I've always wondered how engineers kept train speed under control on long downgrade like Cajon Pass during the steam era. With diesels, dynamic brakes can be used if so equipped. Was there a way to keep a steam train under control other than the train's brakes?
Modeling the Pennsylvania Railroad in N Scale.
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The train's air brakes were basically it. One of the reasons diesels were less maintenance intensive, less wear on both locomotive and car wheels.
NorthWest pretty much said it all. Back in 1989 Steve Lee of the Union Pacific steam program wrote an article in "Trains" that pretty much explained how it was done. The article concerned a freight tun with 3985. If you've got access to the "Trains" archive I'm sure you can find it.
It was a very well written article and I've never forgotten it.
Engineers were the main computer on board. They used throttles, strokes, steam, water, engine air, train air, experience, knowledge, and the seat of their pants.
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One word
Retainers.
Manually operated valves on each car that can be operated in a number of positions that will keep brakes applied to the cars that brakemen set them up on. Before descending a serious grade, the train would be stopped and retainers set on a percentage of the cars, normally starting from the head end. Once the descent of the grade began and a brake application was made to the train, the brakes would stay applied to the cars that had retainers set, even when the brakes on the rest of the train were released. At the bottom of the grade, the brakeman would turn off the retainers and the brakes on those cars could then be released.
Excessive use of engine brakes on a steam engine 'could' overheat the tires (the flanged outer portion of the steam engine drive wheel) which had been attached to the wheel by heating the tire until it expanded to be slightly larger than the room temperature wheel - the cooling of the tire then affixed to solidly to the wheel center. If the tire got overheated it could work itself off the wheel. Extended use of engine brakes was seriously frowned upon.
Never too old to have a happy childhood!
My understanding is that the retainers were designed to leak air at a very slow rate (though could be wrong). The retainers would hold long enough for the brakeline could be brought up to normal running pressure and prevent p***ing off the air.
The D&RGW had some of their locomotives equiped with La Chatelier brakes.
- Erik
Retainers retain brake cylinder pressure.. otherwise they would be called train wreckers..
Randy
The 'exception' to this otherwise universal rule (at least in North America) is something called the water brake - particularly the "Le Chatelier Water Brake", which was apparently used only by the D&RG and the Duluth, Missabe & Northern. See:
http://www.trainweb.org/utahrails/drgw/waterbrake.html
http://www.trainorders.com/discussion/read.php?10,656803
It might have been mentioned in one of these articles - but I'm not at all confident about that:
"Monarch Branch revisited - using several kinds of brakes" by Blaine, David G., from Trains, March 1977, p. 30
- Paul North.
GP_9man,
First, thanks for a very interesting question. It's something I had wondered about but never researched.
Balt,
Makes sense the retainers would be used frequently in the days before dynamic baking was available.
Paul,
Thanks for an interesting and informative article on the La Chatelier brakes. It appears they had to be used judiciously the prevent damage to the steam cylinders or the drivers.
Norm
Randy Stahl Retainers retain brake cylinder pressure.. otherwise they would be called train wreckers..
That's correct when they are in low or high pressure hold mode. What I had remembered was the slow release mode (checked Al Krug's article on www.railway-technical.com), which was probably intended for short trains on very steep grades, e.g. the D&RGW Monarch branch.
....Along with the "retainers"....Why wasn't it possible to use the valving to the cylinders to produce a bit of resistence from steam pressure...?
I realize it probably wasn't done, but why....within reason...? Couldn't the pistons and rods stand the force against them up to the point of sliding the wheels.....That's what they had to withstand when starting out....
Quentin
Quentin,
That's what the Le Chatelier brake was all about, problem was that it heated up the cylinders something fierce. See's the links on Paul D. North's post for more info.
Never mind the Le Chatelier brake, engineers had to keep steam on the cylinders to ensure that lubrication still occurred. I'm no expert on steam engine lubrication systems, but I recall reading that some amount of pressure had to be kept on the cylinders to make the lubricators lubricate.
As mentioned, the engineer was the "computer," and his knowledge of his train and the territory made all the difference. Having run trains in hilly territory, without dynamics, I know one has to be very mindful of exactly what one can "get away" with - especially when one can knock off the brakes and have enough time for the train to recharge before making another application. We run short trains, compared to most freights, but it's still something to keep your head working.
There are almost always variations in the grade, as well as curves, both of which can serve to hold speed somewhat in check.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
The use of retainers while descending long grades generates a lot of heat in the wheel tread. Most long down grades where retainers were used typically had special instructions that called for stops to cool the wheels at specific locations. IIRC these stops were generally for 10 minutes. I also seem to recall that speeds were limited to 10-15 MPH.
Dynamic brakes revolutionized train handling on mountain grades, greatly speeding up the process. With dynamics speeds are generally limited to about 25 MPH. No stops to turn up and turn down retainers, no stops to cool wheels. Remember also that "back in the day" tons per operative brake were much less than is the case today so each brake did not have to work as hard as would be the case today.
Mac
NTSB in it's testing of a CSX runaway derailment on 17 Mile Grade back in 2000, determined that 15 MPH was the maximum speed that air brakes alone had sufficient stopping power to bring a train to a stop without overheating the braking equipment (brake shoes & wheels) to the point of fading. Note-this is based on 286K cars with state of the art high friction composite brake shoes - neither of which existed in the steam era.
