Pianotech

  • 1.  Kimball grand rep springs

    Member
    Posted 04-10-2018 00:01

     I need to get some tension in the rep springs of a kimball grand. The rep spring does not have an adjustment screw nor is it a butterfly stype spring. There is a   loop that the end of the spring is connected to. the jack spring has a  loop  on the jack just below the jack adjustment button & felt. The springs are independent of each other.  The balamcier spring end is hooked to a  loop that  passes up through a hole in the balancier. The question is how do I add some rep spring strength so the hammer will come up after checking and key release ? do i message the spring where is has a coil on the balancier , pull up on the spring with a hart tool, put a bend in the spring or push down on the spring back near the coil  .? few if any rep levers seem to have any rep strength at all

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    James Kelly
    Pawleys Island SC
    843-325-4357
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  • 2.  RE: Kimball grand rep springs

    Registered Piano Technician
    Posted 04-10-2018 01:50
    James

    Two things. To increase the tension on the spring, unhook it from the loop and pull the spring towards you. Then try the repetition. If it's too strong, then push down on the spring. Keep doing this until you get the right tension. 

    Before you do this, however, make sure the hammer is correctly regulated. I don't regulate rep springs until let off and drop are set, and, the most important part, all the hammers are checking at the right height. I find most hammers check too low. They should check at about 5/8" below the string on a "normal" blow. Of course, key height and dip needs to be set at the right height, too, to get correct checking height. 


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    Willem "Wim" Blees, RPT
    Mililani, HI 96789
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  • 3.  RE: Kimball grand rep springs

    Registered Piano Technician
    Posted 04-10-2018 08:39
    James,

    Hammer rise after back checking is the traditional indicator of whether or not there is enough repetition spring tension. However, in our shop we call it "manifest" repetition spring tension, as a reminder that there are other factors in play besides the spring itself. In other words, while hammer weight is a constant (from one blow to the next, if not over the life of the hammer), friction at the various contact points can change (such as key bushings and action centers, particularly the repetition lever/balancier and hammer centers).

    So, if hammer rise is insufficient to indicate that the jack is able to promptly return under the knuckle ("follow the jack!"), it is a good idea to carefully inspect the relevant friction points before adjusting the repetition springs themselves.

    Alan

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    Alan Eder, RPT
    Herb Alpert School of Music
    California Institute of the Arts
    Valencia, CA
    661.904.6483
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