North African railroads

Discussions on WW2 in Africa & the Mediterranean. Hosted by Andy H
User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 17 Apr 2006 20:25

JonS wrote:Gents,
'Diesel fired' in the 1940s could mean one of two things:
1) A diesel-electric, similar to the ones we know and love from today
2) A steam train, which uses diesel instead of coal.


The lend-lease US locomotives were clearly in the first category, and so were the Italian machines being assembled on the Barce track (they were kind of revolutionary, or at least the Italians thought so).

I don't know about the German locomotives unloaded in Tobruk, though looking at a picture they look like a diesel engine and not a steam locomotive burning diesel.

JonS wrote:Whether a diesel steam train uses less water than a coal steam train I don't know, but whatever the answer it is likely to be significantly more than the zero gallons used by a diesel electric.


There's no reason why it should be more efficient, the efficiency of a steam engine depends on the mechanism and on the exchange surface within the boiler. Not on the combustible used to put the water to the boil. I can see how a more efficient combustible would increase overall efficiency a bit, but the saving would mostly be in the weight of coal, not water.

JonS wrote:As an aside, and as I understand it, the 2-8-0 (or 1-4-0 for a single side) refers to the little free-wheeling steering wheels at the front, then the large drive wheels, then the trailing freewheeling wheels under the cab. So the Hartmann has a front freewheeling axle, four driven axles, and nothing under the cab. It obviously says nothing about the power output of the engine, merely the way that power is applied to the rails, and the weight of the engine is distributed.


Thanks for the information, all the same. If I ever re-install Railroad Tycoon on my computer, I'll remember that fondly. :-)

JonS wrote:The book mentioned above has an extensive discussion about the means of supplying water on the Western Desert line. Some numbers: "At the peak of railway operations in 1940, a daily supply of 138,000 gallons was required at El Dabaa, and another 43,000 gallons was required at Mersa Matruh." This was provided by two trains daily, carrying only water. Ships were also used to carry water forward from the delta, as well as local wells. Interestingly, they couldn't use any old water as acidic or dirty water would wear out parts too quickly. There was a special water treatment facility in Alex, which the Axis obligingly left completely alone. It's loss or damage would have seriously compromised British rail ops


This is interesting. At 4,250 gallons per locomotive, it translates to a bit over 42 locomotive refills per day or some 2,600 locomotive-miles daily. El Daba is roughly 120 miles west of Alexandria, Matruh is 180 miles so if the average distance is 150 miles that's enough water for 17 train trips, minus two for the water this leaves 15 per day. That figure assumes no waste and is therefore optimistic, a more reasonable estimate would be 10-12 trains a day.

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 17 Apr 2006 20:33

JonS wrote:
Bronsky wrote:But extending the RR into Libya doubled the length of the railway with no corresponding increase in intermediate coaling and water stations.

I may be reading your quote wrong, but the British did put quite a bit of effort into making the line usable. It wasn't just a single track line from Alex to Belhammed. There were shunting yards at regular intervals, and loop sidings even more often. Re-coaling and re-watering needs were definately taken into account, and catered for.


What I meant was that the water and coal had to come from Alexandria and could not be procured locally, so this placed an additional burden on the previous (Alex to Matruh) rail line, in addition to its own logistical needs.

I know that the British provided for more than the single line, the Axis found these provisions so generous that they dismantled some of the line for their own use as well as for repair purposes.

JonS wrote:BTW, it is obvious to me now that the British never intended to take the line into Tobruk. By the time the line got there it seems they'd pretty much given up on that town as a port. The effort involved in building a line down into Tobruk, then the ongoing effort (in terms of coal, water, and wear) of running trains up and down the escarpment was too much. For the same reason, the main shunting yards at Mersa Matruh were a few miles out of 'town', near Charing Cross. There was a branch line that went into MM, but there was no point in running every train up and down the rise to get there


On the contrary, the line went to Tobruk and delivered some 2,000 tons per day after El Alamein, this allowed the British to use Tobruk as a port for export (supply is loaded onto ships which sail to points farther west, mainly Benghazi) which is more efficient than exporting from Alexandria and using Tobruk as an importing port. I'm quite positive that this was done, though I forget if I found this mentioned in Playfair, the REME history or another one.

By contrast, the British didn't have much use of Mersa Matruh as a port so the line followed civilian needs, not military ones.

