously only a short-term possibility, but long enough perhaps to surmount a severe gradient?

Back in 1973 I was the guard on a goods coming up from Alec Dock to Edge Hill, the Class 40 was on maximum load and not at all happy about it. The driver was constantly moving the controller to deliver maximum power without going over the limit as we crawled up the steep gradients, all the while muttering curses or encouragement in turn. But even I was surprised when he turned to me and said, "I wish I had an 8F instead of this bl@@dy thing!"

 

Many many years ago I was talking to a former Chief Engineer of the Maid of Kent - Denny built steam turbine cross channel ferry.

He said that it was a dream, if you were running late you just opened everything up to full and away she went whereas on a motor ship the alarms would start to go and either you slowed down or it shut itself down. What of course running at full blast did to the Maids machinery who knows.

There was of course oil pressure and temperature gauges monitored by the MK1 eyeball.

 

Electrical equipment has a "Continuous Maximum Rating" (CMR) which, as the name implies, is the maximum output it can produce continuously before its life is shortened by excessive temperature. For short periods the output can be much higher, in very simplified terms it is limited by the volt drop through the various components of the electrical system. Of course the protection is likely to be set to trip at lower current levels than this. I used to calculate the protection settings for equipment in power stations, and the fire pump was always configured to operate in a "run to destruction" mode. There is no point in switching the fire pump off to save the motor if the building is burning down!

Sorry about the thread drift from GWR four cylinder arrangement!

 

You really don't know much about the work of Chapelon, do you, but that is easily rectified.

 

This is all absolutely true but fixed and marine plant tends to work at a constant speed and power output over a long period so the 'maximum' and 'continuous' ratings are vital and staying within them is critical. A railway locomotive however, whether steam, diesel or electric, is constantly varying both so the continuous rating would not normally be exceeded for any length of time. But the driver using full power, even for a short time, would watch the outputs to ensure that the maximum was not exceeded with all the immediate consequences that would bring.

 

That doesn't answer the question of why you'd continue to develop the steam locomotive rather than other technologies that give significantly greater efficiency across the piece. In the early 90s, I remember braking for the summit at Shap when hauled by a (mid-60s) class 86, hauling (late 60s) Mk2s. That shift was the future, not eking out the residual potential of the steam locomotive

Chapelon was doing remarkable things in the late days of steam, but the external combustion engine was being superseded by the internal combustion engine and, especially, electrification. In just the same way, what Hitachi and Cummins do with the diesels under the Azumas is excellent engineering, but it's ultimately trying to answer an already solved problem with a different, already superseded, solution.

 

The N&W in 1952 came out top against the EMD F7 demonstrator during testing. Other railroads found diesel cheaper, but on the N&W the steamers were almost always running. The coal they burnt came from the mines the N&W owned, so the fuel cost was less vs diesel. Thanks to the N&W lubritoriums, the crews could service a Y6 faster than an F unit, and the Y6, A and J classes were more powerful than the demonstrators. It was calculated that 6 F7's would be needed to replace one Y6. The only reason N&W finally gave in around 1959 was parts for feedwater heaters, water pumps ect., could no longer easily be found to keep the giants running.