Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Easy way to reduce dynamic touchweight?

As I understand it, an action leverage of 5:1 on a grand piano means that a 1g reduction in hammer weight translates into a 5g reduction in static downweight at the front of the key, not taking friction into account. Is that correct? If so, does anyone know what a 1g reduction in just the capstan weight would do to the downweight at the key? Since the capstan isn't as far back as the hammer, I'm thinking it's a smaller ratio.

Now if I replace a brass capstan with a WNG aluminum one, the weight reduction at the capstan is about 3.4g. Let's say the action leverage from the capstan to the front of the key is 3:1. That would mean a 3.4g reduction in capstan weight would result in a little over 10g reduction in downweight at the key, again not accounting for friction. This would make the teeter totter heavier on the front and lighter on the back than it was before, so to speak. So in this scenario, if I removed each front key lead, assuming each lead weighed 10g, would the action leverage basically return to how it was before?

The reason I ask is because the keyboard on my grand feels pretty good. It feels uniform and smooth. The only thing I'd like to reduce is the dynamic touchweight. I don't want to alter anything else. Therefore I'm thinking a uniform reduction in weight at the back of each key (via the WNG capstan) and a uniform reduction at the front (by removing the front key lead) would be a good way to achieve this. My only worry is that the front key leads aren't all the same weight, and they aren't all the same distance from the front, so I would wind up with an uneven downweight if I do this.

What do you all think?

Thanks.

The way i squeeze out an advantage in inertia is by running the action ratio measurements through the Fandrich/Rhodes weightbench and see what i got to work with. That way there is no guessing as to capstan weight or position, hammer weight, lead weights.

I understand your goal to be to reduce mass in the key without messing with the balance of the action. You can use a digital scale to evaluate what you are doing. Front weight is the downward force measured at the front of the key when the key is balanced at the balance hole. Here's a picture: http://www.stanwoodpiano.com/ptgjune96photo1.jpg If you change the weight of the capstan, then change the front key weighting so that the front weight returns to where it was before the capstan modification, you have achieved your goal.

I encourage you to become well versed with at least one of the action balancing protocols. Stanwood, Gravagne and Fandrich/Rhodes have all offered excellent learning materials in this regard. I would be glad to help you find the sources for learning, if that would be helpful.

Thanks guys. I am familiar with these 3 protocols but admit I don't understand how to use them yet. From what I can tell, they help you isolate issues in the action and help you forecast what any given adjustment will do to the rest of the system. I think this is very helpful if you're trying to diagnose issues.

In my case, however, I am happy with how the action feels except I just want to reduce the inertia a little. I'm thinking that if all I do is swap out the capstans for WNGs, I have changed only one variable and have changed it uniformly across all the keys. I am not moving any pivot points or changing any geometry. Therefore if I reduce a corresponding amount of weight at the front of each key, and do it uniformly as well, nothing else needs to be altered. I will effectively have the same balance/geometry as before, only with less mass in the system. The only question then, is how much weight to take off of the front of the key, and how best to do it uniformly across the keysticks. Maybe the lighter capstans will feel fine without rebalancing the front. But if I do need to reduce the front weight...

For my purposes I think it will be sufficient to weigh off each key as Floyd's picture suggests to see how much weight I need to take off the front. My guess is that it will be less than a whole front key lead. This brings up another question: I see Nick Gravagne drilling out key leads with a Forstner bit on YouTube. However, I have read that this releases lots of toxic lead dust into the air. Are there safer ways to remove lead? Maybe pop the lead out and clip it, then put it back in? Use a hot knife to cut it?

Thanks for any observations or suggestions.

Dynamic touch effort (the actual "playing feel" of the action) does not correspond exactly to static measurements.
So, don't be confused by static measurements and allow those measurements to dominate your decisions. Instead, just replace the capstans and see where you're at. Then, punch out lead if need be. It could be the first lead or the second one. Just understand that mass, leverage and friction feels different even if changing any of them can produce the same static measurement.

The various systems out there can be helpful -- sometimes. They can also lead to wildly erratic results. Actual empirical testing is by far the most reliable.

Oh, a typical front-to-back key leverage is 2:1.

Thanks Keith. So does that mean theoretically to balance 1g reduction in capstan weight, you should take 2g off the front of the key?

The key ratio is 2:1, but it's the other way around. 1g off capstan will reduce down weight by .5g. I don't replace capstans for weight reduction because the effort is not worth the return. If I do need to replace capstans for other reasons I usually do use WNG.