Jon G.
Member
Posts: 6647
Joined: 17 Feb 2004 01:12
Location: Europe

Post by Jon G. » 18 Apr 2006 08:19

JonS wrote:Gents,
'Diesel fired' in the 1940s could mean one of two things:
1) A diesel-electric, similar to the ones we know and love from today
2) A steam train, which uses diesel instead of coal.

That may be obvious, and it's something I kind-of knew, but it's significance didn't occur to me until reading the above mentioned book which has a pic of a German diesel-fired Hartmann 2-8-0 used by the British in Palestine (it arrived there in the 1920s). The pic is obviously of a steam train. Whether a diesel steam train uses less water than a coal steam train I don't know, but whatever the answer it is likely to be significantly more than the zero gallons used by a diesel electric.


Sure, one of the advantages of a steam engine is that it can run on several different fuels. IIRC the Germans converted some of the steam engines they used on the Eastern Front to run on oil, for example. Water use would be fairly constant I think, irrespective of which kind of fuel was used.

As an aside, and as I understand it, the 2-8-0 (or 1-4-0 for a single side) refers to the little free-wheeling steering wheels at the front, then the large drive wheels, then the trailing freewheeling wheels under the cab. So the Hartmann has a front freewheeling axle, four driven axles, and nothing under the cab. It obviously says nothing about the power output of the engine, merely the way that power is applied to the rails, and the weight of the engine is distributed...


Yes, and I think the German system would call the 2-8-0 a 1-D-0 - i.e. they count axles rather than wheels; driven axles are numbered with letters in order to distinguish them from non-driven supporting axles. Provided you know the weight on the driven axles (72.10 on the Stanier, for example), that figure does say something about the power output of the engine, particularly if the total weight of the engine (127 tons for the Stanier) is also known.

But enough of the technical stuff :)

I think it's a good read so far (about halfway through), and besides, how many books on logisitics and railways in the North African Campaign are there anyway? ;)


Far too few. I recall poster Edward Kelly talking about a book about the logistics aspect of the North African campaign being in the works. I'm looking forward to reading the NZ rail book. I'm certainly not put off by anecdotical stuff; in the right doses it should make for a better read.

Bronsky wrote:
OK, now I get what you meant with the CV figure :)
It's the abbreviation for "steam horsepower" and identical in Italian and in French, so I forgot that I had to translate it one more time. That and the fact that I don't know the correct term in English...:)


I'm sorry if I come across as a little dense here, but why would the Italians and Germans measure their diesel locomotors' power output in steam horsepower? I took the 250/340 figures as straight hp numbers - with these power ranges the Axis locomotives would be clearly inferior to the Staniers.

Yes, but this calculation does not take the performance of the engine itself into account.
I didn't say it did, since in case it wasn't completely clear the first 3 times that I wrote it, I don't know the exact performance figures for either locomotive... :wink:


True, but with the infrastructure for steam engines in place, the comparison to how much less a diesel uses of oil, water and so on becomes less meaningful. Indeed, the moment you switch from one propulsion system to another, you will need to replace old infrastructure with new in order to keep your new engines running.

On the other hand, the Stanier wasn't considered a particularly effective locomotive IIRC (I forget where I read that, so it could be wrong) so it wasn't a case of substituting an obviously inferior type to a state-of-the-art but infrastructure-intensive one. The point of having a powerful locomotive is to move more stuff to the front. As the figures I posted indicate, switching from steam to diesel saved a lot of "deadweight" i.e. load needed to operate the logistical system, not sent to the troops. It would take a significant performance hit to justify not switching to diesel.


It is worth noting that diesel locomotives were in their infancy at the time. The first Alco RS-1 diesel-electric machines were built in March 1941; the initial production batch was immediately purchased by the US Army. Some of these machines later entered service on the railroad through Iran.

Contrast that to the British desert railroad, which had operational significance as early as November/December 1940 in the build-up for Operation Compass. Considering what was available outside of the USA at the time (the Axis engines may be a useful yardstick for that), building a rail line for steam engines was the right choice if you wanted to pull as much stuff to the front as possible. In other words, it took the invention and production of a reliable, powerful diesel-electric engine to even make the switch possible.

