Did steam engines ever have brakes on the tenders, leading and trailing trucks, that could be operated independantly of the brakes on the drivers?
Were steam engines traveling alone restricted as to speed because of the danger of overheating main driver brakes? Was it legal to dispatch an engine by itself without a "train" for braking?
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Did steam engines ever have brakes on the tenders,
Yes.
leading and trailing trucks,
Trailing trucks, yes. Very few railroads had brakes on the engine truck. Sp is one of the few examples of brakes on the engine truck.
that could be operated independantly of the brakes on the drivers?
Generally no. However, the SP, UP and the N&W J Class had a "mountain cock" in the cab, located down by the Engineer's feet, which was used to cut-out the air brakes on just the drive wheels, so as not to overheat the tires, during long down grade braking.
Were steam engines traveling alone restricted as to speed because of the danger of overheating main driver brakes?
Yes. Also due to the great stopping distance without a train.
Was it legal to dispatch an engine by itself without a "train" for braking?
Of course. That's how helper locomotives moved back down grade after helping a train upgrade.
Thank you hot water for taking the timer to reply.
... Was it legal to dispatch an engine by itself without a "train" for braking?
in the live steam hobby, locomotives are routinely run without a train, but brakes are rarely used unless it is to hold an engine already stopped or just slightly rolling. not sure if this practice is used on full size locomotives, but using counter-steam is a very effective way to slow a train on a downhill grade. the reverse lever is pulled back to a neutral position and then gently eased into reverse to port steam against the piston travel.
cheers...gary
in the live steam hobby, locomotives are routinely run without a train, but brakes are rarely used unless it is to hold an engine already stopped or just slightly rolling. not sure if this practice is used on full size locomotives, but using counter-steam is a very effective way to slow a train on a downhill grade. the reverse lever is pulled back to a neutral position and then gently eased into reverse to port steam against the piston travel.
cheers...gary
Such use of the reverse gear on full size steam locomotives will cause BIG problems within the running gear machinery, and is exactly how the drive wheels were flattened on UP 844 just 3 years ago.
Also, at least some railroads, if not all, equipped the tender with a retaining valve, as is used on freight cars.
Here are some actual speed restrictions from a 1950 Santa Fe timetable:
Light engines, Summit to Cajon (3 % grade in Cajon Pass)
On the 765, the only time the independent brake (the "engine" brake) is applied when moving is if the engine is moving light (without a train) in the yard. In that case the engine brake is the only brake you have available.
Out on the road, the train does all the braking. The steam locomotive actually pulls against the train brakes to keep the slack stretched. It's called "stretch braking" and it is the braking technique used on passenger trains so there is no slack action back in the train.
We would NEVER - EVER put the valve gear in the opposite motion to stop the engine. That may work on a model steam locomotive, but can cause BIG problems on a full-size steam locomotive.
Believe the Denver & Rio Grande Western employed the Chatelier Water Brake on engines going down mountain - - in which boiler water was admitted to the cylinders, compressed by the pistons (providing braking) and released through the cylinder cocks.
DM&IR 2-8-8-4 #224, leased by the 'Grande during WWII, was not equipped with the water brake, lost it's air, derailed, and went on it's side, coming down the Big 10 curves, at Fireclay, CO. The DRGW rebuilt the engine before returning it to the DMIR for the next ore season. http://digital.denverlibrary.o...oll22/id/67330/rec/1
Believe the Denver & Rio Grande Western employed the Chatelier Water Brake on engines going down mountain - - in which boiler water was admitted to the cylinders, compressed by the pistons (providing braking) and released through the cylinder cocks.
DM&IR 2-8-8-4 #224, leased by the 'Grande during WWII, was not equipped with the water brake, lost it's air, derailed, and went on it's side, coming down the Big 10 curves, at Fireclay, CO. The DRGW rebuilt the engine before returning it to the DMIR for the next ore season. http://digital.denverlibrary.o...oll22/id/67330/rec/1
Mark,
The "water brake" is a whole different operation, as it designed to admit a small amount of boiler water into the cylinders, which flashes to steam. With the reverse gear positioned slightly in the reverse direction, and cylinder cocks open, the Engineer can adjust the retarding affect on very steep down-grades (like Soldier Summit) simply by adjusting his power reverse gear. The Santa Fe also tried this system, but the Santa Fe Engineering Dept. eventually decided against the system, since it was VERY dependent on the Engineer's skill, i.e. one slight mistake and cylinder heads could be blown off, or worse.
