Repetition mechanism for upright pianos

CrisOliveira

Or "Why are most makers not trying to develop repetition mechanisms for all upright models?"

Grand pianos have a repetition mechanism that resets the jack before the key is fully released. Such mechanism isn't present in upright pianos. Some makers and technicians, however, have offered alternatives.

One Japanese vendor installed magnets that repel the hammers back to resting position, so repetition can happen sooner. I can't say how good or fast that mechanism is, since all information I have is from a single tv interview (which I can't seem to find on YT now).

Seiler Pianos seem to offer another magnet-based system, with hammer and jack repelling each other. Piano Buyer states some top tier European models also include similar feature.

Feurich has their KAMM action, which adds a little felt pulley, attached to the hammer by a spring, that forces the jack back into place.

This Russian dude has invented an action featuring what looks like a repetition lever, but I can't understand Russian. Too bad war and politics will stop major brands and him from making deals. Unless he moves out of the country, I guess.

Some players and vendors state Kawai uprights from the K500 to K800 offer faster than average repetition. And at least one technician on YouTube states repetition in uprights is a matter of regulation. Pianists, however, agree that uprights are not as fast as grands.

What prevents piano makers and parts makers from making fast repetition in uprights universal? Apart from the Russian new action, all those systems seem fairly simple. Do they add up and increase cost and price significantly? Do they make regulation harder? Is consistency achievable with relatively cheap and simple magnets or do you need them to be made with such precision as to make it all too complex for most piano models? I mean, if cheap magnets would do, what stops you from gluing them yourself on your piano's action?

If piano students had access to upright pianos with faster repetition, would moving to a grand be an unquestionable necessity?

WieWaldi

Basically, actions for a grand piano are easier to make. After hitting the string, gravitiy helps the hammer going down very easy without bouncing or any unwanted side effects. (before 1800)

On an upright, the mechanism is more complex. More levers are included to let the hammer hit the strings horizontally. Gravity alone won't let the hammer go away from alone that quickly. More parts are needed to do that.

But Sébastien Érard found some room to improve the grand action, making it more complex. He added what we call double escapement. For sure, this increases the complexity of a grand action. This makes the action of a grand piano even more complex than the one of an upright piano. But not too complex, it works.

But if someone would make a double escapement action for an upright, the complexity would be way higher than the one of an grand piano. And probably more error prone as well. Therefore there aren't so many in the field. The Feurich action looks promising, but an additional spring is a part that can tire over time. Then there is Kawai with a distinct advantage, because they do the mechanic with carbon fiber instead of wood. I am sure, carbon allows for ligher weight, more precision, more longevity, even lower cost when mass produced. I really don't understand, why the entire piano industry hasn't changed to modern materials, yet.

So the anser in short: Because physics and gravity helps the action of a grand piano

it is either less complex
or it offers more playing comfort (aka double escapement = higher repetition speed)