At 4,250 gallons per locomotive, it translates to a bit over 42 locomotive refills per day or some 2,600 locomotive-miles daily. El Daba is roughly 120 miles west of Alexandria, Matruh is 180 miles so if the average distance is 150 miles that's enough water for 17 train trips, minus two for the water this leaves 15 per day. That figure assumes no waste and is therefore optimistic, a more reasonable estimate would be 10-12 trains a day.


In comparison to van Creveld's calculation according to which Rommel needed half of his fuel to deliver the other half (plus everything else) to the front, your calculation shows that the railroad is a more efficient way of delivering supplies to the front, even with the exorbitant needs of the desert railroad's locomotives.

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 18 Apr 2006 10:13

Jon G. wrote:Yes, and I think the German system would call the 2-8-0 a 1-D-0 - i.e. they count axles rather than wheels; driven axles are numbered with letters in order to distinguish them from non-driven supporting axles. Provided you know the weight on the driven axles (72.10 on the Stanier, for example), that figure does say something about the power output of the engine, particularly if the total weight of the engine (127 tons for the Stanier) is also known.

But enough of the technical stuff :)


In fact this makes me feel that I really must get into this technical stuff to derive a useful understanding of these issues: see all the messages where we're speculating about whether locomotive X is better than locomotive Y and not getting anywhere.

Jon G. wrote:I recall poster Edward Kelly talking about a book about the logistics aspect of the North African campaign being in the works. I'm looking forward to reading the NZ rail book. I'm certainly not put off by anecdotical stuff; in the right doses it should make for a better read.


Paul Collier, the guy who wrote the bit on the Afrikakorps forum quoted by DrB, is an Australian whose thesis was on North Africa logistics. Some time ago (2002) he told me that he was going to publish it into a book but it looks like the project didn't pan out or was delayed. He did author one of the Osprey books on the Mediterranean theater, though, so there may be useful stuff in that one. I'm somewhat reluctant to buy Ospreys blind, because I'm uninterested in uniforms and they can turn out to be very expensive compared to their useful content, also I don't need another campaign account which is what that particular volume looks like. So I'm waiting until I can browse it in a bookstore or until someone else reads it and fills us in on its contents... ;-)

Jon G. wrote:I'm sorry if I come across as a little dense here, but why would the Italians and Germans measure their diesel locomotors' power output in steam horsepower? I took the 250/340 figures as straight hp numbers - with these power ranges the Axis locomotives would be clearly inferior to the Staniers.


You're not the dense one, I'm the one who's not techno-savvy enough and who is relying on 90% forgotten high school physics classes. I pulled these numbers from an Italian source, where they were "CV". In French, this means "chevaux vapeur" and in Italian the initials would be the same. This is a kind of horsepower, and I don't know if it's the exact equivalent to "hp" or if there's a tweak. From my physics classes, I remember that there were lots of traps in the horsepower business, which is why I mentioned that.

So I don't know what the Germans did, but converting all in "steam horsepower" would make sense in a time and age when most engines were steam engines.

Jon G. wrote:True, but with the infrastructure for steam engines in place, the comparison to how much less a diesel uses of oil, water and so on becomes less meaningful. Indeed, the moment you switch from one propulsion system to another, you will need to replace old infrastructure with new in order to keep your new engines running.


No you won't. The US diesel locomotives could run 24hours on 280 liters of fuel, which means that they could make a round trip to el Daba with zero infrastructure being needed, or could go practically all the way to Tobruk while only needing to carry 280 litters (less than 0.25 ton) i.e. not a significant load. By contrast, the Stanier locomotives needed 19 tons of water to run an average of 60 miles, which means that they needed 0.3 ton (i.e. a bit more than the amount that the US diesel loco needed to run for 24 hours) per mile. For example, a round trip to Mersa Matruh would require 115 tons for water alone (I don't know how long the 9 tons of coal lasted but would be very interested in that kind of information). With the average train at a little under 500 tons, probably less for this desert rail line, that's almost a quarter of the load being used just to resupply the train itself.

If a steam engine needs to devote 25% of its average load to its own needs while a diesel engine needs to devote 0%, then the steam engine has to be 33% more powerful than the diesel loco to be competitive.

Jon G. wrote:
Bronsky wrote:At 4,250 gallons per locomotive, it translates to a bit over 42 locomotive refills per day or some 2,600 locomotive-miles daily. El Daba is roughly 120 miles west of Alexandria, Matruh is 180 miles so if the average distance is 150 miles that's enough water for 17 train trips, minus two for the water this leaves 15 per day. That figure assumes no waste and is therefore optimistic, a more reasonable estimate would be 10-12 trains a day.


