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Offline Vladki

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steam to diesel transition
« on: November 21, 2019, 08:25:16 PM »
Hello James,

On the stephenson-siemens game we are now in 1950's - the end of steam era. But when comparing the steam and diesel engines, I can't find a good reason to abandon steam in favor of diesel. Diesel engines have half the power (gear = 0.5) and double the running cost (per km). Only the monthly costs are lower (no need for fireman on diesel engines). Was it really so that the running costs of (early) diesels were higher than of steam engines?
Also the electric trains have gear = 0.8. Is there any reason for this gearing?

Offline Freahk

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Re: steam to diesel transition
« Reply #1 on: November 21, 2019, 09:27:45 PM »
Is there any reason for this gearing?

I don't know why it was decided but I guess it is to compensate loss and power curves.
Power curves for diesel engines are pretty rpm dependant. You can't spin the engine infinitely faster, the power will start decreasing at some point, that's why these have a gearing.
Also, power at least for diesel mechanic or diesel hydraulic engines is always (at least i don't know any other source) given for the engine. There will be much more power loss in between the diesel engine and the wheel than there is power loss in between an electric engine and the wheel, simply because electric engines are more or less directly connected to the wheels or at least the axles. There is not much loss.

You can see this pretty well at most diesel-electric engines. Most sources provide diesel engine poer and electric engine power. Electric engine power is most often much lower than diesel engine power.
However,diesel-electric trains pwerform roughly the same as a purely electric train using the same engines, given the diesel engine can generate enough power for the electrical engines, which is most often the case.
Thus, diesel-electric engines should use a gearing of 0.8 and the electric engine power.

 which are for diesel pretty rpm dependent, whereas for electric engines rpm doesn't matter.


Edit: About steam and diesel engines, I guess these are handled slightly different ingame, at least this is what I encountered when I had the same problem as you do now.
Just give the new diesel engines a try and watch their maximum speeds and travel times in between stations. Steam engines will accelerate veeeeeeeeeeery slowly, when travelling at "higher" speeds, let's say ~100 km/h. Diesel engines will do better even though technical data suggests something else.

I guess I have eeven read something about decreased power of steam engines at higher speeds due to some real world economic factors which were implemented in simutrans-ex, but couldn't find it in the quick run. However, I guess James mentioned this so I guess he can better explain this.

Offline Rollmaterial

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Re: steam to diesel transition
« Reply #2 on: November 21, 2019, 10:12:36 PM »
It seems to have to do with the 1955 Modernisation plan being poorly thought-out: https://en.wikipedia.org/wiki/History_of_rail_transport_in_Great_Britain_1948%E2%80%931994#The_Modernisation_Plan
« Last Edit: November 22, 2019, 01:29:28 AM by Rollmaterial »

Offline freddyhayward

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Re: steam to diesel transition
« Reply #3 on: November 21, 2019, 10:16:44 PM »
The actual performance of vehicles needs to be simply communicated somehow. It is too difficult to mentally calculate it using force, power, weight, gear, etc, especially for new players. Something like:
50km/h: 12-15s
100km/h: 32-36s
150km/h: 72-84s
etc etc until top speed (e.g. 160km/h): 80-96s
Or perhaps a graph.

Offline Freahk

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Re: steam to diesel transition
« Reply #4 on: November 21, 2019, 11:02:42 PM »
Ye, that would be great!
In the best case we get a graph, alternatively we should be able to enter a speed.
The least useful variat would be a "accelerates to max speed in", however, this is not pretty useful especially for steam engines and local trains with small stop distances as these won't hit their maximum speed at all
For these it's much more important to reach slightly lower speeds very fast..
Especially to compare slow trains with faster trains for tracks where they can't hit their max speed anyways (or it's pretty unimportant because they can only reach it for very short times) it would be nearly useless to only show "accelerate to max speed in"
« Last Edit: November 21, 2019, 11:21:37 PM by Freahk »

Offline DrSuperGood

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Re: steam to diesel transition
« Reply #5 on: November 22, 2019, 12:02:02 AM »
According to some TV programs I watched, early British diesel engines were totally rubbish and often called worse than steam engines. They tried to build the diesel engines in the UK without foreign help so where as places like Gemany already had several decades of experience building them, they literally started from scratch. Further more government policy forced them to rush into the technology to meet artificial deadlines rather than when the technology was actually ready. The end result were some engines with extremely poor reliability and performance that were arguably worse than the complex and well refined steam engines they knew how to build.

