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#2311878 - 08/06/14 09:19 AM Bobbling When Hard Blow
Weiyan Offline
500 Post Club Member

Registered: 10/04/11
Posts: 773
Loc: Hong Kong
This piano bobbling when play hard. If play soft, its ok. The hammer bounce back when touch the backcheck. The catcher buckskin are worn out.

Any suggestion?

Thanks

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#2311880 - 08/06/14 09:39 AM Re: Bobbling When Hard Blow [Re: Weiyan]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
the hammer go faster than letoff
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#2311907 - 08/06/14 11:15 AM Re: Bobbling When Hard Blow [Re: Weiyan]
Weiyan Offline
500 Post Club Member

Registered: 10/04/11
Posts: 773
Loc: Hong Kong
Had tried set wider backcheck, the catcher touch backcheck then bounce back. The letoff seems work.


Edited by Weiyan (08/06/14 11:15 AM)
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#2311909 - 08/06/14 11:18 AM Re: Bobbling When Hard Blow [Re: Weiyan]
BDB Offline
Yikes! 10000 Post Club Member

Registered: 06/07/03
Posts: 21926
Loc: Oakland
Sometimes the geometry of the catcher and the backcheck is wrong, and you need to bend the wire to suit. If the leather is worn, it should be replaced. If the piano is not that valuable, you can glue new leather over the old. If you use the right glue, you can take off both layers later.
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#2311922 - 08/06/14 12:17 PM Re: Bobbling When Hard Blow [Re: Weiyan]
TunerJeff Offline
Full Member

Registered: 06/22/11
Posts: 498
Loc: Oregon Coast
Listening to the sound, I'm not sure you are getting let-off on the notes. Is the hammer actually bouncing off the catcher, or is it bouncing off the top of the jack? Let-off is not just the jack starting off the hammerbutt, it must include enough aftertouch to get the jack CLEAR of the hammerbutt.

You may need to slightly raise the hammer rail (closer to the strings) to make sure the jack actually has time to clear the bottom of the hammer.

Or you may need slightly more keydip to insure let-off & aftertouch.

A quick check would be to move a backcheck well clear of the catcher (bend back) and see if the hammer still bobbles off the jack on that medium blow. On a soft blow, the hammer hasn't enough energy to bounce back into the string from a jack that isn't well clear of the hammerbutt.

If the hammer still bobbles; you need more motion on the jack to clear the hammer. Either by reducing hammer to string distance (raise the hammer rail) or increasing the depth the key travels.

BDB's point on geometry is also correct, and the possibility that the catcher leather is too worn may be your problem, too. But, my ear and eyes would be looking at the jack clearing the hammerbutt first. Let-off & aftertouch. OK?

.02-ching!
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#2311947 - 08/06/14 01:57 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Johnkie Offline
500 Post Club Member

Registered: 06/04/11
Posts: 740
Loc: England
Bear in mind though, if you do opt to decrease the hammer blow, you must then re - adjust the pilots to take up the lost motion, otherwise it'll make no difference.
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#2312100 - 08/06/14 08:09 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Weiyan Offline
500 Post Club Member

Registered: 10/04/11
Posts: 773
Loc: Hong Kong
Its Kawai US-55. The pinao has poor dynamic. The letoff distance is around 1 inch. I set to around 2mm, the power and dynamic back. Tried to set deeper aftertouch, still bobbling.

Above posts inspired me another idea: The Hammer Butt Buckskin worn out. High friction between jack and buckskin bounce the hammer back.

The piano is worthless. Tuning pins are cracking. Can only tune to 3 cents precision. He bought this piano last September, $4,100. A "tuner" sold him.
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#2312523 - 08/07/14 04:12 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
Worn buckskin and or worn cushion can send the hammer so fast let off does not happen, only on return of the hammer it touch the Jacks and rebound. (or the jack is blocked by his limiting rail, did you check that ? )

In first case it should work better with 3,5to 4 or 5 mm let off, whatever make let off early enough.

Also if hammers are worn and short the normal let off is 4 to 5 mm if you consider the size of original hammers.

that may be was done by the other tuner. On a vertical, do not change the let off without being sure of a all other parameters.


