Valve Gear Question

Discussion in 'General Steam' started by gbmott, Dec 27, 2014.

  1. gbmott

    gbmott Member

    In looking through the "Description of Locomotives, Passenger, Freight and Miscellaneous Equipment of the Frisco Lines" issued by Geo. A Hancock, Gen'l Sup't Motive Power and dated July 1, 1906, I noticed one symbol used in the "Remarks" columns that was "A. - Allfree Hubbell Valve Gear". The symbol only appears one time, in the entry for former BE&SW 4-6-0 749. Does anyone know about this valve gear and even better, does anyone have a photo of 749?


    Gordon
     
  2. Oldguy

    Oldguy Member Frisco.org Supporter

    [​IMG]

    It says where I borrowed it from.
     
  3. frisco1522

    frisco1522 Staff Member Staff Member

    Looks like Fort Smith was an elephant graveyard during the Depression.
     
  4. JamesP

    JamesP James Pekarek

    First of all, let me start off by saying I know very little about the Allfree - Hubbell arrangement. It was one of many attempts at improving upon the normal slide or piston valves of the steam era. My understanding is that it wasn't a valve gear; rather, it was a type of inside admission piston valve to be used in conjunction with a standard valve gear. It's claim to fame was to reduce the amount of clearance at the end of the cylinder, thereby improving economy since less steam was wasted filling the empty area at the end of the cylinder. This can be accomplished physically with normal valves, but in practice doesn't work too well due to excessive compression under part throttle conditions. The Allfree-Hubbell used some sort of extra exhaust valves to reduce compression under these circumstances, which allowed the reduced clearance. I have never seen a clear drawing of the valve arrangement, and since it was a minor blip on the radar of steam locomotive development, never gave it a lot of thought. Interesting that the Frisco had a locomotive with it!

    Edit: I can't say I know this for a fact, but I would suspect that Frisco quickly modified 749 to have normal slide valves. I can't imagine that the oddball valves would have lasted past their first problem, especially with the Frisco's prowess in rebuilding. But... just a suspicion on my part. 749 look like a standard slide valve engine in the picture.
     
    Last edited by a moderator: Dec 27, 2014
  5. gbmott

    gbmott Member

    Thanks for the explanation, James, and for the photo Bob. Actually once I saw the photo I realized that I had it if I just hadn't been to lazy to dig it out. It was one on a large box of 616 contact prints that Charles Winters gave me 60 or so years ago. And yes, Don, an elephant graveyard is not a bad analogy. From that box of Charles' photos there are eight 4-6-0's that were stored in Fort Smith in the spring of 1936. I don't know how many survived to be put back in service during WWII, but I doubt if all of them were. 4-6-0's seem to have been the favored power for working the coal mines on the Mansfield Branch until finally quite late in steam 1626 was brought in to do the job. Even so, 709 was one of the last survivors of the dead line in Fort Smith at the end of steam.

    Gordon
     

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