How Does a Steam Locomotive Drive in Reverse?

Go to google,type in "steam locomotive gear train". This gives a good illustration of a moving drive system on a steam locomotive.

Altering the position of the reverser in the cab alters the action of the valve gear from 90deg lead to 90deg lag. 90deg lag acts on the engine in the same way as 90deg lead with the engine turned round to face the other way.

One might be tempted to visit a nearby heritage railway to inspect the valve gear of a cold locomotive in relative safety and to talk to a member of the locomotive staff about it? Volunteers in these sorts of organisations are always willing to explain things to interested visitors.

Here's one that certainly will: http://www.earm.co.uk/

HI THERE ; some of the engines use a lever called 'JOHNSON BAR' others use a lever inside the cab to reverse / either way the arrangement of the valve setup at the steam chest is reversed /speed can be limited in reverse/

This is how it works back and forth

Good animation.

But this explains as how the engine runs, not how it reverse.

I think the bell crank (Janson Bar?) shifts the slider valve (by operator) to other extreme position. This should send the steam to other side of piston, thus pushes it to the opposite direction to its earlier movement.

By the way, is it now possible to add animated clips!? Very good. What formats are acceptable?

Many, if not most, used a version of the slide valve (see http://oldenginehouse.users.btopenworld.com/slide.htm).

It is a truly simple device (not necessarily simply machined) that obviated the need for any type of transmission.

The locomotive has been covered well by other posters.

Just to add an interesting side note:

Some small, low rpm internal combustion engines had an adjustable cam shaft that could be "slid" back and forth when the valve train was held open. One position was for CW rotation, and the other position was for CCW rotation. An example of this was on one cylinder marine engines on small boats. To reverse, the engine would be stopped, a lever thrown which opened the valves (to remove their actuators from the cams and unlock the camshaft), the camshaft slid to the reversing position, the lever thrown back into the lock position (placing the valve actuators back on the reversing lobes), and the engine restarted in the reverse direction.

While cumbersome in some respects, it only took a few seconds to accomplish and eliminated the need for any transmission. The particular one cylinder engine I am describing was, I believe of Dutch origin, however this general technique was used on larger multi cylinder engines made in a variety of places also.

Regards, Greg

Owww Greg, that reminds me of the old 2 stroke engined three wheel cars back in the late 50s.

They had a switch for the ignition, normally the ignition point was set for forwards being a firing position of a few degrees before top dead centre, but when you wanted to reverse you stopped the engine moved the lever over to reverse, which just change the ignition timing to after top dead centre, and the engine was re-started in reverse, and it ran! but not very efficiently!!

John.

The pistons are double acting . That means the piston has two power sides , like a top and a bottom . To go in reverse the engineer stops the revolution of the driver wheels and slides the valving mechanism so that the steam supply sequence is reversed and the piston travels backwards on the first power stroke. . It is just like pedalling a tricycle backwards . I believe large marine diesels on freighters do much the same thing as they are direct drive as well .

I am dragging this out of my memory . My dad was a steam engineer on a restored tug and the principals are the same as I recall.