Oorebeeks Punch'ns

[Roger Jolly]

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Hi Stephen,
                        I'm glad to hear you are going to do some more in 
depth scientific testing, with actions using state of the art 
equipment.  One thing not to over look in your motion analysis, is to keep 
the centre pinning fairly tight. All bushings should be accuately reamed 
with a parallel reamer, to ensure equal friction on both sides of the 
bushing. It will help to reduce some of the erratic behavior, of the 
components.
  Very accurate boring of the hammer, so there is no heavy/ light side will 
also be important. Harold Conklin found this out in his 1970's SloMo 
analysis. The bore angle will make the  tenor/ bass hammers behave 
differently than the non angled treble bores.

I am sure you have thought of these factors.  But some food for 
thought.  If you can get your hands on, a set of Steinway Teflon bushed 
wippens and shanks, you could reduce the felt bushing anomaly,  and more 
accurately see the timing and flexing motions.

Regards Roger

At 01:52 AM 4/4/2005, you wrote:
>Roger proposed some explanations for tonal changes with Andre's Wurzen 
>punchings:
>>Moral of the above points:   The pianist works with after touch to create 
>>tone. Any and all things that we can do, to make this accurate and 
>>reliable, the happier our clients will be.
>
>Yes. True in multiple ways Roger.
>
>Andre was kind enough to send me some sample punchings which I have done 
>some preliminary investigation with. Some of the behaviour which has been 
>discussed here can be seen, as well as some surprising results. Before I 
>can make proper conclusions I'll need to do some more controlled 
>experiments, as well as compression tests....the latter I'm waiting for a 
>new Instron testing machine which has finally been ordered and should 
>arrive within about 2-3 months.
>
>For now, high speed videos (forte blow) show that there is an obvious 
>mechanism whereby the properties of the punching can influence the hammer 
>during escapement, and consequently the touch and tone. [It's not easy to 
>set up these videos with a single high speed camera oberving events that 
>are not in close proximity] I've also looked at the dynamic behaviour of 
>the punchings themselves using macro high speed imaging. Green woven felt 
>punchings show a definite sloppiness and tendency to shear on impact, and 
>a much less clean deceleration, with distinct wobble of the key off the 
>vertical as the punching is compressed. These observations are not seen 
>with the Wurzen punching, presumably because the superior interlocking of 
>fibres prevents the shearing observed with the woven material.
>
>I intend to do more testing of these phenomena and will report back on the 
>conclusions (probably write an article about this), but it won't be till 
>I've got the new testing machine installed in the lab and operational. In 
>the meantime, if anyone would like to discuss the observations or examine 
>the videos, I'll be attending the MARC convention this week, so just 
>introduce yourself when you spot me and I'll be pleased to meet you.
>
>Stephen
>--
>Dr Stephen Birkett, Associate Professor
>Department of Systems Design Engineering
>University of Waterloo, Waterloo ON Canada N2L 3G1
>Director, Waterloo Piano Systems Group
>Associate Member, Piano Technician's Guild
>
>E3 Room 3158
>tel: 519-888-4567 Ext. 3792
>fax: 519-746-4791
>PianoTech Lab Room E3-3160 Ext. 7115
>mailto: sbirkett[at]real.uwaterloo.ca
>http://real.uwaterloo.ca/~sbirkett
>_______________________________________________
>pianotech list info: https://www.moypiano.com/resources/#archives

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