I was wondering if there was any sort of way to tell the differences between them all. All i know are the Stephenson, Southern and Baker valve gear systems. I know there are more and if anyone can tell me all the types and ways to identify them that would be great.

Brian

PRRsteam4lyfe@aol.com

Brian,

The easiest way I know to show you is to download Charlie Dockstader's free valve gear modeling program at the link below. It can be used to model all the different types of valve gears and allows you to change dimensions to see what affect this has on the valve action (pretty handy for designing a live steam locomotive). The program actually animates the valve gear to let you see it in action and includes practically every form of steam engine (not just steam locomotive) valve gear.

Hugh

> I was wondering if there was any sort of way
> to tell the differences between them all.
> All i know are the Stephenson, Southern and
> Baker valve gear systems. I know there are
> more and if anyone can tell me all the types
> and ways to identify them that would be
> great.

> Brian


Valve Gear Simulation Program
whodom2001@yahoo.com

> Brian,

> The easiest way I know to show you is to
> download Charlie Dockstader's free valve
> gear modeling program at the link below. It
> can be used to model all the different types
> of valve gears and allows you to change
> dimensions to see what affect this has on
> the valve action (pretty handy for designing
> a live steam locomotive). The program
> actually animates the valve gear to let you
> see it in action and includes practically
> every form of steam engine (not just steam
> locomotive) valve gear.

> Hugh

The valve programs are great! But I'm yet to find a discription or discussion of the realitive merits of each valve type. I guess there would be two issues to consider, the engineering reasons and then the actual use in the field issues. I can see the pivoting valves (Baker, Southern) are less affected by wear than would be a sliding block type (Walschert) but the steam diagrams don't explain to me why Walschert and Baker were the most popular valve motions. I've always wondered why the Young motion wasn't more popular having no eccentric rod. It would seem to have less moving mass which should be a bit more efficient and easier to counter balance.

Ed

"(Walschert) but the steam diagrams don't explain to me why Walschert and Baker"
There is actually an "s" on the end so it is "Walschaerts" because his name was Egide Walchaerts. I learned this not too long ago.

There is the Hackworth valve gear. first and second motion.

jsfrost@mtu.edu

> "(Walschert) but the steam diagrams
> don't explain to me why Walschert and
> Baker"
> There is actually an "s" on the
> end so it is "Walschaerts" because
> his name was Egide Walchaerts. I learned
> this not too long ago.

> There is the Hackworth valve gear. first and
> second motion.

Actually I'm going to blame Mr. Drury of Trains Magazine. To attempt to get the spelling right, I copied the spelling from the diagram on page 411 of "Guide to North American Steam Locomotives." But in fairness, he does spell it correctly in the text.

Ed

> There is actually an "s" on the end so it is "Walschaerts" because his name was Egide Walchaerts. I learned this not too long ago.

"In 1844, Egide Waschaerts, at the time chief shop superintendent of the Brussels Southern Railroad, invented the type of valve gear which bears his name. (The final "s" has been dropped in naming the gear.)"

Locomotive Valves and Valve Gears
Yoder and Wharen 1921 p. 96

brianf425@yahoo.com

> The valve programs are great! But I'm yet to
> find a discription or discussion of the
> realitive merits of each valve type.

I am no expert, but I will give it a try.

The Stephenson gear had the advantage that as you brought the reverse lever toward center, the lead of the valve opening would increase, that is when using less steam, it would open the cylinder quicker to the incoming steam. (The later radial valve gears would not do this). However, as locomotives became larger, their axles became larger, and stronger frames with more cross bracing were needed, so the space around the axles for the eccentrics and the room to swing them dissapeared. Also, there was a maintenance issue of getting inside the frames for lubrication and care.

The advantages of the Walschaert's gear over the Stephenson gear are lighter weight for work done, accessible for maintenance, and lower maintenance costs that the four eccentrics of the Stephenson, and that it was said to hold its valve timing better between shoppings.

The biggest advantage of the Baker gear is the loss of the sliding link (wear and maintenance) however against the addition of many more pins and bushings. It was said that a Baker could be overhauled faster and easier, and also, the basic gear came in several standard configurations, for interchangability. Baker could also be set up for longer valve travel, which was a later desirable development of the locomotive (Lima super power, etc.)

Southern valve gear , like the Young gear, has no combination , or lap-and-lead lever. It seemed to enjoy some popularity on the Southern Rwy, where it was invented, and on quite a few Baldwin narrow gauge engines, where the works were kept up from the ground, and were simpler than Walschaert's. Bruce, in Steam Locomotive in America, claims that the gear "possessed littlle lateral stability", whatever that means.

The Young gear did away with the combination lever also, but was considered more expensive to maintain that Walschaiert's due to the bushings and shaft that had to go from one side of the locomotive to the other. With no operational benefits like increased lead with hooking up, Walschaert's was again cheaper to maintain. Remember here that most of the Walschaert's gear works in a straight line, while the Young gear has the torsion of the crossover shafting to contend with.

A good bibliography for valve gear study would be the ICS "Locomotive Valves and Valve Gears (503)" by J. W. Harding for basics, Stephenson and Southern; ICS "Walschaert and Baker Valve Gears (504)" J.W. Harding; "Modern Locomotive Valves and Valve Gears" by Chas. McShane (also appears as a major portion of later editions of "Locomotive Up to Date" by McShane and Vol 1 of "Library of Railway Practice" Railway Educational Press); and the "Steam Locomotve in America" by Bruce give a more up to date overview of the subject.

