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Kranich & Bach Player System

These pictures were supplied to Player-Care.com by Tim Geinert.
The effort here is to increase the amount of available information about this player system. If you have any additional pictures or information, please send them to John A Tuttle.
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Tim Geinert
Registered Piano Technician
Wapin Company, LLP
http://www.wapin.com

Unlike any system I have ever seen, the Kranich-Bach employs a (what I call) "through the valve" method of delivery vacuum to the striker pneumatic (note bellow). Initially, when I learned that the valve gap was a very shallow 0.020", I thought, 'How can this thing work efficiently?'. Then it dawned on me that the vacuum doesn't pass around a valve and through the gap to reach the bellow. It passes right through the valve facing. So, that started me to thinking about the square area of the gap in a 'normal' system verses the square area of the 'through the valve' system. Using some fairly common figures, I started doing the math. Let's say the size of the intake valve port is 5/8" and the gap is 0.035". The total square area through which air can pass is 5/8" x 0.035", or 0.0219 sq. in. Now. looking at the Kranich-Bach valve facing, you have an I.D. of 0.425" with a crossbar that's 0.135" wide. (see Fig 3.1) So, doing some simple math, we have the square area of a circle , or 3.1417 x (0.2125" x 0.215") = 0.1418 sq. in. minus the area of (basically) a rectangle measuring 0.135" x 0.425", or 0.0574 sq. in. That leaves us with a total square area through which the vacuum can pass of 0.0844 sq, in. As you can see, even if the holes in the valve facing were 1/2 as big, the area for the vacuum is still twice as much as it is with a Standard-type valve. Let's say we increase the valve gap of the Standard to 0.040". Then the total square area equals 0.025 sq. in. Still much, much less than the Kranich-Bach.

Now, concerning the narrow 0.020" valve gap, the question arises, 'Doesn't it impede performance? Well, let's examine that. Since we have already eliminated the aspect of 'sucking' the air out of the bellow, the only thing that remains is letting the atmosphere back into the bellow. So, let's take a look at the I.D. of the (what is essentially the) exhaust valve port (which is part of the bellow). (see Fig 7) It has an I.D. of 0.485". With a gap of 0.020", the square area through which atmosphere enters into the bellow is 0.485" x 0.020", or 0.0097 sq. in. So, based on those figures, one would have to assume that the narrow valve gap is problematic. What happens if we increase the gap to a more normal 0.035"? Then the square area is 0.0169 sq. in. Now we're getting closer to what one might expect is normal, but we're missing one important part of the equation, and that is the size of the striker pneumatic. While there are no pictures that actually show the exact measurement of the bellow, in Fig 7 we can see that it is almost exactly 5" long and about 3/4" wide. If it's like most striker pneumatics, it has a span of 1-1/4". That equates to a working area (internally) of 1.875 sq. in., or about 2 sq. in. or air space. Comparing that to the size of a regular Standard striker, which measures 4" x 1/1-4" x 1-1/4", we find that the internal square area is approximately 2.5 sq. in., or just over 30% bigger. The point I'm trying to make is that it seems that the small gap is more than adequate to allow air to 'fill up' the bellow almost as fast as the larger gap and a larger bellow. I admit that I don't have the math skills to figure these things out precisely. However, in terms of expression, the ability to suck the air out of the bellow at a very fast rate seems to me to be the important operating characteristic. Here's why.

In order to perform a stacatto, the bellow has to close very fast. We've already proven that the Kranich-Bach valve can do that very well. But why? We have to remember that there is 14.7 lbs/sq in of 'pressure' at sea level. If we create a vacuum of let's say 7"-10", that brings the lbs/sq in down to

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This page was last revised February 26, 2010 by John A. Tuttle, who Assumes No Liability
For The Accuracy or Validity of the Statements and/or Opinions
Expressed within the Pages of the Player-Care Domain.
Cartoon Graphics by E7 Style Graphics (Eric Styles)


Since "Player-Care" is an internet business, I prefer that we correspond via E-Mail (click here to fill out the 'Request Form'). However, if I'm not in the middle of some other activity, you can reach me at 732-840-8787. But please understand that during the hours from 9AM-5PM (EST), I'm generally quite busy. So, I probably won't answer the phone. If you get the answering machine, please leave a detailed message stating the reason for your call. Also, repeat your name and phone number clearly and distinctly. By necessity, I prioritize everything in my life. And, if you call and just leave your name and number, and ask me to call you back, it might be a day or two before I return your call. Why? Because I don't know why you want me to call and I might not be prepared to assist you in an effective and efficient manner. If you leave me an E-Mail address (which I prefer), spell it out phonetically. The more you do to help me, the more I can help you in return. Don't rush. You have four minutes to record your message.



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