Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum spring tension, let-off and repetition

Revisiting the topic, but with special attention to fast trills:

Q: In general terms, once spring tension is properly set, is there an optimal setting for back-check combined with let-off to produce the fastest, most even trills possible? For example, if let-off and drop are set very, very close (say 1/64") and back-check is at say 10mm, would repetition/trills be compromised? Would a less aggressive setting for either or both of the above be likely (in theory at least) to improve repetition?

Subsidiary question: is there a tool that measures spring tension super-accurately?

Hello, it is not about trills but fast repetead notes, trills always work fine with any standard regulation.

High checking lower the power and raise repetition speed limit.

The spring havesome importance but the jack winking and rest position have much more, in my opinion.

Also, overblow reduce the friction of the jack to come back under the knuckle.

Basically the spring must be strong enough to maintain the whippen in open position when the hammer leave the backcheck. but at that moment, unless the key have tons of lead, the key is not pushing on the whippen , it sort of float for a moment that must be enough for the jack to rengage .
As say Ed Foote lower the spring helps to break the key inertia but the jack rengage soon

the spring strenght depends of the spread, and the level of drop.

Jack back can be using strong spring but small drop.


if both are used the touch is sort of sluggish
Jack in standard position need a less strong spring.

Of course different jack elevations offer different possibilities.

enlarging the vertical dimension allow to have the jack centered, small spring stress, I believe that then you align the sharps at rest to be on the mid blow line and you have a very fast action with easy sharps, and whites passing the convergence line a little before half blow (control being better at that point).

As seen on some grand piano I know

Greetings,
Repetition speed is determined by two things; how fast the key will rise, and how far it has to go to allow the jack to reset.

The first is controlled by the repetition spring, it is what powers the key upwards upon release, using the hammer weight as countering resistance. (under fast repetition, the hammer doesn't rise toward the string between cycles, the whippen is, instead, driven down by the rep spring working against the drop screw).

The second is checking height. This is where variability comes into play. If the hammers check lower on harder blows, forte trills will require more work than pianissimo ones will, because the hammer will be checked lower and the key will have to rise farther to allow the jack to reset. Evenness of checking shows itself in evenness of action response. Increasing after touch will also slow it down, as that represents dead space the key must travel through before allowing the jack to reset.

Checking too high will reduce the power of repeated notes, since with a blow of, say, 7/8", a hammer is not going to carry the same speed into the string as it will from 1 7/8"

There is no practical difference in repetition speed between an action with springs that throw hammers off the jacks upon release from check, and springs that give a smooth rise that is just below the threshold of being felt in the key. The harder springs may cause slightly higher checking on light play, but their resistance makes the pianissimo touch a lot more difficult to control and an action that is more work to play than needed.
Regards,

Agreed with that..



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Very helpful.

Follow up:

Am I being a little precious in asking about precise measurement of spring tension, ie getting it uniform across the instrument? ie is there a device that will do that.

Also, just for clarification, "higher checking" means checking that is closer to the string, I assume, which tends to produce faster but less powerful repetition?

Or have I overgeneralized?

Yes, and Yes. The precision of spring tension is only important to a certain degree. If it meets the criteria, it may actually vary in strength to do that, since we test with the mechanism, itself. The normal test for spring tension is observation of the hammer's return rate. Shank pinning is a factor, so springs might vary to adjust for that. A tighter pinning of the balancier will require a stronger spring to lift the hammer the same speed as a looser pinning with a weaker spring. (I like 7 grams on the balancier). The two approaches give different levels of performance, with the former being mine.

If all the springs were identical, the hammer lift rates would be all over the map, and that would make it difficult to set the drop, i.e.. everybody would have to be far from the string to accomodate the few that are jumping.
Regards.

"Yes and Yes" Ed Foote. 'Agree. Standard regulating measurements are specified by the manufacturer for a good reason. That range is where everything works well. It sounds like you are not a technician and are basically trying to "prep" your piano. 'Good luck.

I am a total amateur, as I've said here before. It's a hobby for me, and I LOVE it. I have taken a few courses; but there is less than unanimity on many things! Drop and let-off, for example, I adjusted much closer than spec(Reblitz and Hailun suggest the standard 1/8" and 1/16"), and the result was a vastly improved feel and touch. Backcheck, says Reblitz, should be "exactly" 5/8", and Hailun's spec is the same; but my 218 arrived with a much smaller backcheck distance; so again specs and reality are never the same. Naturally I'm curious about these issues, and where the "truth" so to speak lies.

specs may vary if the touch is bettter for the pianist (more key dip, more or less hammer stroke, differnt types of letoff)

But those modification may be done with a good understanding of all consequences.

