This week,I tested my DCC converted N scale Challenger on the club’s layout and have been delighted by flawless running,which makes the conversion complexity worthed it.
After a little while,I elected to test its power by adding cars and having it pull the string up the layout’s “Peninsula climb”,which is the most demanding section of our N scale layout.Amazed I was by how powerful this baby is as I added 18 cars to it without any real sign of being overloaded while my other strongest locos (Kato SD-90’s) can’t reach the top of the hill with only 12 cars.They start spinning and speed soon fades away.
I understand that the difference is in the traction,as the Challenger probably is heavier (I didn’t weigh them) and the fact that it’s wheel diameter is larger may affect also,since both have 12 wheel drive.
But this got me wondering if this was also true in the real life,meaning that a steamer would in many cases have much more pulling power than many big diesels.If so,then how many big D’s would it take to match let’s say a Big Boy?
I think I remember reading somewhere that a Big Boy could pull over 100 loaded reefers at over 100 MPH. Assuming 50 tons (cargo) per car plus empty weight of 25 tons each, that would equate to 7500 tons. It would probably take at least 3 modern SD’s to pull that tonnage, and not even at the same top speed.
On the other hand, Southern Railway had 2-8-2 Mikado’s running on the “Rat Hole” division, which were rated at 1750 tons on the division. When the FT’s first arrived on the scene, a 4 unit set was rated at 3000 tons on the same division, and saved over an hour on the running time (presumably, no fuel and water stops).
Keep in mind today’s railcars are much heavier than those of the '40’s and '50’s, so a train of the '50’s with 50 cars may weigh 3750 tons (at 75 tons per car), a modern train with 50 cars may weigh 6250 tons (at 125 tons per car).
I love steam engines too, but more like the other way around. How many big boys to match one diesel? However, I do not know.
If steam engines really had a big advantage in power do you think the world’s railways would have changed? Especially in countries where coal is plentifull but oil has to be imported. Maintenance was a drawback with steam engines, but if they were much more powerful than diesels they could have found a way around that.
Sorry, the steam engine is spectacular but far less efficient and effective than a diesel electric. Of course if you put wires overhead you can dice the diesel part. Just electric and that is efficient (apart from the cost of those wires)!
Only the latest generation of diesels can match the most powerful steam engines one on one. On level track, a UP 4-8-8-4 could pull a train 5 miles long by itself. I seem to remember reading somewhere that an FT A-B set had about the same pulling power as a 2-8-0 or 4-6-0, and a 4-unit A-B+B-A set was like a 2-6-6-2 or 2-8-8-2 mallet.
The primary advantages diesels had over steam was greater availability - being able to make more runs per week or month than steam, and greater flexibility - you could use 1 diesel or 10 depending on how much power you needed…and only use one crew instead of one for each engine. But generally you had 3-4 diesels taking the job one steam engine had performed.
Why steamers were dropped isn’t even questionable.These beasts were messy,noisy,took a long time to get started and needed outrageous maintenance so no wonder why railways gladly parted with them when another option became available,even when considering their immense power.
But as wisely stated,I don’t think railways were too glad to lose all that power,wich pretty much explains the births of other very unique designs like the Veranda’s,GE’S Turbines and the DD series wich in fact were experiments trying to obtain the best of both worlds.But still,these all died for mostly the same reasons the steamers did,being mostly maintenance,fuel costs,noise and lack of flexibility and/or efficiency.
Now we have reached an era where even diesel’s days are counted,being replaced quite efficiently by electric powerhouses in many countries who are more and more aware of the pollution damages.They are a lot less noisy and messy and their maintenance is much simpler too.The electric traction motors have been here for decades so the only thing that keeps diesels alive are the enormous costs of building the network of supply lines.
I love steamers for modeling purposes indeed,but would certainly hate to have a Big Boy pass three hundred feet from my home ever so often.But i feel that steamers had a character of their own.
I don’t know how accurate is the info on Wikipedia, but according to the articles there the Big Boy tops out speedwise at around 80mph (and its TE reaches a maximum of 135,000 pounds at a lower speed range, around 40mph or so).
If the Wiki TE figures are right, then one of the more modern 6-axle AC-traction diesels should give the Big Boy a run for its money… I seem to recall the GE AC4400CW can develop a maximum TE of around 140,000lbs.
SW-1500 with 42,000 lbs.
RS-3 with 62,125 lbs.
SD40-2 with 83,000 lbs.
SD70MAC with 137,000 lbs.
GE Evolution series 166,000 lbs.
So, as you can see, initially, diesels could not compete with steam engines on tractive effort, one for one. But there were many other reasons which tilted the balance, some of which were mentioned in other posts here. A good list of many of the reasons can be found in answer 11 at this site: http://exotic.railfan.net/dieselfaq.htm
Hey guys, 2 points. First who ever designed a road diesel to be regularly operated as a single unit? Here in God’s Country the Milw took delivey of one of the first FT sets (ABBA) to run in the non-electrified gap between the Rocky Mountain Divn and Coast Divn electrified zones. One of the first changes they made was to the number board on the nose door. It originaly read 40. They changed it so that it could, by slipping in the appropriate letter, read 40, 40A or 40D because they found that generally two units could handle trains that previously had been handled by a Mikado or 2-6-6-2. (In train order territory on most roads the train was identified by engine number in which case you wouldn’t want two different trains running around the RR identified w/ eng.40)
Another factor nobody is addressing is the difference in series and parallel wiring on a diesel. To start, their motors are connected in series which provides maximum torque. After the train gets a roll on the wiring is changed (called transitioning) to parallel which utilizes the engines HP to provide speed. A modern steam engine could produce around 6000 HP, but only after it got up to speed (40 to 60 MPH depending on the engine). The diesel could exert maximum HP to start.
