Lever Called Johnson Bar?

Patrick Mar 23, 2000

  1. Patrick

    Patrick Guest

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    Can anyone tell me what this lever in the cab of a steam locomotive was used for? Did it controlled forward and reverse? I don't know for sure if Johnson is the correct name of the bar. Just a little mystery that I am trying to solve. It would be nice to have a glossary of railroading terms available for us rookies. Thanks to you all. This board is great!

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    Tehachapi
     
  2. eddelozier

    eddelozier TrainBoard Member

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    Johnson Bar is correct name. It's the Valve gear Adjustment lever on a steam engine.
    It's positioned about waist high and in front of the engineer's right.
    It controls the steam shut off for the piston. Push forward to get shorter piston strokes for starting power and pull back to get longer piston strokes at high speed.
    Just watched a TV program on steam engine operation last night! The engineer explained it all.

    This site explains steam well.
    http://www.steamlocomotive.com

    Eddie
     
  3. LnNrr

    LnNrr Guest

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    Johnson bar is a slang term for the cutoff
    lever. On some non-power reversing locos
    it could stand head-high with a fulcrum
    well below the cab deck. The lenght was
    needed to give enough leverage to lift the
    valve gear links and change the valve stroke.
    To "put her in the corner" meant
    pushing or pulling the lever to the extreme
    ends of travel. This gave steam admission
    through the maximum lenght of piston
    travel, usually only done to start a
    heavy train. Loco boilers could not sustain
    full-stroking at higher speeds, and it
    was not economical to try.
    To conserve steam (costing fuel and
    water), locomotives were operated with the
    shortest admission duration that the load
    on the engine would permit. At say a 50%
    cutoff, the steam admission would close
    at 50% of piston stroke, then letting the
    expansive power of the steam already admitted
    finish pushing the piston through the rest
    of the stroke up to the exhaust point.
    On power reverse equipped locomotives,
    the cutoff lever could be much smaller.
    Some power reverse locos had a handwheel
    and/or crank arrangment to operate the
    power reverse control valve.
    The engineer could help or hinder the
    fireman a great deal by careful or sloppy
    use of cutoff.

    Hope this helps,
    Chuck P.
     
  4. Just a note for the new kids. Most steam engins couldn't go backward. Hence the need for a round house. Really a u house.
     
  5. Maxwell Plant

    Maxwell Plant TrainBoard Member

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    That's the first time I've heard that....Are you sure? Yes, steamers were not designed to run backwards for the whole trip, but how did they pickup and drop cars or couple into there own train? Even the "Tom Thumb" would run in reverse. The "Great Locomotive Chase" which took place during the Civil War had the TEXAS running in reverse trying to run down the GENERAL (which it eventually did, the GERNERAL ran out of fuel to burn.). I don't want to doubt your word, but I'm not real sure you are correct. Can anyone else shed some light on this? It's always been my understanding the "Johnson Bar" was the reversing lever on a steam locomotive but it also adjusted the stroke as LnNrr stated.

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    RAILROADING-TO-THE-MAX, Burlington Northern/Santa Fe Style!
    Brent Tidaback

    [This message has been edited by Maxwell Plant (edited 18 April 2000).]
     
  6. Ironhorseman

    Ironhorseman April, 2018 Staff Member In Memoriam

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    Max (and RR's. daughter),

    Not true! Turntables were used to set the locomotive in the direction they were to travel at the front of a train. This was not only done for safety for better visibility, (because often the tender would obscure vision of the crew, and a relatively light tender is more prone to derail when set ahead of the locomotive). A steam locomotive will run just as fast in reverse as it does forward, but the seat and controls are not physically set up for the engineer to run the engine in reverse for long periods of time. When he does, he will normally have to sit on the window sill or some other unorthodox position to allow him access to the controls and to see what's ahead. Also, because the crew wanted as much locomotive in from of them in case of a collision with another train. (Don't ask me why! It may have given them a nanosecond longer to live under those conditions). When SP developed the cab-forward Mallies, nobody wanted to run them

    Bill

    "Get Goosed on the Yreka Western"

    [This message has been edited by Ironhorseman (edited 18 April 2000).]
     
  7. Maxwell Plant

    Maxwell Plant TrainBoard Member

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    Thanks for backing me up (No pun intended...), I was positive they could always run backwards, which of course is not the normal direction of travel (unless an SP mallet). Yes, the turn-table was to set them in the right direction for their trip, but not to "reverse" them because they couldn't back-up. Wyes are another common way of "turning" a steamer.

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    RAILROADING-TO-THE-MAX, Burlington Northern/Santa Fe Style!
    Brent Tidaback

    [This message has been edited by Maxwell Plant (edited 18 April 2000).]
     
