Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Effects of Polishing Capstans

Polishing and/or lubricating capstans can make an action feel lighter and can brighten the tone. Why is this so?

Is there really that much friction between the capstan and the whippen cushion?

depends just how much lateral movement there is as the capstan grazes across the rep bottom felt....and how much of a dimple there may be..and how much crud and verdigris there may be in that dimple.

When I pep new Steinways, 50 to 75 each year, I always lube the top of the capstan before I put back the stack....I do so because I can...and as far as I know there is no downside and that is how I was taught at the factory...if you want to flip the stack you can always pop some juice on the underfelt.
I use prolube...just a couple of drops.

Going after points of possible friction is a moot point in some quarters...but as I have the keys out and the stack off during the prepping process I take full advantage of that situation to lube the key bushings and ease the keys as well....it is recommended that some lube be put on the damper lift cushion on the back end of the keys...

Hope that sheds a little light!

Exactly what does this 'pepping' procedure involve? I want my piano pepped, now!

It's a technical term Charles.:-)
It's like prepping but hotter!

P

I know a technician that was getting a piano ready for a concert and the pianist wanted more power from the piano at the last minute. The technician removed the fallboard and rubbed four times each the tops of the capstans with a treble stick mute, the one with a buckskin covering. The pianist played it and said, "perfect, what did you do?" Hard to believe.
I like to dip the tip of the mute in prolube and go over the capstan tops when I feel it is needed.

In the old days the capstans were also heavily burnished with a peice of smooth thick glass. Not so sure they do that now from the factory since its pretty time consuming, laborous work.

I find it hard to believe as well.

Depending on the length of the keys—and assuming the action geometry is reasonably well set up—the sliding motion between the capstan and the capstan block felt is about 0.1 mm to 0.2 mm (0.004” to 0.008”). I can’t see any kind of lubricating or polishing making that kind of difference.

I’m willing to be convinced but I’d sure like to see the results actually measured somehow.

ddf

The placebo effect doing it's magic

Musicians love fairy tales, they don't need no fancy mechanical mumbo jumbo!!!

I agree. Unless there is excessive lateral movement which would be the problem to solve, the difference between a shiny capstan and a crusty one is hardly worth consideration. Polishing or lubricating the capstans would be treating the symptom, not the cause.

The placebo effect can be just as powerful, however. If it was seen that you did something, that may be all it takes in that circumstance. If however, you say that nothing is wrong and refuse to do anything at all, you have a client who no longer wants your services.

It sometimes works that way in medicine although as a last resort. The same should be the case in piano technology.

Interesting Del, Bill, and Erus. The answer from Delwin is what I was looking for. 0.1 to 0.2 mm is not enough to make much of a difference. I believe that the person who told the story, a Kawai technician that we all know, was illustrating an example of the artist and the placebo effect, since he was grinning when he told the story.
However, sometimes I do notice a difference in the feel after they are lubricated, but it is subtle.

Byron,
If you have gram weights, take careful measurements of key up and downweight before and after polishing and tell us what you find.

Thanks Gene, I am considering doing that, but I think the effect (if there is one) might occur during a blow rather than during a gentle vertical motion.

I like to polish everything. Capstans, balance and front rail pins, drop screws etc. Especially the key tops. I like to lubricate the wippen cushion cloth, let off buttons, knuckles etc., with powdered soap stone.

I use the soap stone as a paste mixing it with alcohol until it becomes pasty. (Pastie?) The alcohol helps it to penetrate a little bit more, I think, and it dries quickly. Plus, after the alcohol dries in the bowl, I have all of the powered soap stone left over yet. I think when I do the entire action like this, cleaning everything first, that it does give a cleaner, easier feel and a better touch. Of course it also eliminates the creaking and sticking feeling that it might otherwise give with a softer blow on older or more neglected pianos.

My 2 ¢ worth FWIW.

I occasionally use a buffing wheel. However, I think that if there is much of a difference, it comes from dealing with the action cloth, not the capstans. After all, playing the piano polishes the capstans.

