it is just the laws of inertia. the drivers were needed to move heavy loads over hill and dale. ask any passenger engineer who ran steam. once moving it takes less energy to keep it moving. i.e. inertia
wjstixThat means 15% of the X goes to each of the four cylinders - 60% divided by 4. If you "turn off" two cylinders, you still need 60% of X to pull the train, so you'd send 30% of X to the two working cylinders - 60% now divided by 2.
You seem to think that the same losses occur with four cylinders as with two, and that reverse and valve arrangements will be precise down to very short cutoff. (There may also be issues associated with increased lubrication requirements if both engines are under steam, but I suspect these would be minimal.)
I thought that Paul clearly stated that his locomotive was much more powerful (in cylinder hp terms) than one engine at full throttle and best economic cutoff would produce. As with a booster: the 'whole' locomotive would be capable of starting any train it could pull -- and need both engines operating at relatively full 'capacity' at low speed to do that -- but then be able to move the train over the road with one engine operating up at the peak of its efficiency curve. So the question then becomes whether it's more cost-effective to run one engine (probably the rear one) at full power, and use the forward engine only as 'make up' (vs. adjusting the two engines in sync, as in normal operation).
The real issue is whether one engine uses the available boiler steam more efficiently than two at lower load, not whether there's not ample steam for the cylinders. It's explicitly a part-load-optimization discussion, not a maximum-performance question.
Overmod wjstix ... it seems to me that if you stopped sending steam to two cylinders, you'd have to send twice as much to the other two to compensate...so you'd still be using the same amount of steam. This would be true if the object were to make the same peak power from the locomotive during the 'interruption' in steam flow to one or more engines. But what Paul was saying is something quite different, and in part specific to the way locomotives operate. He is saying that precisely at those times the full output of the locomotive is NOT required, it may be better to operate with one engine (probably the rear one on a Mallet or simple articulated) at full power, with its valve gear positioned for more admission, and with the other one configured to use proportionally less steam (right down to 'drifting' level or even with flow cut off) instead of changing settings proportionally on both engines to achieve the same instantaneous or demanded drawbar HP. This is not a concern either of peak power or peak TE, but it is a concern with general train handling for loads below the full capacity of the locomotive, specifically including operating profiles with relatively steep grades but substantial downhill running. It's also a concern where valves or valve gear are not precise, or optimizable, for effective operation at short cutoff. If we think of a 2-6-6-4 as a "Berk and a half" with the running gear divided somewhat differently, what Paul is saying may be clearer: if the locomotive is operated as a long 2-6-4 with a variable-power six-coupled booster capable of operation as efficient as the 'main' engine at all speeds, Paul would say that the baseline use of water (and fuel) can be lower than with both engines working together continuously. (Implicitly included here is the recognized issue that an engine smaller than six-coupled is more than usually difficult to keep controlled, so dividing the drive into 'eight and four' is going to lead to more operational issues than it solves. That's not a point Paul raised, but it's useful to consider it in context.)
wjstix ... it seems to me that if you stopped sending steam to two cylinders, you'd have to send twice as much to the other two to compensate...so you'd still be using the same amount of steam.
This would be true if the object were to make the same peak power from the locomotive during the 'interruption' in steam flow to one or more engines. But what Paul was saying is something quite different, and in part specific to the way locomotives operate. He is saying that precisely at those times the full output of the locomotive is NOT required, it may be better to operate with one engine (probably the rear one on a Mallet or simple articulated) at full power, with its valve gear positioned for more admission, and with the other one configured to use proportionally less steam (right down to 'drifting' level or even with flow cut off) instead of changing settings proportionally on both engines to achieve the same instantaneous or demanded drawbar HP. This is not a concern either of peak power or peak TE, but it is a concern with general train handling for loads below the full capacity of the locomotive, specifically including operating profiles with relatively steep grades but substantial downhill running. It's also a concern where valves or valve gear are not precise, or optimizable, for effective operation at short cutoff.
If we think of a 2-6-6-4 as a "Berk and a half" with the running gear divided somewhat differently, what Paul is saying may be clearer: if the locomotive is operated as a long 2-6-4 with a variable-power six-coupled booster capable of operation as efficient as the 'main' engine at all speeds, Paul would say that the baseline use of water (and fuel) can be lower than with both engines working together continuously.
