Nice summing up, David! I think what you describe should be within the capabilities of anyone who is replacing hammers on a quality grand. And certainly that should include any caut. In cases where "original weight" hammers are available, and reliably so, reproducing original conditions is no problem. But hammer weights are all over the place. There are a lot more options available to us now, but it takes a lot of knowledge to select an appropriate set, and even then there is no guarantee, unless one has the budget and/or time to have many sets available. In any case, it is necessary to know how much weight to remove from whatever set you have (tapering and tailing) to get good results. So you have to have the basic abilities David describes to come up with good results. I would add that an action rebuilder should also have knowledge and experience to use (if needed) wipp's with assist springs (with accompanying adjustments), and possibly to do minor capstan movement. This is not extraordinarily complex stuff - though you do have to be on the ball and skilled in precise work. But again, that _should_ describe any caut. at least on a good day, ;-). Regards, Fred Sturm University of New Mexico --On Saturday, January 3, 2004 9:56 PM -0800 David Love <davidlovepianos@earthlink.net> wrote: > Jim: > > I agree with you generally. But there are times when modest redesigns are > in order and to fail to consider them will often lead to bad results. > While a thorough understanding of design elements will always give you a > better result, there are some simple ways to approach things if you don't > yet have that type of expertise that will often give you a better result > than what is there. > > An overall look at the action before it is disassembled can give you a lot > of information without taking the extensive measurements that Stanwood > suggests. I do think it is important to adopt the balance weight as a > standard rather than simple downweight, but understanding that is not > difficult and is outlined well in one of Stanwood's articles in the PTJ a > few years back. (You also mentioned the formula in you previous post.) > )Measure the knuckle to center distance, a few sample hammer weights (try > measuring all the C's to give you a sense of the weight curve), the up and > down weights and look at the number of leads in the keys and their > placement. That information will give you a lot with which to make > decisions about changes. > > If you don't have extensive knowledge, then the simplest changes that can > be made, if you think there is a problem with the action set up, will > involve adjusting hammer weight or selecting a knuckle-to-center pin > dimension that is different than the existing one. If the old action > weighs off where you want it to and there aren't an excessive number of > leads in the keys, then you can try to simply duplicate what is there, > weighing the hammers and following the procedures you laid out in your > previous post. > > Without weighing the front weights of the keys it is difficult to > determine precisely what constitutes excessive front weighting, but as a > general rule no more than four in the low bass, three in the low tenor, > two in the mid treble and one in the high treble. That's assuming they > are placed toward the front with moderate spacing between them. If the > leads are placed back toward the balance rail, then you can add one more > lead and probably not get excessive. If your desired hammer weights > will cause you to have to add more leads to achieve the balance weight > you want, then consider using a knuckle to center dimension that is 1 mm > longer than the existing one. A move of the knuckle by 1 mm will usually > change the BW by about 5 grams ( a longer knuckle to center pin dimension > will also reduce friction slightly). Try a few samples to make sure > that they will regulate properly. If you are unable to alter the > knuckle dimension and your existing hammers are producing excessive > balance weights then you will have to reduce the hammer weight. > Depending on the action leverage, a reduction in the hammer weight by 1 > gram will cause a reduction in the BW of 5-6 grams, or it will allow you > to take one 12 gram lead out of the key from midway between the front of > the key and the balance rail. Not hard stuff. I use a balance weight > range of 36 - 40 grams (lighter - heavier). While there are times when > one might want to go lower or higher, I would generally recommend staying > in that range. I default most actions to around 38 grams. Of course, be > sure whatever you do that you test for regulation with samples. It is > likely, however, that an action that requires a modest number of leads to > achieve a medium balance weight will, by definition of action ratios, > regulate properly. > > These sorts of simple design changes are routinely made and usually > without any problems. I don't think technicians who aren't well versed > in action design need fear these types of changes. Just sample things > methodically and take care to create a smooth hammer weight curve by > whatever your favorite tapering system is (mine is with a table saw). > Though I prefer a more thorough approach as is offered by Stanwood > methodology, you can get good results making modest changes to the action > without all the platforms and detailed formulas. Just work carefully > and think through cause and effect before you glue it all together. > > > David Love > davidlovepianos@earthlink.net > > >> [Original Message] >> From: James Ellis <claviers@nxs.net> >> To: <caut@ptg.org> >> Date: 1/2/2004 4:21:11 PM >> Subject: Touch Weight >> >> David Love's point is well taken, and I agree. However, my previous post >> titled "Touch Weight" was in response to Paul Legard's request for a > simple >> routine to follow that would produce good results. From reading some of >> the posts on this list, it seems to me that many technicians out there do >> not have a sufficiently clear concept of action dynamics to attempt any >> sort of re-design of an existing action. Hammer weight (mass) is >> dictated by string mass and the sound one wants to produce, but >> constrained by the mechanical limitations of the system. John Hartman's >> description of > moment >> of inertia is correct. You must look at the entire compound lever >> system, but it all boils down to static weight, leverage ratio, time, >> mass, and distance traveled. No matter how you describe it, the basics >> remain the same, and it is not just "theoretical". It is very real, and >> provable. The simple point I am making is: If you really know what you >> are doing, > go >> ahead and re-design the action. If not, don't do it. >> >> Sincerely, Jim Ellis >> >> >> _______________________________________________ >> caut list info: https://www.moypiano.com/resources/#archives > > > > _______________________________________________ > caut list info: https://www.moypiano.com/resources/#archives
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