Manufactures provide good bases, the key heigh level being the most useful.

Some action allow for very little modifs, others are tolerant.

those things cannot be done by an amator, but if cooperation exists with a good tech, some actions are possible from the pianist part.

In general, of course, I agree. But I am not your typical piano owner. I'm just one of those folks who has difficulty surrendering technical work of any kind to the skilled craftsman: plumbing; carpentry; framing; drywalling; pouring foundations, laying flagstones; roofing; electrical work, etc. I do it all. I will make mistakes, for sure. But so far, so good. Excellent, in fact.

The pleasure to have the thing done by yourself generally tweak tge perception of the final result. That is what I notice even on dedicated amateurs wanting to do all by themselves.

There is a training and experience that count for 40 % of the quality in tge end.

Piano actions are very forgiving, it is easy then to be happy.

So be happy (dont worry !)

I should add, probably, that it's important to note that although Toronto (Canada, home of Glenn Gould) is where I live and grew up, it has about 1/2 the GDP of that other beautiful hogtown called "Chicago."

Ergo: there are not that many really skilled piano technicians in our fair city. World renowned orchestras and performers don't drop in to Toronto that often. We are probably better known for our film festival than for our "art", in ALL the senses that ill-used word.

Cutting to the chase, there really aren't a whole lot of skilled techs here. Case in point: I've just returned from a life-altering concert by the Russian youngster, Daniel Trifonov, at a wonderful hall in Toronto, and who should be re-tuning the Hamburg Steinway at intermission? My tech-connection; and I can assure you that he is very young and has many years of learning the ins-and-outs of pianos ahead.

There are no super-techs in this Town.

This is a no-man's-land up here musically, you must understand. This is not Chicago, New York, L.A., Paris, Hamburg, Moscow, etc., etc....

It ain't easy to get the best....

And I am an inveterate do-it-your-selfer, anyway!

Just curious. What was the original hammer blow distance on your Hailun?

Most common is 45 mm but my Hailun 178 came from the factory having 40 mm blow distance in the treble and tenor and 45 mm in the bass.

You make it sound like the dearth of decent piano technicians in Canada's largest city forces you as a piano player to do do your own tech work. Of course, that is absolutely laughable. Toronto is blessed with a good number of very fine piano technicians. The best technicians in any given place essentially pick and choose for whom they work....

Often the exact objective of the original poster can be left in the dust by the time a few responses have gone by.

I hope that three key issues have come to the forefront for John within these responses. These points come from reviewing what others have already pointed out:

1. Repetition spring tension, adjusted with a properly pinned rep. lever center pin friction to give a smooth rise of the hammer will lend itself to a proper repetition.

2. Backcheck distance, if set to the spec for that piano, will give a good average repetition at various volume levels- regardless of whether a trill is involved. When you move checking up (closer) you will gain speed and lose power. The inverse is also true.

3. John was seeking a way to use a device to set rep. spring tension. It has been pointed out to him that this is not how it's done. Instead, this adjustment must be made in situ. By using the rise of the hammer to judge spring tension, the technician is able to incorporate the effects of not only the rep. lever pin friction and the spring tension itself, but also the hammer flange pinning friction variation and hammer weight variation. Granted, these should be theoretically correct and evenly gradated. In reality they may not be.

There is a reason for the anecdote below:

Two weeks ago I had offered to try to solve some issues on a college Steinway B which is around 18 months old. Personally, I had noticed shallow dip, probably due to some key settling. A young Russian associate professor had noticed "something...I can't put my finger on it..., uhm...." (Ever heard that comment?) Although the dip truly turned out to be insufficient, the problem which had made the action feel sluggish to the players was actually the fact that the key holes at the center rail were tight - tight enough to prevent good repetition, but not so tight as to cause a key to actually stick, or to even show visually. I only found it by removing the keys as I was spot-leveling, prior to working on the dip issue.