Doh! Yes, I do have everything backwards. Thanks for the correction Bill. Since I'm not getting paid by the hour here, my efforts aren't worth much so it might be worth doing for me

I really like how the action feels already, just want a slight reduction of the inertia. Also, since we're now only talking about needing 1.7g weight reduction at the front of they keys, I could probably do that by just drilling a 1/4 inch hole in the side of each key. As you say, however, it may not be worth the effort.

Thanks for the advice guys. This is all very helpful.

I’m no specialist in this regard but I have a few thoughts. Lightening the mass of the keystick, keeping it in balance, would not do much to reduce inertia since the key moves so little compared to hammer. Think in terms of effort required to lift the whippen, and thus the hammer, if you removed the key altogether.

There are ways to reduce the weight of the hammer or its related lifting parts. One could also modify the geometry. But such changes would come at a cost. Reducing inertia also reduces power. It could result in a weak, thin sounding instrument.

Anyone who wants to tackle an inertia situation needs to fully understand the problem.
I would suggest to familiarize yourself with what inertia actually means (the factors and formulas involved) and also with the inertia loci in the piano mechanism.
Hint: surprisingly little inertia is found in the keystick -> don't expect to solve an inertia problem by barking up that tree.

Thanks you guys. So I don't have an inertia problem to solve per se. I just prefer a slightly lighter touch, so just want to uniformly reduce inertia by a small amount. I agree that the keystick is less a source of inertia than the hammer, but a 3+ gram reduction at the capstan x 88 keys is a significant reduction across the entire keyboard. I think it could make a difference for the player, especially on very fast passages.

I've also followed Ed McMorrow's posts on this forum, and I think there is something to his light hammer ideas. WBLynch, Ed may be a good person to ask about how much you can lighten a hammer before it starts affecting the sound, as he seems to take his hammers to the edge in that regard.

Finally, as to lightening hammers, it has been suggested to me that a way to do it is to drill holes in the hammer moulding. I like this idea because unlike sanding a hammer to lighten it, it's easy to take off a uniform amount of weight across the hammers by drilling the same size hole into moulding, and in the same position. A 3/8" hole, for example, may take .2g off each hammer, which should translate to about a gram difference at the key. Again, I see these as small tweaks to adjust inertia across the board, rather than fixes to actual inertia problems.

But, I may be completely off base, so welcome all comments. Thanks.

You can feel the difference in switching out brass capstans for W,N&G aluminum ones. It may be enough to allow removing the lead nearest the balance rail, it may not.

For soft playing, many actions move so easily that you end up creating much tension in the arms and shoulders holding the hands up. It can seem counter-intuitive but a higher gram resistance is often easier to play when the hammer is light enough already to not kill you when trying to play with force.

The amount the capstan contributes to action inertia and therefore dynamic touch weight is too negligible to bother with. The real solution is to reduce hammer mass, but that's an expensive proposition, and may well not be worth the expense for you.

Thanks Roy. Are you talking about filing and thinning the hammer tails? I'm concerned about ending up with the wrong hammer shape, since I'm not experienced with this. Drilling uniform holes I can do, however. I figure if I put a simple jig on my drill press, I can get the same hole in the same place on each hammer. As I recall though, a 1/4" hole only accounts for about 0.2g of weight. I can probably get at least 2 holes into the larger hammers, so let's say I can achieve a 0.5g reduction that way across the bass and up to hammer 60 or so. Multiply that by 5, and that's about 2.5g reduction at the key, right? Do you think that would be noticeable? Any reason to adjust anything else if you're simply reducing hammer weight uniformly across the board?

BTW, Emory, my brother just bought a house in Portland OR and I'll be up there to see him after the Covid is over. Maybe we would have a cup of coffee and share war stories of our restorations?

Definitely. PM me when you're coming up, it's rare to find someone who likes to geek out about pianos!

Check out the instructional pamphlet on touchweight (free) at spurlockspecialtytools.com

Awesome, I'll read up on it. Thanks.

To reduce hammer weight enough to bother you have to taper the hammers. This is definitely not a job for an amateur. After reducing hammer mass the keys will most likely have to be reweighed off, which is also a tricky business.

Tapering the hammers is not difficult with the right equipment, nor is reshaping the tails. But really this will make a little difference, but nothing radical. You are only taking off about a toothpick or two's worth of weight.

As long as you are doing this uniformly, the mass will be reduced uniformly, so the feel will be changed uniformly. You probably do not have to reweigh the keys if you do not want to.

But overall, the only reasonable way to change the touchweight is to change the piano. I said this before, and when I asked, the critics who said that you do not have to change the piano said that the only thing you can do with a Kimball console is, you guessed it, change the piano.