Robert LaMassena, author and steam locomotive analyst, described the operation of the water brake, in a cab ride on an L131 2-8-8-2, coming down Tennessee Pass from Summit, "He/the engineer, opened the water-brake valve, cracked the throttle, opened the cylinder cocks and moved the cut-off control somewhat back of center. The 3619 would now roll down grade at a steady 20 mph, restrained by only the water brake. The 3600's (there were two locomotives coupled, returning to Minturn) engineer left the throttle slightly open to provide lubrication for the pistons".
According to LaMassena, the DRGW employed the water brake for many years. Clearly all of the operations running multiple enormous articulated locomotives on steep mountain grades with heavy tonnage freights and passenger trains, involved tremendous skill...including the operation of the water brake! Intersting that the Santa Fe dismissed the water brake, as Cajon was comparable (3%?) to Tennessee Pass?
That's very interesting about the "water brake", a type of compression braking on a steam locomotive? I would be interested to hear more about which railroads used it, what locomotives, what era? From what Hot Water says, it was perhaps too problematic for widespread use.
That's very interesting about the "water brake", a type of compression braking on a steam locomotive? I would be interested to hear more about which railroads used it, what locomotives, what era? From what Hot Water says, it was perhaps too problematic for widespread use.
Only tried on the D&RGW and Santa Fe, and then "widely used" only on the D&RGW, pretty much right up to the end of steam. As I recall, it is a French design, from the late 1920s or 1930s. As explained to me by the late Vernon L. Smith, who was familiar with the Santa Fe tests, the system and use thereof, is VERY dependent on the skill of the Engineer. Mr. Smith commented that the D&RGW was such a "small railroad", when compared to the Santa Fe, that their Engineers where much more equipped & experienced at its use.
Thanks for the info, Hot water. A mountain railroad like D&RGW presumably had more interest in that kind of system.
I believe the French had some other complications like independently controlled cutoff for compound operation, but that was another one of those innovations that was highly dependent on an engineer's finesse.
Suspect only the Rio Grande had widespread need for the water brake, as it was described as "the toughest railroad in America to operate", what with severe grades and curves. As Hot Water noted, continuous use of brakes on the down grade (Tennessee Pass: 3%) would sweat off the tires!
"Rio Grande - Thru the Rockies, not around them!"
RGS #20 (under restoration at Strasburg) still had her water brake when she arrived. It is simplicity itself. Nothing but a 3/8” pipe tapped into the boiler about 1’ below the normal water level, going to a globe valve, and then leading to the exhaust passages of the cylinder block.
Normally an engine rolling forward with the valve gear in reverse would be pulling smoke and hot gas into the cylinders. By supplying that hot water to the exhaust passages, as it exits the pipe, it flashes into very wet steam, displacing any exhaust gas before it gets pulled into the cylinders, so all that they see is that wet steam. By opening the throttle, the engineer prevents the engines from compressing that steam to a pressure higher than boiler pressure, reducing the chance of sliding the wheels. From there it’s just a case of the more reverse on the Johnson bar, the more braking.
My biggest question about a water brake is how much does that boiler chemistry laden very wet steam wash off cylinder lubrication, causing wear and tear on the cylinders.
That was another very big concern of the Santa Fe Mechanical Dept..
I note that the C&TS engines no longer have water brakes (though the pipe fittings are still connected to the cylinder exhaust passages), instead having “drifting throttles”, ball valves tapped into saturated steam from the turret, and plumbed into the steam chests (not the exhaust passages). With 14 miles of 4% grade to descend, I understand that light helper engines still go down the mountain with the valve gear in reverse to help hold them back, but without the supply of wet steam in the exhaust passages to protect and cool the engines. I’ve often wondered why the water brakes were removed.
Back to using the reverse position to slow/stop the train. Unless I miss my guess, I've seen/heard this done countless times with smaller steam engines. Specifically at Cedar Point Amusement Park, where they routinely run restored sugar cane engines with Stephenson valve gear. I'm not exactly sure what happens mechanically to reverse the follow of steam, but it obviously happens. You can always tell when they are in braking mode as the train slows for a station, you can hear the steam escaping from the pistons. It is a very unique sound. When I've looked at the engine, I see no brake shoes on it at all, but the train cars do have the shoes. I've felt their effect as well, which is quite different.
Chris
LVHR
Using the Johnson Bar to stop a light engine is how it's done at Walt Disney World--where the locomotives don't have brakes on the engine or tender.
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