I confess, I have always been a “roundy round” layout builder. There is much to be said for continuous running.
However, the thread on shelf layouts prompts me to ask, how do you operate these layouts without benefit of turning the locos? A lenghty shelf would mean large distances in reverse. Something not usually done as I hear.
Shelf layouts tend to be switching layouts–thus using switch engines. They were designed to pretty much be bi-directional (at least as much as diesel switchers, anyway).
Ed
A switcher, steam or diesel, spends half its working day going in reverse.
The are many myths among uniformed modellers, running in reverse seems to be one them.
It’s amazing how little many, if not most, modellers know about how a railroad works.
I know the PRR put slope back tenders on a lot of their steam switchers to facilitate better visibility in reserve so I would have to deduce that they spent quite a bit of time operating in that direction.
Chris
Don’t bet that steam locos didn’t run long distances in reverse - unless you like to give money away.
On many of the branch lines that ran up West Virginia hollows to the mines at the end, a Mallet would either back in tender first or back out tender first. There wasn’t enough flat land at the end of the line for a turntable long enough to turn a C&O H(whatever) or an N&W Y(whatever).
I am familiar with several branch lines that were running steam when I railfanned them. The locos were tank engines (look, Ma, no tender!) and ran equally well in either direction.
I am modeling a situation that wasn’t unknown in the prototype - a fairly lengthy route (2 intermediate stations) on which the locos are never turned. The management considers keeping water over the crown sheets on the 4% grade more important than running the motley collection of tank locos smokebox first.
Chuck (Modeling Central Japan in September, 1964)
Bruce, if you look at the tenders on most steam switchers you will notice that they are lower, sometimes with a sloped back, and/or they have a high narrow coal bunker extension. All of these features allow for better visablity in reverse.
It is true that the valve gear of big mainline steam is generally “tuned” for forward running, but on switchers it is set neutral for equal power in both directions. Switching speeds are always slow and these locos were designed to be slow but powerful for their small size.
A USRA 0-8-0 can generally move as much as any 2-8-0 and many Mikado’s, just not at the same speed!
As for steam running in reverse - have you ever been to the Strasburg Railroad? They have no locomotive turning. The loco runs backwards pulling the train out of the station. At the end of the line it runs around the train and pulls it the train going farward for the return trip. Once back in the station, the loco then runs around the train again to pull the next trip out in reverse - anywhere from 4 to 6 times a day and more in the peak season, every day, for about 9 months out of the year. This tourist operation has been going on this way for some 5 decades with a loco built in the 20’s. It is a slow and scenic ride in both directions. I think steam locos can run in reverse just fine.
http://strasburgrailroad.com/gallery-photos.php
In this video you get to see the whole thing, in the second half of the video they leave the station pulling the train in reverse
Steam locomotives are not exclusively directional. There was a commuter railroad between Ogden and Salt Lake around 1902. They were far too cheap to build turning facilities, so instead, they purchased pilots and cowcatchers for the tenders of their locomotives. All the locomotives on the railroad were northbound, and merely ran around the trains to turn them back. Another example is logging railroads. Because logging railroads had steep grades, a locomotive always had to point up hill, or else water would flow to the front of the boiler, and cool all the steam, making the locomotive no more effective than the cars it was hauling.
So running steam locomotives backwards is not at all unprototypical. But you do bring up a point. Locomotives, especially on mainline trains, would need to be turned. However, if it was a shorter run through the city or switching a yard, or who knows what, direction usually wasnt a problem.
If locomotives usually had extensive backing moves assigned to them, they would often have one of three characteristics: 1) chains running from the corners of the trucks on the tender to the tender itself (to keep the trucks on the track by preventing them from turning too far, often on older locomotives), 2) no tender at all (they often derailed in such situations regardless) 3) rear pilot wheels (Unlike on large locomotives, where rear pilot wheels were designed to support the weight of the firebox, these were for the same purpose as the front, to guide the locomotives into turns, a function which the tender often inadvertently held).
“large” (or long) is a relative term. Most home layouts do not cover anything the real railroads would have called a “long distance”.
Say you have a home layout with 120 feet of mainline in H0 scale. That corresponds to about 2 miles in real life. Not at all an unrealistic distance to back up for a train on a branch line.
Here is my local steam line - the engine has just run around, and has been coupled to the rearmost passenger car, before backing back down the line trailing the coaches behind it:
Smile,
Stein
Other way around - the problem is not that the front of the boiler get too cold. It is having the rear of the boiler (especially the top of the fire box - the crown sheet) get too warm. Take some very hot metal, and then inject some more cold water - metal gets a shock, twists and break, creating a steam explosion that will do unpleasant things to the locomotive and it’s crew.
