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String gauges for restringing. As labelled or as measured?

  • 1.  String gauges for restringing. As labelled or as measured?

    Posted 03-15-2020 14:27
    We're continuing work on restringing the 1869 Broadwood Cottage Grand number 475 with the label signed by Mr Love and having problems between discrepancy of specified string gauges as indicated by small paper labels and what we've measured.

    Attached is a JPG of string tensions and the spreadsheet from which they were derived.

    On the JPG the red dots are from the string gauges as measured and the blue dots as specified.

    I am taking the conversion between string gauge and measurments from  https://www.pianophile.com/LI/0453-A.htm 
    To figure the wire gauge subtract from 29 the number 5. Now divide by 2.
    So for example 29 - 5 = 24 / 2 = 12
    Where does that come from?

    On the spreadsheet column H is as specified and column I is as measured.

    Clearly we need to go back and measure note 6 again.

    To which sizes would anyone restring this instrument?

    The instrument is bicord up to note 46 (A440) and tricord from 47 to the top.

    Best wishes

    David P


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    David Pinnegar BSc ARCS
    Hammerwood Park, East Grinstead, Sussex, UK
    +44 1342 850594
    "High Definition" Tuning
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    Attachment(s)



  • 2.  RE: String gauges for restringing. As labelled or as measured?

    Registered Piano Technician
    Posted 03-15-2020 14:52
    David,

    What kind of wire are you measuring and what are you  using?  Metric wire is lightly smaller than American wire. For instance 13 gauge ASW reads .031" approx whereas 13 gauge metric will read around .0305" or so. It varies a little with tolerances.

    It gets confusing sometimes.

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 3.  RE: String gauges for restringing. As labelled or as measured?

    Registered Piano Technician
    Posted 03-15-2020 23:08
    I would not assume that stringing gauges of today are the same diameters as those of 1869. Wire composition is certainly different as well. Montal gives some equivalent gauges for English and Berlin manufacture in chapter 12 of Art of Tuning (this was from 1865). He also gives equivalents between Berlin and Nuremburg wire. Paul Poletti gives what he considers to be reasonably accurate figures for Nuremburg wire here. There may be other sources of information for gauges of that time, but I am not aware of them.

    I would select an appropriate wire from Paulello, and consult with people who are more familiar with Broadwood than we are in the US.

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    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
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  • 4.  RE: String gauges for restringing. As labelled or as measured?

    Posted 03-17-2020 16:06
    Hello Fred - in fact I am going to be restringing this 1869 Broadwood Grand. David is assisting me in being there to take the strain (or whatever - such as creating spreadsheets of the tensions which he is particularly good at) and supplying me with coffee! - and we've just finished removing the strings. I have been mic'ing them up as we go and, like that time a few years ago when I restrung his 1854 Emerich Betsy Fortepiano (last of the leather covered hammers) I am replacing the covered strings with copper. The bottom 5 singles are copper but the remainder of the covered seem to be iron covered. All will be copper covered and Gregor Heller is going to spin them (again - as he did for the Betsy) The steel (or metals) are annotated by small round labels at their change of gauge stuck to the bearing cloth next to the agraffes. Having mic'ed those up they can be restrung according to the mic'ed diameters in Thous". No question there. Like the 1854 Betsy, I will use use Roslau Blues - which will also be used by Gregor as cores to the covered strings. Two of the bottom singles wrest pins broke on de-stringing. Interestingly, the covering on the original bass covereds goes right over the bridge terminating at the Hitch pins. Here's the interesting part, though: the bottom five single covered have felt 'sleeves' on as they go over the bridge to the hitch pins. Thereafter the bridge is cloth covered under the covered strings and, of course, the bridge pins are much thicker and stand higher than the bridge pins for the metals. Whether we shall replace the 'sleeves' and/or the felt covering on the bridge will be determined by their sound - for we can always loosen off and insert  felt if the bass notes sound too 'bright'. About the 'Screw-Pins - these are not the usual wrest pins but (according to the green 'Notice to Tuners on the Soundboard) are: 'PATENT PIN-PIECE SCREW PINS The Pins, being screwed into the metal and wood, muft not be struck with the hammer.' I like the 'f' in must - reminds me of the olde Bibles and Psalters we used in Peterborough Cathedral when I was a Chorister there. So I had to make some 'new' wrest pins, converted from old Bechstein Grand pins, but with threads of the correct size and tpi. Fortunately I have a Lathe and all that goes with it - such as taps and dies &c. and had to drill out the kneb-hole again after cold forging the square top to oblong top. Then back in the Lathe chuck to turn down the tops to the same distance between kneb-hole and top of pin - 'cos there's no bonking these pins in to make the tops all the same distance off the 'Patent Pin Piece' it all has to be done with measurement and number of turns before inserting the string into the pin.
    But with this Covid-19 around I just don't know when I shall be able to get back to the piano to do that restringing. Well, it's been waiting around longer than me -  it:1869  me:1935 so a few more weeks isn't going to upset it any!      Michael G.  UK