A thought that came to mind is of a wet bar of soap vs a dry bar of soap. What happens when a capstan pushes into the whippen cushion? It makes a small dimple and the whippen pushes off but stays in contact. What happens when you squeeze a wet, slick bar of soap? Shoots across the room. A dry bar of soap? Not much.

But, even if some of the weight of the whippen did move away from the the key with more force because of lubrication, there are so many other things going on with regards to friction within the action that should matter more.

Hi BDB,

Yes, I agree but only to a point that it will polish them but at the same time, as years pass, it also lets off this brassy green substance from the capstans onto the cushions too which I like to burnish and eliminate. I usually use Nevr Dull when polishing the capstans. It does make them more slippery and cleans some crud off at the same time.

Right Byron. There are many other factor's that come into play in an action besides just one or two areas. If we clean and work in all of these areas, I believe a difference will be had over all. I won't do tests to prove it but, I can feel the difference when I'm done.

If memory serves, the pathnis around 0,2-0,4 mm Depending of the size of the grand (Pfeiffer 'the piano key and whippen).
The friction , to me, is exacerbated at full speed, and one of its most important result is what happens to the whippen center, I mean, how is the force coming from the key compress the whippen bushing and in what direction.
In that sence, a little more rubbing capstan could well compress the spread a little,, hence influence the action ratio at last above a certain strenght.

Placebo is also an option, but, for instance, rubbing a little hardly the letoff buttons, with a hard plectra, a hammer shank, will change the letoff sensation, make it a little bit larger, smoother,
for whatever reason you may find ! (any idea ?)

I am not as availeable than I wish, so no posting for some time. I hope that will be better in some time.
Best regards

My memory didn’t serve—so I pulled up the drawings, cycled the key and wippen through their arcs and measured. It would take a very poorly set up action for the sliding movement to exceed 0.2 mm. Even in a small grand action (i.e., short keys).

I agree with those who polish and lube—I also buff capstans and shoot a coat of dry Teflon powder into the capstan block felt. I’m not sure it does much good but it makes me feel better and it doesn’t hurt.

ddf

I lube capstans when replacing the stack, but I get a better result by lubing knuckles and key pins with teflon. Lubing those areas is always part of my concert prep.

Del, as I have a little time to read and think (not too much !) those days, I verified the data given in Pfeiffer s book.

You are right indeed, I confused with the comma placement :
level of sliding path (grand) is, depending of the sharps/ white keys placement (magic line)
0,139 mm for white and 0,2 for sharps (optimized for white keys)
0,195 for white and 0,1442 for sharps when optimized for sharps.

On a vertical, slide path is larger with 0,3 to 0,4 mm so indeed it maybe considered minimal

That said ;
The cushion take more or less the concave shape of the capstan.

The friction is high just at the Beginning of the stroke , enough to be considered as a mean to tighten the pinning (pull the whippen toward the player) the initial position of the whippen is then considered important as supposed it can vary the precision of the fit of the whippen center because of the direction of the force at the beginning of the stroke.
Due to the upward pressure coming from the hammer , the one coming from the key, the deformation of the cloth under impact the level of friction there can be higher than one imagine, and in any case it does not work as smooth as a Ball bearing.
I had not thought of that by myself, those ideas come from a well know brand that use a particular whippen position in order to smooth the circular motion of the whippen..

Pfeiffer state that under good placement and profile conditions, the wear of the heel, cloth may be minimal , but he seem to say that things can get bad easily, if cloth is not quality enough, or too soft, if capstan profile is not smooth, if magic line is not respected enough.

A full study with all the moves and work decomposed, the 2 books, one on the hammer, the other on the key/whippen (the last mostly for direct blow action ), are nice to read, I have no animated cad sketch to play with, but the paper works well enough when the demonstration is good.

Btw do you know the level of efficiency of the grand action ? surprising it hardly get above 14% . while the vertical action is more than 20%

above a certain force of play, the action simply saturates, no work is gained at the hammer level.

But all those losses are what allow the pianist to control tone, and a linked action (linked hammer, but it apply also partly to the linked key/whippen) have even a poorer result in term of energy transmission.

Best regards

Isaac