Baker vs Walscherts

[train18393]

I am in my late 50s, so excuse my ignorance. I have read up as much as I could on various valve gear arrangements, but I have not been able to figure out something.

I think from what I read that Baker went to the long frame style due to an instability of some sort on the short frame version. Why didn't the Walscherts suffer from a similar problem? Were the moving parts  less weight on the Walscherts, did they move less distance, or what? I would assume the valve rods moved the same distance no matter what style of valve gear as dictated by main piston travel, valve port size ect. I would also assume the piston rod travel was a function of diameter of the drivers, the stroke of the piston and offset of the eccentric.

Any information, or place to get such information would be appreciated. I do have a 1948 Locomotive Cyclopedia from my Grandfather, and that does give me some information, but I see nothing I can put my finger on.  

Paul

Dayton and Mad River (model) Railroad

[selector]

Paul, piston rod travel would be related solely to the distance of the main crank center from the driver axle center.  Nothing about valve motion would affect piston rod travel, except that motion permitting ingress and egress of steam would cause the piston to be displaced laterally in the bore.  That motion was controlled by the adjustable expansion link and the motion of the radius arm in it once set in a position along the expansion link by the lifting lever.  The actual motion itself of the valve was generated, as you must know, by the eccentric crank and rod.

[onequiknova]

I'm only 30 and by no means an expert, and what I do know is mainly about what I've read on CB&Q steam. From what I can tell the long frame was not a replacment for the short frame. The long frame Baker showed up on the Q in 1930 on their Hudsons, but there were steam engines built well into the 40's with the short hanger. (NKP Berk's for instance)

   I do know the original long Baker valve gear hanger installed on the Q Hudsons suffered from instability which led to modifying the existing hangers and an eventual redesign by Baker all together.

 FWIW I've seen the short frame refered to as frieght valve gear and the long frame refered to as passenger valve gear. So maybe it has somthing to do with the speed at which the valve gear was designed to work at?  Thats just my guess. I would love to heard from somebody "in the know".

 

 John.

[BigJim]

From what I can tell the long frame was not a replacment for the short frame.

Reading up on valve gear this past weekend ( Walschaert and Baker Valve Gears by J.W. Harding ), I found that, like the Baker, the Walschaert valve gear also had a long and short version. The reason being was that valve gear frames needed to be supported in different manners with different wheel arrangements. The supports for the valve gear frames needed to be attached to the main locomotive frame. To do that, the supports needed to pass in front of and/or in back of a driving wheel in order to gain the clearance to access the locomotive frame.
Examples given show a locomotive that would have had a two wheel or no engine truck as using the short frame version ( support passes in front of drive wheel ), while a loco that would have used a four wheel engine truck as needing to use the long frame version ( supports pass in front of and behind drive wheel ).
Also and just as important, depending on which wheel arrangement was used, space was needed between the valve guide and the valve gear frame to insure proper room for the valve gear to perform its intended functions.
In a later revision of the Baker Valve Gear book, Mr. Harding states that the reason for the Baker long and short versions was the same as the Walschaert.