Speed Graphic Pacemaker Top Mount Rangefinder Cams

Discussion in 'Large Format Cameras and Accessories' started by ernie57, Apr 21, 2016.

  1. ernie57

    ernie57 Member

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    Help!!!
    Does anyone know where I can purchase or have made a cam to fit an Aero Ektar 178mm f2.8 lens on a top mounted rangefinder?
    If not, doors anyoneb know the specs odd this so I can find a machinist and have one made?
    Thanks in advance!!!
     
  2. Sirius Glass

    Sirius Glass Subscriber

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    ernie57

    ernie57 Member

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    Hi thanks!
    I looked at those and am kind of mechanically inept. Any idea if there's anyone in SoCal who can fabricate one for me? Or anywhere, for that matter?
    Thanks so much for the help!
     
  4. shutterfinger

    shutterfinger Member

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    Back in 1850 I figured out and posted the details on how to make a cam from scratch for the Super Graphic cameras. I stated that if someone would lend me their Crown with a factory matched lens and cam I would work out a technique for making a Pacemaker cam from scratch. No one has ever offered.
    The Aero Ektar is an aerial camera lens and I have no clue if its focusing characteristics will work with a cam or not. It should up to 15 to 25 feet.
    The easiest thing to do is make a focus scale for the lens. Focus scales are attached to the bed block adjacent to the rails with the indicator mounted on the rails. Standard distance markings are Infinity, 100 feet, 25 feet, 15 feet, 10 feet, 8 feet, and each foot thereafter up to the close focus distance of the lens. The close focus distance is the distance the lens has moved forward from infinity that is 1/3 stop bellows extension from infinity or less, roughly 178/3 or 59mm forward from infinity. Extra exposure is needed if the bellows are moved forward from infinity and 1/3 stop is just noticeable in wet printing. Most lens will focus the next foot or half foot with only a few millimeters forward movement of the rails then the amount of forward movement to reach the next half foot in focus doubles or triples over what the previous half foot focus movement was. Example: you focus on 6.5 feet at 200 millimeters bellows extension, focus for 6 feet is 215 millimeters but 5.5 feet is 275 millimeters or more.
     
  5. Dan Fromm

    Dan Fromm Member

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    Charles, did you mean 1850? I had no idea that Super Graphics were made then.

    A seven inch lens is a seven inch lens is a seven inch lens.
     
  6. shutterfinger

    shutterfinger Member

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    Yes, 1850 as in many years ago.:smile:

    When making a focus scale mount the camera on a tripod. Use a target at least 5000 feet away for infinity. Celestial objects make excellent infinity targets. Use a tape measure and measure from the film plane for all other distances. Search engine Test Targets for a target to focus on for 100 feet and closer. Use a loupe on the ground glass for precise focus.
    Pacemaker cams have a number stamped on them. The cam list is here http://www.graflex.org/speed-graphic/top-rangefinder-cams.html A #88, #74, or #62 should get you ballpark close. Lens are rarely their marked focal length. They can be a tenth of a millimeter either side of the marked focal length to a few millimeters either side of the marked focal length. The greater the difference in actual focal length of the lens and cam the greater the focus error at close focus distances.

    A factory service manual for the Top (Graphic) Rangefinder Graphic cameras is here
    http://www.southbristolviews.com/pics/Graphic/manual-pdf/servicemanual.pdf
    It tells how to calibrate the rangefinder.
     
  7. MattKing

    MattKing Subscriber

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    Never mind cameras - I didn't know there were any APUG members made back then!
     
  8. shutterfinger

    shutterfinger Member

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    APUG members were never made. They came into being somewhere between the concept of the Camera Obscura and the first Daguerreotype, but they remained in the background for many years.
     
  9. gordrob

    gordrob Subscriber

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    ernie57

    ernie57 Member

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    Thanks for all of the help.
    I'm a bit daunted by how complicated this is getting!
     
  11. michr

    michr Member

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    It is complicated, and it's a shame there's no where you can just buy what you need. I've asked about Graflex stuff on this forum before, and the answer is usually just a link to the generally useful, but poorly organized and incomplete graflex.org website.

    So I've given it some thought. I don't like the idea of shaving down a piece of metal and having to try it over and over. That seems error prone and tedious, and if you shave off too much, back to the drawing board.

    So what is a rangefinder cam? From the way I interpret it, it is a device to convert the motion of the focus gears to the rangefinder, in what I assume is a linear fashion. I assume that also means that width of the cam for closest focus and infinity don't vary between cams, because those are hard limits of the rangefinder itself, and that the variation between lenses is the slope between these two points. Could designing the cam be as simple as measuring the distance traveled along the lens board between where it is focused at infinity and whatever the closest distance the rangefinder focuses (several feet?), then charting these values in two dimensions?

    Say, for example (with made up numbers), the lens moves 32mm along the lens board and there is a difference of 8mm in depth between the close focus and infinity focus on the cam. So for every 4mm the lens move along the lens board, it needs to move along the other dimension 1mm. The only other value is the actual length of the cam, which should be (I don't know for a fact) the same between all cams.

    For those that have made one, is this sufficient? Is it necessary to map out each few feet and chart those values? Is this idea good to create a cam or is it just a starting point for a rough cam that needs to be finessed?
     
    Last edited: Apr 26, 2016
  12. Old-N-Feeble

    Old-N-Feeble Subscriber

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    Hmm... I wonder if someone could invent an 'adjustable' cam... one cam that can be adjusted to match any lens reasonable to the camera to which it's attached.
     
  13. Arklatexian

    Arklatexian Subscriber

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    O-N-F, have you designed and made one yet? If so (and it works), how much are you asking for one? If it works, I won't need two......Regards!
     
  14. Old-N-Feeble

    Old-N-Feeble Subscriber

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    No, I haven't. After I posted the idea I realized it's probably not possible.
     
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