In researching the type of coal and water towers I’d like to use on my layout I’ve run up against a question of capacity. Not how much the towers can hold- I know that from the plans- but how many locomotives could be serviced with a given capacity.
The data I have on water towers lists sizes from 15,000 to 200,000. And coal towers from 100 upwards of 400 tons. I know that the largest, busiest roads used the larger sizes, but I’m more concerned with the other end of the scale. For instance, how many locomotives could be serviced by a 100 ton coaling tower? And how much water would those same locomotives need?
To put it another way, what kind of daily capacity would a shortline with 10 locomotives or less need?
There are scores of variables needing consideration to answer that question, such as the number of ton miles, the weight of the train, the extent of grades and curves, skill of engine crew, inherent efficiency of the locomotives, energy content of fuel, and so on.
For instance, the amount of BTUs in coal might vary from 7,400 to 13,800 per pound (California asphaltic crude contained 18,750 BTUs a pound.) A superheated-steam loco would be something like 20% more efficient than a saturated-steam locomotive. Tests on the Central Railroad of Georgia showed that for 1500-ton trains, a superheated locomotive used 116 pound of coal per 1000 ton-miles while a saturated locomotive used 150 pounds. Also, the amount of fuel used per 1000 ton-miles decreased as the total tonnage per train increased. (Source: Design of Railway Locations, Second Edition, by Clement C. Williams, 1917, 1924)
Typical locomotive tenders carried about three times as much water as fuel. Nevertheless, water needed to be replenished several times more often than fuel. Capacities of tenders varied widely and typically there was a positive correlation between locomotive and tender size. A smallish tender might hold 13 tons of coal and 8,000 gallons of water. A larger tender might hold 20 tons of coal and 12,000 gallons of water. (Source: Southern Pacific Common Standard: Diagrams of Tenders)
Mark
This is a bit of a tricky question because it comes down to how heavily used the locomotives were (and as a direct result, how much fuel/water they used).
Fur argument’s sake, let’s say this fictional rr had 8 USRA mikes (approx 12t coal and 10,000 gal water capy) and two switchers (lets say 5t coal and 5,000 gal water).
obviously not all the fuel/water is used all day. If the rr was going through full loads of fuel & water every day, they were burning 106 tons of coal and going through 90,000 gallons of water. For a more realistic number, let’s say somewhere between 50-80% of the fuel and water is used (approx 53-85 tons of coal and 45,000-72,000 gallons of water). With that in mind, a 100t coal bunker would be being refilled pretty much daily, so the RR might have a 200t bunker (or larger) to help offset the frequency of re-filling it. Water probably wouldn’t be as much of an issue, provided that there was a water tower of sufficient capacity (150,000 gals or so) and it could be refilled in good time (let’s say 8-12 hours) by municipal sources.
Now, this is all pretty much derived from what (limited) details I know of servicing steam locomotives…
I realize that there are a number of variables, but the info you’ve given me goes a long way towards solving them. Thank you.
One more question… how does one calculate ton miles? Is it as simple as tonnage divided by miles, or am I missing something?
To take an extreme example, the pedestal tenders used by the UP were 25 x 25 - 25 tons of low-grade local coal, 25,000 gallons water. A Big Boy working hard would be looking for water in not much more than an hour and would burn the bunker empty in less than four (7 tons of coal and 15,000 gallons of water per hour.)
Another extreme example, the NYC’s somewhat dissimilar pedestal tenders, 40 tons, but only 18,000 gallons. A Hudson refueled once between Harmon, NY, and Chicago - but could pick up water on the fly (at track speed!) about every 25 miles. Not saying that they did, but that was the approximate distance between track pans.
OP said, “10 locomotives.” BUT, what size locomotives, and how are they run. A bunch of light 2-8-0s that mostly rest in the roundhouse will give one answer, a bunch of 2-10-2s and articulateds that get run hard all day lifting copper ore out of a really big hole in the ground will give another, very different answer.
One final factor. How quickly can the coaling tower be refilled, assuming the availability of loaded coal hoppers and a switcher. The answers varied with the size and design of the coaling facility - anything from two carloads every 20 minutes (some trestle-style coal loaders) to one car every 2 hours (slow mechanical skip) to one carload a day (hand-shoveled into oversize metal pails moved by hand-cranked crane…) Likewise, how long does it take for the water tank to refill? It’s the total throughput, not just the capacity.
