Lacquer fight!/ Internal friction

[Richard Brekne]

Hmmm.. A rather non-committant posting if I may say... tho if I may read 
between the lines, and go along with the few specifics you give as to 
raw felt behaviour towards the end of this posting... I am lead to 
believe that what my ears and experience tells me is probably rather on 
track.... namely that treatment of hammers (applied felt as it were) 
with needles has neccessarilly and decidedly different affects then 
lacquering.  Again... leaving whatever value judgements one can make out 
of the question for the present, that rather defeats any argumentation 
that claims both proceedures accomplish the same thing.

It may be true then that both methods can achieve a similiar (for not to 
say nearly identical) rebound time, which may account for why some find 
some similarities in sound charachteristics... yet  you hint at the 
possibility that this rebound time is not as great a determinant factor 
as has been assumed up to now... and , it seems to me that  implied in 
your lines below is a possiblity that even same rebound time 
accomplished as a result of differring combinations of stiffness and 
internal friction factors can also account for a variance in the 
<<signal>> (if I may use that word)  transfered to the string during impact.

Again...   just so no one misunderstands... which proceedure or sound 
characteristic one prefers is really not of interest for the present 
discussion... only whether or not the two approaches do indeed lead to 
significant differences in sound, which in turn give a basis for 
preferences in the first place.

Thanks for the reply Stephen.  I am sure many of us are looking forward 
to seeing more formal results of your studies as they become available

Cheers
RicB



Stephen Birkett wrote:

> Ric rote:
>
>> Grin... prodding is what I do best me thinks...   so let me prod once 
>> more.
>> You seem to make the clear statement that internal friction moments 
>> are critical to the sound resulting in the piano when a felt hammer 
>> hits the strings.... tho you dont go much into detail as to the 
>> hows/whats/whys... perhaps understandably so... but since this 
>> tangent of the discussion seems intent on comparision (for not to say 
>> competition) between <<lacquered up>> and <<needled down>> hammers it 
>> seems central to ascertain whether or not either approach results in 
>> anything particularilly negative in relationship to this internal 
>> friction capacitance
>
>
> Methinks that "you" is me. A little backtracking is necessary 
> here....my research so far has related primarily to the felt material 
> itself, trying to understand the dynamics of felt compression in 
> isolation of the various complications that come from the use of felt 
> in the context of piano hammers. The cart quite clearly needs to go 
> before the horse when working with a material as bizarre as felt (or 
> leather).
>
> We're also in the process of  exploring the effects on felt dynamics 
> due to procedures like needling, tensioning, heat and pressure, 
> softening agents, and including lacquering. This work still focuses on 
> felt  pieces rather than hammers so that the effect of each procedeure 
> can be studied separately with targeted experiments.
>
> The next step (which we want to start on now) is to study the 
> application of felt in hammers, comparing different manufacturing 
> techniques, and especially approaches such as being discussed in this 
> thread.
>
> So Ric, Topperpiano,  Dale, et al, you can see its a little early to 
> be able to go into too much detail yet, if only because it's work in 
> progress. I'm convinced we need to understand the material and 
> processes separately, before we'll have any real understanding of 
> hammers. The work will all be published eventually.
>
>> The following quote from Bernhards last claims authority on a a 
>> related issue of this subject matter...
>>    "Measurements on hammers parameters has been done by Anatoli Stulov,
>>    where he measured felt stiffness and rebound time.He found
>>    differences of a factor of about 100 % in the rebound time between
>>    different new hammer sets made by diverse makers. (Abel, Renner,
>>    Imadegawa)
>>    The rebound time is in correlation with the felts /inner friction
>>    losses/ (or imaginary part of elastic modulus) , not to /stiffness/.
>> Which states outright that rebound time is not correlated to hammer 
>> stiffness.
>
>
> I'm not familiar with any Stulov article which reports what Berhard 
> has indicated above (maybe it's not published). But, in one of 
> Stulov's articles he states: "...it is obvious that the dynamical 
> features of the hammers produced by various firms are very similar 
> indeed, for the various rates of loading. Thus we may state that in 
> spite of the different technologies that the manufacturers of the 
> piano hammers are using, the mechanicaI features of their hammers are 
> rather comparable." This is in reference to the three types of hammers 
> (Abel, Renner, and Imad.).  Those comments, at least, are not 
> consistent with major differences reported above.
>
> I would expect *both stiffness and internal friction to be relevant to 
> rebound time. On the other hand, I'm not convinced that rebound time 
> per se is the important factor that needs to be given such prominence.
>
>> So my prodding leads me to ask do you agree with the quote...
>
>
> See above.
>
>> and would you say that the addition of  lacquer has any affect on 
>> this internal friction, and if so what... and the same question again 
>> with respect to needling.
>
>
> I have yet to do those experiments even for felt itself. But I would 
> be surprised if both of these do not affect both stiffness and 
> internal friction....in other words the loading and unloading curves 
> are independently controlled by needling and/or lacquering. The 
> effects on felt vs hammers will, of course, be different too, and need 
> to be separately studied.
>
> Here's an interesting example illustrating a point. There's a quite 
> large difference in the dynamics of a piece of felt vs the same piece 
> cut into two layers and re-assembled. The latter will never behave 
> like the former. Or, equivalently, layered felt stacks with identical 
> felt behave differently according to the number of layers (even after 
> factoring out the thickness). Now consider needling and lacquering and 
> go figure....
>
> One point that's also worth mentioning. All of the work you see 
> reported on "piano hammer felt" is actually working with piano hammers 
> as objects, not felt itself. These are typically struck against 
> immovable surfaces, which don't necessary have the shape of strings. 
> Also the manner in which "forces" and "displacements" are measured can 
> have a dramatic impact on the interpretation of those variables, and 
> the results. Unfortunately, these things are very often not disclosed, 
> let alone discussed, in articles (one of my beefs against Stulov's 
> articles for instance).
>
> Stephen