Hi. I’m wondering if someone could tell me if the eccentric crank for the Walscheart valve gear mechanism is fastened to the drive wheel at a standard angle to say the diameter through the connecting point or were different angles tried. It appears to me to be at about a 45 degree angle (or 135 degree from the other side of the vertex). Thanks for any input.
Well it was adjustable - unlike our models!! For example, when the engine was set to go forward, it leaned forward, when the engineer wanted to back up, he would change valve gear to be leaning backwards. This could be done by a big wheel and screw in the cab (usually this was done in the UK more than here) or by the reversing lever. It was all controlled by the engineer. Also there were subleties on the exact angle to allow the right amount of steam into the cylinders to use the steam the most efficiently.
I’m sure there was a maximum angle it could go to one way or the other, but not sure what it was…
If you meant what you said, then the poster above misread your post.
The angle formed by the two lines–
Center of axle to main pin
Center of axle to back end of eccentric rod (i.e. the outer end of the eccentric crank)
will usually be close to 90 degrees. As I recall it would be exactly 90 degrees if the link foot were level with the axle (at the midpoint of its swing), which usually isn’t the case.
The exception is those few engines that are not set for constant lead.
The Eccentric Crank is attached rigidly to the main driver crank pin at an angle of 30 degrees to the right of center (if you look at the locomotive directly from the side and the rods are down, the crank will be to the right of vertical by 30 degrees).
To further add to the confusion, when an engine w/ outside admision valves (a kind of box on top of the cylinder as opposed to a second, smaller cylinder for the valve above the piston cylinder) was equipped w/ walchearts valve gear the excentric crank leaned away from the cylinders instead towards them. Admitedly it would be a rarity for engines w/ outside admission valves to be equiped w/ anything other than between the wheels Stephenson gear but some rebuilt older engines did get walschearts valve gear w/o having the cylinder/valves rebuilt.
Also, if you don’t mind the correction, it is Walschearts , with the s. It is not the possessive form with an apostrophe missing, and it is not Walscheart. The gentleman’s name was actually Walschearts.
I was surprised, too. [:)]
Here is a web page with animation for you to view;
Or thereabouts. The angle will vary somewhat from engine to engine.
And of course some of them were left of center.
Or maybe Walschaerts?
Also, whether the eccentric crank leans left or right doesn’t determine whether the engine has inside or outside admission. (Or vice versa.)
Yes, I transposed the a and e… [:I]
It’s Walschaert.
To quote from that nice link Wallyworld provided:
By the way, Walschaert gear is correct; Walschaerts gear is not (unless it is used in the possessive case, with an apostrophe, eg: “Walschaerts’ design”). The inventor’s name was (Egide) Walschaerts (pronunciation: ay-gee-day val-sherts), but the design was patented under the name Walschaert for political reasons. Ref: Publications Style Manual, Pennsylvania Railroad Technical and Historical Society.
Thanks everyone for the replies. The 30 degree (or thereabouts) angle from the vertical with rods down basically answers the question I had. Also thanks for the tip about the website with the animation. P.S. Sorry about the initial mispelling.
Okay, let’s call it a draw.
Then again, let’s don’t.
I agree that the valve gear is called Walschaert and the inventor’s name was Egide Walschaerts. However, after looking at some French language sites on the subject, his first name would be pronounced something like ay-zheed. The first “e” has an accent indicating its pronounciation is similar to but not quite the same as a long “a” in English. The final “e” is unmarked which means it’s silent, unless you happen to be from Provence area, then it gets a slight nudge. The source that claims the last “e” is pronounced the same as the first is suspect.
Interesting thought …there are still folks who must design and build valve gear for steam locomotives albeit on a smaller scale…downloadable design programs…it never occurred to me how obvious there would still be a need to do this…
This is off-topic but the Walscheart vs. Walschearts vs. etc. made me think of something I came across a while back. The man who invented the Gatling gun (early crank machine gun, as used in the Civil War and later in the West) was actually name Gatlin. Apparently people hearing the gun called a “Gatlin Gun” by soldiers assumed they were dropping the g (“Gatlin’ Gun”) so to seem educated started calling it a “Gatling Gun” and that name stuck.
Indirect Walschaert valve gear has the eccentric cranks set in the opposite position from normal -i.e., for outside admission, the eccentric crank will will follow the main crankpin; for inside admission, the eccentric crank will lead the main crankpin. Indirect gear was common on pre-power reverse locos, as “hooking up” the loco in forward motion, the mass of metal link blocks, linkage, etc. was lowered into the desired position, a much easier task than raising it. This info was gleaned from an article by E.W.King Jr., in the May 1984 issue of Trains magazine, which offered insights into all of the major variations of valve gear.
Wayne