HAMMER WEIGHT, RATIO AND THREE ALTERNATIVES FOR KEY BALANCING
Hammer weight and action ratio must be included in discussions of touch weight if they are to have meaning in relation to what pianists feel when they play the piano. By knowing the hammer weight and finding the action ratio we can determine, far more reliably than ever before, how the action will feel to the pianist. The use of lead weights, springs or magnets to make a desired down weight in the key will not make up for badIy matched hammer weight and ratio. Methods for measuring and adjusting hammer weight and action ratio MUST be included in our set of skills if we are to offer fully comprehensive service to our piano playing clients. First you balance the hammer weight with the action ratio, then you balance the keys.
We must realise that "Down weight does not indicate the play weight". Those of us who have taken the time to measure touch weight sooner or later come to find that while one piano with a 50 gram down weight may feel normal when played, another piano with a 50 gram down weight may feel heavy, or even light by comparison. In fact, down weight has very little to do with how the piano feels to the pianist when it is played. When the key is moved at higher speeds during playing, much higher forces are needed to overcome the inertia of leveraged weight components. These forces are into hundreds of grams for medium volume playing and into thousands of grams in fortissimo playing.
A majority of the force needed to play a piano key goes into moving the hammer and a significant force is needed to move the lead weights in the keys. Imagine a piano key as a simple lever like a catapult with a counter weight on the short end. You, the pianist, have to push down on the short end to move the hammer out on the long end. If the hammer is too heavy and/or too far out on the long end then it will take more force to accelerate the hammer. If the force needed to move the hammer is too high we can make the hammer lighter and/or move it in closer to the pivot (reduce the ratio). Our challenge is to find and use a combination of hammer weight and ratio which produces a playing weight that matches and is balanced with the physical capacity of the pianist.
Hammer Weight in Relation to Tone and Voicing (Fig.1 )
Hammer weight not only has a major effect on play weight, it also has a major effect on tone. For this reason we need to include the tonal effects of hammer weight in discussion of designing touch. I'd like to offer a model for thinking about the relation between hammer weight and tone. Voicing quality emanates from how the hammer hits and rebounds off the string. Energy goes into the string and causes it to vibrate as a result of the hammer weight and its velocity at the time of impact. The string vibration and resulting tone quality is a function of the harmonic mix, which is influenced by how the hammer damps the string as it bounces off and this is a function of the weight, density, and resiliency properties of the hammer.
The pianist controls the velocity of the hammer. This leaves hammer weight, felt density and felt resiliency as the factors which the piano technician can control in the process of voicing.
Voicing is typicallv associated with such methods as needling, ironing, shaping, and lacquering by which we effect the density and resiliency qualities of the hammer felt. Setting the hammer weight has not been included in what we traditionally call voicing and this is a major oversight in our profession. Over the last ten years the use of methods that make it possible to study and change hammer weights in working pianos are proving that hammer weight is the foundation of voicing.
To illustrate the point I'd like to share a real world experience, the likes of which we see time and time again. Last Spring my Dutch colleague, Frans Pietjouw was helping Wim Feldhaus, Reint Ezenga and Arie Lugtenburg evaluate a Steinwav S grand: The hammers were light -in the low zone, the tone seemed ok. Frans clipped several grams of weight onto some sample shanks bringing the weight up to 114 high zone. When thev listened to the change in tone jaws dropped in astonishment. Not only was there more tone, YOU could feel the fullness of the tone in the room. The difference was so dramatic that Wim proclaimed "What is voicing?". His words speak to all of us. We need to re-evaIuate what voicing is and understand, through shared experience, how hammer weight plavs a fundamental role in tone production along with the density and resiliency of the felt. Whenever we stick a needle into the hammer we should be questioning -"Is it the right tone weight?"
Hammer Weight and Spielart (Fig.2)
In this model we see hammer weight as the primary and common element in touch at tone which together have a profound influence on the quality of the "Spielart". Hammer weight is the primary element in the play weight. Secondary to the hammer weight is the action ratio, which must be designed to be compatible with the hammer weight along with whatever method is used to balance the keys in order to produce an acceptable down weight and play weight. Hammer weight is the primary element in tone. Secondary to the hammer weight in terms of tone are voicing methods that effect the density and resiliency qualities of the hammer feit. This model supports the view that the action is built around the hammer weight. Hammer weight is the primary variabie in play weight and tone and the resulting spielart.
