A quick query for some experienced opinion:

When regulating the action to counter lost motion, should the goal be to eliminate it entirely, or to reduce it so a small amount remains?

My previous tech did the former, but the subsequent tech considered reducing lost motion to zero to be potentially harmful in the long-run, on account of the effects of the hammer butt on the jack? And while I admit I don't like a 'sloppy' feel to a piano, I actually think I prefer a small amount of lost motion to its complete absence.

So two questions here, one for the techs, and one for the players. Lost motion: To eliminate, or reduce?

With thanks in advance,

P.

This is really just one question and that is, "What works?"

Vertical piano actions need a slight amount of free play between the tip of the jack and the hammer butt leather to function reliably. There should not be so much free play as to be noticeable by the pianist but enough for the jack to slip back under the butt leather reliably on a very soft blow. Or, more correctly, when the pianist releases the key very slowly.

I've know technicians who pride themselves on regulating capstans so there is zero lost motion and these are usually the technicians who lost the customer to someone else who actually knew how to regulate these things properly. Nobody likes playing a piano that does not repeat reliably.

ddf

As Del said, plus, In UK the factory technicians used a thin card as a gauge for adjusting this dimension. The operation of adjusting lost motion was actually called 'carding'.

This dimension is also seasonal in many pianos so allowance should be made for seasonal changes.

We were taught at school to regulate so that when the rest rail was pulled back, the hammers should move the slightest amount visible, and they should all move the same amount!
Regards,

Can someone give as untechnical explanation as possible of what lost motion is?

I'm not a technician but I don't like lost motion in the sustain pedal. As soon as the pedal is depressed, I want to hear that the dampers are lifting off of the strings. If there were lost motion, the pedal would travel before anything happened.

It's the same thing with the workings of the keyboard action ... immediate results and no ... lost motion.

Greetings,
It is a gap, somewhere in the series of levers, between your finger and the hammer. It means that the key will move a very slight amount before it encounters the resistance of the hammer. The key may move a lever that is not in contact with its next component, and the "lost motion" would be there rather than at the key, but in any event, the lost motion is the amount of key motion that takes place before anything else happens. you can usually feel this on uprights, and if you press the "soft" pedal, there is usually an huge increase in the amount of it. press lightly, and think about what your finger is feeling in the first perceptible amount of motion of the key.
It is needed in uprights to let the parts separate enough to slide by one another without hanging up.

If you DON"T have any lost motion in your sustain pedal, you will likely have some issues with proper damping. NO lost motion in the pedal would mean that the damper heads are 'just' sitting on the string with no ability to follow the motion of the strings. If the damper lift rail is not allowed to separate some distance from the bottom of the damper under-levers (in the case of a grand) the result will be bleeding dampers. Same thing in the upright, just different parts and slightly different system.

The normal generic setting is about 1/4" or 6mm of travel at the pedal before the dampers begin to lift. Less will work, none will not.

As to pianoloverus question. A simple definition of lost motion in an upright piano is as follows, the gap between the top of the jack and the bottom of the hammer butt leather when the note is at rest.

"No lost motion" results in a situation where the jack will not reset under a soft release because the butt leather gets in the way of the arc of the top of the jack.

"Too much lost motion" is when the gap is large enough to be felt by the player and in some cases can result in a regulation which will allow hammer bobbling as the note will not have enough aftertouch to ensure that the jack will get cleanly out from underneath the hammer butt, and thus not allowing proper checking.

IOWs, some is necessary, too much is not.

And this is exactly how a properly regulated damper pedal works. There is some lost motion in the damper trapwork mechanism. If there were none, you would hear ringing notes.

There have been good answers given so far, so I will add only that lost motion is not unique to pianos.

For example, when engaging a clutch on a manual car, there are zones in the range of motion. At the top will be some lost motion (maybe 1" on a family car) then pressure from lifting the clutch, then the zone where it engages and finally, closest to the floorboard, free motion (neutral).

Next time you get in an older car, you will probably notice lost motion in the gas pedal or brake pedal, too.

If you want to experience the feel of an action with excessive lost motion, just play a modern upright with the left pedal down.

Playing long and hard with excessive lost motion in the action will eventually wear the action leathers to where a fine regulation is not possible.

Lost motion is simply the movement of the key, (rocking down at the front playing end and up at the back end), before the back end of the key, engages the hammer/butt assembly to push the hammer toward striking the string.

Lost motion presents just enough space between the top of the jack and the Hammer/butt assembly to allow the jack to reset without drag or interference.

I don't notice this lost motion when playing on a well designed upright action.

Lost motion creeps into vertical actions no matter what the quality of them is. It manifests itself in different ways. In spinet actions, it often only seems to be a reduction in the key height and dip, since the keys are weighted towards the front. But it is still detrimental to performance.

I'm certainly no piano tech but did encounter this in my former occupation in regulating pnumatic controllers. It was referred to as hysteresis. It caused a lag in reponse to a given signal from the controller. I suppose this might apply here though. Or maybe not so forgive the presumption on my part if not.

Yes, lost motion does cause a slight delay in the transfer of energy from the front of the key to the hammer. So do several other factors such as the compliance of felt and leather, but flexibility of wood, etc. Unfortunately, given the sorry state of vertical piano action design, the alternative is an action that doesn’t work.

ddf

One thing that can work in certain circumstances is to catch the hammer close to the strings so that the jack can slip back under the butt first. In fact, when catching is sufficiently reliable, there is no need for the jack to escape from under the butt. Two advantages are reduced key dip and repetition without extra springs and magnets.

No doubt some design and development work would be necessary to do this effectively in volume production, and that's assuming it's possible to come up with a geometry that allows for wear tolerances, etc.

In a vertical action (unlike a grand), the hammershanks actually rest on the hammer rest rail when the key is at rest. The rest rail therefore functions similarly (in a weird way) to the repetition lever in a grand: it holds up the hammer away from the jack so that the jack can reset underneath it.

The main reason regulation is needed is to compensate for wear. As the rest rail felt gets grooved from the hammer shanks over time, the hammers start to rest farther and farther back, closer to the jacks, and lost motion disappears. It's common to have to shim the whole rest rail forward a bit to get enough clearance with a reasonable amount of key dip.

A good test to see if you have enough lost motion is to hold down the sustain pedal (to eliminate assistance from the damper springs), play a note softly, and then release the key as slowly as possible. If you can play the note a second time, the jack has reset under the hammer butt, and all is good.

The heads of some jacks have the back edges beveled so that, along with strong jack spring tension, they can force themselves back under with very little lost motion.

I like the analogy of a clutch in a car! Good analogies are very helpful.

--Cy--

Yes, Cy. One manufacturers tech rep informed me that their uprite actions will still work if humidity forces the action into a slight amount of negative lost motion. (In case that sounds like a double negative, perhaps I mean found motion).