dale8chevyss: The US seems to be the only country who's railroads embraced the Baker gear to any great degree. N&W loved it and no one could question the quality of their locomotives! PRR tried it early in the 20th century (on a H6b 2-8-0, I think) and didn't like it. But, during WW2 they bought 125 J1's with Baker gear and they were great engines. The RF&P had it on some Pacifics early on, only to replace it with Walshaerts pretty quickly. They bought some 2-8-4's during the war equipped with Baker and the crews and shop people hated it. Go and figure!
rfpjohn Though some roads embraced the Baker gear as superior, Walshaerts was by far the preferred arrangement worldwide. The last great steam fleets all used it.
Though some roads embraced the Baker gear as superior, Walshaerts was by far the preferred arrangement worldwide. The last great steam fleets all used it.
I've always been a fan of the baker IMO.
Modeling the N&W freelanced at the height of their steam era in HO.
Daniel G.
I can see where a static display engine with Walshaerts might drop into normal forward if the engine was equipped with power reverse. I wouldn't think Baker would do that.
Dr D, you give a good presentation of the workings of valve gear. However, Egide Walschaerts (at some time in his life, he stopped writing the final "s" on his name) (1/21/1829-2/18/1901) was not a German, but a Belgian who worked for the Belgium State Railways. At age 24, he became the foreman of the shops in Brussels, and he there completed his work on his valve gear in 1844. It was not until about 1897 that manufacturers in this country began applying his gear to their products. His basic design certainly stood the test of use on railroads.
For further information, see Wikipedia, both for a discussion of the valve gear and for a discussion of M. Walschaerts, or The Locomotive Up To Date (The1922 edition of the last is my primary source).
Johnny
Thanks for the replies. I enjoyed the story of the locomotive under steam rolling out of the roundhouse- made me chuckle at the thought of it.
The valve gear in question was on the C&O at the Henry Ford museum and that gear is Baker.
It might be useful to include the function of snifter valves and how they might have contributed a very slight braking action, depending on the circumstances.
Daniel,
To elaborate on an explanation of your locomotive observation here, the steam locomotive was always in a "drive" mode.
When the throttle was opened the pistons went to work. If the cylinder valve was set forward, it went forward, if it was in reverse it went backwards.
The control of the cylinder valves (also called valve gear) did much to control the power and function of the locomotive. By moving the cylinder valve gear - this adjusts the length of the piston valves could travel.
The valve travel could be lengthened or shortened. Longer cylinder valve movement gave more boiler power at low speed by giving a longer time interval for steam pressure to flow against the piston.
Shorter cylinder valve movement reduced the time for steam to flow against the pistons and caused the locomotive to use less steam. This might seem bad but it wasn't because instead of steam flow the steam pressure and expansion in the cylinder moved the engine and allowed a faster speed.
You really have to move away from the concept of an automobile engine because the fuel is not burned in the cylinder it is supplied from a boiler and the whole thing functions differently.
If the cylinder valve was placed in a middle position between forward and reverse the locomotive would not move forward or backwards. However, nothing mechanical was changed in the connection of the cylinders and the wheels they could still roll.
Some railroads had to "chain down" the wheels of locomotives when not attended by an engineer because if the fire was banked and the engine idle with steam pressure - if the brakes "lost air pressure" and the throttle "leaked steam" into the cylinders - if the cylinder valve was not set EXACTLY to neutral position the engine would start to move on its own.
When this happened the steam locomotive would often go through the roundhouse wall or into the turntable pit or cause other havoc. These incidents did happen and caused much trouble.
Probably on a "display locomotive" the valve gear was set at whatever helped it move into its location - or it was set in a position that made it look like it was running forward for photographic purposes.
For common knowledge there were two basic types of valve gear. These were WALSCHAERTS - named for the German engineer that designed it. The other was BAKER named for the same reason.
There were advantages and preferences among railroads so you can see both types. Baker was a newer design and its advantage was all the "wear and tear" was on pivot pins. This made for easy repair because all you needed was new pins and brass bearings for them to sit in - cheap and easy!
Walschaerts was older and relied on a large metal "link" (drop link) with a slot cut in it. You can't miss this feature because there is this huge metal link right in view. If the engine is in forward one end of the slot is used if in reverse the other end of the slot is used - middle position means the cylinder valves are not moving - kind of a neutral.
Walschaerts was loved by many and most railroads but repairing the worn out drop link was expensive - Strasburg Railroad offers this repair today. Baker replaced it because of the cost of repair. For example New York Central Hudsons were built with Walschaerts and converted to Baker in their service life.
Surviving NYC Mohwak locomotives - NYC 2933 has survived today with its Walschaerts valve gear and NYC 3001 was built with and still has its newer Baker valve gear.
Hope this helps because it is a really important subject concerning steam railroad locomotives. You can't understand how the engine works and ran with out knowing this.
There was one other important valve gear that developed at the end of steam this is POPPET valve gear. Poppet was named for the type of poppet valve it used - like an automobile engine has. An early Italian design was called CAPROTTI who was a design engineer, and also FRANKLIN an American design was used by Franklin railroad equipment which was much stronger.
Poppet valve design promised great improvement in power and performance. Most railroad were not familiar with maintaince of this poppet valve gear and it never really had a chance to develop.
Some American locomotives were equiped with this such as the Pennsylvania T-1 Duplex drive engines, and some C&O 800 series Hudson locomotives. Poppet valve gear was not widely understood in those days. Only one engine survives with this valve gear - a C&0 streamlined Hudson locomotive in Baltimore, MD.
Dr. D.
A steam locomotive is not like a car where a gearbox could be engaged to turn the motor (to provide braking action) if the car were to roll. Putting a steam locomotive valve gear in reverse does not engage anything that would provide any sort of braking effect.
As to it being in "reverse" instead of "forward"... hmmm... are you sure it was in reverse? What kind of valve gear are you looking at? Those those that have a "lifting link" were usually designed to "fall" into Forward if the link were to break... safer than to suddenly fall into Reverse... Locomotives spent most of their time going forward when going fast and a sudden change in direction would be hard on equipment and passengers. Whereas falling into Forward when backing up would not be as bad since they seldom ran very fast in Reverse. And a link breaking was a rare event anyway.
Depending on the type of Power Reverse in use, more than likely it would be impossible for the valve gear to be moved without steam pressure. Some were like power brakes on a car where it only provided additional power to move the control rods/parts, but others were totally isolated... the lever in the cab just moved a valve and a power cylinder provided the motion to the rods/parts. But even those that were merely "power assists", it would take a strong "visitor" to move rusty parts.
Semper Vaporo
Pkgs.
I've noticed at least two static steam locomotive displays in which the valve gear was set in reverse. Is this common practice to keep the locomotive from rolling, or did years of sitting on display of people pulling the johnson bar ease it into reverse?
That being said, if a loco has a power reverse, can the valve gear be moved when it's not under steam?
Thanks
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