----- Original Message ----- From: <pianos@telusplanet.net> To: <pianotech@ptg.org> Sent: Wednesday, August 18, 1999 4:56 PM Subject: Re: Accu-just Hitch pins - any time, any place! > Hi Del, > > The piano in question is a Baldwin scale "E", which is pretty > similar in scale to the "R" grand. According to my Baldwin shop > manual, Baldwin lists scales for Accu-just and Accu-set hitch pin > pianos, and scales for traditional pianos. The numbers for the E > scale and non-AJ R scale are fairly close, the E scale incorporates > more 1/2 size wire changes in the lower tenor over more unisons. > The R scale for both types of hitch pin arrangement are virtually > identical, with only 3 deviations in number of unisons for identical > wire sizes throughout. I don't think that wire size has much to do > with determining what type of hitch pin layout is used. Nor do I > think that speaking lengths or bridge placement varies greatly > between the above models. The plate structure isn't greatly different > between these pianos either. So is hitch pin layout is the critical > factor in deciding whether or not a piano can withstand retrofitting > to adjustable-type hitch pins? No. It is only one factor. As I said, I have not had any problem converting pianos to vertical hitch pins, but I am fairly conservative. I don't like it when the hitch pins are all closely spaced in a nice neat row. This concentrates all of the stress in that nice, straight -- or, at best, slightly curved -- line. I have done them this way, but only when the hitchpin panel is at least 10+ mm thick and I can keep the wires no more than 4 mm off of the plate surface. > I quickly took some micrometer readings from a new R grand with > AJ hitch pins on the sales floor and a Wurlitzer (Samick) C173 5'8" > with a traditional HP layout for comparison: > > Average hitch pin diameter: > > Baldwin R = .223" > Wurlitzer C173 = .168" > > Average hitch pin spacing: > > Baldwin R = Staggered .3 - .5" apart, some non-staggered, > alternating distances apart, pins no closer than 1" from lip of plate. > > Wurlitzer C173 = .35" apart in treble in even sections of 12 - 16 > pins in a curving row, with a .75" set back on the next row. > Bass alternately staggered .5" apart and .5" offset. > Pins no closer than 1.75" from lip of plate. > > Plate thickness (at lip of plate, adjacent to bridge). > > Baldwin R : treble .362" > mid-tenor .423" > bottom tenor .366" I'm a little surprised at this. I didn't check grand plates for thickness, but I thought the hitchpin panel was thicker than this. > Wurlitzer C173 treble: .4" > mid-tenor .415" > bottom tenor .435" >From the information you have provided, I don't think I'd have any concerns converting the Wurlitzer to vertical hitches. Even considering that the Wurlitzer has a vacuum-cast plate, there is probably enough strength there. (For whatever reason, vacuum-cast plates usually have considerably thicker cross-sections than do sand-cast plates. And, I figure there must be a reason. No one gives iron away just because they're nice guys.) > Hitch Pin Height > > Baldwin R: .467- .545" throughout > > Wurlitzer C173 .415 - .423" throughout (holes drilled straight and > pins bent back. Pin height is total length of pin, not actual height > off of plate). Most pianos being built today have their hitchpin holes drilled straight. Most plates are drilled using CNC equipment and it is just a whole lot easier this way. Makes converting them to vertical hitches much easier. > Height of string above plate > > Baldwin R > top treble .313" to .378" > treble .315" to .202" > tenor .110" to .271" > bass .186" to .229" > > The top section strings are definitely above the 2/3 mark on the > hitch pins, the rest of the strings are below the 1/3 mark. Angle to > the bridge is minimal. There is nothing magic about this 2/3 mark. It is just a guide line to keep the stringer, or whoever is setting the bearing, from getting the string excessively high and over-stressing the plate. (Assuming, of course, that the pins are driven in to the correct height. These were.) The treble section of this piano has the strings running from 7 to nearly 10 mm above the plate surface. That is pretty high. This is placing quite a bit of stress on the hitchpin panel. And it really isn't necessary. Bearing in these pianos is a function of pinblock thickness, bridge thickness and whatever casting anomalies exist. All of which are fairly easy to control. It should have been possible -- simple even -- to set the plate closer than this. Structurally, I'm sure this is not dangerous, although the piano might be a bit unstable during a pitch-raise. I think they also might whip around a bit which could lead to some interesting sounds. Frankly, though, I'm glad to hear that they aren't any higher than that. I have seen them much higher than that in years past. > Wurlitzer C173 > flush to plate at hitch pin, however the string angles steeply up and > over an aliquot bar on the plate and continues to the bridge. The > angle of deflection of the string leaving the hitch pin is significantly > sharper than the string leaving the Baldwin hitch pin. How high are the aliquots? Passing the string up from the bass of the hitchpin and over the top of an aliquot places a very similar stress on the plate to that of the vertical hitchpin arrangement. > So what the heck do all these numbers mean? > > 1) Baldwin hitch pins are not significantly bigger than other hitch > pins .223" compared to .168". You can buy smaller diameter pins > than the type Baldwin uses if you need to. Actually, as close as these pins are to one another, this can be a significant difference. The pin that we normally use is nominally 0.187". We sometimes alternate these with a nominal 0.219" pin. The larger pin is used in the center of each group of three pins for better string spacing. > 2) The plate thickness and hitch pin spacing are thinner and closer > on the R grand than on the Wurlitzer. Does that mean that the > Wurlitzer would be a good candidate for adjustable pins? The holes > are drilled straight and spaced farther apart than the Baldwin. Probably. Keeping in mind that the Wurlitzer uses a vacuum-cast plate. (I think.) > What would influence you to replace a set of 'standard' hitch pins > with adjustable, if these plate and hole measurements 'seemed' to > meet or exceed what is currently used on new manufactured > pianos, such as Baldwin or Charles R. Walter? Several things. I like the vertical hitchpin better from a purely acoustical perspective. Especially in the bass section. I believe it to be a better string termination. That is why I designed them into the Walter 190 from the very beginning. They were not adapted to an already existing plate design. I most often use them to give me a longer back scale that is easily available using the original hitchpin arrangement. This is especially true in the treble sections of some pianos using very short "tuned" aliquot systems. The backscale is so short as to restrict the motion of the soundboard. And, as I mentioned above, I often use them in the bass section for these same reasons. Most of the backscale string lengths used on pianos under 185 to 190 cm are woefully short. Vertical hitches can help quite a lot. It is pleasant hearing a bass section in a short piano that actually has some fundamental in it. Del Delwin D Fandrich Piano Designer & Builder Hoquiam, Washington USA E.mail: pianobuilders@olynet.com Web Site: http://pianobuilders.olynet.com/
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