Of course this quickly changed and engine quality caught up. After all they are simple diesel trains and not space rockets. Now the UK does not even make a lot of its engines, instead buying them in from Europe or at least from foreign controlled countries.

The cost per km was balanced very quickly from a spreadsheet to kind of match the maximum power produced. The costs were very rough estimates, which due to my limited knowledge on the subject are probably completely wrong. You can always pull request a patch to the GIT with balance improvements.

Offline jamespetts

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Re: steam to diesel transition
« Reply #6 on: November 22, 2019, 12:50:36 AM »
The physics should be balanced correctly; the costs have been subject to an interim balance very helpfully done by Dr. Supergood, but are not fully balanced yet.

The main reason for the move from steam to diesel in the UK (and elsewhere) was that steam power was very labour intensive, and become uneconomic as labour costs increased as they did rapidly after the Second World War. The early diesel locomotives were not always faster or more powerful than the steam locomotives that they replaced, but they were invariably much cheaper to run, especially in conditions of high labour cost. To simulate this properly, we will need to simulate the varying costs of labour over time. This is planned, but is some time off. They also had a higher availability as they needed less frequent maintenance, so fewer diesel locomotives could do the same amount of work than any given number of steam locomotives. To simulate that, we need to simulate differing availability rates. This is also planned for the next set of major updates, but I will not be able to resume work on this until I am able to put together a new computer as discussed elsewhere.

However, diesel and electric locomotives, as has been observed, do accelerate better than steam locomotives, by a long way. This is because diesel and electric locomotives are constant power machines whereas steam engines are constant force machines. The consequence of this is that steam locomotives have a lower power at lower speed, and so accelerate poorly. Also, steam locomotives were about 4-7% efficient whereas diesel locomotives were about 30% efficient; however, the saving in fuel is somewhat offset by the fact that coal is generally cheaper than oil.

The gear factor of 0.5 for diesel locomotives and 0.8 for electric locomotives is to enable us to use power figures taken directly from official sources without modification whilst at the same time simulating powertrain losses realistically. A diesel locomotive's quoted power figure is usually at the point of the output of the diesel engine. Thus, the losses in converting that power to hydraulic or electric force to drive the train, as well as direct transmissional losses between the final drivetrain and the wheels need to be taken into account. For electric locomotives, the power quoted is the output from the electric motor, which means that only the second type of losses have to be taken into account. For a steam locomotive, power figures are not generally given and I have had to calculate and extrapolate these using a spreadsheet with data from real steam locomotives correlated with certain essential power characteristics; but, unlike with a diesel or electric locomotive, there is no engine that is in any way separate from the transmission, so the only possible power measurement is power at the rail, which is why these have a gear factor of 1.0. The comparison between the power at rail for all three types of locomotives (taking into account what Simutrans calls the "gear", i.e., the power reduction factor) should be accurate.

Offline DrSuperGood

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Re: steam to diesel transition
« Reply #7 on: November 22, 2019, 04:13:56 AM »
They also had a higher availability as they needed less frequent maintenance, so fewer diesel locomotives could do the same amount of work than any given number of steam locomotives.
This might not have been the case with early British diesel. They were prone to breaking down and if they were weaker than the steam engines they replaced they would not be moving as much around per journey or unit time.
However, diesel and electric locomotives, as has been observed, do accelerate better than steam locomotives, by a long way. This is because diesel and electric locomotives are constant power machines whereas steam engines are constant force machines. The consequence of this is that steam locomotives have a lower power at lower speed, and so accelerate poorly.
Steam engines also have less tractive effort for their weight. All the weight applied to the leading, trailing wheels and tender is not used for driving wheels so cannot help increase total tractive force. An electric or diesel locomotive can drive all its wheels so all the engine weight can be used for tractive effort. On top of this the smooth motion of the electric motors allows more tractive effort to be produced from the same weight on driving wheels. The diesel and electric locomotive acceleration at low speed is limited by this tractive effort.
Also, steam locomotives were about 4-7% efficient whereas diesel locomotives were about 30% efficient; however, the saving in fuel is somewhat offset by the fact that coal is generally cheaper than oil.
Steam locomotive efficiency could have been improved if the idea was developed further. Fundamentally the same principles are still used for coal and even nuclear power generation today. For most countries power efficiency was not a major drive to move away from steam, rather the other benefits/efficiencies that diesel and electric locomotives brought were.