Edited by Olek (08/08/14 06:03 AM)
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It is critical that you call your Senators and Representatives and ask them to cosponsor S. 2587 and H.R. 5052. Getting your legislators to cosponsor these bills


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#2312577 - 08/07/14 06:20 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Weiyan Offline
500 Post Club Member

Registered: 10/04/11
Posts: 773
Loc: Hong Kong
Next time will test some notes first. In my experience, wide let off is for bobbling. So tested soft blow bobbling. But now he can play romantic pieces. His teacher complaint him for non-expressiveness.
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#2312652 - 08/07/14 08:45 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Jon Page Offline
Full Member

Registered: 03/13/09
Posts: 388
Loc: Harwich Port, Cape Cod, Massac...
Solid checking is a balancing act between hammer blow, key dip and let off.


Edited by Jon Page (08/07/14 08:54 PM)
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#2312809 - 08/08/14 06:33 AM Re: Bobbling When Hard Blow [Re: Jon Page]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
Originally Posted By: Jon Page
Solid checking is a balancing act between hammer blow, key dip and let off.


Yes.

What I hear in the video is hammers that are send too fast.
(I just listened once or twice - it is good to make videos in that sort of case)

May be simply having them too angled at rest can create that (rest rail too thin)

Remember vertical actions are way more "efficient" than gran actions, the hammer is not retained by inertia.

A small dip on the buckskin leather may be enough to have the angle of the jack send the hammer extremely fast, faster than the normal motion of the jack. that create a loss of contact hence a loss of touch at FFF, but generally, on a vertical in any case playing strong means the hammer is immediately out of control.

Always control that the jack have a little space to move farther when the key is at full dip, this problem is rare but happens.
The catcher also can block the action somehow an then adding some key dip does nothing. you can have 11 mm key dip and the key stopping at 10m mm with some actions. the same if the jack limits the system (and very rarely the dampers).

Anyway if the butt have some trouble :

that can happen if the piano played for long with too much space between key an action for instance, or if the piano is fitted with a "silent" system and letoff is too much near the strings.

It will be impossible to allow for a small let off, unless the butt can be "bolstered" or the buckskin and undercloth changed.

Some otherwise good actions will need a large let off, some U1 for instance. if not checking will not be firm.

Testing with the backcheck wire bend is the most precise way to control the whole motions (and the final position of the jack vs the butt)

You will have other experiences like that. Before touching the regulation of the precedent tech, as he sol the piano, it may be up to him to correct regulations problems (guarantee ?)

If not the customer need to pay for a +- complete regulation work, anyway at last 3 parameters going together, you need to influence them all generally.
That is when you nee to understand well what goes on (pianistic touch helps , also) so to use shortcuts, as papering under the key frame, changing the hammer travel distance, and so on, so you need less time to make the action work.

Voicing help checking by helping hammer rebound, I find.
You also need to synchronize the key bottom with the tone production, that is what gives the utmost control on tone for the pianist.

So there may be you may hae nee to reduce key dip a a little.

PS it is extremely rare that too small key dip make the jack block the hammer, it only happen in extreme bad regulation, and do not create that sort of double strike , or only when playing lightly mostly bad checking at FFF playing and hard tone as the key make noise before the hammer make tone.

good luck

You are self employed now ? refrain please to be critical about what did the precedent techs, it may be more complicated to solve the issue than it looks at first sight.

No piano can be regulated with "standard distances" even if they help. one that matters is key dip around 10 mm and key level depending of manufacturer specifs. the rest is up to you.

Regards









Edited by Olek (08/08/14 06:36 AM)
_________________________
It is critical that you call your Senators and Representatives and ask them to cosponsor S. 2587 and H.R. 5052. Getting your legislators to cosponsor these bills


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#2313156 - 08/08/14 08:19 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Greg the Piano Tuner Offline
Full Member

Registered: 11/16/08
Posts: 43
Loc: Boston
would the condition of the balance rail punchings be a factor? In an older piano, they'd be compressed, changing the geometry as well.

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#2313195 - 08/08/14 09:41 PM Re: Bobbling When Hard Blow [Re: Weiyan]
Weiyan Offline
500 Post Club Member

Registered: 10/04/11
Posts: 773
Loc: Hong Kong
Olek: Yes I am self employed. Thank you for your advice. Piano 'tech' here is not same as in Eroupe.
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