Glide bolts

[Isaac OLEG]

Hi ! what a complete treatment of the operation !

What happens with repetition when a very little too much pressure is
used. I Just come from an action that loosed its responsiveness after
a 2/12 turn was given (Kaway RX2 new). just tried to reach the 65 mm
height (from 64.5) and was obliged to go back, as things where getting
bad for repetition.

I suspect that the back of the frame was not seated firmly enough
then, but it was not visible (no hammers jumping when playing staccato
chords for example)

These grands seem to like to have really not a lot of pressure, or is
it a matter of tone (voicing) that links to bad repetition ?

Thanks for any idea.

Izaac O Z


> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de antares
> Envoye : lundi 28 octobre 2002 14:54
> A : Pianotech
> Objet : Glide bolts
>
>
>
>
>
>
> > From: Richard Brekne <Richard.Brekne@grieg.uib.no>
> > Reply-To: Pianotech <pianotech@ptg.org>
> > Date: Sun, 27 Oct 2002 23:31:11 +0100
> > To: Pianotech <pianotech@ptg.org>
> > Subject: Re: SV: OT - Treating Centers with Alchohol
> >
>  > What about those glide bolts ?? :)
>
> Awright bud,
>
> Key frames tend to move, due to changes in humidity. I have
> seen this often
> with especially larger instruments. One season key dip is
> too deep and then
> the next time it is too shallow. It also happens many times
> that the left
> and right ends of 'certain instruments' curl up, which is
> very annoying, the
> more so, because it still happens and they still have not
> changed their
> design.
> The invention of glide bolts did not end these complaints
> but made the key
> frame more stable and gave the technicians the possibility
> to quickly alter
> key dip and key height which was not possible before in
> such a short amount
> of time.
>
> As older key frames tend to curl up and thereby cause
> instability and noice,
> the idea was to create an arch in the new frames. An arch
> from North to
> South and in the case of Steinway also from West to East to
> accommodate the
> arch of the soundboard.
> When we put a modern key frame on a straight table/bench
> without keys and
> action, we will notice that the arch is higher and that the
> glide bolts are
> not in contact with the surface of the bench/table.
> As soon as we put the keys and the action back on the key
> frame, the arch
> has flattened and the glide bolts may touch the surface underneath.
> Because the glide bolts are screwed in the balance rail, we
> can screw them
> up or down, according to what is necessary.
> All factories have specific measures for their key height
> and this means
> that every instrument will have about a standard amount of
> paper punching
> under balance rail punching and front rail punching, to get
> the desired key
> height and key dip.
> With the glide bolts we can alter key dip and key height,
> but there is more
> to it.
> A glide bolt has two other options :
> With the glide bolt we can also control the pressure, put
> onto the key bed
> by the glide bolt in combination with the weight of action
> and keyboard.
> If too much pressure is applied, the key frame is probably
> pushed up too
> high, causing all kinds of regulation problems, but at the
> same time the
> quality of the tone will change.
> That is option number 2 : the glide bolts have more or less the same
> capacities as a tuning fork.
> We can not hear the vibes of a tuning fork if we don't put
> it down on an
> amplifying object. By pressing down a key and making a tone
> we create a
> vibration transmission between our finger and the generated
> energy of string
> and sound body which is the sound board and actually the
> whole instrument.
> The less deviation in the energy transmission, the more
> energy is being
> transmitted and the more power we literally feel in our
> finger. With less
> deviation I mean : a well regulated action, a well tuned
> unison and, very
> important, a firm front rail punching.
> A less firm front rail punching sucks energy, creates a
> very  'soft landing'
> of the key and thereby causes an unclear and diffuse after touch.
>
> By regulating the key frame and the glide bolts, which is
> the beginning of
> the regulation process - with the cheek blocks fastened
> please -,  we can do
> a few very important things at the same time (in Holland we
> say "kill two
> flies in one stroke') :
> We check the key dip first and measure the key height (from
> the key bed to
> the underside of the key top covering).
> If the key height should be 64 mm but is (on average) 63.5
> mm we should turn
> the glide bolts just a little to the right to bring the
> balance rail up a
> bit, but before we do so, we measure the key dip.
> As the key height is too low, the key dip 'should' be too
> shallow too.
> If that is the case, key dip is for instance 9.3 mm, we can
> be assured that
> we do the right thing and we start by turning the middle
> glide bolt just a
> tiny bit to the right while at the same time feeling with
> our left hand (if
> we are right handed) the movement in the key dip measuring block.
> A quick short turn is usually enough.
> We repeat this process with every glide bolt, but with the
> one most on the
> left we have to depress the left pedal as the action will
> be obstructed by
> friction between action and the left side of the rim.
> When we 'think' that on every place of the keyboard the key
> height and the
> key dip are corrected we tap with protruded fingers (or the
> side of the
> hand, or a fist) on the balance rail near every glide bolt
> to make sure that
> every glide bolt makes a firm contact with the key bed.
> This is not as easy as typing in these words. It needs a
> lot of practice
> before we do it right at once and actually a seminar on
> this subject should
> at least take a few hours.
>
> OK...after we have made sure that every glide bolt hits the
> key bed and key
> height and key dip are still what they should be, we should
> take care of
> eventual glide bolts on the under side of the key frame,
> which is the case
> with Yamaha grand pianos.
> On the left side we will see two glide bolts in two
> sections, which we were
> not able to service from above as there is no place to
> stick them through
> the keys. Yamaha sells a special tool for glide bolts with
> a possibility to
> grip and screw the bolts underneath. By pulling out and
> lifting up the
> keyboard and action, be careful not to damage the piano
> with the drop
> screws!
> Again we tap for rattling and when we are sure the work has
> been done, we do
> a 'weighing test'. If it is an instrument with a hammer
> rail which is easy
> to lift by hand, like a Yamaha, we lift the hammer rail
> with our left hand
> and knock on the balance rail at the same time to find out
> how easy or
> difficult it is to create a knocking sound. between the
> lifted balance rail
> and the key bed. It should not be too easy, and it should not be too
> heavy.(this is something I can only demonstrate during a seminar)
> The weight should be the same overall but we can can choose
> for a difference
> in pressure/weight in regard to 'tone'. We will notice that
> when a lot of
> pressure is applied the tone will have a sort of
> 'grounding' quality. We can
> hear the same if we pit a tuning fork - lightly - on a
> wooden surface or
> press it down very hard. If we press it down very hard the
> tone will change
> to what I call this 'grounding' quality. (I am sure  a
> native speaking
> American or other English speaker will find a better word)
>
> When all this work has been done, there is a final test :
>
> We bang on the piano (on the wooden beam that is situated
> against the iron
> frame and directly over the keyboard, what is the name?
> please) and listen
> for a rattle.....
> If we hear a rattle we put one finger lightly on each bolt,
> ubtil we have
> found the one that causes the rattle.
> Tighten bolt, end of story.
>
>
>
> friendly greetings
> from
>
> Antares,
>
> Amsterdam, Holland
>
> "where music is, no harm can be"
>
> visit my website at :  http://www.concertpianoservice.nl/
>
>
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