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Anybody ever have a complaint that the harder and faster the piano is played the more the touchweight increases to the point that some notes will not play - with no examples of high friction notes when arriving to check it out??

I suppose it may happen with geometry problems, surface, problems, high inertia.

That is something I can imagine as a piano player, it rings something to my memory as a technician, as scratchy knuckles, lot of undercentering (you play FFF easily but the action get harder to move)

Also lots of overcentering with too much shank flex (seen that in old Bechstein) as we attain soon the action limits, what remain is more friction without any rise in power.

I think friction is always variable depending of the force or speed of the key.

If there is too much resistance at the beginning of the stroke, for instance, this friction raise when one want to play faster

Piano is a new Broadman. 7'6"
Action may be a Chinese copy of Renner? Not certain.
However, geometry is great - not an issue with this problem.
Touchweights range from 50 to 55 g down and 23 to 26 g up.
No friction in keys, jacks, repetition levers, knuckles are round with added Teflon.
No alignment issues or anything else.

Could it be that problem of the hammer shank centres that start to seize up with lots of movement?

The problem could be that their fingers get more tired the longer and faster they play.

However, I might check the repetition springs.

Lol
I did check the rep springs - smooth with no deposits or grooves in the seats.
Action regulation was good, no issues with geometry either.
Several years ago I had to re-pin re-bush hammer flanges on a 80's Japanese upright.
The center pins were plated and the plating was flaking off getting into the bushing cloth.
Not the case here.
What it turned out to be (I hope) was poor bushing job on the whippen flanges. Excess felt not trimmed flush rubbing on the birdseye so it was measuring 3 g +/_ when removed and tested with the gauge so assumed ok, within a normal enough range. But when I pushed the center pin out there was the problem. Need to re-bush and re-pin the whip flanges.
Actually, I hope that was the problem. I could not play hard and fast enough to recreate the complaint or find increased friction.
I can't figure what else could it be.
No parts rubbing, hammer tails not contacting catchers, ???
No binding at the key slip.
Hammers voiced good enough, not too soft, good power.

Take a look at how many lead weights are in the keysticks. Too many weights can cause this sensation.

Hey Ed,
Three leads in the bass tapering to zero in the top octave.

I still like the tired finger explanation.

I think you find it.

I thought of action cloth and knuckles missing resiliency.

Let off rail not secured /tightened

Hey Olek
I had not considered soft knuckles nor did I look at what the let-off buttons were anchored to. On my list for the next visit.

Hello , the letoff button rail did leave me scratching my head for some time on a small grand; much friction during letoff at normal playing speed.

The soft knuckles is the impression I had when trying some of those Chinese action, some are probably Renner copies but the materials used differs.

I believe this action is indeed a Chinese copy Renner
Thank you.

+1 There is a lot of subjectivity at play in piano playing. ('Sorry for the overuse of the root word "play".)

I noticed that techs that are not trained classical pianists can miss a somewhat too firm touch, a jumpy touch that can be suitable for jazz can N be trouble for a classical pianist.

I have seen enough pianists left unsatisfied after hood technicians did work, to be sure of that.
Well balanced regulation allows the pianist to "chase for tone" when too pronounced let off for instance, reduce the possibilities.

Subjectivity can be on the technian side too.

Too soft cloths and woods are also absorbing too much energy before their compression transmit the energy.

You've probably already checked this but it's worth mentioning anyways. Check that the backchecks are not rubbing under a hard blow. While pressing on individual keys, put some pressure on the hammer and watch if the tails rub on the backchecks.

Thanks Ed, and yes, I did check for hammer tail interference at the back check and it is ok.

Action saturation? (parts and felts flexing... specially keys).

Possible but the client states that the effected notes are not playable for a short time after they tighten up. It takes hours or a day to loose the friction and become playable.
Action saturation comes and goes with playing I believe.
Id like to think the same about soft knuckles but I am a bit uncertain about that right now.
I did ask specifically about what he meant by not playable. When you push the effected key, do you get sound? he says no. That means to me that the jack is not resetting.
I could not make it happen and the regulation is very accurate.
But if the description is accurate, possibly soft knuckles plays a roll that I dont quite understand.

The clue for me is that the piano reverts to playable so relatively quickly. maybe there's something very borderline here and often the solution is the simplest which nobody seems to have mentioned yet.

Is there something that your client is doing on commencing to practice?, like opening a window, switching on a light or fan, switching off the heat, closing drapes or even perspiring profusely while practicing?? I had something similar once where the piano was in a very small bedroom and wasn't there something a few years ago on this forum where someone turned out to be perspiring over the strings?