Smile,
Stein
Depends on the switching layout, which could represent a branch line terminal. Said terminal could have engine turning capability, in which case a steam loco could bring a train in with the smokebox leading, do the required switching, take a ride on a turntable or go around a wye and return smokebox first.
There’s not a big deal operating a steam in reverse for several miles on a branch line. SP’s line from Santa Cruz to the cement plant at Davenport is (or rather was since the SP no longer exists) about 10 mile. Steam locomotives would operate in the “normal” way out to the plant and return in reverse. Same for the line that rain from Santa Cruz up the hill to a quarry at Olympia. IIRC, SP had a 25 mph speed limit on steamers running in reverse, fine for branchlines, not so good for mainline operations. The branch out to Hollister from Gilroy (still in existence ) was operated in reverse in one direction during the steam era.
Andre
Temperature as little to do with it other than the firebox is really hot. [:)]
The crown sheet, even if exposed for as little as a few seconds, will collapse and send scaling water and steam into the cab. This is why on some steep grades, steam locos tended to run with the firebox on the downhill side of the grade. Keep in mind that water always stays level and that with a 25 foot long boiler, on a 2% grade, the water in the uphill end of the boiler will be as much as 6 inches deeper than in the down hill end of the boiler.
I am no expert on steam engines.
Only thing I know is that the oft stated reason for keeping the firebox downhill on steep inclines (logging style places) is to keep the crown sheet covered, and that a failure to do so could cause a steam explosion. It is fairly obvious that being scalded by hot steam (or being torn apart by an explosion) is not necessarily a good way to go.
I am not clear on exactly why exposing the crown sheet could/would lead to it’s supposedly rapid collapse.
My assumption was that lack of water over the crown sheet would heat the crown sheet, both weakening the metal somewhat, and making it more exposed to contraction stresses when more cold water was injected into the boiler from the tender or water tanks, making the crown sheet (which is under considerable pressure) crack.
What is, in your opinion, the real reason that crown sheets crack, if it is not related to the crown sheet getting too hot?
Edit - got curious and decided to read more about this. Here is a link to a NTSB report on a crown sheet failure on a tourist railroad in 1995:
Without the protective covering of water, the crown sheet will glow cherry red within a few seconds and loose it’s strength allowing the boiler pressure to buckle and collapse the crown sheet. The temperature of the flue gases in a steam engine firebox can reach 1000 °F (550 °C). Prompt action by the fireman injecting cold water into the boiler and covering the crown sheet may, in fact, save the crown sheet and possibly prevent catastrophic collapse, although the crown sheet may still be damaged enough to leak and or require replacement. Keeping the crown sheet covered is one of the fireman’s prime responsibilities.
Although practically unknown in North America, hence the frequency of North American firebox collapses even into the 1950s, countries like the UK used fusible plugs in thier crown sheets. North American low water alarms could be and were ignored by crews. The fusible lead plugs used in UK fireboxes would melt the instant the crown sheet was uncovered and permit steam and boiler water to gush into the firebox. While this was dangerous it was the lesser of two evils. The water and steam would tend to dowse the fire and the fireman, keeping his wits about him, would turn on both injectors to c
The reason that it´s dangerous to let the water go below the surface of the Crown-sheet is of course what´s stated above.
Yes, a cracked Crown sheet might cause a serious steam release, but what happens when cold water is injected and hits a red Crown sheet? A big explosion!
The same thing is what happens if a loco is going on an incline with the “wrong side” down, If the crown sheet gets exposed and when leveling out and the water runs back onto the crown sheet, you get instant steam, and lots of it! Kaboom!
Although practically unknown in North America, hence the frequency of North American firebox collapses even into the 1950s, countries like the UK used fusible plugs in thier crown sheets.
I don’t know about North America in general, but the Southern Pacific certainly used fusible plugs in their crown sheets. However, even when they worked, it wasn’t a slam dunk guarantee that a crown sheet failure wouldn’t happen. SP 4-10-2 #5048 had a catastrophic crown sheet failure at Bosque, AZ, in 1948. Examination of the wreckage indicated that the fusible plugs worked as designed. The engine was climbing a grade and being force fired at the time, so the designed failure of the plugs was apparently not enough to extinguish the fire.