In comparison to van Creveld's calculation according to which Rommel needed half of his fuel to deliver the other half (plus everything else) to the front, your calculation shows that the railroad is a more efficient way of delivering supplies to the front, even with the exorbitant needs of the desert railroad's locomotives.


Yes, and of course rail is more efficient than trucks, but the calculation depends heavily on distance.

Let's go back to JonS' figures. 138,000 gallons were delivered to El Daba, 120 miles from Alexandria, and 43,000 gallons were delivered to Mersa Matruh, 180 miles from Alexandria. Then we know that each Stanier needs 4,250 gallons to do an average of 60 miles. So for a round trip to Mersa Matruh a train leaves Alexandria, waters halfway to El Daba (I assume a plentiful water supply there, in addition to the figures mentioned by JonS), picks up 4,250 gallons at El Daba, reaches Mersa Matruh, picks up 4,250 gallons, back to El Daba, again 4,250 gallons and back to Alexandria. With 43,000 gallons in Mersa Matruh, that's enough for 10 round trips (including the one carrying the water), which will require 86,000 gallons from El Daba, leaving 53,000 i.e. enough for 12 train trips Alexandria - El Daba including the one with the water. So when the front is 180 miles from Alexandria, 9% of the overall traffic and 10% of the traffic to the front are self-consumption. I'm assuming that with 2 water trains and a total of 814 tonnes (metric tons) of water delivered, each train carried 400 tonnes with the Mersa Matruh train dropping some of its load at El Daba. If the trains carried their own water in addition to what they delivered, then that translates to an additional 191 tons so we would have 500 tons per train instead of 400 and I need to redo all the calculation, but this doesn't seem likely.

So we have 11 trains + 1 water train to El Daba and 9 trains + 1 water train to Mersa Matruh. Let's now assume that the front moves another 180 miles, to the vicinity of Tobruk. Assuming 60 miles between each watering stop, you will need two intermediate stops between Mersa Matruh and Tobruk (the stations already existed, and I'm assuming that the infrastructure is teleported locally, all I'm interested in is the flow). As I'm still assuming that the stretch between El Daba and Alexandria takes care of itself, the trip looks like this: El Daba - Mersa Matruh - Watering stop 1 - Watering stop 2 - Tobruk. Technically Tobruk should be a bit too far, and if someone cares to assign more accurate names to the last 3 stops, that's fine with me.

If you want to deliver 5 trains to Tobruk, you need a 6th train for water, so that's 12 round trips, consuming a total of 1,032 tons of water all the way to El Daba, including 344 tons between Tobruk and Watering stop 2. So you need more water trains along the way. I'm not going to detail all the math as it's simple enough to reconstitute for those interested, and boring enough for those who aren't. Suffice it to say that, assuming 400 tons per train, supporting 5 trains to Tobruk, 360 miles away, requires 3 water trains working full time (only 15 tons left from the last train). So at this point, the cost of the supply line itself amounts to 37.5% of the whole traffic, with 1185.75 tons of water transported at various points just to push 2,000 tons of supply to the front. It's better than 50% but Alexandria to Tobruk is only about half the distance between Tobruk and Benghazi which is what the Axis had to deal with most of the time. This is fairly linear i.e. the ratio doesn't decrease much if you double the load carried to the front. After that, you probably exceed the line's capacity since getting 10 supply trains to Tobruk would require 31 trains going through Mersa Matruh.

JonS
Member
Posts: 3935
Joined: 23 Jul 2004 01:39
Location: New Zealand

Post by JonS » 18 Apr 2006 11:34

Some more numbers from 'the book':

"Except in the case of a daily passenger train, all train locomotives were changed at El Dabaa. Incoming goods trains from the east terminated at El Dabaa and drew 4000 gallons for the return journey to Alex. The locomotives assigned to continue to Mersa Matruh also drew on the ED water reserves to the extent of 8000 gallons each. At MM they then topped up with 3000 gallons to enable them to return to ED. The Egyptian locomotives had large tenders because of the long distances between stations where coal and water could be replenished. They carried approximately 10 tons of coal and about 5000 gallons of water. This quantity of water, however, was not always sufficient to take them to their destinations or allow for delays en route. Therefore, attached to each locomotive (waboor) was a large water battery (sahreeg meeyah) capable of holding 8000 gallons."