In India there are still some commercially orientated lines operating with steam locomotives. The reason for this is because labour is cheap in India so the return on investment for new rollingstock, tooling and line modifications would be bad.
For electric locomotives, the power quoted is the output from the electric motor, which means that only the second type of losses have to be taken into account.
Surely this should be close to 0 loss since the electric motors are very close to the wheels? Where is that 20% loss coming from? It was my understanding that most of the loss was due to power circuitry and the motor internal operation, which are irrelevant for the output power of the electric motors.

Offline freddyhayward

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Re: steam to diesel transition
« Reply #8 on: November 22, 2019, 06:54:47 AM »
Is there a reason why the 4EPB EMUs have a gear of 1.0?

Offline jamespetts

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Re: steam to diesel transition
« Reply #9 on: November 22, 2019, 11:33:36 AM »
Even the relatively unreliable early British diesel locomotives generally (apart perhaps from the classes that were considered failures and withdrawn within ~10 years of being introduced) had a higher availability than steam locomotives. This is not because they were more reliable than steam locomotives, but rather because steam locomotives needed about 20 hours' of continuous maintenance (a boiler wash out) every 4-6 days or so. This is why some of the better classes of early diesel locomotives (e.g. the "Deltic") were able to replace twice the number of steam engines that their numbers constituted.

As to the 4EPB EMUs, this lack of gearing may be an error. However, for gearing generally, the figure of 80% is what I understand the correct (approximate) value for transmission losses for electric locomotives to be if starting from the quoted power figure.

Offline DrSuperGood

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Re: steam to diesel transition
« Reply #10 on: November 22, 2019, 05:16:13 PM »
This is why some of the better classes of early diesel locomotives (e.g. the "Deltic") were able to replace twice the number of steam engines that their numbers constituted.
This only influences purchases of new rolling stock. Based on that alone, if you already have 2 steam engines then there is nothing to gain replacing them with a single diesel.

What would commercially drive such replacement is the savings on servicing costs, simplified track infrastructure, fuel and labour. Yearly this has to add up to a significant fraction of the cost of a new diesel or electric locomotive. If it does not, as is the case with some lines in India, it does not make any sense to do such a replacement.

The UK did not phase out steam for economic reasons directly. It did so for national/political reasons. The government set deadlines for when all steam be removed from service. The result could be considered an economic blunder as reasonably new steam engine locomotives had to be scrapped and replaced just to meet targets. Since there was a deadline for steam to go, the quality of the replacement diesel or electric locomotives was inconsequential. This is very different from the more natural economic phase out that other countries had. Within industry in the UK (not main lines), steam locomotives continued to be used for many decades until either the industries shutdown or it stopped making any financial sense due to the availability of cheap second-hand diesel locomotives.

Offline Octavius

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Re: steam to diesel transition
« Reply #11 on: November 22, 2019, 09:01:59 PM »
However, diesel and electric locomotives, as has been observed, do accelerate better than steam locomotives, by a long way. This is because diesel and electric locomotives are constant power machines whereas steam engines are constant force machines. The consequence of this is that steam locomotives have a lower power at lower speed, and so accelerate poorly. Also, steam locomotives were about 4-7% efficient whereas diesel locomotives were about 30% efficient; however, the saving in fuel is somewhat offset by the fact that coal is generally cheaper than oil.

The difficulty is that for steam locos there are two powers involved.

At low speed, all types of locos have their acceleration limited by wheelslip. Assuming the full weight of the loco is on the powered wheels (which is the case in your typical 0-6-0T, used for local trains), a steam locomotive can reach the same acceleration as a diesel or an electric. (Actually slightly less. The driving force for a steam locomotive varies significantly over one revolution of the driving wheels. Wheel slip sets the maximum force; the average force is less. This is less of a concern for locos with three of four cylinders.)

A steam loco is indeed a constant force machine (more or less), so at high speed its power increases without bound and does get higher than that of a diesel. However, that's the power flowing from the boiler to the wheels. The power it can send from the fire to the boiler is much less than that of a diesel, let alone an electric. When the first power exceeds the second, boiler pressure drops and the loco won't be able to accelerate for very long. That second power is roughly proportional to grate area, which is usually mentioned in the technical data of a steam loco.