It is the season for rising humidity levels in so many places. It could just be a situation where the humidity is close to the tipping point anyway.

Thanks for your input rXd.
The piano resides in the sunny, hot and dry California Sierra Nevada Foothills and humidities are low and consistently in the high 20's / low 30's .
The piano is in a very large room, no direct sunlight nor is it near any direct heat or air conditioning sources.
If the client perspires profusely while practicing I would need to ask him and I had not considered that but I would think there would be some visible remnants or spotting, stained wires or some tell tale clue - not that I remember.
Typically, homes in California are closed up with air conditioning on automatic during most of the day, temperatures outside are in the mid 90's F. This is the case for this client.

why not low quality center pins that enlarge when played enough (heat, enlarging of the metal)?

I never noticed that myself but certainly some heat is created at the hammer center level.

did you check friction for all centers ?

maybe something edgy, as propose rxd

opening a window would add moisture ? this can reduce the play above the jack

also if there is too much aftertouch, the back of the jack can get stuck in the stop cushion for too long and then the jack do not reset on repeated notes...(I have seen that, the back of the jack is not as smooth as expected, and not graphited,

It's a new piano, almost a year old. If anything with regulation needed touch up it was adding punchings at balance rail, after touch was minimal.

Bingo. Felt centers do increase resistance with heat buildup from friction.

Could be other things in addition ...

The client says it seizes up.
Seizing up and increased resistance leaves a big gap here.
In either case, I am investigating this at the request of the sales person who is trying to identify a factory defect.
The only thing that I see is the poor workmanship at the whippen flanges mentioned earlier.
All of the possibilities from everyone are appreciated but none are really factory defects. I learned some new possibilities as well, thank you.
I suppose I should have mentioned this in the beginning - sorry about that.

It could be the jack buttons set too close, and perhaps the repetition lever too low. This may not be an issue when playing slowly, but the jack slipping out could mean the hammer first rubs on the backcheck, and then later catches on it. That can also be a symptom of a problem with the jack center pin joint.

Knowing exactly what the owner means by "increased resistance" and "seizing up" would really help with diagnosis. Good communication is an important part of troubleshooting.

Well it did pass the "wink the jack" test so I assumed the rep lever adjustment was ok. I even burnished teflon on the knuckles to help make it a bit better.
For the whippens I removed when checking flange resistance, I did uncouple the rep spring and the jack felt ok, I did not do a gauge measurement on that.
I suppose it is possible that poor workmanship for the whippen flanges is not limited to the whippen flanges.
The only test I tried for hammer/backcheck interference was watching clearance as I push the keys while on the bench. It looked ok but not so easy to tell if this is happening when playing hard.
Your right about communication.
Also, if the tech can't be presented with anything more than a description, Im only guessing. Try as I did I could not duplicate the problem.
There is also the possibility of a client that wants to get work done and not pay for it, or changed their mind about their purchase, or otherwise taking advantage of a store that wants to make customers happy, complaining about something that is not real.

To check rubbing tails I refrain the hammer lift a little strongly while moving the key.
Rubbing signal itself by the rubbing noise.
If the shanks are supple they can rub more easily

A big source of defects are the glide bolts screwed too much. But it happens rarely on a new piano

I would still take off a hammer shank and shake the flange vigorously to see what happens.
I've seen them completely seize up before,and the action behaved like you described in your initial post.

A good diagnostic no matter what the recovery time. At least you would know what's happening or what to discount. Moving the shank beyond their usual arc of operation can also cause them to seize but flapping them would give a more definite diagnostic.

Having the client play for a few hours immediately before your next visit could create the condition although sods' law states the the condition will not occur if you do that.

Yes out of their usual range is better avoided
I have seen seizing on a Yamaha where the centers have been treated with a lube.
I did not notice, used clp, and 3werks later the hammers where stuck.

Still no idea of the product used precedent, nothing apparent but the
centers have some gunk building on them.

Raising shanks to vertical is sometimes enough to seize them.

May be the pins can deform, if they are soft enough.

For what its worth I finally got the action to the shop.
Variable friction was caused by more than one problem.
The majority was about 70% of the jacks, at the raised circular piece of machined wood that surrounds the birds eye - they must have had dull cutting tools when they machined this as they were very rough with occasional small splinters of wood that could easily interfere and bind at different times, only visable when unpinned. This explains how they could pass the wink test but bind while playing.
About 40% of the whippen flanges did not have the center pin felt trimmed flush with the flange and had the same dull tool machining as the jacks.
About 25% of the rep-levers had the same machining issues as the jacks.
I found 5 that the jack was rubbing the edge of the rep lever window when key was fully depressed but that is more typical kind of stuff.