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Morgenstern & Kotrade piano action #2899364
10/11/19 06:12 PM
10/11/19 06:12 PM
Joined: Oct 2019
Posts: 3
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Babboz Offline OP
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Babboz  Offline OP
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Joined: Oct 2019
Posts: 3
Hi folks, would really appreciate some help identifying this element screwed on catcher shank :

How do you call it? What is it for? And especially what is procedure for regulating?

Thanks



[img]http://imgur.com/a/fxd72lW[/img]

[img]http://imgur.com/a/X3jUliW[/img]

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Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899366
10/11/19 06:26 PM
10/11/19 06:26 PM
Joined: Sep 2018
Posts: 533
Chernobieff Piano Offline
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I'd say it's an adjustable jack assist spring and the spring is broken. Looks like you can punch out the dowel to remove the broken spring and put in a new one.
-chris


Chernobieff Piano Restorations
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Morgenstern & Kotrade piano action [Re: Chernobieff Piano] #2899378
10/11/19 07:39 PM
10/11/19 07:39 PM
Joined: Oct 2019
Posts: 3
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Babboz Offline OP
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You're certanly right.
Still don't get how regulation works, the screw tip holds the cork of the bridle strap which is also glued to the catcher and even secured with a nail, not allowing much movement of the screw.
Guess it must be all set before glueing the bridle strap. But how?

Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899417
10/12/19 12:37 AM
10/12/19 12:37 AM
Joined: Jul 2019
Posts: 20
France
U
ulrichg Offline
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Posts: 20
France
The spring doesn't look to be broken. Its purpose is to help the jack return to its rest position. Whereas the green felt may serving as back-stop for the jack.
If it's the case, the screw will regulate how strong the spring acts on the jack

Last edited by ulrichg; 10/12/19 12:38 AM.

Ulrich Guillerm, Piano technician, owner

Ti Piano

France
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899418
10/12/19 12:39 AM
10/12/19 12:39 AM
Joined: Jul 2019
Posts: 20
France
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ulrichg Offline
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France
The bridle strap must be glued on the dowel, but I wouldn't use the nail : it weakens


Ulrich Guillerm, Piano technician, owner

Ti Piano

France
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899420
10/12/19 01:09 AM
10/12/19 01:09 AM
Joined: Jun 2003
Posts: 27,799
Oakland
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BDB Offline
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The exact geometry is missing when the parts are removed from the rails. The back of the jack tip may hit against the button, but I am not certain how the spring would come into play. I would have to see the parts in the action frame to speculate.

If there is a patent you could look up, that may explain it.


Semipro Tech
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899438
10/12/19 06:59 AM
10/12/19 06:59 AM
Joined: Feb 2017
Posts: 2,646
New Hampshire
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P W Grey Offline
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Joined: Feb 2017
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New Hampshire
Possibly a very good design. Would like to see it in action.

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
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Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899476
10/12/19 10:51 AM
10/12/19 10:51 AM
Joined: May 2015
Posts: 1,349
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Ralphiano Offline
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Might it be an attempt cause greater hammer shank acceleration, and, to mimick the repetition abilities of a grand piano? In other words, make the repetition of the action faster like a grand piano?

This presupposes that there was a problem with hammer speed in the first place (it seems safe to assume that some problem existed that justified the attempt at improvement).

If the hammer was not departing the top of the jack at sufficient speed, the top of the jack would next strike the metal wire sticking out of the green felt/button. This might have been designed to impart greater acceleration to the hammer. The little curly Q tip of that wire suggests it was intended to receive a blow from the direction of the top of the jack, with the curved tip guiding the jack toward the other end of the wire.

And, the bottom surface of the "button" at the bottom of the mystery device appears to be slightly lower than the bottom of the hammer butt leather. If the jack could be caused to travel underneath this button as the button and hammer return to rest, the jack would now rest under the button instead of the higher hammer butt leather. In this elevated position, the hammer would be poised for another strike from a resting position that is closer to the strings, without requiring the piano key to return fully to the top of its travel. So, fast repetition is enabled.

That's my amateur guess! laugh

Last edited by Ralphiano; 10/12/19 11:00 AM.

Ralph

Kawai VPC1
Garritan CFX Lite
Pianist since April, 2015
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899561
10/12/19 03:56 PM
10/12/19 03:56 PM
Joined: Oct 2019
Posts: 3
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Babboz Offline OP
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Thank you guys for all the best interest!
Here's a short video of the action.

http://imgur.com/a/t1CaktT

The cork is quite tight in the screw, probably glued, was thinking to get away with it just living it there and replace the bridle with the "strap only" kind glued to the cork.

Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899573
10/12/19 04:44 PM
10/12/19 04:44 PM
Joined: Jun 2003
Posts: 27,799
Oakland
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BDB Offline
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Oakland
Sorry, I cannot figure out what those things are supposed to do.


Semipro Tech
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899586
10/12/19 05:26 PM
10/12/19 05:26 PM
Joined: Sep 2018
Posts: 533
Chernobieff Piano Offline
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Posts: 533
Thanks for the video. Still looks like a jack assist spring to me. Looks like the jack is suppose to be force up into the spring and the spring then will assist it back under the the hammer butt. The leather on the jack is also another clue for me. Looks like the screw adjusts the spring up and down. Also fix that lost motion please.
-chris


Chernobieff Piano Restorations
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
Re: Morgenstern & Kotrade piano action [Re: Chernobieff Piano] #2899607
10/12/19 07:08 PM
10/12/19 07:08 PM
Joined: Oct 2013
Posts: 31
PNW
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MilePost51 Online content
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I agree with Chris.
If everything is well regulated and the piano is being played in a normal manner things would look much different.


Working on being a retired piano tuner.
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899656
10/13/19 01:44 AM
10/13/19 01:44 AM
Joined: Jul 2019
Posts: 20
France
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ulrichg Offline
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France
Yes, that's what I wrote

But without proper regulation nothing will work evently


Ulrich Guillerm, Piano technician, owner

Ti Piano

France
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899700
10/13/19 08:04 AM
10/13/19 08:04 AM
Joined: Feb 2017
Posts: 2,646
New Hampshire
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P W Grey Offline
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Joined: Feb 2017
Posts: 2,646
New Hampshire
It would make more sense to me if the spring was inverted and bearing on the back side of the jack so ad to push it back into position. As it is, it appears more likely that the spring would actually catch and hold the top of the jack...not an efficient design.

There have been many attempts to improve this issue in uprights. The best I have seen thus far is the Fandrich model.

Pwg


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899706
10/13/19 08:26 AM
10/13/19 08:26 AM
Joined: Jun 2011
Posts: 536
Chesterfield. MA
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Craig Hair Offline
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Chesterfield. MA
It prevents the action from collapsing if backcheck fails.

Craig


Craig Hair
Hampshire Piano
Chesterfield, MA
Conservative Piano Restoration
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Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899717
10/13/19 09:06 AM
10/13/19 09:06 AM
Joined: Aug 2013
Posts: 171
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Ed Sutton Offline
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Posts: 171
The intention is to provide a separating force between the jack and the hammer butt, similar to the repetition lever in a grand.
While the hammer is in check, the spring is slightly compressed against the jack top.
When the key is released, the spring pushes the hammer away from the jack, and perhaps also gives the jack a little push toward the butt. This will enable the jack to reset sooner in the cycle, giving repetition sooner in the key rise.
Try turning down the screw until the spring contacts the jack tip. Search for the adjustment that allows the hammer to move toward the string when the key is slowly released, as you would test the rep. spring in a grand action.


Ed Sutton, RPT
Just a piano tuner!
Durham NC USA
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899723
10/13/19 09:43 AM
10/13/19 09:43 AM
Joined: Sep 2004
Posts: 2,371
Old Hangtown California
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Gene Nelson Online content
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Old Hangtown California
I’d try taking up some of that lost motion and bending the wire.


RPT
PTG Member
Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899736
10/13/19 10:28 AM
10/13/19 10:28 AM
Joined: Dec 2012
Posts: 5,342
Seattle, WA USA
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Ed McMorrow, RPT Offline
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Seattle, WA USA
I agree with Ed Sutton. The possible "unintended" consequences of this design is that the CG of the hammer assembly is greater towards returning the hammer from the string because of the weight in the screw/sliding button apparatus affixed to the catcher than it would be with the standard vertical action configuration.

As always, hammer weight would be pivotal to making the action function well.


In a seemingly infinite universe-infinite human creativity is-seemingly possible.
According to NASA, 93% of the earth like planets possible in the known universe have yet to be formed.
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Re: Morgenstern & Kotrade piano action [Re: Babboz] #2899843
10/13/19 03:11 PM
10/13/19 03:11 PM
Joined: Jan 2011
Posts: 1,656
Canberra, ACT, Australia
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Chris Leslie Offline
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I would try removing the lost motion and using the mystery adjuster to cause the spring to start contacting the leather on top of the jack. Then see what changes happen.


Chris Leslie
Piano technician
http://www.chrisleslie.com.au

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