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Steam & Excursion > Steam locomotive independent brake question . . .Date: 02/01/25 11:28 Steam locomotive independent brake question . . . Author: eljay Pretty basic, but I never thought of this 'til recently: Does an independent set apply only to the drivers or to pony- and trailing-truck wheels as well? Thanks much!
Date: 02/01/25 11:36 Re: Steam locomotive independent brake question . . . Author: HotWater eljay Wrote:
------------------------------------------------------- > Pretty basic, but I never thought of this 'til > recently: Does an independent set apply only to > the drivers or to pony- and trailing-truck wheels > as well? Thanks much! An independent brake application has the brake shoes apply to ALL wheels that have brake shoes, including the tender. Many railroads did NOT have brake shoes mounted on the engine/pony truck. Plus, some railroads, like the SP and UP, had a "mountain cock" mounted so that the Engineer could cut-out the air application on just the driver brake cylinders, thus allowing the air application to the engine and tender brakes. Date: 02/01/25 12:05 Re: Steam locomotive independent brake question . . . Author: wcamp1472 Typically, all brakes on a loco are applied and released at the same time.
Often brake shoes on the pilot truck wheels were not as rugged as the other brake rigging.... So, they tended to be the cause of pilot-truck derailments... SO..... many RRs had those braking components removed from the pilot trucks. A fine-point... The loco brakes can be applied and released by either, or both the Automatic Brake, trainline. And, by the engineer's Independent Brake. The Independent Brake can apply and release the individual loco's brakes at any time. You will not find steamers with MU'd air brakes, loco to loco. On steamers, the loco's "brakes control valve" applies the Train brakes according to the handle position of the engineer's Automatic Brake valve. ( The name "Automatic Brake Valve" terminology came about in the 1880's when George Westinghouse invented train air brakes that applied the brakes even if the train separated. Each car has it's own compressed air storage tank, and if a train segment comes uncoupled, each cars' control valve directs the stored-sir to apply brakes and stop each & all the train segments, "automatically") The smaller handle is used to apply-and-release the brakes on the loco --- ONLY. When loco brakes are applied using only the Automatic Brake handle, a smaller port applies the driver-brakes, at a much slower rate of application, compared to the other train-brakes. The danger to locomotive brakes, is that the drive wheels, powered by the pistons are fitted with steel tires shrunk onto the cast-iron driver-centers. The tires are replaceable, and are machined a few-thousandths smaller at their inner diameter, than the diameter of the cast wheel center. At time of application, the new tire is warmed-up ( around its circumference) to a few hundred degrees --- warmed; but, not TOO hot... The tire expands slightly, and is fitted over the wheel-center to cool.. When cooled, the tire shrinks and grips the wheel center, Nice and Tight ! When braking for extended time periods, those driver tires can heat--up and expand ---- with the resultant loosening & calamity and derailment. To avoid over-heating the driver-tires, the engineer always keeps the loco's brakes RELEASED, applying them only to hold the train, once stopped.... Thanks for the clear question ....it's a core concept. W. ( As noted by HotWater, some RRs had cut-out cocks so that engineers could prevent air pressure from activating the brakes on pistons that applied the drivers' brakeshoes). Edited 2 time(s). Last edit at 02/01/25 12:26 by wcamp1472. Date: 02/01/25 14:58 Re: Steam locomotive independent brake question . . . Author: eljay Thank you both for your informative replies!
