[pianotech] high leverage action

Richard Brekne ricb at pianostemmer.no
Fri Mar 13 16:10:51 PDT 2009


Hmmm... I think we'll have to be a bit more specific then that.  A 10 
gram strike weight in the top low strike weight zone equates to 
something around hammer number 5.  A weight of 5 at key 88 is perhaps a 
quarter zone higher... that means you have really low hammer weight if 
this is reflective.  Front weights... assuming we are balancing the 
same  notes you mentioned for hammer weights then you have an action 
ratio of 6.2 in the bass ranging to 7.8 in the treble.  Kind of wild... 
but suffice to say you have a high action ratio... which fits at least 
your KR and Knuckle configuration.  Without more specifics this is just 
ball park.  I'd ask for  at least 7-8 samples of SW, FW, BW, and KR 
along with your WW to get a more accurate picture of your situation...  
say all C's but  I think its safe to say you have a pretty high action 
ratio....no matter which way you look at it.

Why you end up with such a short blow distance and deep key dip to get 
any aftertouch is a good question if the above is close to the truth of 
the matter.  A short bore length would force you to raise the shank 
closer to the strings... ie raise the underlever (whippen) which should 
not require a deep key dip to get aftertouch. A long one would keep your 
shank just off the rest cushion at a shorter blow distance... and 
perhaps fit the condition of a high action ratio thats heavy, has keep 
key dip and short blow with minimum aftertouch. But if you are certain 
about bore length being at String height - hammer shank center height 
then something is not quite right with this whole picture.... grin.. or 
its just so late over here that I've got things backasswards again.... 
wouldnt be the first time. :)

As far as minimum 44 mm.  I think thats about as short a blow as you can 
allow for without sacrificing too much power.  Usually you find 
somewhere between 45 and 49... sometimes 44... sometimes 50.... rarely 
outside that because of what implications it has for the rest of action 
regulation specs.  We have this ideal of about 10 mm key dip, and about 
1.5 to 2.5 mm letoff... which more or less dictates blow for any given 
amount of aftertouch.  It all adds up usually to somewhere between 44 
and 50 for blow.

Cheers
RicB


> >/ What are your Hammer Strike weights
> /*****10 in the bass and 5 in the treble - no corrective weighting action 
> taken yet.
>
>  and key Front Weights ?
> *****
> 30 in the bass and 6.8 in the treble
>
>  Your dip
> >/ and blow say low ratio but your KR and knuckle distance says high. How 
> />/ much aftertouch are you getting with things as they are...
> /***** about 1.5mm or slightly less.
>
>  how far out
> >/ from under the knuckle does the jack move ?
> /*****Just enough for drop and aftertouch to happen.
> >/
> />/ 41 mm is on the short end of the stick to be sure.  I usually dont see 
> />/ under 44 and never allow for less when redoing an action.
> /***** Do you have a reason for maintaining 44mm or greater blow distance?
>
> Regards,
> Gene
> >/
> />/ Cheers
> />/ RicB
> />/
> />/
> />/    Hello list,
> />/    Thought that I would seek comments on an action with high leverage.
> />/    Key dip is 10.5mm and blow distance is 41mm.
> />/    The touchweights are in the low 50's down and low 30's up.
> />/    Knuckle spread 16.5mm
> />/    Key ratio is 1.81
> />/    Action spread is 113mm and is adjustable.
> />/    Any more dip will make the sharps about level with the naturals when
> />/    depressed. The feel of the samples are acceptable. Seems that 41mm
> />/    blow distance is short - but is it too short? Maybe some loss of
> />/    power? Is there a down side to this action? Any corrective
> />/    suggestions? It is in the sampling - disassembled stage.
> />/    Thanks,
> />/    Gene
> />/
> />/
> />/ 
> /



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