Roskopf photo wanted

Discussion in 'European & Other Pocket Watches' started by Richard Watkins, Nov 7, 2007.

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  1. Richard Watkins

    Richard Watkins Registered User
    NAWCC Fellow NAWCC Member

    Having checked all the books I have, there is not one photo of under the dial showing the arrangement of the canon pinion/motion-work.

    Does anyone have an early genuine Roskopf watch (it can be a trash movement) that they can photograph for me?
     
  2. Dushan Grujich

    Dushan Grujich Registered User

    Jun 20, 2003
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    Good Day Richard,

    A time to try and return a favour, perhaps. :)

    I do not think that I have an older Roskopf movement in my junk box. I shall have to look for it but I do have tech guides/parts lists for newer movements, circa 1963. You can download them at:

    Click Here

    I hope this helps and if I find an older Roskopf movement I shall post the images in a day or so.

    Cheers

    Dushan
     
  3. Richard Watkins

    Richard Watkins Registered User
    NAWCC Fellow NAWCC Member

    Dushan, the tech guides are too late. In fact they are not genuine Roskopf calibres because they have center wheels and ordinary motion work.
     
  4. Michael Harrold

    Michael Harrold Registered User
    Fried Watch Award NAWCC Fellow Old Timer NAWCC Member

    Jun 18, 2005
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    http://farm3.static.flickr.com/2406/1966700744_ca8ebe0ca0.jpg

    Richard,

    If this works, there is attached a photo of a mid-20th century Austrian Roskopf watch, having the traditional hand drive mechanism. There is even less to see than on a normal watch. The cannon pinion in the center of the movement turns freely on a post riveted to the pillar plate (there is no friction fit), and the large mainspring barrel protrudes in under the post. The minute wheel is only partially visible, because it is on the under-side of the pillar plate (you might call it a down under minute wheel). The minute wheel is friction fitted to the barrel arbor, in the manner of a normal cannon pinion. In essence, the mainspring barrel occupies the minute wheel position in the gear train, so turns faster than a normal barrel, which is the underlying principle of the watch. The following is a functional description of the Roskopf design, from an unpublished manuscript.

    The traditional three-wheel train suffers several problems. Its 30-tooth escape wheel at four RPM implies a balance rate of only four beats per second, precluding this gearing from quality timekeepers. Early American industrial watches beat 4.5 per second, and five beats per second becomes standard over subsequent years for more stable timekeeping. Another difficulty is that traditional three-wheel trains use six leaf pinions in order to achieve escape wheel speed with fewer gears. (Pinions have leaves, for some reason, rather than teeth.) Unless well made, such low count pinions operate poorly and can bind the train. Coarse trains in early American industrial watches use eight leaf pinions, followed by improved fine pitch trains having ten leaf pinions. Free of size limitations, precision clocks use higher tooth counts for smooth low-friction operation. The traditional three-wheel train layout is basically conventional in configuration, with the second wheel rotating once per hour in the center of the watch and the 4th wheel eliminated.

    Roskopf’s variation on the three-wheel train is ingeniously non-conventional. He desires an economical design having the performance of a fast beat balance, in order to market an inexpensive modern timepiece. A solution is for the entire time train and mainspring barrel to rotate faster. For locating a faster mainspring barrel, a convenient wheel resides in the motion work, which drives the hands. Motion work gearing under the dial consists of two wheels that rotate progressively more slowly than the center wheel, one of them turning somewhat faster than the barrel. The overall gear ratio for these two wheels is 1/12, so that the second motion wheel is placed concentric with the second time train wheel, and carries the hour hand. A faster mainspring barrel can reside on the first motion wheel (commonly called the minute wheel), rotating in four hours, instead of the standard 6.5 to 7.5 hours, and in the correct direction. The hands can be driven off this mainspring barrel, the minute wheel turning four times faster than the barrel, and the hour wheel three times slower.

    Roskopf’s faster mainspring consequently needs almost 50% more coils to run for a full day. Also, he has established precepts for a simple watch of mechanical robustness and solid value, which include: “maximize motive force”. His mainspring is accordingly both strong and long, so that its large barrel extends beyond the center of the watch. The second wheel of the time train cannot reside in the center of Roskopf’s timepiece. The huge mainspring barrel has a lot (128) of teeth, thus driving the second wheel of the time train at four revolutions per hour. An unconventionally large second wheel then drives the third wheel at 48 revolutions per hour, and the escape wheel (there is no fourth wheel) rotates eight times a minute. Having 18 escape wheel teeth, rather than the usual 15, Roskopf’s balance then oscillates at 4.8 beats per second, faster than standard slow beat watches then being manufactured by the American watch industry.

    Roskopf’s large mainspring barrel dominates his watch layout, pushing the three-wheel train off to one side. None of the wheels rotate at normal rates, so there is no seconds hand on the dial. Conventionally appearing hour and minute hands rotate around a solid post staked into the center of the pillar plate on its dial side. Roskopf enlists the older pin pallet escapement, there are other unusual features, and the overall arrangement constitutes an unusual new design. A 20th century Roskopf variant has gear ratios altered to yield a seconds bit on the third wheel, which rotates backward.

    Mike
     
  5. Richard Watkins

    Richard Watkins Registered User
    NAWCC Fellow NAWCC Member

    Thanks for the info. I have sorted out my problems having found a couple of useful photos.
     

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