Now that I've hopefully sorted out some of the complexity of touch weight components that contribute to spielart I would like to proceed by outlining and discussing the three basic components of play weight also known widely as "dynamic touch weight" or the amount of force the pianist exerts on the key to elicit a desired tone.
I. Hammer Weight
If we are to know the weight of a hammer we need ta measure it ourselves. Hammer weight mav be measured "on the shank" by tipping the hammer onto a digital scale -a measurement called Strike Weight.
Extensive studies of pianos have produced zones for rating strike weight and hammer weight. Hammer weight levels vary widely and hammer weights from note to note vary greatly. This creates great variation in tone and touch, both in level and note to note consistency. Hammer weights may be measured and errors in level and smoothness fixed by adding or subtracting weight as needed. The improvement to the quality of the piano as perceived by pianists can be enormous.Hammer Weight Balancing is a new class of service that technicians may offer their clients.
The ratio indicates the amount of leverage that the plaver exerts on the hammer. In the catapult analogy a higher ratio means the hammer is farther out on the end of the lever, and when closer in to the pivot the ratio is lower. Leverage is easily measured by finding strike weight ratio which is the amount of weight on the front of the key needed to balance 1 gram of hammer weight. Strike Weight Ratio is found by measuring Front Weight, Up Weight, Down Weight, Kev Weight Ratio, Whippen Radius Weight and Strike Weight. The values are plugged into the Equation of Balance and the strike weight ratio is found by calculation. Also useful, and intuitively simpler for the novice to understand is the "Short Cut" method. With this method the hammer and shank are lifted out of the way and the weight of the key, key leads, and whippen are zero balanced using temporary weights on the back of the key. The hammer is then flipped down and the Up and Down Weight found and averaged to find the balance weight of the hammer/ shank. Dividing this by the Strike Weight gives the strike weight ratio which indicates the overall action ratio:
a. Ease the key bushings and lubricate with dry Teflon powder or talc. (Consider this as standard preparation for key bushings)
b. Flip up the hammer and zero balance the key and whippen using temporary weights. The key is zero balanced when moving the key up and down by the front or back end with a gram gauge gives equal readings in either direction, or when the key bounces in a like manner in either direction.
c. Flip down the hammer and measure Up Weight and Down Weight. (Leave the tem- porary weights on the key!)
d. Find the Balance Weight of the hammer (Strike Balance Weight) as (D+U)/2
e. Measure the Strike Weight
f. Divide the Strike Balance Weight by the Strike Weight R=SBW/SW
g. Repeat for at least 6 samples to find average level. Recommended sample notes are #16,17,40,41,64,65.
Ratio may also be measured by using distance by measuring the movement of the hammer compared to the movement of the key.
Ratio may also be calculated by measuring the 6 lever arms and plugging the figures into a formula. I offer the weight method here because we are concerned with weight and weight ratios when balancing actions. We find that weight ratios are more relevant and easier to measure than distance ratios.
The Strike Weight Ratios are usually found to be between 5.0 and 7.0. Variations of plus or minus 0.3 are normal.
High Ratio levels give the pianist less leverage on the hammer, are compatible with lower weight hammers, and require longer blowand shallower dip. Low Ratio levels give the pianist more leverage on the hammer, are compatible with higher weight hammers, and require shorter blow and deeper dip.
Ratios as low as 5.0 may be made to work with a blow distance of 44.5mm and a key dip of 10mm if the action is set up optimally. In some instances when the ratio is found or made to be 5.0, a 44.5mm blow the dip may require an excessively deep dip, like say 11.0mm. This indicates the geometry of the action is not optimal and variables such as whippen and hammer centre pin elevations and/or spread, hammer bore, magic line, shank length, knuckle position, and key elevations need to be looked at and improved as needed. Geometry is a whole other subject which deserves and needs our attention.
As a general rule a high zone hammer is a good match for ratios closer to 5.0. Medium zone hammer weights work weil with a ratio of 6.0, and low zone hammer weights closer to 7.0.
Ratio is a function of distance parameters in the action and maybe changed by moving distance components such as balance rail pin position, capstan, knuckle, and the shank length. Changing the ratio can bring enormous improvement to the quality of the piano as perceived by pianists. This is a class of service that technicians mav offer their clients. My extensive experience as a Touch Design consultant has taught me that pianists respond most positively to ratios levels in the range from 5.0 -6.0 range.
