Diane, One way I look at capstan placement is to position it to move the wippen through the optimal distance. I have applied these ideas to the last few actions and have had good results: I start with four fixed components in the action system; letoff, hammer length & blow and key motion (establish key height and desired dip). Action spread and/or knuckle /center pin radius determined by having the jack perpendicular to the shank at the rest position, never greater (less maybe). Depress the key fully and notice the location of the jack. If it is buried into the stop felt at the end of the repetition lever, the capstan will have to move forwards. If the jack is barely clearing the knuckle it will have to move back on the key. Sometimes just changing the angle of the capstan will alter the arc motion enough to accomplish this. I like to think of it as range of motion. A capstan placed further back on the key will move the front of the wippen through more distance causing the jack to be forced further from the knuckle at the end of the key stroke. Even though a knuckle placed further out on the shank will delay the time the jack encounters the letoff button, the range of motion is the same in regards to the wippen. (having a damper lift later does not mean it does not lift as high) So capstan location is selected by ultimately having the jack in close proximity to the knuckle at check-in or the end of the key stroke resulting in minimal (perfect) after touch. This will also help with repetition since the jack is not in another time zone. Starting the Capstan Relocation Program: With the key partially depressed, holding the hammer at half blow (a tri-square set to this hammer height and held in a vertical position with a spring clamp to stop the hammer while a light weight maintains key position allows hands free juggling), a thread is drawn from the bottom of the balance rail hole to the wippen center pin, a mark is placed at its intersection with the wippen cushion. (remove a few adjacent keys to facilitate measurement). Remove the wippen and mark a line on it perpendicular to the cushion at the pencil mark. Replace the wippen and reset the key for the half-blow position. Extend the new line on the wippen onto the side of the key. This is the angle and position for the capstan at that balance rail/center pin median, the angles between the wippen and capstan will be about equal and opposite from rest to check-in. I think this is an optimal attitude for the least friction with the perpendicular line at half blow, Set a trial capstan to this position and notice jack proximity to knuckle. If the jack is away from the knuckle, the capstan needs to be located more forwards to decrease the motion of the wippen. Reposition the trial capstan until the jack is where you want it at check-in. Many times I have not had to change the capstan's position to the degree to alter the Key Ratio but a slight change in angle made all the difference by altering the arc travel of the capstan and wippen for a positive result with the jack. The median line of the balance rail and wippen center have to be rechecked after relocation. The cushion height may have to be altered or relocated altogether. There can be considerable experimentation. The Renner USA universal wippen comes in handy here. Relocating capstans takes about four to six hours. To expedite the procedure get a long plug cutter from the hardware store (Irwin 1/4:" x 1" long). Cut plugs from old keys. These are made beforehand. Remove capstans, drill holes to 1/4", glue in plugs (align grain), by the time all the plugs are in, you can start from the beginning to drill the new holes. Replace capstans. As easy as 1,2,3. (capstan drilling jig jpg avail.) Once the capstan has been relocated for optimal regulation, measure UW/DW and Front Weight. Now you can determine Strike Weight and whether you can get your desired Touch Weight with simply adding or subtracting keyleads or if spring assisted wippens are the best route to go. With spring assisted wippens, I have reduced friction to average 12 gr bass, 10 gr treble. All this is just tip tip of the iceberg, there are other considerations which would make this post excruciatingly longer but getting with David Stanwood's system would make it easier. While you are drilling the old keys, get tapered plug cutters (3/8", 7/16", 1/2") from Woodworkers Supply. These will plug the holes left by removing the unwanted original key leads. Regards, Jon Page PS I'm sure I forgot to mention something . . . At 03:49 PM 06/06/2000 -0700, you wrote: >Great idea about a thread on action geometry, Rob! It seems that that is >the most useful >thing for a _real_ understanding of what we are doing when we regulate. > >We are currently working on a JC Fischer grand, converting the action to a >modern one. >The old whippens have no balancier, but a large circular spring that >attaches to a thread on >the hammer butt (that's right, hammer butt on a grand). The old action >parts are >considerably lighter in weight than the new ones we hope to make work. >Catch is the >customer never liked the piano because it felt so "heavy". Another issue >is that the new >hammertails are 3/16" shorter than the originals. > >We put a new whippen and hammer assembly on a note and weighed it. We got >a down >weight of 85g and an upweight of 53g. This results in a friction reading >of 16 and a >weight reading of 69. Then we weighted the key with leads to result in a >downweight of >48 which gave us an upweight of 19, friction of 14.5 and weight of 33.5. > >Hoping to improve these results we experimented with moving the capstan >forward. We >tried two new positions, .2" and .4" forward (toward the front of the key.) > >Results: > > Original position Original position .2" > forward .4" forward > no leads with leads with > leads with leads >----------------------------------------------------------------------------------------------------- >Up >weight 85 48 48 > 48 > >Down 53 19 21 > 22 >weight > >Diff. 32 29 27 > 24 > >Friction 16 14.5 13.5 > 12 > >Weight 69 33.5 34.5 > 35 > > >So... what should we do? > > >Thanks, > >Diane Hofstetter >Jeff Williams >________________________________________________________________________ >Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com Jon Page, piano technician Harwich Port, Cape Cod, Mass. mailto:jonpage@mediaone.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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