(Implicitly included here is the recognized issue that an engine smaller than six-coupled is more than usually difficult to keep controlled, so dividing the drive into 'eight and four' is going to lead to more operational issues than it solves. That's not a point Paul raised, but it's useful to consider it in context.)
ACY In the early 1960's, all switching locomotives on B&O's Akron Division were Alcos. Except at Lordstown, Ohio, where GM has (has) a stamping plant. That plant was switched by EMD switchers. At that time, a B&O shop electrician in Akron told me an Alco showed up to switch the plant when it opened, and the crew was ordered off the property and told to come back with an EMD. I can't vouch for the story's accuracy, but it's consistent with other things I've heard. If it's not accurate, it's a fun story anyway. Tom
In the early 1960's, all switching locomotives on B&O's Akron Division were Alcos. Except at Lordstown, Ohio, where GM has (has) a stamping plant. That plant was switched by EMD switchers. At that time, a B&O shop electrician in Akron told me an Alco showed up to switch the plant when it opened, and the crew was ordered off the property and told to come back with an EMD. I can't vouch for the story's accuracy, but it's consistent with other things I've heard. If it's not accurate, it's a fun story anyway.
Tom
In the late 70's GE had a plant in Columbia, MD which was served by the B&O yard at Jessup, MD. Jessup got allocated GE engines from the C&O roster. Crews hated them - but you have to please your large customers or the end up being small customers - if you are still in business.
At that point in time, Baltimore Terminal was using Fairbanks Morse yard power and transitioning to EMD as the FM's began their march to the scrapers.
Never too old to have a happy childhood!
As an architectural acoustical consultant, I did work closely with both Eero Sarinan and Minoru Yamasaki, and both turned out to be favored architects of Pat Maginnis and did some work for the NYNH&H, as well as GM, with both having offices in the Detroit area. Eero was fond of telling the story that he used to pull up to the GM office parking lot in downtown Detroit in his rather beatup looking Plymoth Suburban station-wagon, until he got a note from his GM contact they would prefer him to arrive in a GM product.
daveklepperI do not know why you had to bring up GM and NCL in a discussion of steam.
It was initiated by the closing comment from rbandr:
I am sure GM would not have wanted this 2 come about. not then or now?
There's a fairly common 'conspiracy theory' that much of dieselization (with EMD power) was driven by GM threatening (implicitly or explicitly depending on who tells the story) to withhold their new-automobile shipping from any road that retained stesm, or did not buy EMD products. What I wanted to illustrate with the bus comparison was that innovative technology and design was much more likely to have produced the observed 'market success' -- both in the design of the E and then F and GP locomotives, and in the design of the monococque buses with Austin's V-drive and practical diesel power.
In essence, adding just a bit to Dave's comment, the 'conspiracy' if I remember correctly was to establish sweetheart deals for parts and support that favored GM -- wasn't there a similar problem for many years with key parts of the EMD 567 engines being 'dealer-only' at an artificially high profit margin? That doesn't (significantly, imho) affect the underlying efficiencies and economies that made even first-generation diesel power preferable over steam.
I do not know why you had to bring up GM and NCL in a discussion of steam. There were specific streetcar lines that would have been kept if economics and city planning considerations had governed. Roy Chalk wanted to keep the all-PCC well maintained Washington DC streetcars but Congress voted a law to force bus replacement. NCL actually wanted to keep Townsend-Catonsville and one other line (Elliot City?) running but Baltimore revised its one-way street plan, which would have required much major track reconfiguration at considerable expense. Now streetcars are returning to DC and have in effect already returned to Baltimore.
But I second you on zero "conspiracy" regarding bus replacement of streetcars. GM and its NCL partners migiht be accused of aggressive business practices, but the only conspiracy, and a consent decree and fine concerned the exclusion of other bus manufactures, and was not related to streetcar replacement.
Just to ampllify on this, saying a Mallet "has" two engines would be a better way to put it, making the technical distinction a bit more clear. If you have problems with the semantics, remember that a Mallet is technically a 'locomotive', to distinguish it from confusion with the technical use of the term 'engine' which is substantially as Crandell has described it.