Steam locomotive efficiency could have been improved if the idea was developed further. Fundamentally the same principles are still used for coal and even nuclear power generation today. For most countries power efficiency was not a major drive to move away from steam, rather the other benefits/efficiencies that diesel and electric locomotives brought were.
Steam locomotives have a steam engine that's highly optimised for power to weight ratio, else it would be too slow to be useful. Power stations have a steam engine that's highly optimised for efficiency. You can't optimise for both at the same time.

Interestingly, the main reason to move away from steam (to electric, mostly) in the Netherlands was fuel efficiency, along with acceleration. During WW2 they even coupled triplets of electric passenger railcars together to haul goods trains, as that was a more efficient way of using coal than in a steam loco, and even during the war, despite shortage of copper and steel, electrification continued. They used gothic arch shaped reinforced concrete gantries (still present on the line Hilversum - Utrecht) to hold the overhead wires, specifically designed to minimise the amount of rebar required. In the early 1930s it had been planned to completely phase out steam by the late 1940s, but the war interfered, pushing it to 1957.

Offline DrSuperGood

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Re: steam to diesel transition
« Reply #12 on: November 22, 2019, 09:41:27 PM »
Interestingly, the main reason to move away from steam (to electric, mostly) in the Netherlands was fuel efficiency, along with acceleration. During WW2 they even coupled triplets of electric passenger railcars together to haul goods trains, as that was a more efficient way of using coal than in a steam loco, and even during the war, despite shortage of copper and steel, electrification continued. They used gothic arch shaped reinforced concrete gantries (still present on the line Hilversum - Utrecht) to hold the overhead wires, specifically designed to minimise the amount of rebar required. In the early 1930s it had been planned to completely phase out steam by the late 1940s, but the war interfered, pushing it to 1957.
It varied from country to country. Switzerland also moved away from steam early as it has hydropower and no coal or oil so electric trains made both financial and strategic sense.

Offline CK

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Re: steam to diesel transition
« Reply #13 on: November 23, 2019, 11:08:33 AM »
According to some TV programs I watched, early British diesel engines were totally rubbish and often called worse than steam engines. They tried to build the diesel engines in the UK without foreign help so where as places like Gemany already had several decades of experience building them, they literally started from scratch. Further more government policy forced them to rush into the technology to meet artificial deadlines rather than when the technology was actually ready. The end result were some engines with extremely poor reliability and performance that were arguably worse than the complex and well refined steam engines they knew how to build.

The fact that BR's regions were effectively a nationalised continuation of the previous railway companies with all their rivalries and own practices probably didn't help either. (notably the Western Region opting for diesel-hydraulics whereas the other regions generally went for diesel-electrics).

It varied from country to country. Switzerland also moved away from steam early as it has hydropower and no coal or oil so electric trains made both financial and strategic sense.
Not to mention Switzerland's terrain, which is very conducive to electric locomotives (especially the Gotthard railway, which always received the latest locomotives because it was in a constant need of more power)

Offline jamespetts

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Re: steam to diesel transition
« Reply #14 on: November 24, 2019, 12:16:56 PM »
That fewer diesel/electric locomotives are required to replace a given number of steam locomotives is of significance economically as it affects return on capital; if one is replacing the steam locomotives in any event (e.g. because they are worn out - something not yet simulated in Simutrans-Extended, but this is planned), then this is a relevant consideration.

However, in the UK, the main reason for replacing steam locomotive was the much higher labour cost. The politicisation in the UK happened earlier, when the government deliberately stifled development of diesel engines on the railways (which the companies had been experimenting with before the Second World War, and which experiments continued after the War) for political reasons because of a desire to run a coal based economy rather than one requiring oil. This delayed replacement of steam technology by about a decade; if it had been pursued from the late 1940s onwards, as it would have been had the state not seized control of the railways in 1948, there would have been no rush as diesel and electric could readily have replaced steam locomotives within their natural cycle by the time that the labour cost issue had become critical. The government also suppressed railways' financing after nationalisation by artificially suppressing rail fares to give the false impression that the inflation rate was lower than it really was, which caused the railways to make a loss every year after about 1952, which stifled investment in new technology and made any capital expenditure by the railways dependant on subsidy from central government, which was always based on what would benefit the politicians' political careers, not what was best for the railways in the long-term.