Train handling considerations would seem to dictate that bailing the independent would need to release all brakes, engine and tender, but I've also been aware that indiscriminate independent use was bad practice because of the effect on the steel tires . . . the notion of minimized application of brake shoe pressure on the drivers is something I had no awareness of but it certainly makes sense--splitting the difference so to speak. Date: 02/01/25 15:41 Re: Steam locomotive independent brake question . . . Author: wcamp1472 What's "very-dicey" is descending a long down-grade, as a light-engine
( no cars), and no driver-brakes 'cut-out cock' . Being 400 tons, or so, some locos want to gain speed very rapidly, even on only a slight down-grade ..... an all-roller-bearing engine rolls very easily. So, you must be very cautious, and go very slowly down any hills. Adding traction sand adds a little more rolling friction, too.. That can help... if you've got like 6-wheel tender trucks. NKP Berks did not use brake shoes on pilot trucks, or on the trailer truck's 4 wheels. Being a flat-land loco... that worked-out well for them. When going down hill, you must travel very slowly because friction and heat build-up VERY quickly..... so, 10 or 12 mph is very difficult to maintain.. .. and you gotta' keep the driver tires as cool as possible. With a few cars behind the tender, it can make all the difference in the world ....as far as keeping the driver tires cold. W. Date: 02/01/25 15:48 Re: Steam locomotive independent brake question . . . Author: Frisco1522 It's important to "bail off" the independent brake when using the automatic brake. Only occasion I can think of is going into emergency using the automatic.
If the train goes into emergency while you're going down the main, you should bail them off and keep going until you know where the rest of the train is and what it is doing, lest it runs into you. Since 1522 rarely had a high tonnage train, when coming in for a stop I would use the automatic until we were just about stopped and apply the independent and kick off the train brakes. In the few feet until full stop, the trainline would be charging while we were stopped. Always dropped the reverse down in the corner when coasting or coming to a stop. Don't know if that's protocol, but always worked fine for me. When going downhill always had her in the corner also for lube purposes. Date: 02/01/25 17:10 Re: Steam locomotive independent brake question . . . Author: eljay This idea was what led to my question in the first place. I was imagining running a steam cab hop down the grade between Ash Hill and Siberia on the Santa Fe Needles Distric in California. Figured that putting a lot of air under the caboose--but NOT enough to slide the wheels--might let the hogger avoid using the independent at all. Thanks again for your inputs!
Edit: I left the word "not" out of the phrase. Very confusing result, indeed. > > With a few cars behind the tender, it can make all > the difference in the world > ....as far as keeping the driver tires cold. > > W. > > Edited 2 time(s). Last edit at 02/05/25 09:42 by eljay. Date: 02/01/25 18:43 Re: Steam locomotive independent brake question . . . Author: wcamp1472 I'm not sure about your comment about sliding the wheels.
I'm confused by your wording. In fact, what happens when sliding the the wheels, is that the friction between the stalled wheel and the rail causes local heating of the wheel's steel at the rim to turn to liquid,.... so that the wheel rides on a liquid lubricant, rather than grasping to the rail-head. Braking has gone to zero. Remember that each wheel's braking area, at the rail head, is about equal to the area of a dime-coin. That's where all the braking force is concentrated. Just a little more pressure from the brake-shoe, and you've got a sliding wheel. You also get sliding wheels on empty freight cars.... who's braking is proportioned for 100-ton loads... But, the empty car weighs maybe 30 tons. Many cars are fitted with spring compression measuring devices that detect empty load conditions, and a binary valve limits the brake cylinder pressure and prevents locking the rolling wheel-sets, on empty cars. W. Edited 2 time(s). Last edit at 02/02/25 08:34 by wcamp1472. Date: 02/02/25 10:31 Re: Steam locomotive independent brake question . . . Author: eljay All I meant was to let the caboose do the braking, or as much of it as possible, to minimize or avoid the need to use the engine brakes.
Date: 02/02/25 11:15 Re: Steam locomotive independent brake question . . . Author: wcamp1472 Yes...