Duplex-drive locomotives also are said to have two 'engines', even though there is no hinged physical separation between the chassis of the engines.
If you want to distinguish a separate term such as 'motor unit' or whatever to allow you to make continued reservation of the term 'engine' for the locomotive as a whole, and define your term as such in discussion, you are certainly free to do so. Just don't start claiming it's a correction... ;-}
Actually, a Mallet is two engines. Two sets of valves, pistons, rods, and drivers. They are under one boiler, but the boiler furnishes steam to two engines.
-Crandell
I think the OP stems from a misunderstanding of how steam engines work. The Genset type diesel, where you can have one, two or three diesel motors running to generate power, isn't at all like a steam engine. A Mallet isn't two steam engines, with two fires and two boilers. If it was, maybe there would be a way to turn one engine "off" when not needed. But a Mallet or articulated engine is one engine - with one boiler, one firebox - and two sets of drivers.
Besides, it seems to me that if you stopped sending steam to two cylinders, you'd have to send twice as much to the other two to compensate...so you'd still be using the same amount of steam.
rbandr the germans built a working V-8 steam engine that was not saved after the end of world war II. it was envisioned to be used as the building block for multiple use steam engines. ie multiple engines controlled by one pilot as is some times used to call a euro engineer. I am sure GM would not have wanted this 2 come about. not then or now?
the germans built a working V-8 steam engine that was not saved after the end of world war II. it was envisioned to be used as the building block for multiple use steam engines. ie multiple engines controlled by one pilot as is some times used to call a euro engineer. I am sure GM would not have wanted this 2 come about. not then or now?
Why's that? GM already had a better answer to steam of any kind, including the Besler designs or the International rail motor that did not depend on a firetube boiler (as the 19 1001 did) or on a great number of precise parts in each motor with the valve gear synchronized by a great number more precise parts.
The roughly contemporary American counterpart of the German motor locomotive was the proposed B&O W-1 class, engines also by Besler. This design progressed to the point that the boiler and at least one of the motors was built for testing -- but it was not 'proceeded with' because, in a word, the EMD EA was a better solution for B&O, even at its higher cost for a chronically cash-starved railroad.
It would be difficult to coordinate multiple units of DR class 19, particularly since the particular topic of this thread, the selective 'depowering' of some of the motors on the locomotive, or on some of the locomotives in a "MUed" consist, would be technically difficult if not practically unworkable given American maintenance practices. It is difficult to imagine running steam boiler-equipped consists with the trailing units 'unattended' unless oil fuel were used, perhaps adapting the systems used on the LBE push-pull train locomotives. Then take up the question of water supply.
Now go back and look at the copetitive advantages that Dilworth, Hamilton et al. were putting into the competitive approach to road power. It was simply a much better way of getting most of the parts of the job done. GM needed no 'conspiracy' to get it to displace steam, any more than they actually needed NCL to get streetcar lines to replace their old physical plant with the new monococque diesel coaches...
There were evidently people in the United States interested enough in 19 1001 to have her brought over here after the War. However, things changed so dramatically even by the time the locomotive arrived here that no one cared to take it up. DB was offered the locomotive for the cost of shipping it back -- but declined. It was probably scrapped as an expedient piece of PR due to scrap requirements during the Korean War... but no one cared enough to pay the scrap price to preserve it, which I think is pretty telling.
MU operation is possible with diesels or electrics. USA steam locomotives were never built for mu operation, but I understand there was at least one European example. When I posted double-heading I was referring to steam and only steam. And sure, nearly all double heading and many helper districts were ended by dieselization.
Regarding CP's lack of really large power despite the continuous 2% eastbound, before WWII and for a few years after, CP had zero trouble being a profitable concern. Its railway connected the population centers and by comparison, CN ran through a lot of wilderness - at the time. Today with import and export busines being a far greater percentage of the freight carried, CN has the better route with a far lower grade eastbound and about the same westbound. CP's steam locomotive design was more concervative than most North American railroads (Southern of course being even more conservative, and there were others), with the locomotives of medium power being of more universal applicaton, and when more power needed, double and even triple-heading and/or use of helpers. With labor costs less of a factor, in those days.
