Grand Action Touch-Weight Analysis & Regulation ~~~~(Also similar for Upright Pianos)
By Rich Van Slooten – A440 Precision Piano Tuning – Ph: 719-685-1417
Pianists are often are called upon to practice or perform on instruments (sometimes their own) which differ quite widely in touch, feel , dynamic range, and responsiveness from key to key. Obviously, regulation of the action is a significant factor related to the tone and dynamic range of the instrument, and is a necessary prerequisite step to touch-weight regulation. However there are certain mechanical fabrication ‘action build’ issues that regulation or voicing won’t change. Some pianists will comment that it takes an overwhelming amount of energy to play a certain instrument or that they tire very quickly when playing their instrument.
- Pianists generally do not realize that even the most prestigious piano manufacturers do not perform touch weight analysis/regulation on the actions that go into factory built pianos. This is left to the after-market service industry – i.e., a piano technician such as myself, who has acquired specific training, expertise, and has the necessary tools and equipment to perform intricate touch weight regulation.
- The proper balance weight of the three major elements of the piano action (key stick, whippen and hammer) and the minimization of dynamic friction in pivot points, felt bushings and action centers is essential to building an action that has consistent touch and feel across all keys in the keyboard.
- Besides tonal quality, this evenness of touch and response from key to key is what pianists appreciate in an instrument that has been touch-weight regulated.
Often while tuning a piano, I will encounter keys that are harder to depress or are sticky or unresponsive. Typically, I will quickly test the down-weight and up-weight of the particular key with my gram weight set. The down-weight, or the weight required to set the key stick, whippen and hammer in motion should be around 50 grams. Conversely, the up-weight, or the amount of force that the hammer, whippen, etc. will push back – once depressed should be in the range of 30 grams.
- The amount of Friction in the lever arm assembly is expressed as: Friction = (Down-weight – Upweight)/2. Friction typically should be in the range of 9-10 grams.
- So the ‘key’ parameters are: Down-weight (approx. 50 gms), Up-weight (approx 30 gms), Friction (approx. 9gms).
Surprisingly, I have found keys in the bass section that have down-weights in excess of 80 grams, and in excess of 60 grams in the mid-range and upper treble. Often I will find keys side-by-side with down-weight or up-weight differences of 10 -15 grams or more. This much variation from key to key is readily discernable to the Pianist’s touch and will cause the piano to be very difficult to play or control any dynamics.
- The essence of touch-weight analysis in a well regulated piano is to measure the down-weight and up-weight of each of the keys across the keyboard with the action isolated from the damper assembly, determine key friction and identify which keys are more than +1 gram outside their normal parametric range.
Once this initial analysis has been made, the various component parts are analyzed to determine their contribution to balance weight and friction. Often times, I will find excessive friction to be sourced to tight key bushings or tight action centers – often times hammer flange centers. Conversely, too loose bushings or action centers can contribute to an abnormal up-weight problem.
- My goal in touch-weight regulation is to make sure that touch-weight parameters vary no more than +1 gram from note to note across each section of the keyboard.
- Typical Fees for Touch-weight analysis/regulation range from $400 to $1200 depending on testing and touch-weight-analysis.
Basic Procedure for Touch-weight Analysis and Regulation: Ensure first that the piano action is in good regulation
Initial Analysis, Parameter Measurement and Action Regulation:
Verify/Set initial index parameters for key-dip, hammer blow distance, let-off, key drop, back checking
Take initial measurements of key Down-weight, Up-weight and Strike-weight (grams)
Reshape hammers (if necessary) & reset index parameters for hammers
Level keyboard & recheck for proper key dip: Sharps and naturals
Clean, size, lub all key bushings, burnish balance and front rail pins, burnish capstan top surfaces
Clean key-tops and key bottoms
Clean key-rest felt, hammer rail felt, key-stop felt
Check all flange & action centers for proper friction
Repin loose or overly tight hammer flanges
Repin loose or overly tight whippen flanges
Check jack centers for proper friction and spacing with repetition lever window
Apply micro-TFE or pro-felt to all friction surfaces: key bushings, whippen pads, rep lever cushions
Re-measure Down-weight, Up-weight and Strike-weight parameters for each key
Apply correct strike-weight curve for hammer strike weight correction vs key weight parameters
Remove or add weight as necessary to hammer head or key-stick
Verify that key stick weighting parameters are within specification
Burnish all nickel-plated and brass hardware
Re-install piano action inside key-bed and fine regulate action parameters
Verify proper travel of all hammer heads to equally strike string unisons
Re-tune piano, perform fine regulation
Recheck adjusted touch-weight parameters while bedded in the piano.
Re-assemble all piano cabinet parts and confirm proper under lever & peddle action.
Re-tune Piano and check hammer voicing.