David, Newtown and all, David wrote: >Historically, many of the European makers short-bored their hammers >and raked the hammer out a degree or two to insure the hammer was >perpendicular to the string at impact. I wonder if they didn't do >that for a reason. Because it moves the contact point between the jack and the roller closer to the line of centres when at rest, thereby reducing friction. Hamburg Steinways are bored in a similar manner. It's the sort of stuff folks get up to, to make a poor design function a little better. In 'standard' actions, the jack/roller contact is typically about 8 mm off than the line of centres when at rest, while the figure in our action is just 3.5 mm. >. . By short-boring the hammers, the shank can be set a little >higher and the touchweight is reduced (according to Richard >Davenport's experiment) by a few grams per 1/6". Richard is absolutely right. With our own action the design allows for this condition to be optimised when the hammers are bored to the string height minus the hammer centre distance. >With recent talk from David S. about what he calls "breakaway", that >is, the change (reduction) in resistance as the key progresses >through the stroke; by starting with the shank in a little higher >position, that overall change should be reduced. In practice, you >would be able to control ppp playing better by not having to start >the key with a certain amount of force and back off as the >resistance diminishes. The reduced change in resistance from >beginning to end of keystroke should result in a smoother feeling >action. It will and it does. The other factor at play in actions with a large jack/roller contact offset from the line of centres, is that the leverage ratio is relatively higher when the action is in the rest position. Standard actions tend to have a very wide range of leverage ratio change during the execution of the key stroke. This also will tend to cause the action to feel a little heavier at the start of the key stroke. > I guess the question is, what do you sacrifice in regulation to get >that? And, is the trade off worth it? If the action is designed to be set with these factors optimised you don't have to resort to any fudging techniques, such as short boring the hammers, to get the action to work. >In addition, I'm not sure that boring the hammer for future wear is >such a good idea. If the action benefits from a certain bore >distance, why increase that distance resulting in a mechanical >disadvantage until such a time that you wear the hammer down to a >point when you can adjust the blow distance to be where you should >have been in the first place. This is an interesting point that Newton raised, and one which has been debated in our workshop on many occasions. No answers yet, this one still remains a question. >Just a thought. All good thoughts nonetheless Dave. Regards, Ron Overs -- ______________________________ Website: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ______________________________
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