III. Key Balancing -Three Alternatives
The weight of the hammer, shank, and whippen, sitting on the back of the key, translates to an upwards force at the front of the key. Without keybalancing down weight and up weight are too high. To reduce the down weight and up weight to levels that pianists like, the keys must be balanced. There are three alternatives: lead weights, springs, and magnets.
1. Key Leads
The most common way of balancing piano keys is to installlead counter weights in the front of the key. The amount of counter balancing force that the key leading provides may by measured by removing the key from the action, tipping it on its balance point, and resting the front of the key on a digital scale. The measurement is called Front Weight. There are three methods for installing key leads:
a. Smooth Down Weight
The traditional method is to put whatever amount of lead weight is needed in the key to make the key have a specified down weight, usuallv in the vicinity of 50 grams. From an engineering standpoint, this is a crude way to set the downward balancing force. The downward balancing force of the keystick component maybe measured directIy by tipping the key onto a digital scale. The measure is called Front Weight. It's a shock when you start looking at front weights resulting from industry standard weigh offs even on high quality pianos. One immediateIy becomes aware of many variations from piano to piano both in level and note to note. These wide variations are even found in like makes and models made during the same period in the factory.
These variations are caused by variations in strike weight. ratio, and friction which combine to create enormous inconsistencies in the key leading. In reality there is no such thing as a standard leading when down weight was used as the primary specification to set the key leads. When hammers or parts are changed the meaning of the key lead pattern is lost and the keys need to be re-weighed. Most technicians don't bother to reweigh the keys and a lower standard of touch weight is the rule once the piano is out of the factory.
b. Down Weight specification with Smooth Strike Weight and Friction
A finer quality of tone and touch results from down weight balancing when hammer weights are made to a smooth curve at a level that matches the ratio combined with smoothing or accounting for the friction during the down weight weigh off. This results in more consistent front weights from note to note and it is noticed that pianists feel and hear the improvement, but variations in Ratio still make for significant inconstancies in the front weights. Therefore even with this rigorous approach the meaning of the key leading pattern is lost when parts are replaced.
c. PTD balanced keys
The highest standard is produced with "Precision Touch Design" or PTD which is the trademark name for the patented method of balancing keys using Front Weight specifica- tions that are generated by calculation using the "Equation of Balance". PTD instaliers are trained to work in conjunction with a Precision Touch Designer who provides consultation and specifications for Front Weights, Strike Weights and Ratio. The designer creates front weight specifications which follow a perfect curve. The Front Weight curve mirrors the Strike Weight specification which also follows a perfect curve. PTD instaliers instalI lead weights with the keytipped on a digital scale, adding lead weights to the key in order to make the Front Weight specification. The result is a perfectIy smooth scale of front weights with no inconsistencies from note to note.
The advantages to this precision approach are two fold; The keys respond more accura- tely to the desires of the pianist with smooth front weights by virtue of a more smooth inertial characteristic and the keys need not be re-balanced when hammers or parts are replaced. The integrity of balance is maintained when replacing hammers by making hammer weights conform to the original strike weight specification that was used in the design of front weight. My vision for the future is that keys are balanced to smooth front weight curves in the factory. When technicians want to improve or change the touchweight in the field they refer to the strike weight specifications and raise or lower the level of hammer weight in order to make the action heavier or lighter. It's a new way of thinking!
2. Wippen Support Springs
Whippen support springs have long been used by even the finest of piano makers for over 150 years. Whippen support springs are always used in conjunction with key leads. By countering the weight of the parts sitting on the capstan, less balancing force is needed by use of key leads. Whippen support springs may be safely used to reduce down weight and up weight by as much as 17 grams and are more conservatively set to work about 12 grams off the touch weight.
There are many misconceptions about support springs that comethrough their misuse. Unfortunately all piano manufacturers, as far as I know, and most piano technicians don 't understand how to use springs optimally and typically set the down weight with key leads with the springs attached. Variations in spring tension create huge inconsistencies in the front weight and this is not appreciated by pianists. Many piano makers make the springs to work too hard, in some cases taking as much as 40 grams off the touch weight. This causes "Bouncy key" and a poor feeling action. 50 it is not the springs that causes the problem it is how they are misapplied. Whippen support springs are an underutilized resource and deserve our re-evaluation.
