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1950s "bearing " ?

Discussion in 'Electronic Repair' started by N_Cook, Dec 5, 2012.

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  1. N_Cook

    N_Cook Guest

    In a German Minifon P55 from the 1950s , pocket size wire tape recorder ,
    even more surprisingly with a capabilityof 5 hours of continuous recording
    If disbelieving , Excellent pics etc of one on
    http://vintage-technics.ru/Eng-Minifon_P55.htm

    Anyway part of the complex drive mechanism is a steel barrel (with torsion
    sprung pulley at the centre so when it stops, the mechanism rotates
    backwards to reset the end-stop trigger position).
    The barrel has an axial 1.2 mm diameter pin each end that sits in an end
    anchor of a hollow brass cylinder each end . These cylinders have a sprung
    loaded pin inside them but there is no sign of any bearing material. Running
    lubricated there is too much resistance to rotation. Robbed a pair of 1.1mm
    balls from the tiny ring bearing inside a scrapped VCR pinch wheel. But
    there is only 1mm or so of springing at either end so again not free
    turning.
    What may have been in the ends in the 1950s.?
    I will next try rolling a ball of PTFE tape or a 1mm disk punched from PTFE
    but what would have been in there , bearing in mind German engineering so
    would not have been steel faces bearing crudely against steel at either end
    , surely?
     
  2. N_Cook

    N_Cook Guest

    Feeling with a needle , the sprung bits of steel are curved, I think, so
    original balls in there but fixed intentionally, or by rust, to the spring.
    For ease of assembly , they were probably spot welded together. Like the
    ferrite carying ends of springline/joy-spring reverb tanks the springs are
    then soldered to the brass cylinders at their fixed ends
    The problem was one of the anchors was slightly out of alignment , in one
    attitude , by a couple of degrees and so the rotating pin of the barrel was
    binding on the brass of an anchor.
     
  3. Guest

    You really should get up some pictures. Your phone or $49 camera isn't really going to probably do it, throw these little gizmos on the flatbed scanner and set it to high resolution. Then crop it down so it's not ten gigabytes.

    A couple years ago I got my hands on the print and a picture of this doodad, and actually it is cool as hell and a feat of engineering for it's time. I didn't realize it recorded that long, I was swept away by the compactnessof it.

    Have you actually taken the bearing apart yet ? There should be signs of what once was. I believe IIRC this thing was made in Germany right ? If so expect surprises.

    Normally I would say it's a brass bearing and if it has a mount, turn it, but you seem to be talking about a rotating member.

    I am having alot of trouble visualising it. That it backs up ? Like a one tape answering machine would ? Doesn't sound right. I am not quite getting it right now. If I had one in front of me that would be different I'm sure.

    It is cool though to even have one of those things, is it older than you ornot ? I have a scope that is older than me. You should take a shitload of pictures and throw them up on imageshack or dropbox or whatever. I bet a bunch of people would love to see the mechanics of that thing.
     
  4. N_Cook

    N_Cook Guest

    You really should get up some pictures. Your phone or $49 camera isn't
    really going to probably do it, throw these little gizmos on the flatbed
    scanner and set it to high resolution. Then crop it down so it's not ten
    gigabytes.

    A couple years ago I got my hands on the print and a picture of this doodad,
    and actually it is cool as hell and a feat of engineering for it's time. I
    didn't realize it recorded that long, I was swept away by the compactness of
    it.

    Have you actually taken the bearing apart yet ? There should be signs of
    what once was. I believe IIRC this thing was made in Germany right ? If so
    expect surprises.

    Normally I would say it's a brass bearing and if it has a mount, turn it,
    but you seem to be talking about a rotating member.

    I am having alot of trouble visualising it. That it backs up ? Like a one
    tape answering machine would ? Doesn't sound right. I am not quite getting
    it right now. If I had one in front of me that would be different I'm sure.

    It is cool though to even have one of those things, is it older than you or
    not ? I have a scope that is older than me. You should take a shitload of
    pictures and throw them up on imageshack or dropbox or whatever. I bet a
    bunch of people would love to see the mechanics of that thing.

    +++++

    That Russian site has a massive collection of internal pictures. His is
    museum quality condition, my one is full of the grime of rust and spider
    piss or whatever after being in a shed for decades (before my ownership).
    Since posting that I've got the motor, governor, weird drive to spools and
    "counter" and tapehead lifter mechanism all working at a regular (strobed)
    rpm .
    But I'm now snowed under with other people's repairs.
    Next time I will try a wire and spools and then connect the tapehead to a
    modern player
     
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