Edit: It isn't abundantly clear from the book, but these numbers seem to specifically relate to 1940/early 41. Later the consumption is likely to have improved somewhat as the NZ railwaymen fully took over from the Egyptian State Rail drivers. There is frequent comment about the wastage of water due to poor discipline of the Egyptian drivers.

Alex is listed as 200 miles from MM, and 120 miles from ED. At each place (MM and ED) the Egyptian State Railways had constructed underground reservoirs that could hold 100,000 gallons. In addition, military reservoirs were built at each place and at El Alamein, and old Roman(!) reservoirs along the route were also pressed into service. There was also a water pipeline laid from Alex.

There are bits and pieces about refuelling with coal, but I can't find them now, sorry. Overall, water seems to have been the big concern. Coal was necessary, naturally, but far more effort and worry was needed to ensure a regular supply of water.

Finally, as pointed out earlier in this thread, there is also some info about the NZ Railways Group in the NZ Engineers OH, available online at NZETC. The units concerned are 10th and 13th Railway Consruction Compaies, 16th and 17th Railways Operating Companies, and HQ Railway Operating Group.

Regards
JonS

Edit: Oh, BTW, the Western Desert Rail extension was ballasted. The sleepers and rails were initially laid straight onto the desert by one of the Railways Construction Companies. The second RCC was following along behind lifting the track and ballasting it, as well as building all the other infrastructure needed for a rail line. Laying then lifting-and-ballasting seems an odd way of doing things to me, but then I know about this much -->| . |<-- about laying track ...

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 18 Apr 2006 12:30

JonS wrote:Some more numbers from 'the book': "Except in the case of a daily passenger train, all train locomotives were changed at El Dabaa. Incoming goods trains from the east terminated at El Dabaa and drew 4000 gallons for the return journey to Alex. The locomotives assigned to continue to Mersa Matruh also drew on the ED water reserves to the extent of 8000 gallons each. At MM they then topped up with 3000 gallons to enable them to return to ED. The Egyptian locomotives had large tenders because of the long distances between stations where coal and water could be replenished. They carried approximately 10 tons of coal and about 5000 gallons of water.


Thank you very much. This means 11,000 gallons for the round trip between El Daba to Mersa Matruh and back, which is more than the 9,500 that I had calculated. Also, 4,000 gallons (i.e. one tender's worth) of water wouldn't be enough to reach Alexandria from El Daba, which indirectly confirms that there was a watering point halfway between El Daba and Alexandria.

JonS wrote:This quantity of water, however, was not always sufficient to take them to their destinations or allow for delays en route. Therefore, attached to each locomotive (waboor) was a large water battery (sahreeg meeyah) capable of holding 8000 gallons."


Cool information, makes sense, too. Doesn't change the overall model, though.

JonS wrote: Coal was necessary, naturally, but far more effort and worry was needed to ensure a regular supply of water.


Well, intuitively 9 tons of coal (per the diagram that you sent Jon G) should be enough to last for more than 60 miles. Even if the coal tender was emptied as fast as the water reserves, that would still amount to 9 tons of coal for 19 tons of water.

JonS wrote:Edit: Oh, BTW, the Western Desert Rail extension was ballasted. The sleepers and rails were initially laid straight onto the desert by one of the Railways Construction Companies. The second RCC was following along behind lifting the track and ballasting it, as well as building all the other infrastructure needed for a rail line. Laying then lifting-and-ballasting seems an odd way of doing things to me, but then I know about this much -->| . |<-- about laying track ...


Looking at pictures of sections of captured track, it looks like there was ballast in selected areas but not everywhere, though with the sand covering everything it's hard to tell. That being said, Ogliari has a definite nationalistic agenda so I wouldn't put it past him to deliberately ignore the second team (or the parts of the line that were ballasted). On the other hand, I think I remember a specific report mentioning un-ballasted track by the Italian engineers that Ogliari drew upon to gloat, so I'm not sure that the extension was 100% ballasted. Not that it matters all that much, though: after having reread the relevant notes, it is abundantly clear that the British in the Western Desert had both far more resources than the Italians and an easier task (practically no gradient, favorable soil compared to the marshes in Tripolitania or the hills between Benghazi and Tobruk). Again, they laid down some 200 miles of track in 18 months, which is almost ten times more what the Italians did in almost two years and that doesn't count Syria. The Italians had surveyed, picketed and levelled the ground / laid down plates along a great distance, but the crippling shortage was simply rails. It sounds idiotic, but there you are...

