Hi Everyone, I have a question regarding train handling with steam locomotives, specifically on a down grade. I know that brakemen would set retainers to keep brakes partially on. Could the engineer also apply slight reverse power using Johnson Bar, throttle and cylinder cocks? Theoretically this would set up a cushionioning effect in the cylinders. Was this method actually used? Thank you in advance
The engine had an independent brake but the engineer could control the length of the stroke of the cylinder with the Johnson Bar. Reversing the engine per se was not an elective in normal train handling but the reverser (changing the direction) was known to be used in emergencies. If retainers were to be used on a hill, the train would be brought to a stop and the retainers set up on selected or all cars (and train stopped at bottom of hill and retainers returned); this could not be done while running. Setting brakes by hand was a way of doing things, yes, but before there were air brakes. In other words, it was not exactly like it is in a diesel or electric locomotive. And the advances in the air brake system also plays a part in how things are done today…
Yes, this does actually work and was used at times. However, I have read of at least one railroad that prohibited the use of reverse for braking purposes, while there were others that added appliances to make it more effective. The problem with braking by reversing for long periods of time is that the cylinders actually act as a pump, drawing in exhaust fumes and trying to pump them back into the boiler, or at least out the cylinder cocks. Sucking the abrasive products of combustion (soot, carbon, ashes, etc) into the cylinder could and did cause excessive wear on the cylinders and valves. Also, the fire’s exhaust fumes are considerably hotter than the steam, and caused overheating problems in the cylinders, breaking down the lubrication. The cylinders also weren’t receiving proper lubrication while “braking” in this manner, anyway. I don’t have the reference in front of me, but I do remember reading about a device that injected water while braking in reverse to keep the cylinder from overheating. One other problem on slide valve locomotives without power reverse was unlatching the Johnson Bar to move it from reverse back to forward while the engine was in motion… with the lack of lubrication during the braking, combined with the breakdown of oil due to the ingestion of hot exhaust gasses, the slide valves didn’t want to slide very well - unlatch the Johnson Bar and it would move violently and unexpectedly under these conditions, usually injuring the engineer! As a side note, the lack of proper cylinder lubrication in the early days of steam could cause this problem anytime, which is why many engineers of the era would just set the Johnson Bar and leave it, running the engine by throttle alone, wasting fuel and wearing out the fireman! Such engineers were nicknamed “rappers” - not exactly a term of endearment from the bakehead.
With the advent of air brakes, it seems like the practice of stopping the train by rev
Extensive use of the Independent Brake on a steam engine could cause overheating of the driver tires. Since the driver tires were shrunk fit on the center part of the driver, overheating could cause the tire to expand and come lose from the wheel center…creating BIG problems.
Car wheels do not have tires shrunk fit on wheel centers as the wheels are all one piece and can withstand much more heat than the tires on engine drivers can. Car wheels are shrunk/press fit on the axles so it is possible under extreme circumstances for a wheel to heat enough to dislodge the wheel from it’s fitment on the axle.
Braking a train by reversing is ineffective and a definite no - no though I’m sure it was tried in cases of extreme emergencies when the train brakes failed. When reversed the drivers would simply spin wildly and the slippage would result in loss of traction making even the independent engine brakes ineffective. In the days before power reversers the Johnson Bar was almost sure to result in broken bones when attempting to reverse the engine at anything but the slowest speed.
I disagree that the cylinders would “act as a pump, drawing in exhaust fumes and trying to pump them back into the boiler . . .”. When the engine was reversed steam was still supplied to the cylinders which would prevent this. This would be no different than running the engine in reverse which of course was routinely done for long times and distances.
All the steam locomotives I am familiar with had drifting valves which opened automatically to equalize the pressure on both sides of the pistons to prevent them from pumping air when the throttle was closed. I can’t recall if the drifting valve could be manually over ridden but if that was possible, this would be a more effective means of braking that reversing.
Mark
Braking a train by reversing is ineffective and a definite no - no though I’m sure it was tried in cases of extreme emergencies when the train brakes failed. When reversed the drivers would simply spin wildly and the slippage would result in loss of traction making even the independent engine brakes ineffective. In the days before power reversers the Johnson Bar was almost sure to result in broken bones when attempting to reverse the engine at anything but the slowest speed.
