You have all given me a tremendous amount of information to digest and I am doing so as rapidly as possible. The project developed as a rather simple replace hammers and shanks because of heavy verdigris and worn hammers. The "feel" of the original configuration was difficult to determine because of the verdigris. It is a good lesson in how to take something simple and make it very complex. I am not committed to any set of parts (my approach is to do it right even I have bought and paid for them anyway). The original knuckle was 16 mm. I opted to use 16.5 because it offset a small amount of additional weight with the new hammers and still gave me adequate aftertouch with dip of .395 with and a 1 3/4" blow. I didn't want to compromise either of those any more than that by going to a 17mm knuckle if I could avoid it. The 16.5 also allowed me set the project up for the least amount of lead reorganization. I dry mounted the hammers and could tell immediately that something was amiss just by how it felt. That launched me on this particular thread. The KW ratio does vary from top to bottom. B0 is 5.0 B7 is 5.5. Moreover, the capstan line itself is a bit snakelike creating some inconsistency in both directions. But the capstan is clearly shifted out in the treble and the leading is significant in the upper range of the piano (three leads into the last section) albeit they are set near the balance rail. That did give me some clue that there might be a problem which is why a dry fit everything first. The customers are undoubtedly totally unaware of these problems and might not even notice. I am pursuing this for the most part because something is askew and it has offered a tremendous learning opportunity. I have begun to play with David Stanwood's ideas over the past year and this has been a crash course. The relationships between all his variables is still something I am working on understanding. Because there are limited funds to resolve this by a major redesign, I am trying to decide what gives me the best result and falls within the budget limitations--a common problem. Wally Brooks' quote is apropos. At the moment I am leaning toward further reducing the strike weight by thinning the hammers and possibly going to a 17mm knuckle. I am not that happy about the regulation compromise, but I am double checking my samples to be sure that my original regulation specs are correct. If I can keep the dip under .400 and the blow not less than 1 11/16 and remove a bunch of lead, I think it will be adequate for now. David Love David Love >From: Ron Overs <sec@overspianos.com.au> >Reply-To: pianotech@ptg.org >To: pianotech@ptg.org >Subject: Re: Ideal leading pattern: more questions >Date: Sun, 1 Apr 2001 10:56:46 +1000 > >David, Bill and list, > >>On Sat, 31 Mar 2001, "David Love" <davidlovepianos@hotmail.com> wrote >> >>>Without even looking at the belly rail felt I can tell that >>>everything is to far in. The position of the hammer #88 is well >>>over 5 1/8" and any attempt to reposition to action brackets and >>>reset that capstan line would move the hammers way out on the shank >>>in the upper end of the piano. >> >>(Bill Ballard replied) The factory strayed from their own procedures >>on this on. The reason for sliding the top action in/out on top of >>the keyboard is to make a standard 5-1/8" shank length work with >>whatever plate location the belly room may have given the piano. > >Exactly Bill, they've cocked up in the procedure. Setting the action >stack position to get a correct strike line, since the plate was >poorly positioned, is just plain stupid production. I can't >understand how factories can allow such sloppy practices to persist. >Where was the jig to enable the plate to be set in the correct >position relative to the case? If the plate was positioned correctly, >the rest of the piano should fall into place, allowing the action to >be set up in accordance with the original specification. Assembly >line workers should not have to calculate work arounds for poor >dimensional control. Of course, the reality is that they don't even >when its necessary. So the pianos get sent out with any old action >geometry set up, and they play like it. > >For our third production piano (presently under construction), we >have built a special assembly jig which is placed in the key bed of >the piano before the pin block and plate is lowered into the case. >The jig shows the correct position of the strike line in the case, >with the first and last strike points for each string section marked. >With the hitch pin and agraffe holes undrilled and the bridges yet to >be positioned, the height of the plate and pin block is set relative >to the key bed. The plate is then positioned with reference to the >strike line on the jig. After positioning the plate, the agraffe and >hitch pin hole groups are positioned for each section, using datum >measurements taken from the CAD drawing. The datum lines run from >specific strike points on strike line. Using this set up procedure, >we can be sure that the strike ratios will be set as per the original >design and the action can be assembled and installed to a standard >specification. Futhermore, every piano will have the same action >geometry and strike line standards. Product uniformity should result >in pianos which are true to the original blueprint, and much more >consistent in tone and touch. > >>>(David L wrote) . . . .Given the plate location, I'm not sure how I >>>would go about solving the problem anyway. At least not without >>>remaking the entire action, keys and all. The best solution short >>>of that, to my thinking, is to go to a spring assisted whippen to >>>at least allow me to remove as much lead as possible. I haven't >>>yet tested that idea. Any comments? >> >>(Bill replied) These are two sure ways to lower FWs (read: remove >>leads). Actually, if you know how to do it, bringing the capstan >>line back towards the balance rail and (if necessary) relocating the >>the rep heels . . . > >Good suggestion Bill. If the action stack is incorrectly positioned >relative to the key frame (to correct other anomalies), the capstan >line can be repositioned to achieve the desired hammer/key leverage >ratio (the hammer/key ratio will need to be checked at both ends of >the action to determine a corrected capstan line). Don't consider the >key ratio alone to be important. It doesn't matter what the key ratio >is, as long as the hammer/key ratio is correct. Sure, when the >capstan line is repositioned to correct for the overall hammer/key >ratio, the wippen speed may vary a little, but it will be of little >consequence to the player as long as the variation is not too great. >If the wippen speed does vary considerably, it may effect the jack >escapement speed during let-off. I have found that the jack tip/key >ratio should be at least 1.8:1. > >>(Bill continued) . . . Why though, if you have a perfectly >>reasonable key ratio of 5.0 should you have to do any monkeying >>around there. Have you bought, paid for and installed the shanks >>already. I think you have alot more to gain by basing this action on >>17mm shanks. What is this "best combination of >>regulation/downweight" which hooked you up with 16.5mm shanks? Or >>was it that 16.5 was what was in there and you're sticking with it. > >If David were to reposition the capstans as Bill suggested, he may >still be able to get the hammer/key ratios he's looking for without >changing to 17 mm shanks. Relative to the 17s, the 16.5 mm shanks >will require the capstan to be positioned a little closer to the >balance pin (which will slow down the wippen speed - therefore, check >the jack tip/key ratio also). I believe that attention to the >hammer/key ratio should be the first consideration with any action >set up. The use of excessive amounts of lead to get the required DW >is a sure sign that there's something wrong with the basic geometry >(assuming that all of the usual suspects, centre pin, bushing and >balance pin friction have been checked). > >Ron O >-- >Overs Pianos >Sydney Australia >________________________ > >Web site: http://www.overspianos.com.au >Email: mailto:ron@overspianos.com.au >________________________ _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com
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