Changing roller size.

[Jon Page]

Graeme,

I have not experimented with this alteration but I can envision a few of 
its consequences.

With each size smaller roller, the capstan would have to be turned up to 
raise the wippen
to maintain hammer blow. My concern would be where the 'magic line' 
intersects the
capstan/wippen cushion contact. So if it came down to altering knuckle 
height to correct
the magic line juncture (I'll call it the median line); I'd sooner change 
the capstan location
to improve leverage.

Also a smaller knuckle would have the jack clearing it sooner due to its 
diminished radius.
With this decreased connection period, will it affect the dynamic control?

As to how this attenuation might affect leverage, I can not speculate.

I've limited my knuckle selection to the center pin to roller core radius. 
As pointed out
during the Renner USA  class in Arlington, as the c/p to knuckle radius 
increases; so does the
knuckle diameter so as to maintain wippen attitude within the system. So 
the 15.5 mm radius has
the 9mm knuckle and the 16.2 & 17 mm radii have the 10mm roller.

Anyone do some "scientific" rescearch?

Jon Page


At 08:52 PM 09/01/2000 +1200, you wrote:
>Hi list,
>
>I was speaking with a technician friend last night and we were discussing
>another tech acquaintance (quite respected locally) who has been replacing
>grand rollers (knuckles to some of you) with smaller sized ones.
>
>In his opinion he achieves a finer regulation, faster repetition etc etc.
>So as I understand it he is say replacing a 10mm roller with 9mm and
>sometimes 8mm.
>
>My take on this is that the geometry would be altered elsewhere. I'm not
>knowledgable enough though to know what the possible negative effects could
>be, if indeed there are any.
>
>Could some of you with experience in this throw some light on this, whether
>it works well or not at all.
>
>I'm curious to say the least.......
>
>Many thanks,
>
>Graeme Harvey
>New Plymouth
>New Zealand.

Jon Page,   piano technician
Harwich Port, Cape Cod, Mass.
mailto:jonpage@mediaone.net
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