I disagree that the cylinders would “act as a pump, drawing in exhaust fumes and trying to pump them back into the boiler . . .”. When the engine was reversed steam was still supplied to the cylinders which would prevent this. This would be no different than running the engine in reverse which of course was routinely done for long times and distances.
All the steam locomotives I am familiar with had drifting valves which opened automatically to equalize the pressure on both sides of the pistons to prevent them from pumping air when the throttle was closed. I can’t recall if the drifting valve could be manually over ridden but if that was possible, this would be a more effective means of braking that reversing.
Mark
Thank You.
Good discussion! Kootenay, that is pretty much how my smaller steamers react. But for the sake of clarification, I do want to address a couple of points that Mark brought up. Hopefully, I can shed some light on my logic behind my statements.
Mark said, “I disagree that the cylinders would “act as a pump, drawing in exhaust fumes and trying to pump them back into the boiler . . .”. When the engine was reversed steam was still supplied to the cylinders which would prevent this. This would be no different than running the engine in reverse which of course was routinely done for long times and distances.” I agree that running an engine in reverse isn’t a problem - the steam engine itself operates equally well forward or backward, not withstanding pilot or trailing truck geometery. However, I was talking specifically about a locomotive that is moving forward with the valve gear in reverse. Under this condition, the locomotive will certainly draw a vaccuum in the exhaust while building a pressure in the admission side. It is different than the locomotive actually running in reverse, because the engine is rotating in the wrong direction, so it is trying to suck air in the exhaust and blow it out the admission. With the cylinder cocks and throttle closed, it will soon build enough pressure to close the snifter (or drifting) valves - more on them in a minute - and start building pressure in the drypipe. Unless the cylinder cocks are opened or the Johson Bar moved to the proper direction of travel, the pressure will build to a point where it will overwhelm the traction of the drivers, causing them to slide, or stop the train if the speed is slow enough, train weight is light enough and there is enough traction. The reason why I phrased my initial response as the engine “trying to pump them back into the boiler” (referring to exhaust gasses) is because in reality the boiler pressure would be more than enough to cause the driv
Here are some random thoughts and items of my own personal experience over the years. When I reversed the steam locomotive to use the two engines as compressors, I CAREFULLY moved the Johnson Bar, keeping clear of it’s arc, ( NO power reverse ) and positioned my hand so it would get yanked away. No change in manual operation of Johnson Bar at the low speed while ‘working air’, it had a counter weight between the frames, and a large coil spring in a tube for normal operation. Piston Valves, Inside Admission. I read somewhere that reversing a slide-valve engine, outside admission, balanced slide valves, with Stephenson Valve Gear could be exciting, and dangerous. I also read, that in ‘the old days’, if an engine was reversed with the throttle closed, the back air pressure, depending on Johnson Bar position, would spring the latch on the throttle and it would hit the Engineer in the face. I do not want to find out!!! Thank You. I was reading an a account recently of the British steam locomotive ‘Blue Peter’ which ‘lifted’ water from a too-full boiler into the superheaters while starting a train in the rain. The thusly-generated steam spun the drivers up to 130 MPH? ( Video from train on YouTube. ) and the Engineer on the footplate was injured from trying to bring the locomotive back to centre-gear. Photos on Internet of damage done to rods. I also wondered if it would be safe to move the engine to centre gear at high speed with tonnage if the throttle stuck open on the road. What WOULD happen?? On a coal burner on the road the fire would be very hot and what was drawn thru the tubes would go down thru the nozzle in a much hotter condition than when drifting downgrade, blower on, throttle closed. ( A Hostler story, here. This one Hostler was lazy and hated running steam engines beyond the points in a trailing-point switch move, stopping, getting off, walking back to the switch stand, setting the new route, walking back to the cab, and backing up. With another Helper in the
Kootenay, very interesting reading… I enjoyed it tremendously - not boring or rambling to me! If you ever get down to the Ozarks, come by and we’ll shoot the bull and inhale some steam, cylinder oil and coal smoke (I’ve got some dirty Illinois coal that is just wonderful)!
- James