Walshaert's Animation Page

SZuiderveen@aol.com

Very nice summary, Steve. I believe Ed King wrote an article in Trains ~10 or so years ago which gave a similar overview.

Here are a few additional points I can think of:

Baker valve gear supposedly allowed longer valve travel without distortion of the valve events (compared to Walschaerts) which became important on modern U.S. locomotives. It also allowed standarization of parts between different locomotives since it was a commercially manufactured assembly. When needle bearings were used (instead of bronze bushings) it could go long distances between shoppings.

Poppet valve gears allowed the admission and exhaust events to controlled separately, and allowed very rapid opening and closing of the valves. It allowed large flow areas which minimized steam pressure drops, and required less power from the engine to operate compared to link valve gears. Some types were not very durable and/or required specialized maintenance. Interestingly, L. D. Porta and his successor David Wardale concluded that poppet valves were not beneficial on modern steam locomotives compared to optimally-designed piston valves.

The "lateral stability" comment regarding Southern is addressing the way the motion pivots; wear in certain pivots could allow the eccentric arm to move laterally a great deal (perpindicular to the engine frames). One other interesting feature is that because of the way the motion is derived from the eccentric, the movement of the main axle in the engine frames (allowed by the engine's suspension) caused the valve timing to change. It was said that you could hear the change in a Southern-equipped locomotive's exhaust when it entered a curve at speed. As the engine "leaned" slightly to one side, the valve timing on each side of the engine changed slightly. Another interesting note- L. D. Porta planned to fit Southern valve gear to several of his locomotive designs. He liked it for 3-cylinder engines because it minimized the amount of linkage which had to be between the locomotive's frames.

One other valve gear I can think of was used by the Glover Locomotive Works (small builder in Marietta, Georgia); it was called "Smith" and is very similar to Southern. It substitutes a link and pivot for the stationary slotted member mounted on the engine frame with Southern Valve Gear.



Valve Gear Simulation Program
whodom2001@yahoo.com

The Smith gear was mounted on a large Y shaped bracket mounted on the side of the frame where the links would hang on a Walschaert geared engine. It was used on a small order of locomotives built for the Haitian - American Sugar Co. Smith was the master mechanic fore the sugar company and wanted a gear that could be maintained with minimal tooling without a pit.

Interestingly enough, an order from the 1940's for replacement eccentric sheaves for the locomotives is in the file. Glovers sent back a telegram explaining the the Smith gear used no eccentric sheaves, Stephensons did. The sugar company returned the information that Smith had been replaced several years previously with a French engineer who didn't like that ugly outside motion and had retrofitted Stephensons!

Interesting cultural dichotomy at work........

dave



irondave@bellsouth.net

Ok, I was wrong. Thank you for correcting me.
Jeff
> "In 1844, Egide Waschaerts, at the time
> chief shop superintendent of the Brussels
> Southern Railroad, invented the type of
> valve gear which bears his name. (The final
> "s" has been dropped in naming the
> gear.)"

> Locomotive Valves and Valve Gears
> Yoder and Wharen 1921 p. 96


jsfrost@mtu.edu

Find a copy of "Basic Steam Locomotive Maintenance" by D.C. Buell, pubished by Simmons-Boardman for some good explanations of the various valve gear types. One thing about Walschaert, it has the most variations of spelling out of all of them.

fitzrr@pioneer.net

> The "lateral stability" comment
> regarding Southern is addressing the way the
> motion pivots; wear in certain pivots could
> allow the eccentric arm to move laterally a
> great deal (perpindicular to the engine
> frames). One other interesting feature is
> that because of the way the motion is
> derived from the eccentric, the movement of
> the main axle in the engine frames (allowed
> by the engine's suspension) caused the valve
> timing to change. It was said that you could
> hear the change in a Southern-equipped
> locomotive's exhaust when it entered a curve
> at speed. As the engine "leaned"
> slightly to one side, the valve timing on
> each side of the engine changed slightly.

This would make some sense to something that I read once (I believe in Model Engineer), to the effect that Southern gear is realy a reconfigured Hackworth; a gear notorious for going out of time with the change in the position of driving boxes within the pedestals (or "hornblocks" in the mother tongue)!

Steve


SZuiderveen@aol.com

> Ok, I was wrong. Thank you for correcting me.
> Jeff

Please! Don't take it personally!

In one of my (many!) books... on one of my many bookshelves, I have a book that told me (more or less) that ENGLISH was the language that english speaking peoples speak... If it passes into common usage that the Walschaert valve gear is/should be called the Waleshaerts valve gear, then that is language at work...

I say tomato you say tomato... I say mikado you say mcarthur... I say northern you say dixie...

brianf425@yahoo.com

Don't worry, I am not taking it personally. If what I said was wrong, I would rather be corrected than keep on saying it the wrong way.
Do you know why the "s" was droped when naming the valve gear?

> Please! Don't take it personally!

> In one of my (many!) books... on one of my
> many bookshelves, I have a book that told me
> (more or less) that ENGLISH was the language
> that english speaking peoples speak... If it
> passes into common usage that the Walschaert
> valve gear is/should be called the
> Waleshaerts valve gear, then that is
> language at work...

> I say tomato you say tomato... I say mikado
> you say mcarthur... I say northern you say
> dixie...


jsfrost@mtu.edu

As to the variable lead feature of the Stephenson gear, there was also a modification to the Walschaert's gear that was employed by the Denver and Rio Grand Western that provided the same effect using a sliding block in the combination lever.
Roger Mitchell
Master Mechanic
Fort Collins Municipal Railway
Ham Radio N0MCR


n0mcr@netzero.net