With all the talk about super power and big boilers, did the old steamers in the early 1900's ever run out of steam thus limiting their top speed.
Also it seems everwhere I read the old americans, 4-4-0 didn'nt have much top speed. They had big enough drivers.

The 4-4-0 was usually capable of speeds beyond the safety of the track it rolled on. One limit would be the nerves of the engineer when trying to make up time when running late. Remember John Luther "Casey" Jones? Oh well, he had a 4-6-0, but the work is the same. NYC's 999 was an example of high-speed capability
for a 4-4-0, running well over 100 mph 'way back then with a short train of about four cars.

Yet trains were run by schedules. They dictate the speed required between stops. Schedules were set up to be within the capability of the motive power used and provided an element of safety as well. Further, limiting factors of the terrain also had to be taken into account - grades, curves, bridges, tunnels, etc. However, not within the schedule is the weather - fog, dew, rain, snow and ice (weeds too!), any of which can reduce effective tractive effort when out on the line.

The load of hauling a train is another speed-limiting factor. While a steam loco can run with a train it may not be able to start, if the speed drops too low or it stops on a grade there can be a problem. Such a stalled train then needs to be 'doubled' that is, moved in two parts or sections. This was so even in later times.

Fuel quality was yet another factor. With a tender load of poor coal that was laced with 'real estate' (rocks, dirt, spikes, pieces of wood, etc.) one could run out of steam if demand was near the boiler's capability. A fire using such fuel would not be hot enough to maintain the required evaporation rate.

This affects load hauling capabilty as well as speed. In such cases the train stops. Time is taken for a 'head of steam' to build up which when back underway, is consumed faster than the fire can replenish it. So another stop would be needed and so on, until the run was finished.

Or, have the engine or the fuel replaced somewhere along the run. No doubt there were some interesting 'conversations' while on the carpet of the super's office following such an event.

Ed Bommer

quote:

With all the talk about super power and big boilers, did the old steamers in the early 1900's ever run out of steam thus limiting their top speed.

The short answer:

yes they did.

The long answer:

Steam locomotive design is a balancing act. Many evolutionary steps took place in the early 20th century to increase the speed potential of steam locomotives.

A common freight locomotive of 1900 would have been a 2-8-0 with a grate area of 30-40 square feet with its fire box confined between the rear driving axles and using saturated steam at 150-180 psi and slide valves. A locomotive like this might have a tractive effort of about 40,000 lbs and its horse power (and therefore speed) limited by the restricted size of the fire box. A locomotive like this could pull a train of several thousand tons over a level district at 10 to 20 MPH.

By 1910, heavier track on many lines allowed higher axle loadings and therefore a heavier and more powerful 2-8-0. A good rule of thumb for steam is to design a tractive effort of about 1/4 the weight on the drivers. A higher tractive effort to weight ratio (factor of adhesion) would produce an inefficiently heavy locomotive, much less and it couldn't efficiently utilize the available power. Our "super consolidation" could now have enough weight to produce 50,000 to 65,000 lbs of tractive effort. It would need larger cylinders to produce the extra force even with a boiler pressure of 180-200+ lbs. It likely uses superheated steam and piston valves. Improvements in materials and lubricants allowed the use of higher temperature steam, improving thermal efficiency. Our bigger, heavier, higher temperature, higher pressure, more efficient machine still needs more energy so a bigger fire box is required. To do this on a 2-8-0 frame the only way to increase the grate area is to make it wider than the drivers by lifting the boiler high enough for the wide fire box to clear the wheels. This made for some locomotives that looked short, fat and very top heavy. Our big consolidation might now be able to pull 3000-4000 tons on a level district at 15 to 25 mph.

To improve our freight locomotive with a similar axle load limitation something had to get longer. The best solution was to take our boiler and add an even larger fire box, up to about 70 square feet and moved down and back over a trailing truck. With a longer 2-8-2 wheel arrangement we can now have a combustion chamber in front of the fire box and longer flues for more efficient heat transfer. The tractive effort and train size will be about the same as for our heavy 2-8-0 but we can now move the train at 30-40 mph and maybe even pinch hit on a passenger train if needed.

By the mid 20s and into the 1930s the super power concept yielded 2-8-4s and 4-8-4s with about the same tractive effort as a heavy 2-8-0 but 90-100+ square foot fire boxes, 225-300 psi steam, longer flues, more superheater surface area and the ability to move a 3000-4000 ton train at 40-50 mph, still track speed on many main lines and about as fast as you would want to sustain in the era before roller bearing equipped freight cars.

The super power locomotive might not move a larger train that a consolidation, but it will be serviced and back out on the road before the slower locomotive brings its train into the yard, moving more ton miles per day and earning us a good return on our super power investment.

See http://en.wikipedia.org/wiki/PRR_E6

Pennsy designed its E-6s Atlantic with an especially large boiler to allow sustained high speed running and/or frequent starts and stops. Apparently a very successful design.

Read more in the Kalmbach book from the 1960s entitled "Apex of the Atlantics".

Most passenger train schedules (and Employee Time Tables) limited speed to about 70 MPH, and less on many roads, until the Depression-era speedup which came with lightweight trains. Fast trains normally were not long trains in that era. Also, the lack of really fast speeds was compensated for by limited stops, a concept that went out the window in the 1950's as secondary trains were pulled off and limiteds had to absorb their head end cars and extra stops.

There were exceptions for certain trains, but that was the norm. However, most railroads had a special instruction which permitted Engineers to use prudent judgment and exceed authorized speed when running late and trying to recover time to get back on schedule. The Santa Fe's version of this contained an admonition to consider passenger comfort on curves and to be mindful of dining car mealtimes.

A question that has rattled around in my head for awhile is whether or not Lima's super-power technology could have alleviated the Triplex's penchant for using up steam faster than it could supply itself.

---PCJ

Probably, but a boiler/furnace system THAT big would have, most likely, requried a separate tender.

Both the Erie and the Virginian triplexes had several problems. They either needed a bigger boiler or smaller cylinders. As built, they were out of balance. However, the whole concept had another less obvious flaw - half the exhaust steam was sent to the rear engine and went out a separate stack. This deprived the boiler of much-needed steam to produce draft. In other words, the locomotive had to produce say 100,000 lbs of steam/hr with a draft produced by 50,000 lbs of steam/hr. This problem would have to be addressed in any revised triplex design.

Lima's super-power concept of a larger firebox in proportion to the cylinder volume would have certainly helped!

When the tender got low on coal and water that 3rd engine must have gotten very slippery due to less weight on its drivers, unless it was sized to only produce the max TE a nearly empty tender would allow.

Wyhog