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    Michael Gamble
    semi retired
    Brighton
    01273813612
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  • 5.  RE: String gauges for restringing. As labelled or as measured?

    Registered Piano Technician
    Posted 03-17-2020 18:43
    Michael,
    Very curious that they were still extending the wraps over the bridge in 1869. Montal said he pioneered soldering the ends of the wrap to the core in the 1840s, and by the time he wrote his 1865 edition, makers were either doing that or some alternate. I'm not sure I would bother replicating that feature, but Gregor will duplicate very well. The felt was probably to keep the wrap from buzzing against the bridge pins. That was a real issue according to the testimony of Montal and others. Also, when you are trying to bring them up to tension, the wraps don't really want to slide past the bridge pins. What's going to happen? 

    I believe the wrest pins are held by friction in the wood, and are threaded and screwed only on the top cm or so of the thickness of the plate webbing, so you could tap them in until the threads are about to touch the plate. The purpose, as I understand it, was to support the pin and protect the block against strain. The pin is held against the tension of the string by the friction in the block (meaning that if it is loose, there is little to be done - I suppose you could remove the pin, put a shim in the wood hole, pound the pin so it catches the shim, screw the rest of the way, replace coil on pin. Or, instead of a shim, you could swab some CA in the wood, taking care not to get any on the plate screws).

    In stringing, I would have the pins installed already, and make coils on a dummy pin and transfer them. Making neat coils while turning the pin in the block is possible, but pretty troublesome. But I am very used to restringing with pins in place (the original ones), so it doesn't bother me. 

    Iron covering was fairly common, mostly to make the bass strings less apt to go out of tune with the plain wires when temperature changed. That was pioneered by Érard by the late 1820s. While there is some tonal difference, that wasn't the purpose.
    Regards,
    Fred Sturm
    "Travel is fatal to prejudice, bigotry, and narrow-mindedness." Twain






  • 6.  RE: String gauges for restringing. As labelled or as measured?

    Posted 03-17-2020 19:34
    Fred - thanks so much for your input and help here.

    Yes - the iron plate was really so as to enable really high tension to be achieved whilst the plank underneath supplied the friction. We've been really careful in the size of drill used and Michael's got the two new pins he's made in there nicely.

    I've been a little distracted by international events to look further at the spreadsheet of tensions but we've picked up the error on string 6.

    We're still scratching our heads on the string scaling, the graph of which is "interesting" and in the quarantine of immediately future days I'll look more at it. Whilst Malcolm Rose's book on string tensions gives many examples they're only up to the 1840s. It would be wonderful to be able to look at the string tension graphs of instruments later in the century.

    With regard to guages http://thepianomechanic.blogspot.com/2011/12/i-need-some-piano-wire-or-string-broke.html - gives the formula for the wire gauge as for instance for 29 thou, subtract from 29 the number 5. Now divide by 2.
    So for example 29 - 5 = 24 / 2 = 12 gauge
    Where does that formula come from? Has it always defined the gauge?

    Best wishes

    David P



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    David Pinnegar, B.Sc., A.R.C.S.
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    +44 1342 850594





  • 7.  RE: String gauges for restringing. As labelled or as measured?

    Registered Piano Technician
    Posted 03-17-2020 20:40
    The string gauge formula you cite is the one currently in use. The unit is thousandth of an inch, and that is how it translates to current USA strings. The rest of the world (I believe) all uses metric, and those sizes are comparable but somewhat different. 

