[pianotech] New string broke twice

[John Ross]

If the company is matching a string that previously broke, and their replacement breaks, you should as John Delacour wrote, give them a fighting chance, by giving them more information.
They can only make a string with the information they are given.
Some pianos have poor stringing scales, from when new.
John Ross
Windsor, Nova Scotia
On 2011-07-12, at 7:01 PM, Joe Goss wrote:

> Should one also order the pair so the partials will match?
> Joe Goss BSMusEd MMusEd RPT
> imatunr at srvinet.com
> www.mothergoosetools.com
> ----- Original Message ----- From: "John Delacour" <JD at Pianomaker.co.uk>
> To: <pianotech at ptg.org>
> Sent: Tuesday, July 12, 2011 3:25 PM
> Subject: Re: [pianotech] New string broke twice
> 
> 
>> At 16:19 -0400 12/07/2011, Noah Frere wrote:
>>> ...I'm thinking of ordering from a different company, being super careful while replacing, and seeing what happens. If it works normally, I could call Schaff and ask for a refund. If they refuse, no big deal.
>> Did you tell Schaff which note the string came from?  If not then they had no alternative but to make the string to pattern, since they lacked the data required to calculate whether the tension was too high.
>>> FYI the strings that broke - and yes I mic'd them before installing - were .040 core; .118 winding; hitch to winding 5 1/8"; winding length 30 3/4".   The new string will be the same lengths but .039 core and .116 winding.
>> So you have a core of 17.5 or 18 with the length of winding 77.1 cm. Let's add 3 cm to get the speaking length (which is the only relevant measurement) and we get 80 cm.
>> O.116" (your lower figure) is 2.95 mm.  The tension you require to bring this string to pitch is 308 lbs. which is miles too high and the string is bound to break.
>> Use a value of 19400 for K in the formula you find here:
>> <http://pianomaker.co.uk/technical/string_formulae/>
>> and work out what diameter you need the string to be, considering that for mwg. 17.5 you should not exceed 70% or 300, ie. 210 lbs., 220 lbs. for mwg. 18.
>> You will find that the proper overall diameter for the string is 0.093" or less if you use a #17.5 core.
>> Do this every time you order an odd string and you will get no breakages.  Otherwise you have nobody to blame but yourself.
>> JD
>> 
> 

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