There were a lot of short helper districts in the steam era that were abolished with the conversion to diesels, long before the development of DPU in the 1960's.
daveklepper And in those days labor costs were not subject to the continual scruteny that they are today, and manned helpers and double heading were much more common.
And in those days labor costs were not subject to the continual scruteny that they are today, and manned helpers and double heading were much more common.
"Double heading" more common? Don't we call that "Multiple unit operation" nowadays?
And as far as manned helpers, the only reason they are less and less common in recent years is the widthspread adoption of DPU's..
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Keep in mind that the idea of 8 powered drivers and 8 idle drivers is what is called a booster or auxilliary engine. Consider a 2-8-0 with two boosters on the four-wheel tender trucks -- the locomotive is essentially a 2-8-8-0 or should I say a 2-8-0+0-4-4-0. Boosters were used to get a heavily loaded train over an adverse grade at places where a helper or larger locomotive was not desired. Boosters were what is suggested in the previous posts -- an engine that was idle when not needed but powered when needed at starting or on a tough grade. Remember an articulated is two engines under one boiler. A tender booster on a non-articulated is a second engine powered by one boiler. Of course there are reasons why boosters were not made as powerful as the rear engine under a 2-8-8-0 for example -- tender boosters generally were built to add about 12,000 to 25,000 lbs. of tractive force -- but if you wanted a very powerful booster it could be done although it wouldn't be the most practical way of doing things.
p.s. I don't think there would really be a savings between having say 8 drivers "idle" and 8 drivers getting steam, as opposed to all 16 drivers getting steam. The engineer could use the throttle and "cut off" to control how much steam went to the cylinders, and good engineers were expert at using steam (and hence fuel and water) very efficiently. At speed on level track, a little steam going into all four cylinders would be all that was needed to keep the train going.
The problem to me is that if you had a situation where you had the need of all drivers on a Mallet or Articulated at the start of a train trip, then had a stretch where you only needed half of the drivers for a long stretch, a railroad would probably just put a 2-8-2 or 2-10-2 etc. on the train, with a trailing 2-8-2 or similar mid-sized steam engine as a helper, which could be cut off when no longer needed.
Railroads generally bought or built steam engines to meet a particular need. The Missabe had 2-8-8-2s and 2-8-8-4s to handle mainline ore trains because it had difficult up-and-down undulating mainlines to the Mesabi and Vermillion iron ranges, so needed the big engines to do the job. Neighbor Northern Pacific had a relatively flat mainline to the Cuyuna iron range, so used 2-8-2 engines with a helper in the first part of the journey from Superior WI where there was a grade for empty trains to contend with.
It's fun to discuss power but as I think we all know the diesel didn't replace steam because steam lacked power. There were so many other better reasons, the multiple unit feature that Paul mentioned being one of the most important. Equally important was that steam was just too expensive to operate compared to diesels. And steam locomotives didn't have the availability of a diesel -- not only was there the lengthy servicing after every run but they needed frequent boiler washouts and other periodic maintenance that a diesel didn't require. I hate to say it but the diesel is so much more efficient and easier to live with. I've been a steam fan since I got dusted with cinders in my baby carriage, or listened to a big mountain type start a heavy freight at the end of the street where I was born, or because of the times my father would drive me down the rutted back road to the roundhouse where dozens of engines were in sight.
Actually what I should be saying is that I enjoy thinking about how steam locomotives could be better vis-a-vis other steam locomotives but I don't think it is really possible to make a steam locomotive competitive with diesels. I'm sorry they are gone but even though I never got excited about diesels they are better. Sorry that I'm off topic.
nhrand Let me give another example. I have a 2-8-0 that produces 45,000 lbs. of tractive force at starting. It has 189,000 lbs. on drivers for a factor of adhesion of 4.2 and an axle load of 47,200 lbs. Let's say I want to make the engine suitable for a light rail branch so I extend the frame and make it a 2-10-0. Another 2-8-0 that is a duplicate costs me two much maintaining all those drivers so I drop an axle and make it a 2-6-0. Each of the engines, the Mogul, Consolidation and Decapod produce the same tractive force, carry the same weight on drivers and have the same factor of adhesion. The only thing that changed is the axle load. The Mogul is suitable for only my heavy duty main line since it now has an axle load of 63,000 lbs but the Decapod is a light 37,800 lbs per axle. Nevertheless, each of the three locomotives will pull the same size train. Here again the point I am making is don't focus only on axles and wheels when judging a steam locomotive.