    The question is when the current gauge came into use. It may be the same, for all I know, but I haven't found a reliable source that tells me so.  It is well worthwhile to read what Poletti has to say on the topic, even though he is writing about earlier instruments. Basically, he says you should take everything with a grain of salt, since standardization and precision was lacking. Until exactly when? That's the question. Also where and what manufacturers. By the 1880s, things were fairly close to what they are today. But what about 1860s? 1840s? Who knows, and who has done reliable research? There is probably something out there, and if so I'd like to know about it. But I haven't stumbled across it yet.
    Fred Sturm
    fssturm@unm.edu
    www.artoftuning.com
    http://fredsturm.net
    "Tradition is not the worship of ashes, but the preservation of fire." -Gustav Mahler






  • 8.  RE: String gauges for restringing. As labelled or as measured?

    Posted 03-18-2020 05:39
    Fred,
    Very curious? The whole project is a learning curve in which one tries to 'correspond' with the Broadwood workforce who designed and who physically made it. 
    An interesting side-issue is that last November I went to the Surrey Archive Centre where all the Broadwood books and documents are gradually receiving treatment from the effects of water ingress through the roof of the Broadwood Mansion 'Lyne House' in which they had been stored. One such tome (big, I mean, very large) I got from the Vaults at the Centre was literally WET. The pages were stuck together and the Copper-Plate ink handwriting in it was blurred so I decided therefore not to attempt opening it fully - but returned it to the Librarian. Another of their Day Books (one of several I got from the Vault via the Librarian, was the horrific statements where vast quantities of Grands in storage were burnt in the horrific factory fire at 6:oo on the evening of Tuesday, 12th August 1856 which destroyed two of the three  Factory premises at Horseferry Road, Westminster. Against the numbers of those pianos was writ: 'Burnt' - and here I was, holding the actual Day Book from that time which showed this. Creepy ain't in it. Spooky is. A book: "Broadwood by Appointment a History" by David Wainwtright  Quiller Press (University of Cambridge) ISBN 0 907621 10 4 is required reading for this amazing Company. Page 172 - 173 describes the event of the fire.
    Wrest Pins: I haven't told you all regarding the breaking off of the two rusted-in Wrest Pins. They sheared off just above the maroon painted 'Patent Pin-Piece' and could not be extracted. The wrest-pin is, you understand, threaded fully from its tip to within 1/4" of the kneb-hole. We attempted extraction, but were in danger of the Left-hand threaded extractor breaking. We therefore drilled two new holes into both Pin-Piece and Wrest Plank beneath it. In fact the standard on that plank is for the holes twhich emerge under the plank to be smaller in diameter. The Pin-Piece was thern drilled 'tapping' size with a slight canting toward the Keyboard the full length of the inserted part of the wrest pin. Then the Pin-Piece was tapped - but not the wrest plank - the thread on the wrest pin would do that and keep it tight. The green 'Notice to Tuners' on the Soundboard reads "Should a String Break. -- Take the coil off, without drawing the Pin, then turn the Pin up 1/8 and 1/16, cut the length of new wire off three inches behind the pin, and insert the end in the Drilled Hole. By 'behind the Pin' is meant, of course, on the keyboard side of the Pin. So these 'Screw - Pins' are about 0.281" dia. and 2 1/4" long. In making these replacement 'Screw-Pins' I first ran a Die down them to within 1/4" of the Kneb-hole, then put the Pin in the chuck to take a smoothing rounded cut off the end. At this point I cold forged the top end from the standard Square to the new standard Broadwood Oblong. The excess over 1/2" from the Kneb-hole to the top I turned off in the Lathe. I also had to drill out the Keb-hole to accept a large 'fit' of the largest core of the new Covered string. It is difficult to cold forge and at the same time ensure the tapered Oblong runs true, so I made more of these Screw-Pins than needed. Fortunately at least two of these new Oblong tapered Screw-Pins do run true. It is a bit disconcerting to turn a wrest pin only to find the 'T' hammer is running out of true - isn't it? And here's the strange part to this Tale of a Screw-Pin - the thread Broadwood used was NOT Imperial - but M7.
    Michael G   UK 





  • 9.  RE: String gauges for restringing. As labelled or as measured?

    Registered Piano Technician
    Posted 03-19-2020 12:33
      |   view attached
    Sounds like an ultra-challenging project! Kudos for accomplishing all that.

    I was just provided with a spreadsheet showing diameters of many historic to modern wire gauges, which I'll attach. It seems that the English wire gauges from the second half of the 19th century are quite close to modern, off by only a half size or so. It was prepared by Isaac Oleg, an accomplished French piano technician.

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    Fred Sturm
    University of New Mexico
    fssturm@unm.edu
    http://fredsturm.net
    http://www.artoftuning.com
    "We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
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    Attachment(s)