I’ve seen several steam videos but I can’t follow all the adjustments made by the engineer. I can recognize the throttle, usually overhead, and the two brake handles (engine and train). It is the fourth that mystifies me. I assume it is the reversing lever, but why would the reversing lever be adjusted in motion?
Bernie
Welcome to the forums.
The engineer has two ways of controlling the amount of steam that enters the cylinders - the throttle and the reverser. The throttle controls the amount of steam and the reverser controls the length of time that the steam is admitted to the cylinders. After the train is at the desired speed, then the reverser can be adjusted so that just enough steam is used to keep the train at speed. That lowers the load on the boiler (and the fireman - for which I am grateful.)
dd
Long story short[:)]: The reverse lever on a steam engine adjusts which end of the pistons the steam goes into; steam going in one end will make the train go forward, steam in the other end will make it go backwards. Once the train is moving, a good engineer can also use the reverse lever to fine tune how much steam goes into the pistons, making the train use steam and fuel more efficiently.
Just to make things worse, some marine steam engines have separate controls for reverse and cutoff. There is a steam stern-wheel towboat on display at Keokuk IA which is a tandem compound and has this control arrangement.
Not quite. Short story LONG…
Steam goes into both ends of each cylinder no matter which way the locomotive is going, but not simultaneously. The valve gear changes the timing of the admission into the cylinder (either/both ends) to control which way the wheels are pushed/pulled by the main connecting rod.
If the piston is in the middle of the cylinder and steam is admitted to the front then the piston will be pushed back, but whether that moves the wheel clockwise or counterclockwise depends on whether the point where the connecting rod connects to the wheel (the main pin) is at the top of rotation or bottom.
Assume you are looking at the right side of the locomotive with the wheels to the left of your view and the cylinder to the right. If the main pin on the wheel is at the top, then the piston will be centered in the cylinder. If you put steam in the front of the cylinder the piston will be pushed back and that will push the wheel to rotate counterclockwise. If you put steam in the back of the cylinder the piston will be pushed forward and the connecting rod will pull the wheel to rotate clockwise.
The wheel will rotate until the piston is all the way to one end of the cylinder. Inertia (or power from the another cylinder, i.e.: the one on the other side of the locomotive, which will now be centered in its cylinder and pushing or pulling the wheels in the same rotational direction) will cause the wheel to continue its rotation. It is at this point that the valve gear swap
this is a Walschaert type of valve motion…going from forward motin to reverse motion…red being live steam and blue exhaust…the reverse lever in the cab thru levers or a steam\air operated piston would move the radius bar up and down in the link…in this diagram it happens when the motion stops…where the radius bar is postioned in the link determines the duration of valve opening and the amount of steam allowed in…short little spurt like when moving at high speed or full stroke allowing lots for starting off
Yup Semper, just like I said…if the engine is sitting still, admitting steam on one side of the piston will make the train go forward, the other side will make it go back. Now whether admitting steam to the front of the piston makes the engine go forward or backwards, that depends on positioning of the rods & valve gear.
I know how it works, I just didn’t want to spend a half hour explaining it in detail!! [:D]
baker valve gear has this innotavative linkage device that controls the cutoff, all while its being moved around by all the attached linkages. The engineer pushed the lever full forward there would be minimal cutoff, just about all maximum steam flies to the cylinders. Good for train starting and slipping drivers if the engineer isnt careful on the throttle. But at speed you don’t need all that power so the engineer will back off the lever and cutoff the steam delivery.
…Baker valve gear had all kinda small lil parts flyin around…to hard to follow…Joy valve gear looked like a grasshopper with the twitch…Southern valve gear looked like Walschearts on its side…all of these had cut-off control…the closer the radius rod is to the center of the link the more steam is ‘cut-off’…Baker was just slightly more precise and had less inheirant creep in valve postion
Minimum cutoff is rough on fuel consumption (and the fireman!)
dd
J Edgar ; A very fine exhibit and description of the way things go round and why . Thank you . Respectfully , Cannonball ( another Jim)
many thanks …just here sharing whatever my lil mind has