BaltACD NTSB in it's testing of a CSX runaway derailment on 17 Mile Grade back in 2000, determined that 15 MPH was the maximum speed that air brakes alone had sufficient stopping power to bring a train to a stop without overheating the braking equipment (brake shoes & wheels) to the point of fading. Note-this is based on 286K cars with state of the art high friction composite brake shoes - neither of which existed in the steam era.
It should be noted that pertained to that particular stretch of railroad.
.
I've seen the download from that wreck. Really scary! I couldn't see where the engineer actually did anything wrong. If I recall correctly, the train was dispatched out of Grafton with only the dynamic brake working on the lead unit. The engineer was not privy to this information as the power was already on the train when he got it. Cresting the grade, he set the dynamics to gather up the slack. He started with a minimum reduction of the train line, made a couple further service reductions, before big holing it at about 32mph (I think). I believe the track speed was 25. At no time did he release the air, disproving my assumption that he had "*** away the air" (taking to heavy a reduction, realizing your mistake and attempting to remedy it by making a running release and taking another reduction on a now depleted trainline). The speed began to fall to the mid 20s before rising (with the entire train in emergency!) and running away. My question to the road foreman was " do you mean, an air hose separation on this grade, with a fully charged train line would result in a runaway?" At this time, much of the motive power fleet would lose dynamic braking form a trainline initiated emergency application. The PCS switch would kick out and that was it for the dynamics! I didn't get a real definitive answer.
As for steam locomotive operation, in the early days, it was common for the hoghead to open the cylinder cocks, horse her over into reverse and use back pressure in the cylinders as a brake. I've seen this done on small engines with relatively light trains. Works pretty good! The one drawback is that a vacuum is created in the smokebox, resulting in dirt and cinders being drawn into the cylinders. Not a good thing. If you look at old pictures of 19th century engines, brakes don't make their appearance on locomotives until well after the Civil War.
BigJim BaltACD NTSB in it's testing of a CSX runaway derailment on 17 Mile Grade back in 2000, determined that 15 MPH was the maximum speed that air brakes alone had sufficient stopping power to bring a train to a stop without overheating the braking equipment (brake shoes & wheels) to the point of fading. Note-this is based on 286K cars with state of the art high friction composite brake shoes - neither of which existed in the steam era. It should be noted that pertained to that particular stretch of railroad.
True, but at 2.2% it is representative of most mountain grade routes still in operation so it is a good benchmark.
PNWRMNM The use of retainers while descending long grades generates a lot of heat in the wheel tread. Most long down grades where retainers were used typically had special instructions that called for stops to cool the wheels at specific locations. IIRC these stops were generally for 10 minutes. I also seem to recall that speeds were limited to 10-15 MPH. Dynamic brakes revolutionized train handling on mountain grades, greatly speeding up the process. With dynamics speeds are generally limited to about 25 MPH. No stops to turn up and turn down retainers, no stops to cool wheels. Remember also that "back in the day" tons per operative brake were much less than is the case today so each brake did not have to work as hard as would be the case today. Mac
descending Saluda Grade must have taken forever in steam days and taken the most well-seasoned engineers Southern had.
In 1936 (referring to Asheville Division TT #82), freight trains were to take a minimum of 20 minutes to traverse the 3.1 miles from Saluda to Melrose; the three freights in TT were scheduled to take 20-27 minutes. Passenger trains were to take at least 8 minutes; the two passenger trains were scheduled to take 11 and 13 minutes.
In 1964 (referring to Asheville Division TT #37), no minimum times were listed, but the four freights were scheduled to take from 35 minutes to an hour and one minute. The single passenger train was scheduled to take 15 minutes. I do not doubt that by 1964 the freights were longer--and the passenger train was shorter than in 1936.
The earlier TT has no special instructions concerning descending the grade; the later TT has close to a column and a half of instructions concerning the handling of trains descending the grade.
Johnny
What truly makes a Engineer is the ability to use the braking power available to safely move trains over the grades on a territory. Most 'idiots' can operate the throttle, only an Engineer can operate the brakes.
PNWRMNM BigJim BaltACD NTSB in it's testing of a CSX runaway derailment on 17 Mile Grade back in 2000, determined that 15 MPH was the maximum speed that air brakes alone had sufficient stopping power to bring a train to a stop without overheating the braking equipment (brake shoes & wheels) to the point of fading. Note-this is based on 286K cars with state of the art high friction composite brake shoes - neither of which existed in the steam era. It should be noted that pertained to that particular stretch of railroad. True, but at 2.2% it is representative of most mountain grade routes still in operation so it is a good benchmark. Mac
From reading the NTSB report, I would also think that the grade % is the critical issue for speed as opposed it being a particular stretch of railroad. The physics would imply that the speed is limited by keeping the wheel tread temperature below ~600F to prevent brake fade. I would assume that the 315k cars would be limited to an even lower speed, though a larger wheel diameter may allow for less of s speed reduction.
The issue of car weight, gradient, bake shoe type and wheel diameter would make for a good discussion in its own right.
BTW, the Milwaukee's electrification was the first demonstration of the advantages of regenerative/dynamic braking for mountain railroading. The reports on train handling stated that brake wear was substantially reduced, safety improved and increased comfort for the passengers. The reports also hinted that the reduction in brake wear as well as wear and tear on the car was a greater cost savings than the value of the regenerated electricity.
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