Jon G.
Member
Posts: 6647
Joined: 17 Feb 2004 01:12
Location: Europe

Post by Jon G. » 19 Apr 2006 10:29

Bronsky wrote:In fact this makes me feel that I really must get into this technical stuff to derive a useful understanding of these issues: see all the messages where we're speculating about whether locomotive X is better than locomotive Y and not getting anywhere.


OK, here is today's physics lesson.

The first object is to ascertain the tractive force yielded by the Stanier locomotive at the rails in pounds.

The bore (18½") is squared and multiplied with the stroke (28"), which in turn is multiplied by the steam pressure (225 psi). Finally, this figure is divided by the diameter of the Stanier's drivers (56½").

Thus: (18.5x18.5x28x225) divided by 56.5, or 38,162.39 lbs of traction.

The next, and trickier, calculation, has as its object to determine the horsepower yielded by the Stanier locomotive while running at an arbitrarily determined speed of 20 mph.

For this calculation we need to know the piston area impressed by the steam from the Stanier's boiler. The radius of the Stanier's bore is 9 1/4"; squared and multiplied by pi this gives 268.66 square inches of piston area. Multiplied with the psi from the boiler, we arrive at a piston pressure of almost 60,500 pounds. For simplicity's sake I've taken the liberty of rounding this figure somewhat. The Stanier's stroke is 28"; the pistons travel 56", or 4.66 feet in each full stoke.

I am assuming that the Stanier has two cylinders. This calculation falls completely apart if it has more.

The Stanier's drivers have a diameter of 56½"which gives a circumference of 177.41 inches, or 14.78 feet . The drivers need to complete approx. 357 revolutions to travel a mile. At 119 revolutions per minute, the Stanier is doing approx. 20 mph - a figure I have chosen because it comes fairly close to the stated top speed of the Axis locomotors.

With these preliminaries in place, let's proceed with the calculation:

9.25x9.25x225x4.66x2x119 is 21,351,522.9375 foot-pounds. One horsepower is 33,000 foot-pounds. Dividing the figure we arrived at, the Stanier develops 647 hp at 20 mph. The only variable in this calculation is the rpm of the Stanier's wheels; if you for example wanted it to run at 40 mph you would find that it developed twice as many horsepower.

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 19 Apr 2006 11:06

Jon G wrote:the Stanier develops 647 hp at 20 mph. The only variable in this calculation is the rpm of the Stanier's wheels; if you for example wanted it to run at 40 mph you would find that it developed twice as many horsepower.


Thanks.

Ok, so I guess that you need the max speed of the Stanier to determine its rated power.

Two small details:

1. 25 kph is the top speed of the Italian shunters, but I assume that German locomotives were faster.

2. Since I'm brushing off on my high-school physics:

1 cheval-vapeur (cv) = 75 kilogrammètres/seconde (kgm/s) = 0,736 kilowatt (kW) = 0,986 horsepower (hp)
1 horse-power (hp) = 0,746 kilowatt (kW) = 1,014 cheval-vapeur (cv)

So the Italian shunters are 64hp, the 3-axle German locomotive is 355hp and the 2-axle German locos are 217hp.

Jon G.
Member
Posts: 6647
Joined: 17 Feb 2004 01:12
Location: Europe

Post by Jon G. » 19 Apr 2006 11:26

Ugh! I just discovered a serious error in my hp calculation for the Stanier, above:

9.25x9.25x225x4.66x2x119 is 21,351,522.9375 foot-pounds.


...I forgot pi in this calculation when determining the surface of the Stanier's piston. The true calculation should read as follows:

Radius of bore (9.25), squared gives 85,5625; this figure should be multiplied with pi (3.14); 268,66625. This figure in turn should be multiplied with the Stanier's stated psi (225); then we have 60,449.90625. Then full stroke*, in feet (4.66); 281696.563125 so far. Then we multiply with the number of cylinders (presumed to be two); 563393.12625; then we multiply with the chosen speed: 119 revolutions per minute: 67,043,782.02375, which is the foot-pound per minute of the Stanier at 20 mph. Finally, we divide by 33,000 to convert foot-pounds into horsepower: 2031 hp when the Stanier is running at 20 mph.

