Grand Regulation – part XXV

Step number 38. Check gram weight resistance all 88 keys (continued) 

The proper method to check the gram weight resistance of the keys is to either block up the dampers if the action is in the piano, or to remove the action to a bench. All repairs and regulations should have been performed to the action mechanism. I like to start at one end of the keyboard, say at A#1, and work up chromatically doing the downweight measurement on every key.

On a typical grand, the proper downweight should be somewhere in the mid 50’s for the lowest notes gradually decreasing to the upper 40’s for the top notes. If the downweight for a specific key is within an acceptable range, like 54 grams for note number 10 in the bass, I’ll pass over that key without making any chalk marks on it. If the downweight is something more like 60 grams, I’ll chalk exactly that number on that key. Once all of the downweight measurements are taken, I do the same for upweight. Again, chalking only those  keys which are out of range. The proper upweight should be 25 to 30 grams less than the downweight. That is, if the downweight was 50, the proper upweight should be 20-25. With a little practice, taking these measurements goes rather quickly. My system is to mark downweight behind the key buttons, upweight in front of the buttons. When finished, all keys out of the proper range can be analysed at a glance. Try to be very accurate when taking these readings. Rarely should a key be chalked for a wrong downweight without also showing something wrong with the upweight, and vice versa.

All measurements should be taken to the nearest gram. Using the downweight as an example, the key may not go down at all with 49 grams of weight, but when another gram is added, the key goes down very slowly. A light tapping on the keyframe to aid the key in going down. is acceptable. Record the downweight for this key as being 50 grams. Likewise, in doing the upweight, the key at the point of escapement may not come up with 26 grams of weight on it. But taking one gram off, the key may rise slowly. A record of 25 for the upweight is correct for this key.

All measurements should be taken to the nearest gram. Using the downweight as an example, the key may not go down at all with 49 grams of weight, but when another gram is added, the key goes down very slowly. A light tapping on the keyframe to aid the key in going down is acceptable. Record the downweight for this key as being 50 grams. Likewise, in doing the upweight, the key at the point of escapement may not come up with 26 grams of weight on it. But taking one gram off...

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Grand Regulation - part XXIV

Step 38, Check gram weight resistance all 88 keys

Step 38 in the 50-point checklist is to use gram weights to help find too little or too much resistance at the key, something the pianist will surely complain about if overlooked. Unfortunately, many technicians do overlook this very important step when regulating an action.

There are two aspects to this step. Through the use of gram weights one can find problems with the lead weighting of the keys, or more frequently, one can find problems with the frictional resistance in the action. Since a fair amount of confusion can result when talking about both aspects, I will attempt to separate the two.

The weight resistance in a grand action can be defined as the equation W= (D+U)/2 . Where W is the weight resistance of the action as felt by a pianist at the key, D is the downweight pressure of the key measured in grams. The frictional resistance can be defined as the equation F = (DxU)/2 . Where F is the friction resistance of the action. How we actually take the down and upweight measurements will be postponed until later. Right now the important thing is to realize the difference between the two concepts.

The weight resistance in an action is the result of the front half of the key having to lift the hammer/shank assembly, the whippen, and the back half of the key. This of course includes any lead weights which have been added to the keys. It does not include lifting any part of the damper assembly. Nor does it include the amount of force needed to push the action through the escapement. Rather, it is the force needed to push the key at rest down to the point of escapement. All measurements are taken with the action in the piano with the dampers blocked up, or with the action out of the piano on a bench. Once the keys have been weighted at the factory, this weight resistance is fairly well established for the life of the piano. It does change a little as the hammers wear and need reshaping, causing them to lose a little weight. But this slight variance can be reestablished when the hammers are replaced, assuming the replacement hammers are the same weight as the original. So, for all practical purposes, if the factory did a good job when the keys were leaded, the regulating technician should not have to worry about the weight resistance of the action. In rare cases, the weighting of the keys may need to be altered slightly. This will be covered later...

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