  8. crash219

    crash219 Guest

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    Running backwards:

    1. Running steam locomotives backwards at speed is an excellent way to derail them. The leading truck is there to help guide the loco into a curve. Note that passenger engines which generally travel at high speed have 4 leading wheels while freight locos have 2 and switchers, which travel only at yard speed, have none. The nature of switching service means that switchers are far more often run backwards, but very slowly.

    2. Train crews do like having some structure out in front of them. It does not help a lot if you hit another train, but it can be a life saver if you hit other obstacles on the rails (trucks, cows, boulders, fallen trees - that sort of stuff).

    3. Running backwards puts the engineer in an awkward position to operate the controls (e.g., the Johnson Bar) and to watch the gages such as the steam pressure or the sight glass (`course, I'd really hope the fireman was keeping an eye on it, too because if there's no water in the sight glass, you're headed for the Promised Land).
     
  9. eddelozier

    eddelozier TrainBoard Member

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    As stated...steam engines have to operate in reverse. They went from old manual reverse methods to power reverse methods.
    Near the end of the steam era, the steam engines were getting too big and heavy to even fit on most turn-tables. Many of the turn-tables were located near engine repair shops and storage yards, one of their main purposes. On the other hand 'Wye' tracks were built where ever engines needed turning. Diesels are little different in their need to turn around for pulling a train, some don't like running long nose forward, some do for safety reasons.
    A few steam engines use to run backward down the mountain around the horseshoe curve in Penna., getting back down to help push the next train waiting. I've seen double headed steam in reverse in the 1950's. I guess it was to save time on the 'Wye' turn arounds at both ends.

    Eddie

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    Eddie Delozier
    PRR N-scale
    deloziers.com
    eddelozier@yahoo.com
     
  10. Ironhorseman

    Ironhorseman April, 2018 Staff Member In Memoriam

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    Crash and Eddelozier -

    Thanks for your input. Your points are well taken. (And women say that men can't converse!) *grin*

    Bill

    "Get Goosed on the Yreka Western"
     
  11. crash219

    crash219 Guest

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    On running long nose forward:
    Went out of style along with high short hoods. Visibility got much better with a low, short nose in front, but guess what is underneath that short hood: collision bars. There are a couple of stout I-beams under the sheet steel up front to give the crew a warm, fuzzy.

    Secretly, I believe that diesels should run long hood forward. I am partial to Alco and Baldwin diesels. You gotta love Alco for the turbo lag alone. They made almost enough smoke to be declared honorary steam locomotives. Too bad they don't make 'em any more. Anyway, Baldwin always ran long hood forward and the RS-series Alco's did, too. You couldn't see out of them worth a durn, but they sure looked cool. Visibility out of the Baldwins was notoriously bad.

    It is all EMD's fault for bringing out those GP's that allowed the option of ordering them with the controls on the "wrong" side of the cab so they could run short hood forward (actually, it was an option to order them with the controls on the correct side!). At that point things became so confusing that the railroads had to paint an "F" for "front" on the leading end of locomotives so the hostler would know which way to point them. And then GE totally bought into the short nose forward heresy when they brought out the U-boat. To add insult to injury, the manufacturers began to chop down those stylish high noses (some of the railroads did not even wait for that - chopped them off in their own shops).

    Now my theory is that if more railroads had bought Baldwins, diesels would still run long nose forward! And if Norfolk Southern had things their way, you can bet that all diesels would still have high short hoods (and no potty - but that's a whole 'nother subject). [​IMG]
     
  12. Ironhorseman

    Ironhorseman April, 2018 Staff Member In Memoriam

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    Crash -

    Funny that you would mention the 'F' painted on the front of locomotives ... I had just posted a question about that in 'On The Rails' forum. (Whistle / Horn signals).

    I'd be interested to hear your opinion on that subject. Take a peek if you have a moment.

    Bill

    "Get Goosed on the Yreka Western"
     
  13. Johnny

    Johnny E-Mail Bounces

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    Chuck P. has the correct explanation for "cut off" and use of the so called Johnson bar. I can only add that the primary use for cut off was to optimize the relationship between steam chest pressure (pressure into the cylinders) and back pressure. Back pressure in the cylinders caused by still expanding exhaust steam was a great inhibitor of effeciency because it worked against the power stroke. In early years engineers controlled cut off using experience and exhaust sound as criteria. In later years the loco. builders developed gauges that constantly monitored steam chest pressure and back pressure thus providing the engineers with a tool to get optimum performance out of the locomotives under all speed and load conditions.

    Insofar as backing up is concerned, the "New Haven" operated most of its local freights in reverse for half of the day due to no turning facilities en route. The local I'm most familiar with operated 40 miles per day in reverse and that was with a mogul with no trailing truck. These trains were limited to 20 mph with the engine running in reverse. Most engineers were contortionists when running backward. It was particularly bad during the winter because their cab windows had to be kept open for visibility. Add snow, sleet, freezing rain, and coal dust to the equation and you can see why most engineers (and firemen) welcomed diesels with open arms.
     

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