In the end, I had slightly increased the dip, slightly tightened up let-off, slightly increased hammer blow - all done to get more horsepower from the keys. But, the issue which probably met the players need the most was probably the tight key holes. That was a surprise, especially since the piano has been served by a Piano Life Saver System. Another surprise to me was how well the rep. springs had been adjusted and how even they still were - not needing attention.

When I tune it next time, I will re-examine my closer let-off, because of the possibility that this could lead to bubbling and blocking, and will make sure of the checking distance.

The reason for the story?
After doing this work for 36 years, my assumptions on the Steinway had only been partially correct. On the other hand, my experience is what allowed the piano to tell me the answers which would satisfy the customer’s needs. Although John is to be commended for his efforts, he won’t have the same perspective, as he tries to regulate his own piano. Perhaps, however, he will feel better about spending good money with a good tech, when required.

Apologies... I overstated my case on tech availability in Toronto. Of course, there ARE no doubt some great techs here; but you really have to be in-the-know to find them.

But that's an aside: I'm NOT interested in using a tech, NOT because I don't think I can find a good one, but because I really get a lot of pleasure out of learning and doing things myself!! I do intend to get a tech to look at my piano, again, not to get work done but to get fine points addressed re my particular instrument.

Practical question:

The tightness of the flange pin relative to spring strength seems to be disputed or at least "relative": Reblitz says that when the hammer's removed and dangled in the air, look for approx. "5" cycles back and forth, before the hammer comes to rest.


Should that "5" arguably be something more like "3", if a somewhat tighter pinning is optimal?

Alternatively, as long as the pinning is absolutely secure, ie with no non-vertical movement, why wouldn't a lighter spring and a looser pin be better?

Re question about hammer blow distance on the Hailun: my experience was like yours. The spec for the 218 is 1 3/4", but the trichords on my piano were set at about 1/4" less. That was not a concern for me, personally, because piano was more than loud enough at ff in that range. And the ppps were excellent. Compared to all the grands I've played over the last 50 years, the touch and the tone of the piano was ... well... superb.

Warning, I've played a number of Hailuns in Toronto, 178s and uprights. Some have been gaawd-aweful; so it is important--as always--to have a reputable tech check out the instrument, even if it is new or near-new. Are the problems simply poor tuning and regulation? Or is the piano a total lemon and unredeemable? I think with Chinese-made pianos this proviso may be particularly important!!!

By way of edit... you'll probably find that hammer blow distance varies from section to section and indeed from note to note. There are innumerable variables affecting tone, needless to say, but don't get me wrong blow distance is definitely one of them! So a careful regulation of ALL the variables, or as many s you can afford, will without doubt improve the touch and tone of the piano.... But unless you're prepared to keep the piano in a pretty constant humidity throughout the year, all the regulating in the world isn't going to amount to much.

I've warmed up to the Hailuns as of late. They have improved greatly in the last few years with good direction and foresight from upper management along with very advanced manufacturing procedures. The hammers still need to be needled/voiced once they are worn in a bit and can also benefit from some precision carding and fitting to the strings.

They are one of the few companies out there that claim easy interchangeability on the actions from similar models, and this requires very sturdy actions, stable materials with tight tolerances on the manufacturing to pull off. One of the best bangs for the buck in a piano lately IMHO.

John, thank you for answering my question on hammer blow distance.

Like you, I find so much pleasure and satisfaction in tweaking my piano to the best it could be. There are no techs in my area and so I'm thankful for the techs in this forum who give help when I need it.

There's an abundance of generousity of spirit here among the techs, and an abundance of knowledge!!!

Another component of regulation that you can experiment with in regard to the "balance" between speed and power lies in the jack's position under the knuckle. You can add power, and improve checking, by moving the jack back slightly so that it stays in contact longer with the knuckle. By moving it forward slightly, toward the player, you will decrease the power but increase the speed of repetition. Many times bobbling at pp levels is directly related to the jack not clearing the underside of the knuckle fully, and can be eliminated with a slight increase in dip, thereby allowing the jack to advance out from under the knuckle. Of course, one thing always affects another, and these adjustments often require compensation elsewhere. As far as working on your own piano, I see nothing wrong with that. There is little irrevocable harm you can do, and a lot of potential for learning. Probably the best approach would be to find one of those excellent techs in Toronto that Supply speaks of and see if one of them would be willing to take on an apprentice, (you). Then, if and when you do screw up on your own instrument, he/she can show you why and, more importantly, fix the problem while you learn from the experience.