what determines pendulum type... rod length or bob size?

Discussion in 'General Clock Discussions' started by bruce linde, Apr 20, 2017.

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  1. bruce linde

    bruce linde Technical Admin
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    Nov 13, 2011
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    just had an interesting exchange w/ an eBay seller who has a 'tall case pendulum' for sale... except that it's an 8.5" fusee pendulum.


    i sent him a PM and suggested that he might have better luck selling his item if he listed it as what it was: a fusee pendulum. i pointed out that a 'tall case pendulum' would almost certainly be on the order of a meter long, and that the only reason i was even mentioning it was because i typically searched for both fusee pendulums AND tall case pendulums... as two different searches.


    his response?

    "It's not the length that makes it a tall case (wall clock) pendulum. It's the diameter of the pendulum."

    i have never heard or read anything like this before. i have tall case pendulums with 3-8" bobs, and wall and shelf clocks with 1.5-9.5" bobs.

    given everything we've discussed in multiple threads about rod length, bob weight and diameter, and center of mass... is there any validity to his claim?

    p.s.: he also calls the suspension spring a 'feather' ... huh?




     
  2. upstateny

    upstateny Registered User

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    #2 upstateny, Apr 20, 2017
    Last edited: Apr 20, 2017
    Smike, the Brits sometimes refer to the suspension spring as a feather. As far as the bob goes, IMHO the guy is full of poo.
     
  3. bruce linde

    bruce linde Technical Admin
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    'feather' did sound like a uk thing to me... he may be a perfectly nice guy, but i can't think of a single justification for labeling his item as a 'tall case pendulum' (which it ain't) instead of as an 8.5" fusee pendulum (which it is).

    i guess some people don't really want to sell their stuff... which might also explain why it's been listed for several months. :cool:
     
  4. Tinker Dwight

    Tinker Dwight Registered User

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    On a tall case with a one second beat, the pendulum rod
    would usually be on a leader. That would take about
    10 to 12 inches off the length.
    If it was a one piece pendulum, it would be faster
    if less than a meter.
    Tall case bobs are usually heavier for longer pendulums.
    Diameter is not always an indication of weight
    Tinker Dwight
     
  5. novicetimekeeper

    novicetimekeeper Registered User
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    We do usually call the suspension a feather, but then we call the clock a longcase.

    We still call it a longcase if it has a lantern clock with a verge escapement in it too but I agree the diameter of the bob is not a defining factor.
     
  6. bruce linde

    bruce linde Technical Admin
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    yes... but overall length w/ suspension spring (or 'feather') needs to be around a meter... and not 8.5".

    as for bob diameter/weight... i think my tall case (and/or seconds clock) bobs range in weight from approx 1lb to 6.5 lbs... most have wood rods, but i do have a couple with metal... either round or flat bars.
     
  7. Tinker Dwight

    Tinker Dwight Registered User

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    I've not seen the sale but I suspect it is
    a 8.5 inch diameter bob he may be referring to.
    Tinker Dwight
     
  8. bruce linde

    bruce linde Technical Admin
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    nope... standard fusee pendulum and bob
     
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