Let me give another example. I have a 2-8-0 that produces 45,000 lbs. of tractive force at starting. It has 189,000 lbs. on drivers for a factor of adhesion of 4.2 and an axle load of 47,200 lbs. Let's say I want to make the engine suitable for a light rail branch so I extend the frame and make it a 2-10-0. Another 2-8-0 that is a duplicate costs me two much maintaining all those drivers so I drop an axle and make it a 2-6-0. Each of the engines, the Mogul, Consolidation and Decapod produce the same tractive force, carry the same weight on drivers and have the same factor of adhesion. The only thing that changed is the axle load. The Mogul is suitable for only my heavy duty main line since it now has an axle load of 63,000 lbs but the Decapod is a light 37,800 lbs per axle. Nevertheless, each of the three locomotives will pull the same size train. Here again the point I am making is don't focus only on axles and wheels when judging a steam locomotive.
A late-era 4-8-4 Northern exceeded the peak HP of a 4-unit EMD FT Diesel locomotive whereas it had about the starting tractive effort of a single FT Diesel locomotive unit.
No, axles and starting tractive effort doesn't equal power. But you have to have enough weight on axles, and since the axle load is limited by the standards to which the track structure has been built, you have to have enough quantity of axles times that weight to get the required starting tractive effort at your working adhesion factor. If you don't start the train, or if you stall on the ruling grade, you ain't going nowhere -- and fast.
Agreed, once you start the train you will need power to run the train at anything beyond a walking pace. I just got through reading Huddleston and Dixon, The Allegheny - Lima's Finest. The C&O replaced the high horsepower Allegheny's with multi-unit DIesels with greater starting or low-speed tractive effort but much less power. They were able to run the same trains or heavier trains through the mountains, but on some divisions it took them more than twice as long.
But maybe that is what the C&O wanted for "rock trains" (bulk coal traffic) -- they wanted to get the train over the hills and didn't care how long it took to get there. Steam is at a disadvantage compared to even first-generation Diesels, where with multiple units, you are only limited by the pulling strength of the couplers.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
To Overmod and others:
You wrote that the point of the discussion is "we're concerned with reducing the power to four of the eight axles" (using a 2-8-8-4 as an example).
The way to reduce the cost of operating the 2-8-8-4 when less power is needed is to reduce the cut-off -- that is reduce steam consumption and thereby fuel use. That is the way it was done in the steam era but if you think that reducing the consumption of just one set of cylinders would be better it could easily be done. All you have to do is arrange separate cutoffs.
Many French locomotives had separate cutoffs to the sets of cylinders on four-cylinder compounds. However, French engineers were noted for their ability to operate locomotives efficiently. American engineers were noted for operating less efficiently -- how many failed to operate with a fully opened throttle or kept the reverse lever in the corner ? American engineers would probably not look kindly on separate cutoffs. How many engineers disliked the valve pilot because they thought they knew better and didn't want the company to have a record of how they operated their locomotive.
I'm reminded of one of the Pennsy Altoona test plant reports - for the 2-10-0 I recall. The Pennsy knew that some engineers failed to fully open the throttle since many felt they did better operating with a partly opened throttle. Therefore the Pennsy tested the locomotive with a partly opened throttle as well as testing properly with a fully opened throttle. As I recall, there were differences but I couldn't see that they were dramatic. In any case, I have this in mind because it shows the Pennsy knew engineers had their own ways of doing things even if they weren't the right way. If you did have separate cutoffs on your 2-8-8-4 which would reduce or eliminate the steam flow to just one set of cylinders you probably would have a hard time getting the engineers to adust the separate cutoffs for the power needs. That is why they kept things simple in this country -- can you imagine an average American engineer in the age of steam trying to operate a french compound ? Some would enjoy it but I suspect most would take the easy way out.
Regarding the use of something like dynamic brakes on a steam engine, I think the so-called "water brake" that was applied to some locomotives used on heavy mountain grades was similar to what you were thinking -- that is using the locomotive's cylinders to control speed on a down grade.
