Sout Bend SB 13" Countershaft Conversion
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    Default Sout Bend SB 13" Countershaft Conversion

    I've just brought home a South Bend lathe. It's a model 132, serial
    17,865 (1919-1920), gap bed 13" x 6', with change gears and automatic
    feeds. The machine appears to be in reasonable working condition. A
    few fellas could have used a chuck cradle more often and maybe not
    rapped out their files on the ways quite so enthusiastically, but all
    in all the old girl is in pretty decent shape. At some point, however,
    a rather ambitious conversion from overhead shafting to electric motor
    drive was performed. I'm hoping some of the South Bend mavens here
    can help me better understand the rationale for this conversion and
    whether or not to retain it.

    I'm not 100% sure what I'm looking at, but I think I've got the broad
    outlines. Someone transplanted half of the original countershaft gear,
    including drive the cone, clutch and assorted hardware, to a pillar
    that towers over the headstock and added an electric motor.

    Both flat pulleys on the countershaft, once used to take the overhead drive
    are gone. One spider (rim-grip clutch) was salvaged, modified and
    installed in the large end of the countershaft cone. This arrangement
    can be seen in the attached photos. Note the friction finger,
    originally used to power the clutch action on one of the flat pulleys,
    is still riding on the remaining half of the countershaft yoke.

    The countershaft yoke lever was replaced by the bell crank shown in
    pics below. At one end, this crank is connected to a fork which
    slides the cut-down remnant of the original countershaft yoke axially
    along the countershaft. This sliding action lifts the friction finger
    up the yoke's conical face, and onto the flat engaged position. This
    crank is connected at its other end to a longitudinal shipping rod
    situated at the back of the lathe at about the level of the operator's
    shoulder. The shipping rod is supported at its far end by a vertical
    strut anchored at the tailstock end of the lathe. When the shipper
    rod is thrown, the clutch connects the the drive cone to the
    countershaft, and when it is disengaged the drive cone freewheels on
    the shaft.

    The remainder of the installation consists of a two-stage reduction
    drive to spin the modified countershaft. An auxiliary shaft is belt-
    driven by the motor in approximately a 2-1/2 to 5-1/2 ratio; a second
    stage reduction of 2 to 6 is accomplished by chain, one sprocket being
    connected to the auxiliary shaft and the other to the countershaft.
    With a combined reduction ratio of 6.6 and a 1750rpm motor the
    countershaft should turn at 265 rpm--which is in the ball park
    of what SB suggests.

    The motor is a dual-voltage, capacitor-start 1/2hp Westinghouse type
    FJ, a unit obviously made later than the lathe. There's also a
    vintage-appearing Westinghouse drum switch, model 103A, fitted to the
    front of the lathe bed at the headstock end. I don't believe the
    present motor is an instant reversing type, but maybe one was present
    at some time. As I received the lathe, the drum switch serves only as
    an off-on control for the lathe's lamp.

    The gent who performed these modifications has done a workmanlike job,
    even though he wasn't an artist with the stick welder. It's one thing
    to dream about something like this and quite another to work out the
    all the details and build a functioning machine, which I believe he
    did.

    Nevertheless isn't this a complex arrangement that could have been
    implemented in large part as a motor switch and a belt tension release
    lever? What was the point? It's true that the shipping rod and
    clutch provide for quickly throwing the lathe into neutral (motor
    running but not driving countershaft cone or the lathe spindle)--but
    so what?

    1) This could be useful for on-the-fly belt changes, especially for
    someone who'd gotten used to this way of working back in the overhead
    drive days. But in the old days, weren't flying belt changes performed
    with the belt under power?

    2) Maybe the idea was to provide a form of emergency stop--the
    shipping rod is always right there in front of the operator. But it's
    just a halfway measure since it only de-clutches the countershaft
    cone. There's no active braking of the rotating lathe spindle, its
    cone pulley or the work.

    3) Was the conversion a scheme for improved quick reverse using an
    instant reverse motor that's been scrounged by some previous owner?
    An instant reverse motor certainly would be happier if the shipping
    rod was used to disconnect the spindle and cone pulleys' inertial load
    before being slammed into reverse. And if the operator paused a few
    seconds to let the machine spin down a bit before pulling the drum
    switch into reverse and shipping the clutch back in, the rest of the
    drive train could catch a break as well.

    4) Maybe there was some production operation served by this system?

    So ... what would you do? Some options:

    1) Retain the existing setup and--if possible--wire the motor for Fwd-
    Off-Reverse using the existing drum switch.

    1a) As above, but dispense with the shipping rod.

    2) Retain the existing countershaft and motor mounting setup, but
    dispense with the shipping rod and present motor. Install a 2/.5 hp
    1750/800 3-phase motor w/ a VFD now collecting dust on the garage
    shelf. The VFD would handle reverse, and with the excess motor
    capacity, some of the speed change duty as well. But how to install
    this nice motor? The flat belt drive presumably would protect the lathe
    from too much horse power. The SB's at community college machine shop
    class certainly weren't shy about throwing their belts. (pls see 2a,
    2b below)

    2a) Install the motor in 3) using the existing setup, possibly
    retaining the bell-crank to operate the clutch in case the friction
    finger falls off the yoke cone.

    2b) Find some vintage SB countershaft and motor mounting hardware.

    3) Something else not dreamed of so far.

    Thanks very much.
    Attached Thumbnails Attached Thumbnails q4.jpg   q0.jpg   q3.jpg   p8.jpg   p2.jpg  



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