Thats the general intent. However, the component with the most mass will govern movement ---as affected by the grade, in degrees. So, a Berk weighing 400 tons is drawing a caboose weighing 15 tons.... that ain't a lot of braking capacity. Remember that each wheel has a very small area of contact at the rail.... each wheel's contact area is about as much area as a 10-cent coin, So, you have 8-wheels in contact with the rail... That's it. Theres not much braking power there... 6 to 8 cars is a good number of cars to keep things under control. Regardless of the size and number of brake shoes, it's the wheels' contact area at the rail that does the stopping. You want the MOST number of wheels in contact with the rails, to get the most braking power. Add more cars... W. Date: 02/03/25 06:47 Re: Steam locomotive independent brake question . . . Author: Worthington_S_A HotWater Wrote:
------------------------------------------------------- > eljay Wrote: > -------------------------------------------------- > > Plus, some railroads, like the SP and UP, had a > "mountain cock" mounted so that the Engineer could > cut-out the air application on just the driver > brake cylinders, thus allowing the air application > to the engine and tender brakes. SOU 4501 and N&W 611 currently have mountain valves installed. I believe 611's was used extensively at Strasburg due to the engine/tender/water bottle weighing as much as an entire wooden consist. Date: 02/03/25 08:08 Re: Steam locomotive independent brake question . . . Author: LocoPilot750 Actually, if the braking ratio is set up properly on an empty car, (or caboose) the brakes are not supposed to slide the wheels even in emergency, if rail conditions are good. If you load 100 tons of coal or grain into the same 30 ton when empty car, you still only have the same braking effort the car had when empty, thats why loadeds take about 5 times further to stop than an empty car. Some newer cars do have a load/empty sensors that allow better braking when the car is loaded.
Date: 02/03/25 13:58 Re: Steam locomotive independent brake question . . . Author: railstiesballast IIRC some RRs had a system to apply a bit of water spray to the driver tires to help keep them cool, particularly in mountain territory.
Also one element of the "bailing off" the locomotives brakes when them came on during an automatic brake application was to keep the slack stretched immediatly behind the locomotive(s) as that mimicked the situation for slack before the brakes were applied. Date: 02/03/25 14:03 Re: Steam locomotive independent brake question . . . Author: HotWater railstiesballast Wrote:
------------------------------------------------------- > IIRC some RRs had a system to apply a bit of water > spray to the driver tires to help keep them cool, > particularly in mountain territory. The Southern Pacific had such water spray systems on some of their passenger steam locomotives. However, the spray was NOT on the drive wheels, as SP locomotives were equipped with "Mountain Cocks" so that the Engineer could simply cut-out the brakes on only the drive wheels. > Also one element of the "bailing off" the > locomotives brakes when them came on during an > automatic brake application was to keep the slack > stretched immediatly behind the locomotive(s) as > that mimicked the situation for slack before the > brakes were applied. Date: 02/03/25 17:22 Re: Steam locomotive independent brake question . . . Author: Frisco1522 Frisco's later steam engines, including 1522, had a water/air jet with a valve in the cab on the rear of the valve gear hanger that if used would spray water on the main rod end. I've never seen that on any other road that I remember.
You can see the spray in this photo. This is on the cover of my book, Frisco Steam Salute. ![]() Date: 02/05/25 08:59 Re: Steam locomotive independent brake question . . . Author: LocoPilot750 Somebody tell me about steam switch engine brakes. Cut out the drivers and just use the tender brakes ? I doubt it, slow speed shoving, pulling, kicking big cuts of cars will wear out brake shoes in a hurry, and without driver brakes, stopping distance might be doubled. Obviously not a problem. I've worked enough Santa Fe diesel switch jobs back in the day, used the brakes as much or more than a steam switcher would, I never felt a wheel that was too warm to hold my hand on.
Date: 02/05/25 17:59 Re: Steam locomotive independent brake question . . . Author: PHall HotWater Wrote:
------------------------------------------------------- > railstiesballast Wrote: > -------------------------------------------------- > ----- > > IIRC some RRs had a system to apply a bit of > water > > spray to the driver tires to help keep them > cool, > > particularly in mountain territory. > > > The Southern Pacific had such water spray systems > on some of their passenger steam locomotives. > However, the spray was NOT on the drive wheels, as > SP locomotives were equipped with "Mountain Cocks" > so that the Engineer could simply cut-out the > brakes on only the drive wheels. > > Per the book Southern Pacific Daylight Locomotives by Robert J. Church on page 35. "The wheels on the engine and tender were also equipped with water tire coolers. The engineer could apply a small stream of water against each tire or cast wheel close to the flange. This helped greatly to keep tires cool when descending long grades, and reduced expansion." |