A better approach with a support spring type action: One might for instance set down weight, with the springs unhooked, to say 62 grams by adding key leads, then the springs are hooked up and tension adjusted to bring the weight down to 50 grams. This keeps the front weight pattern more uniform and the action feeling more smooth. It also means less lead is needed to balance the keys and this makes the action feel lighter when played. Keystick mass is also reduced which is found to improve repetition. This we know from listening to what pianists say about these types of actions.
It must be remembered that the effect of the lead weights in the keys is minor by com- parison to the force needed to move the hammer. To simpIy install whippen support springs in order to lower the down weight without regard for matching hammer weight and ratio islike playing Russian Roulette... Sometimes it works, sometimes not. Whippen supports springs deserve a separate writing as well.
In the year 2000, Stanwood Piano innovations introduced adjustable whippen support springs which give the ability to adjust the touchweight of a note in a matter of seconds. This is not a new idea, but 50 far as we know it's application is new in regards to whippens with the modern configuration of support springs such as we use today. Currently, adjusstable whippen support springparts are made for steinway and Mason Et Hamlin by Tokiwa for Pacific Piano supply and Pianotek in the US. Renner is expected to produce an adjustable support spring whippen for steinway replacement parts in the near future. If the existing parts are of good quality we retrofit the whippens with adjustable support springs. (This is a job for the specialist).
In regards to PTD, we offer adjustable Whippen support springs as a high performance option for those who want the extra special quality and for situations were performance demands are at their highest as in concerts and recording sessions. We find the spring design actions very useful in upper or top high zone hammer weight, low ratio designs because it allows us to keep the front weights down to a reasonable level. On the other extreme they are useful in designing ultra light actions without sacrificing ham-mer weight for clients with special needs. Such actions have allowed pianists who would have otherwise given up playing, for reasons of health or injury, to have a new lease on their piano playing life. I've had two cases were the care givers of terminally ill pianists told me that suddenly having the ability to play and enjoy their pianos in their weakened condition added several months to their life.
3. Velo Magnets
Another recent advancement in key ba-lancing method is the invention of the Dutch inventor Hans Velo who, with the help of his partner Evert Snel, developed a system which relies solely on Magnets -four in each key- to balance the action. It's called MBA Magnetically-Balanced Action. By moving sections of magnets with the turn of a screw the entire keyboard may be adjusted. The installation of section at adjustments is technically complex and haspractical application for pianos on which many different pianists might be playing. Some time ago we expressed an interest in using a simplified version of MBA that we might offer through the PTD world network. In November of last year Frans Pietjouw arranged for me to meet and work with Evert Snel and Hans Velo at Snel's piano shop in Werkhoven, Netherlands. Snel and Velo came up with a very nice simplified MBA system called SMBA which eliminates the adjustable rails and makes the whole system more affordable. Two magnets are mounted in rails attached to the key frame just in front of and behind the balance rail. Two more magnets are mounted in the key in front of and just behind the key button. The magnets may be adjusted bythe turn of the screws to effect a change of plus or minus 5 to 10 grams.
We also found that the two systems, SMBA and PTD work very well together and we look forward to offering SMBA as a high performance option with PTD. We are also finding that SMBA may be used effectively in various combinations with equation designed front weight patterns. I promise to report more on these developments after we've had more experience with this exciting new approach.
I've seen many examplesof fine piano restoration in which the tuning, pinblock, strings, soundboard, bridges, action regulation, friction control and action geometry were all well executed but the more fundamental issues of hammer weight and action ratio were not addressed. I found that pianists tend notice the hammer weight and action ratio first and if it is not right, then all the rest of our work is wasted. On the other hand if we pay attention to hammer weight and ratio and take the time to assure that the combination is ideal then the results of all the other work we do to pianos will be even more appreciated and our efforts produce the most optimal effect. Spielart results from many components, (not the least of which is the pianist), working in combination. When things work weil, the experience for both pianist and listener takes on magical and emotionally transcendent qualities. We know that the piano can either help or hinder the complex and seemingly instantaneous translation of musical and expressive intention along it's path from the mind of the pianist, through the muscular/skeletal body mechanic, across the interface from finger to key. through the action mechanic to the hammer and it's transmission of energy into the string resul- ting in music!
A well balanced action that plays flawlessly supports the artistic endeavour of the pianist because they waste less energy overcoming deficiencies in the action mechanic and they are freer to focus on tech- nical facility and artistic expression. As piano technicians we can help by remembering always: First you balance the hammer weight with the action ratio, then you balance the keys! I sincerely hope that this article will help us to sort out the more fundamental issues of touch weight.