Dpshans@AOL.COM wrote: > List, > > Here's a fairly basic question from a somewhat newbie: I've noticed on a few > grands (new and used, various makes) that a few hammers do a lot of > double-striking on a soft blow. Seems this is a situation of perhaps too > strong a repetition spring, or perhaps improper checking, but I've not read a > proper diagnosis or regulation sequence in any of the literature. Please > help further my knowledge of "Regulation 101," and thanks in advance. You are correct sir, an overly ambitious rep spring or under achieving back check could be the culprit. Look at the back check first, as the spring should be regulated after the hammer is in proper check. A place to start is the hammer tail. Be certain that it is properly shaped. I have seen both new and old pianos with such horrible tails that it makes you wonder how they could ever work at all. Also check the back of the tail to see if there is sufficiant friction that it won't slip out from the back check. Remember however, checking is accomplished by the crossing of two intersecting arcs, NOT friction. SOME friction is necessary for gripping but if the tails are too rough the buckskin will wear out prematurely. Next look at the back check angle. If the head, (not the bottom of the wire), is bent too far in either direction there can be problems. Use a wire bender to adjust this. If you attempt this by hand you are prone to bent the entire wire and not just the top. The lower key half of the wire is the last adjustment. Although many sources say this should not be done by hand I must say that this is my prefered method. I know I am not alone in this by any means. It should be mentioned that both the head end and the lower key end of the wire may require alternate adjustments until the proper position is determined. In any case the wire should not have to be bent in any weird extreme. If this becomes the case then there is likely something terribly wrong with the tail shape or length. Once checking seems to be working properly you can turn your attention to the springs. The proper adjustment should be a slow but definitive rise. If the hammer "pops" out of checking wildly then it is clearly way too strong. You may find that you need to alternately regulate the back check position and the spring tension if they are both radically wrong. One more item that should be considered is inadequate after touch. If the dip is too shallow it is possible that the back check is not traveling upward high enough. If this be the case then you will need to back track until things start meshing together correctly, including possible improper blow distance. If you continue to find these kinds of problems you may reach the conclusion where it is looking more like the action is in need of a complete regulation which must be done in a specified order. Rob Goodale, RPT Las Vegas, NV
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