Andre
In the Prototype Information for the Modeler Section of Forum: Please read the post there, titled: ’ Learn about a UNIQUE NH shortline RR '. and possibly obtain a used copy of the book on Amazon.com, titled: ’ The Blueberry Express: A History of the Suncook Valley RR '. Back in it’s heyday, SVRR ran it’s only steamer (1924 Baldwin Mogul; bought new ) in reverse, whenever necessary and loco was very often mid-train, when switching various industries along r-o-w. The spurs were a mix of trailing/ leading point, which made interesting turn make-ups, on a day-to-day basis. Many times ( as stated in the book ) MTs were removed from industry sidings and pushed ahead of Mogul, to a longer spur for storage, then picked up on return leg to Concord Yard. There WAS a short TT at Center Barnstead ( at end-of-track ), which enabled Mogul and later GE diesels, to be turned for down-valley leg. Since I intend modeling point-to-point on small HO switching layout, t’will be very interesting, with a leading/ trailing point turnout mix, during any OP session. TTFN…papasmurf in NH
P.S. Forgot to mention: SVRR had small US Mail contract / baggage - lcl freight business, so an old 60’ combine almost always accompanied Mogul on it’s twice-a-day, except Sunday, up-valley turns, with conductor inside. This HAD to make switching industries a nightmare at times! Elder local resident I worked with said, combine was often spotted at a convenient siding, picked up later, to make switching easier. And, please remember: this era was in '30s/ '40s, so all grade crossings had to be flagged, as there were NO automatic grade crossing signals ( or any in operating condition ), on entire up-valley line above switchback, after the B&M divested itself of the branch and r-o-w main
There was a very good explanation of boiler explosions and crown sheet failure in the April 1995 issue of Trains magazine.
Lack of water over the crown sheet (top of the firebox) allows that metal to be heated to temperatures in excess of 2000 degrees Fahrenheit, well above that necessary to weaken the steel. As it softens, the holes for its staybolts become enlarged, causing the sheet to drop and tear.
According to the article, adding cold water to the boiler can precipitate this, although it’s not clearly explained how (the check valves are located towards the front end of the boiler). Regardless, the tear provides a vent for the steam, which then allows all of the water in the boiler (often at temperatures close to 450F) to turn instantly to steam. Upon doing so, it seeks to occupy a volume 1430 times greater than it did before - since the boiler is not yet totally ruptured, this creates a momentary pressure estimated to be in excess of 3000psi. The article goes on to detail the sequence of events over the next second or two and there are several dramatic photos showing the outcome. One is a 3/4 view of a U.P. 4-12-2 - the smokebox, running gear, and tender. with the boiler and cab completely gone.
Wayne
How did we get from a discussion of steam operation on switching layouts to what seems to be a thread primarily dealing with the causes of boiler “incidents”?
Some genius somewhere is going to come up with a DCC function that requires you to put “water” in the “boiler” with a frequency that depends on how hard the engine is being worked. Failure to keep the “water” over the “crown sheet” will result in the in a loud “KA-BOOM” from the speaker followed a second later by a sudden stop. If the function is fully thought out, you wouldn’t be able to operate the engine for at least 2 months because it has to go to the shops to be " rebuilt".
Of course, some wag would probably figure out a way to have the speaker emit those immortal words from Marvin the Martian, " Where’s the kaboom? There was supposed to be an earth-shattering kaboom!"
http://www.imdb.com/character/ch0030547/quotes
Andre
From a discussion of why it sometimes was not desireable to turn engines before heading back downhill - why a simple double ended siding allowing a runaround move on top would do just fine (and maybe also having the engine push cars uphill, and then back up downhill, with cars above the engine on the incline.
As these threads go, not too bad of a topic detour 
Smile,
Stein
Then again, some engines could be in danger from low water going uphill. SP’s cab-forwards were banned from the Siskiyou line after one of the earlier 2-8-8-2’s blew up hauling a train up grade on a grade exceeding 3%.
The interesting thing is that an engine is working all out going uphill whereas it is kind of “idling” going downhill and the fire shouldn’t be producing anywhere near the BTU’s/second that it would be producing when the engine is working in full gear at full throttle to move a heavy train (as opposed to trying to keep one from running away). Certainly a raging fire will rapidly overheat an exposed crown sheet, but an engine that’s only working enough steam to keep the cylinders lubricated won’t be inducing sufficient draft to create nealy as much heat. You got a lot better change of inducing catastrophic failure when the engine’s being pushed to its maximum performance.
The Roaring Camp and Big Trees Narrow Gauge Railroad in California has some pretty stiff grades (I forget how steep exactly, but exceeding 6%, IIRC). Locomotives operate smokebox first both uphill and downhill. I thin