At 06:04 -0400 5/6/10, Tom Servinsky wrote: >This is a new revelation for me. I've always assumed that the >general design of the upright action limited any possibility for the >jack to reset in the half position. I have 8 new Steinway 1098 >uprights I'm dying to give this a shot at. The reason upright actions, with very few exceptions nowadays, are equipped with no special device for repetition is that repetition on the properly designed and regulated upright action is excellent even without it. The only period when even high quality uprights, in Europe at least, did use a special repeating action (notably the Herrburger-Schwander spring and loop design) was when the player piano was coming into vogue at the beginning of the century and super-human demands were placed on the action. The early Steinway action with the double flange achieves almost faultless repeatability by geometry alone. The only repeating device I know of in a currently produced piano is that in the Sauter, which is nothing more than a thin flat metal spring stuck in the back of the jack, which is compressed against the jack slap rail and provides extra force to return the jack under the notch. It's always struck me that it does no more than would a strengthening of the jack spiral spring. Nearly all butt springs, at least those attached to the butt as in the European design, but probably also spring-rail springs, are delivered too strong. This not only increases the touch weight unnecessarily but also impairs repetition, as has been said. The butt spring is only needed on certain designs of under-damper action. It is absent on overdamper actions, and by chance I am in the course of regulating a very nice and very normal-looking, underdamper action (by Herrburger-Schwander) which needs no butt springs because the hammers need no special discouragement from burbling, which is the only function of the butt spring. If the centre of gravity of the hammer assembly never crosses a line drawn vertically from the hammer centre, no butt spring is required. The butt sping, therefore, should be regulated so that when the key is pressed down very slowly the hammer falls back slowly and gently as the jack escapes from under the notch. When the hammer is held in check, say 16mm from the string, there is thus the minimum force tending to return it to rest when it is returned to rest. If the centre is on the firm side, as Don says, then so much the better for repetition, since this further reduces the backward force. Provided the keys are back-weighted (forward-weighted keys are the enemy of repetition) then, when the key is allowed to move up even the slightest amount, the considerable weight of the jack lever (normally centred) added to the force of the compressed jack spring, which also acts to lower the lever, means that the lever falls a great deal faster than the hammer. It is not until well after the jack has returned under the notch that the tape, invented for this very reason, comes into action to pull the hammer back to rest. The tape plays no part in repetition in quiet playing but is important for repeating loud notes, since without it, the hammer under its proper weight, would not return quickly enough and the repeated notes would be at half-blow. The Steinway action mentioned above has an unusually shallow, and regular, slope on the notch combined with a jack spring that is stronger than normal so that the jack pushes the hammer forward as it returns under the notch; the hammer moves gently towards the string when the hammer is released from check. Certain old actions (BlŸthner/Driver & Toepfer, Gšrs & Kallmann for example) had the notch angled, so that once the hammer had set off there was almost no tendency for the jack to get back under until a certain point. Repetition on such actions is relatively poor. Most actions, including current actions, are somewhere in between these extremes, allowing the jack to supply a force tangentially to the notch tending to move the hammer upwards. If the touch is too deep in relation to the blow, the jack will come back too far and lost motion will completely replace the virtues mentioned above. The jack should escape from under the notch only so far as to allow the hammer to fall into check without the notch bouncing on the fly. Any more and repetition will be impaired. Given a well-designed action, and the taller the better, and attention paid to all the above items, and probably a dozen other things I have omitted, the upright will repeat very well. JD
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