I very much enjoy thinking about steam locomotive design but sometimes I think we may attempt to redesign the wheel. There were many brilliant men designing and improving steam locomotives in years past. Somtimes they made mistakes but there isn't much that escaped their thinking. They didn't have the benefit of modern technology but they did wonders with what they had. I remember reading an 1840's treatise on steam locomotives and was amazed at how much the ideas were totally modern. However there are very few people still alive with technical and theoretical knowledge of steam locomotive design -- many of us probably know less than they did in 1840.
Thanks. My opinion is that helpers are hard to beat for ruling grades, particularly short ones. But the idea is very interesting for triplexes.
I've discussed this off-list with Paul.
Personally, I don't think many railroads would buy a large, heavy locomotive with two full sets of reciprocating running gear, just so one set could be left substantially idle at speed. That's based on my assumption that operating profiles with long enough ruling-grade sections justifying articulated power, but long enough 'easier' sections to make meaningful gains in part-load running economy exist, and that the capital and basic maintenance charges on the larger locomotive would be less than the fuel/water and marginal-maintenance savings resulting from operation of the system. (I'm presuming these locomotives are equipped to operate across multiple divisions without engine change, and have adequate support in place to make that achievement seem ordinary, as it was in fact ordinary even for first-generation diesels...)
It's just the opposite of the logic of the booster (and to a different extent the asynchronous compound) where the additional power is provided via the auxiliary engine(s) only at slow speed, when needed.
Having said that, I'll promptly make what looks like a flip-flop and note that a comparatively simple set of control changes would enable a simple articulated to operate in the manner Paul describes -- and having that flexibility easily at hand, backed up by the proper training and support to use the features effectively, might easily demonstrate substantial benefit to operations. I do have to confess I'm not smart or sensitive enough to be able to fire one of these things effectively for maximum efficiency, especially with solid fuel... but I can make a very good start on quasi-artificially-intelligent aids to simplify the job.
Overmod, what is your opinion of the original idea? Do you think it is practical, useful...?
This is all getting away from the original point of the thread.
Max practical TE developed by any locomotive is a function of the number of axles and the applied axle load (and hence factor of adhesion). The ideal is to have all the carrying axles powered just up to their practical adhesion limit (and the history of the Duplexes and early diesels with limited slip control will give you additional detail on what 'practical adhesion limit' implies...)
Diesels (and the Jawn Henry TE-1) are horsepower-limited in a way a reciprocating locomotive is not: the engine horsepower limits the rail horsepower, and that in turn can limit the top speed regardless of what the starting TE of the locomotive might be raised up to.
What the original post involved was not using boosters on carrying axles to use 'a bit more' of the locomotive's total weight for adhesion, it was to use a group of DRIVING axles less intensively at higher speed after starting, to save fuel and perhaps wear once the train reaches speed, is on a net downgrade, etc. In other words, it is converting some percentage of the driving axles into carrying axles on demand.
Taking the example of a 2-8-8-4 -- we aren't concerned whether there is a Franklin booster on the trailing truck, or a Bethlehem auxiliary locomotive on the tender. We're concerned with reducing the power to four of the eight axles, perhaps all the way down to zero, relying on the other four's power to handle the train plus the engine mass when only four axles can do the required job.
(I don't believe the subject of a counterpressure brake on the four 'idled' axles exclusively during net-downgrade running has been discussed, and its use is somewhat more limited than the diesel-electric alternative (dynamic braking) -- but it is a potential feature of the approach, whereas it is not practical to do this with a production Franklin booster, and very unlikely with an auxiliary locomotive...)
nhrand ... Here again the point I am making is don't focus only on axles and wheels when judging a steam locomotive.
... Here again the point I am making is don't focus only on axles and wheels when judging a steam locomotive.
You've made your point very nicely. I think the confusion began to arise when a larger locomotive was built so as to produce more power, it generally required more axles to keep the axle loading within limits. The casual and not-so-casual observer is led to believe that more axles means more power. I'm sure designers would gladly have given a 4-4-0 the ability to generate the power of a 4-8-4 if they could have done so without crushing rails, ties, ballast, and bridges..
ChuckAllen, TX
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