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
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.