Factors such as power lost through friction and adhesion aren't part of my calculations, but hp for a diesel engine is usually measured at the engine's output, not at the wheels. Diesels generally have a higher adhesion than steam engines do. At least the above figure should give a rough estimate.

* The full stroke is factored in because the piston is impressed by steam in both directions.

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 19 Apr 2006 13:28

Jon G. wrote:...I forgot pi in this calculation when determining the surface of the Stanier's piston.


At least now I understand the formula... ;-)

This leads me to a secondary consideration i.e. that we may be looking at the wrong indicator. Is hp an important factor ? For example, merchant ships have quite ridiculous power to weight ratios. So they can't accelerate as fast as fighter planes, but who cares ?

Jon G.
Member
Posts: 6647
Joined: 17 Feb 2004 01:12
Location: Europe

Post by Jon G. » 19 Apr 2006 14:04

Well, mea culpa for making an erroneous calculation.

My overall point in fact was that it is, by and large, pointless to try calculating the hp output of a steam engine because it is a constant force machine, as opposed to a diesel, which is a constant hp machine. Hp output of the steam engine is directly related to the speed the steam engine travels at. Theoretically, you could use the above formula to have a steam engine develop as many hp as you want - but you'd hit the limits of physics quickly; the steam needs a certain amount of time to expand in the cylinders, for example, and you will also lose power through friction in the transmission and by friction of the wheels on the rails. The diesel-electric engine has a big advantage there: its transmission is simply electric cables from its generators to electric engines placed directly on the axles - hence far less power is lost in transmission.

Somewhat inelegantly, that leads me back to my original point, which was that the British decision to use steam engines for their desert railroad had everything to do with availability, and nothing to do with whether steam was better than diesel. I'm not contesting that switching to diesels was a wise choice, only I am emphasizing that powerful diesels weren't available as off the shelf products when the desert railroad was being built.

That aside, rail is in fact a very economic way of moving goods overland. I recall a calculation which said that a 1000 hp locomotive can move 1000 tons at 100 kph. If you are going to move 1000 tons of goods over even the best road at that speed, you will need far more horsepower.

Do you know which type of American diesels were supplied for the desert railroad? I almost venture to guess that they were Alco types, similar to the engines used in Iran. Here's an interesting link to a site about the lend-lease railroad through Iran. Staniers (some of them were converted to burn oil) and Alco road switchers were operating side by side on the Iranian line. The diesels were particularly useful in the tunnels on the Persian line. Steam engines run out of breath in unventilated tunnels. Even so, the Americans also supplied USS Mikado steam engines to the Iranian railroad.

Epaminondas
Member
Posts: 282
Joined: 07 Aug 2005 17:28
Location: Raleigh NC

Post by Epaminondas » 19 Apr 2006 15:29

somewhat off topic; but the van Creveld book is Supplying War?

And are there any good books on the German rail net supplying the Ost Front?

Facination and educational discussion!

User avatar
Bronsky
Member
Posts: 825
Joined: 11 Apr 2003 09:28
Location: Paris

Post by Bronsky » 19 Apr 2006 15:39

Jon G. wrote:Somewhat inelegantly, that leads me back to my original point, which was that the British decision to use steam engines for their desert railroad had everything to do with availability, and nothing to do with whether steam was better than diesel. I'm not contesting that switching to diesels was a wise choice, only I am emphasizing that powerful diesels weren't available as off the shelf products when the desert railroad was being built.


Actually, the exchange on this particular point ran (editing out the other bits):

Jon G wrote:
Bronsky wrote:
Jon G wrote: I assume these German locomotives [which I mentioned as unloaded at Tobruk -B] were steam engines?


Steam locomotives were at a severe disadvantage in the desert, which is why the British ordered US diesels to replace their steam locos. The German locomotives sent were diesel...


It should be added that 1940s-era diesels weren't nearly as strong as steam engines were, at least for locomotives built outside of the USA. Therefore you can't really make the direct comparison between steam and diesel engines - steam locos may have been at a disadvantage because they needed coal and water, commodities that were both bulky and scarce in the desert, on the other hand diesels were significantly weaker in performance.


