Changing roller size.

[Roger Jolly]

At 11:21 AM 01/09/00 -0400, you wrote:

Hi Jon,
           Dangerous event, I'm thinking.
Well some thought's on a smaller roller/knuckle.
1. the hammer line drops.
We raise the hammer line to correct blow distance, by elevating the wippen.
 We have changed several parameters.  
1. the jack and knuckle core line has been moved from the ideal of a
straight line. (for max power efficiency) to being slightly angled.  This
will happen because the jack centre pin is being moved because of the fixed
radius of the wippen centre pin.
2. raising the capstan to restore the hammer line, this will change the
half dip, balance rail pin, capstan, wippen centre, straight line. 
3. since the wippen cushion is fixed by the wippen centre radius, raising
the capstan which is turning on a radius fixed by the BR pin. you will note
significant divergence of the two at the increased elevation.

This has changed the dip/after touch, and will therefore change checking
height.
The small knuckle will need less after touch to obtain the 1mm jack
clearance, increasing the change in checking.   Guess why I'm on an inter
active kick.

For an imformative exercise, get a drawing of an action, a set of
compasses, and scribe every radii.  
No conclusions just observations. 
 Little things like the rake angle at the top of the jack becomes
significant, this will determine friction, due to the contact area. But you
change the angle of the jack WRT the knuckle core, it has a similar effect
as changing the rake of the jack tip.

Just some ramblings to drive other's as nut's as I.  <G>

Steam Roller indeed, it's taken me long enough to live down closet steamer.
Regards RJ




>
>The problems I have encountered with S&S replacements have been in the
>center pin to core radius, nothing to connect with actual roller diameter; or
>maybe I just didn't notice.

>>Hi Jon,
>>             So there is some Englishman in you, Roller indeed??????
>>Just the observation's on Steinway's when some one installs the wrong
>>knuckles,and the severe alteration in touch weight, power, and repitition.
>>Not enough case studies to offer an opinion. O ther than the whole action
>>is screwed up. <G>
>>
>>Regard Roger

Roger Jolly
Saskatoon, Canada.
306-665-0213
Fax 652-0505