What are rods inside steam frame doing?

MarkInLA Sep 4, 2013

  1. MarkInLA

    MarkInLA Permanently dispatched

    Not sure if this goes in 'railfanning' catagory...
    Was sliding right under the Atlantic sitting in Traveltown in L.A. today...Seen these before but never understood..Within frame are siderod-like rods which are on a crankshaft type set-up on (I think) 2nd driver axle with counterbalances right on rod ends...Is this a center, 3rd cylinder mechanism ? Or, is this somehow connected/related the booster engine under cab ? ..Awsome sliding under this monster on my back, spine on the railhead....! Funny, no matter how dead as a doornail, cold as ice she is, there's still a built in fear she might start rolling at any second !! Can you relate ? !!!
  2. Hytec

    Hytec TrainBoard Member

    Mark, you may have been looking at a locomotive with Stephenson valve gear. Stephenson valve gear used eccentric cranks on the second axle to drive rods that were connected outside the frame to rods that actuated steam valves inside the steam chest above the pistons.

    Stephenson valve gear was simpler to manufacture, but was difficult to maintain because a machinist had to crawl under the engine to lubricate and repair it. Baker and Walschaerts valve gear seen on modern locomotives was more complex, but easier to maintain because all the rods and bearings were outside of the wheels.

    You'll find more detailed descriptions with drawings using Google and the key words - Stephenson Valve Gear, Baker Valve Gear, and Walschaerts Valve Gear.
  3. fitz

    fitz Staff Member

    The only time I visited Traveltown I only shot video, so don't have a still photo of that Atlantic, but I think Hank has it with Stephenson gear. As I recall that Atlantic had gigantic drivers, maybe 84 inch?
  4. MarkInLA

    MarkInLA Permanently dispatched

    Yeah, checked out Stephenson...That's what it is I was seeing on the Atlantic...And yes, drivers are huge !! Definately a fast passenger engine...I think I heard this particular one was involved with Harry Truman; either a campaign whistle stop tour, or maybe a funeral train...Don't know what road was then, either..NYC..? Too bad these beauties have to be missing their dials, gauges, sight glass, seats and windows due to an element of society who ruin it for everyone else with their vandalism and disrespect of private property...Every time I'm in one and others are climbing in cab I always wonder just how many of them even know these parts of the machinery were ever even present...Or, that the tender is a Vanderbuilt and carried oil, not coal...Or, that this lever up top is the throttle....this is the reverse or Johnson bar....That hump is a sand dome; that hump a steam dome.....a what ? Engineer here; fireman there...But why, most wouldn't know or care, nor that these machines they are standing in are the machines which built the cities and towns they live in across this continent...
    Last edited by a moderator: Sep 5, 2013

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