Chuck (Modeling Central Japan in September, 1964 - with coal-burning steam)
Steam was phased out in my country as late as 1977, so I still have a good memory of the service facilities needed for steam loco. A small terminal, in charge of maybe 10 locos of the size of a USRA Mikado would have a 100 t coaling tower and a storage of up to 1000 t of coal. I remember seeing huge piles of coal next to the coaling tower. There would always be a track for servicing and cleaning the ash out of the smokebox and the fire box. and a sand tower.
Most of the terminals I have seen are unfortunately grossly undersized, with vital facilities omitted.
It’s not the capacity of the coaling tower or water tank that matters so much as the rate of supply. A 100-ton coaling tower can deliver 500 tons of coal in an 8-hour shift, if it’s full at the start and you deliver four loaded 50-ton coal cars in time to replace the coal dumped into tenders. A water tank can be continuously replenished by pumping water from a river or well. My May 2008 Operators column dealt with engine terminal operation in terms of incoming consumables and outgoing waste – don’t forget that coal burning steam locomotives need their ash pans and hoppers emptied.
So long,
Andy
As Andy says, the size is also dependent on how much of a cushion they want to have on the inbound supply. Lets say that for whatever mix of engines, a tower uses 50 tons of coal a day. That means that they need an average of 50 tons of coal a day inbound. That’s 1 hopper. If its a 100 ton tower they can unload 1 car a day and if they miss a day it will be OK.
So what happens if there is a derailment and the hopper gets delayed a day or two. A good rule of thumb might be the same number of days of coal on hand extra as the day’s transit time from the mine. So if it take 3 days to get from the mine to the tower, then the tower needs 4 day’s capacity.
A real railroad could also keep some extra cars of coal on hand and short fuel, etc. to get around a tight fuel situation.
So what would a railroad do if traffic increased dramatically? Say, on a shortline using medium consolidations running a few trains a day to bringing in larger locomotives and running as many trains as possible?
Again, thanks for the information, it’s been very helpful.
I imagine they’d do what any other company who runs out of space does… make do with a temporary solution (such as a few “extra” days of full hoppers/gons) until a permanent solution is completed (such as a 400 ton coaling tower to replace the 200 ton tower).
obviously the “permanent” solution expects that the RR has the money and available real estate to build a larger tower without completely removing the old one first.
Looking at this post, I wonder if it is really necessary, for modeling purposes, to have an exact match between the size of the coal and water towers and the traffic. It seems to me that a structure that creates the right visual effect might be better.
Think you’ve got a point there … though at the same time the “prototype” way might be the best fit; or at least a good model for what to shoot for.
What I’m getting at is having simple coaling operation (let’s say steam shovel and 5 40’ gons on a siding, replaced every 2nd or 3rd day) and a 50,000 gal water tower might create the right visual effect for this particular engine facility initially (bluebird mentioned having a few consolidations bolstered by newer, larger locos); but it probably wouldn’t fit after delivery of the newer locos, which require more water/coal faster than what the older methods can adequately supply.
With that in mind – a good way to cheat with the water (assuming a more modern/urban setting – eg 1930s city rather than 1900s backwoods logging camp) would be to use stand pipes rather than a tower (paint one into the backdrop if you really want one). This way you could have “unlimited” supply of water as the municipal supply coupled with xx0,000 gallon tower off the layout somewhere would be more than enough to handle the needs of the fleet.
you’re right Altonfan, it’s not strictly necessary. But for my freelanced shortline (the Alkali Creek Ry.) I’m trying an approach things the way prototype railroads would have. Which I have not done previously. I still have some wiggle room when there is something I would like to have - provided I can come up with a prototypical justification.
The 100 ton cylindrical coaling tower for example, I found in the September 1959 issue of MR. According to the information in this thread, it would be adequate for the needs of my fictional railway, and from the information in my copy of the 1921 Simmons-Boardman MOW cyclopedia it is appropriate for the early 20’s, a time when my shortline “modernized” the main shop facilities. The justification? The previous roundhouse/shops burned down, taking a few locomotives too.
This discussion is exactly the type of information that we need to share. I can’t possibly model everything prototypical. I have to use the three foot rule. Like everything else on the layout selective compression is necessary for the locomotive servicing facilities. An example would be my ashpit. Yes, it’s there, but the load out to a gondola will be by small bucket and small gantry to a fictitional siding off the edge of the layout.
What this thread has done for me is remind me about how many cars I have to deliver to my coaling towers every day and how may tanke cars of diesel or fuel oil I’ll need to spot. Thanks for bringing this subject up. [:)]