...to which I replied that I didn't know the respective power outputs but that I had no reason to believe that the US locomotives represented a significant drawback. Now it looks like we've established that the steam engines were more powerful but that this was meaningless, i.e. both had sufficient power and the only difference was ease of operations which is what my "steam locos were at a severe disadvantage" referred to (snipped the relevant bits).

So it looks like we're agreed, but not much more advanced regarding how the locomotives compared between each others. Incidentally, doing a bit of browsing it appears that diesel-electric locomotives were beginning to replace steam ones because they were more efficient, though being easier to maintain and more economic to operate were very important factors.

Jon G. wrote:Do you know which type of American diesels were supplied for the desert railroad?


I had already posted this, but as I see I made a typo (shame on me, and to a French name, to boot !) I'll retype.

The British received, in May 1942, two arrivals with a total of 56 "Whitcomb de la Rochelle 65 DE 14 locomotives". The first number is the weight (65 tons), the second number is the type of engine & drive (DE = Diesel Electric), last is the type.

The 65 tons Whitcomb locomotive was a bigger 50 ton loco, which itself consisted of two engines put back to back (the He.177 of locomotive design, except that it worked).

I haven't been able to find pictures of the 65 DE 14, but this link shows plenty of pictures of various types of 65 DE Whitcomb locomotives, and they all look pretty much alike. Further extrapolating, that page shows a Whitcomb locomotive supplied to the French as part of the Marshall plan, with characteristics. It looks very much like a 65 DE 19 which was one of the wartime models, and if it is (but I could be wrong, and the site doesn't say anything beyond the fact that these are Whitcomb locos), then the site gives the following specs:

Builder: Whitcomb (USA)
Engines: 2 x ADN (325CV or 320hp)
Power: 650CV or 640hp
Drive: Electrical
Pull capacity: 1,250 tons (theoretically these should be metric tons, but with such a round figure I presume that the figure was lifted straight from the specifications and therefore that they are short tons)
Max speed: 65km/h which looks very much like a rounded conversion of 40mph.

Again: I am NOT sure that these specs correspond to the actual locomotives supplied to the British, people with access to a genuine picture of a 65 DE 14 Whitcomb and with good locomotive recognition skills, or better yet people with good sources about these locomotives, should be able to confirm that.

JonS
Member
Posts: 3935
Joined: 23 Jul 2004 01:39
Location: New Zealand

Post by JonS » 19 Apr 2006 19:48

US DEs, used by the CW in the WD
You do not have the required permissions to view the files attached to this post.

Jon G.
Member
Posts: 6647
Joined: 17 Feb 2004 01:12
Location: Europe

Post by Jon G. » 21 Apr 2006 04:44

Thanks for the links and the picture of the Whitcomb. I think I may have instinctively dismissed the Whitcomb as a diesel-electric type the first time I read the name in one of your posts because the name sounds so British - and the Brits had nothing comparable to US types in the 1940s.

I think the picture leaves little doubt that the Whitcombs on the desert railroad were of the same type as the types described in the link. Probably the image caption 'These engines relieved the water problems' addresses the overriding benefit of switching to diesels rather succinctly.

It strikes me that the Staniers probably had vacuum-operated brakes, like most UK locomotives do, whereas Whitcomb types probably had a brake system running on compressed air. Since the engine powers the entire train's brakes, that would have been a concern when switching to the Whitcomb diesels.

It should be evident from the formulae that I finally got right, above, that small diameter drive wheels on a steam engine mean both higher traction and more horsepower at lower speeds - the main sacrifice for more muscle is reduced speed, but that's hardly a concern on a military railroad. The Stanier has relatively small wheels for a steam engine.

JonS wrote:Oh, BTW, the Western Desert Rail extension was ballasted. The sleepers and rails were initially laid straight onto the desert by one of the Railways Construction Companies. The second RCC was following along behind lifting the track and ballasting it, as well as building all the other infrastructure needed for a rail line. Laying then lifting-and-ballasting seems an odd way of doing things to me, but then I know about this much -->| . |<-- about laying track ...


Do you know which interval passed between the first, rail-laying construction company and the second, ballasting/infrastructure-building company? It may simply have been faster to use the two-step method you outline by first laying a long line of semi-interimistic track and then following up with the ballast (transported by train, I presume?), rather than have the rail builders wait for the ballast guys.

Return to “WW2 in Africa & the Mediterranean”