I read somewhere “a steam locomotive can pull a train it can’t start, a diesel locomotive can start a train it can’t pull.”
In actual practice during the steam/diesel transition period railroads found that diesel lash-ups, in most cases, could haul heavier trains at higher average speeds with lower costs than the steam locomotives they replaced.
On some grades railroads were able to eliminate helpers and at the same time maintain faster schedules.
One book which addresses this is D Day on the Western Pacific by Virgil Staff.
I guess you haven’t read the reports of the N&W’s Steam/Diesel comparision.
In actual practice, you need to compare the tonnage rating of each locomotive from employee timetables.
For example, the tonnage rating between Roanoke and Waynesboro, Va. for one N&W Improved Y5/6 was 3200 tons. The tonnage rating between Roanoke and Waynesboro, Va. for one GE Dash 9 or EMD SD70 is 2950 tons.
NUFF SAID!!!
FT’s were designed by GM to only be made as A-B sets connected by drawbars - in fact, there were no doors between the A and B unit, so if they had to be separated for some reason, their interiors would be open to the elements. The Santa Fe asked GM to make individual FT’s available, so they rigged up a way to add couplers to replace the drawbars. I think Santa Fe did some coupler modifications themselves.
The problem was that many railroads found one FT A-B set to not be powerfull enough for a typical train, but an A-B+B-A set to be too much power. The RR’s really needed three units (4050 HP). GM did make some A-B-A FT sets for a couple of roads, but many roads after WW2 bought F2’s A-units and added them to FT sets in A-B+A configurations on their own. These sets were sometimes called “FT-2’s”.
Something that needs to be brought up here is that tractive effort alone is not sufficient measurment alone to measure a locomotive. True, it is an excellent indication of it’s starting capacity, but it is not as exact as you might think. Believe it or not, every TE rating you see out there is measured directly from the weight on drivers. Many, many years ago when railroads were in their infancy, tests were done to establish in definate measurments how much a locomotive could pull. It was soon realised that the only factor that affected traction with relation to weight is the adhesion or “stikyness” of the surface of steel on steel. It was decided at the time of the testing to fix the formula for tractive effort slightly less than the percentage of adheasive force of steel on steel, to 25% and 30% of the total wieght on drivers. With the advent of creep control, another set of tests discovered that slightly better traction was developed, and a new standard measurment of 35% for AC creep control locomotives was instituted. These mesurements are standard across the board, for steam, diesel, electric, pnumatic, and all other kinds of locomotives.
What this means in effect is that no matter what two engines you compare, if they have the same weight on drivers, the both have the same starting tractive effort. and to an extent, they can both (in theory) move the exact same load over the same terrain.
This flat measurement is inherantly inaccurite. There are in reality dozens of factors in addition to weight that affect traction. For the sake of expediancy the FRA and NAR decieded to adopt this flat rate measurement, instead of subjecting ever single locomotive to a battery of tests every time it came out of the shop and may have had some of those factors altered by new parts. You see, it’s not just weight or the trucks that influence traction, its also the maintance that goes into it. Things like how the springs
During the transition era, the largest, most modern steam locos had both higher starting tractive effort and higher sustained horsepower than any SINGLE UNIT diesel then available. However, most railroads were not replacing Big Boys, Niagaras and Y6b’s. They were replacing USRA-vintage and older locos, many of which had been run to the verge of collapse coping with WWII traffic.
For that matter, different steam locos developed their maximum horsepower at different speeds. The N&W Class A 2-6-6-4 could measure 6300HP at the drawbar at 50mph, and would lose power as speed came down. The same road’s Y6 class developed its maximum horsepower, about 5400, at 25MPH.
Diesel locos develop their maximum horsepower standing still - or running at track speed. Since the electric drive de-couples the prime mover from the wheels, changing speed does not result in changing horsepower. Electric drive also provides a smoother application of power to the rails, resulting in a better adhesion factor than the 20-25% (of weight on drivers) common to steam locos.
It’s not really fair to try to compare 21st century diesels to steamers withdrawn from service half a century ago. Had reciprocating steam locomotives continued to evolve and develop, who knows what the combined ideas of Chapelon, Porta, Withuhn and others might have produced.
Quite so - just look at the “gas burner combustion” and other work done on South African Railways in the 1980s. In the prototype SAR “Red Devil” 4-8-2 efficency improvements over a standard SAR mountain was something like an 80% improvement in water and coal consumption (approx figures - I’m sure if someone looks this up on Wikipedia they can get the exact figures). However in order to get these improvements they had to use expensive bearing and alloy technologies, and double maintenance schedules, so ultimately diesel and electrics won the day.
The significant changes David Wardale made to the Red Devil were mostly related to the firebox, boiler and steam circuit. None of this required “expensive bearing and alloy technologies” - what is your source for that claim? Maintenance of the Class 26 was not greatly increased over a conventional steam loco, in no small part because the loco did not need to be flogged to achieve high performance. From talking to Mr Wardale, and reading his book, it is apparent that as in so many other cases, the decison not to proceed with steam development was based on political, not engineering, factors. Cheers, Mark.