As your piano tuner Wilmington DE, Kenneth Keith Piano Services, I often encounter pianos where a piano hammer strikes twice when the key is struck only once. The explanation is useful for all piano owners, because this situation is often mistaken by the piano owner as indicating that the piano needs tuning. In our previous blog article, I explained a lot of the background information about double-striking or “bobbling” piano hammers. This post is a continuation detailing the first of the four most common causes.

Bobbling hammers result from the failure of the jack to escape properly as a piano key is depressed and the hammer is propelled toward the piano string. If the jack remains in its original position, then the hammer mechanism hits it after rebounding from the string. When that happens, the hammer is propelled a second time toward the string, resulting in a bobbling hammer.  The most common cause of the failure of the jack to escape is poor regulation of lost motion in the piano action. Lost motion gradually gets out of regulation on every piano action, and needs to be regulated every one to three years. The reason it gets out of regulation is that cloth and buckskin elements in the piano action get compressed with use. This results in “play” in the top of the key, so that there is a small amount of movement at the top of the piano key before any mechanical elements of the action are engaged. This play is termed,”lost motion.” This is because the key has only a certain amount of travel, and the mechanical completion of the action will not occur if there is lost motion at the top of the key travel. When the action does not complete properly, the jack will not escape from under the hammer mechanism. When that occurs, the piano hammer mechanism will strike the jack and the hammer will be propelled toward the piano string a second time, resulting in a bobbling hammer. Our next blog article will detail the second most common cause of a bobbling hammer, poorly regulated hammer blow distance.

If you have any questions about pianos. or their operation of maintenance, please let us know. We are always happy to help out at Kenneth Keith Piano Services, your Wilmington DE piano tuning experts. Along with providing Delaware piano tuning services, we also proudly serve the Philadelphia PA, Eastern Shore MD and Southern New Jersey areas.