Dear Vince, Thanks for your question. <What things tell you when the capstans should be moved?> Answer: We move the capstan line in or out when touchweight indicators tell us the action is under or over leveraged. Explanation: To determine if an action is over or under leveraged we measure the leverage and if it does not conform to our standard then we change it. Leverage may be controlled to some degree by choosing parts wisely. Post '84 Steinway parts with the knuckle further out yield maximum parts leverage. Pre-84 Steinway parts with the knuckle further in yield minimum parts leverage. Japanese, Renner USA, and most others fall in between. ****************************************** Warning!! Pre 84 Steinway parts with stock Steinway hammers are likely to produce heavy action. The owners of Steinway recently told me that "pre 84" does not mean these parts should be automatically used on all pianos made before 1984. Perhaps they should change the name to "low leverage" ****************************************** If the leverage cannot be brought to a desired level by changing parts then the problem most likely is in the key ratio. Key ratio is nominally 2:1 for modern pianos, but for a variety of reasons this is often not the case. Actions with inappropriate key ratio may be corrected by moving the capstan line in or out. This involves altering the wippen heel so that the capstan is centered on the cushion felt and the capstan contact point is in a line between the wip center and the balance point of the key. To measure leverage we use a touchweight parameter called strike ratio. *Strike ratio is the amount of weight needed to balance one gram of hammer weight at the front of the key. Strike ratio gives an indication of how fast the hammer moves in relation to the downward movement of the key. It is therefore a useful indicator of the dynamic quality of the action. In fact we have found that the dynamic playing quality of the action may be predicted if the strike ratio and the hammer weight are known. More on hammer weight later... The strike ratio level of a piano action is determined by measuring strike ratio in sample keys and calculating the average. For minimum significant accuracy we use a sample of six measurements on notes 16,17,40,41,64,65. More accuracy is attained by measuring all the c-c#s. Maximum accuracy is attained by measuring all 88 notes. *****Strike ratio is determined by finding the strike balance weight and dividing it by the strike weight.***** Measuring strike balance weight: 1. Lift up the hammer and shank. 2. Place temporary weights on the back of the key such that the balance weight of he key and wippen becomes zero. 3. Lower the hammer and shank back down 4. Measure upweight and downweight. 5. Calculate strike balance weight as the average of upweight and downweight *Strike weight is the amount of weight that hits the string Measuring strike weight: 1.Remove the shank from the rail 2.place a hard felt wedge on the pan of a digital scale and tare to zero. 3.Place the striking surface of the hammer face down on the felt wedge such that the strike line of the hammer is resting on the knife edge of the felt wedge 4.Tip up the flange so that it is oriented vertically, 5.Rest the bottom end of the flange on a roller bearing such that the axis of the roller bearing is aligned vertically with the axis of the center pin, with the shank perfectly horizontal. 6.The resulting scale reading indicates the strike weight. Again: Strike Ratio =3D Strike Balance Weight/Strike Weight Acceptable strike ratio levels fall in a range from 5.0 to 7.0 If strike ratio level is below 5.0 the hammer will move too slowly in relation to the key and excessive key dip will be required to regulate the action. If strike ratio level is above 7.0 the hammer will move too quickly in relation to the key and excessively shallow key dip will be required. We recommend 5.5 as a modern standard for strike ratio. The best pianos surveyed were close to this level. The 5.5 standard emulates the Hamburg Steinway which is the only piano surveyed that was consistently at this level with consistently the best action. ********************************* I offer the following range guidelines for strike weight and strike ratio. These ranges are the result of 4 years of survey and analysis of piano actions. The primary touchweight studies were carried out by myself and the following technicians: Russell Gordon RPT Tony McKenna, Belmont Mass Bill Ballard RPT John Foy RPT STRIKE WEIGHT RANGE GUIDELINES: Note 1 22 44 66 88 =20 14.8-------13.7-------12.1--------9.8---------6.9 F U L L T O N A L P R O J E C T I O N 12.4-------11.5-------10.2--------8.3---------5.8 M E D I U M T O N A L P R O J E C T I O N 10.3--------9.5--------8.4--------6.7---------4.6 L O W T O N A L P R O J E C T I O N 8.0--------7.4--------6.5--------5.2---------3.5 STRIKE RATIO RANGE GUIDELINES Full Leverage 5.0 - 5.7 Medium Leverage 5.7 - 6.3 Low Leverage 6.3 - 7.0 We have found that if a full ,medium, or low strike ratio is matched with a full, medium or low, strike weight a normal feeling action will result when balanced to a normal upweight and downweight. Problems are likely when ranges are mismatched. For instance: Full projection weight hammers matched with low leverage will yield a piano with high inertia that plays like a truck, or: Low projection weight hammers matched with full leverage will make for an action that is excessively light with low=20 inertia. Refer to the table below: TABLE Dynamic touch as a function of Strike Weight and Leverage (Inertia) Leverage S =A6 LOW =A6 MEDIUM =A6 FULL =A6 t ------+----------+----------+----------=A6 r LOW =A6 Medium =A6 light =A6 Xlight =A6 i ------+----------+----------+----------=A6 k MEDIUM =A6 Heavy =A6 Medium =A6 light =A6 e ------+----------+----------+----------=A6 FULL =A6 Xheavy =A6 Heavy =A6 Medium =A6 W ---------------------------------------+ t One final note: The hammer weight may be found by subtracting the shank strike weight from the strike weight. The shank strike weight is the weight of the shank taken at the strike line radius. Shank strike Weight is generally around 1.8 - 2.0 grams David C. Stanwood Copyrights reserved by David C. Stanwood The document may not be reproduced in any other form other than print outs of this document in this form for personal use. =1A
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