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Morgenstern & Kotrade piano action

Posted By: Babboz

Morgenstern & Kotrade piano action - 10/11/19 11:12 PM

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]
Posted By: Chernobieff Piano

Re: Morgenstern & Kotrade piano action - 10/11/19 11:26 PM

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
Posted By: Babboz

Re: Morgenstern & Kotrade piano action - 10/12/19 12:39 AM


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?
Posted By: ulrichg

Re: Morgenstern & Kotrade piano action - 10/12/19 05:37 AM

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
Posted By: ulrichg

Re: Morgenstern & Kotrade piano action - 10/12/19 05:39 AM

The bridle strap must be glued on the dowel, but I wouldn't use the nail : it weakens
Posted By: BDB

Re: Morgenstern & Kotrade piano action - 10/12/19 06:09 AM

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.
Posted By: P W Grey

Re: Morgenstern & Kotrade piano action - 10/12/19 11:59 AM

Possibly a very good design. Would like to see it in action.

Pwg
Posted By: Ralphiano

Re: Morgenstern & Kotrade piano action - 10/12/19 03:51 PM

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
Posted By: Babboz

Re: Morgenstern & Kotrade piano action - 10/12/19 08:56 PM

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.
Posted By: BDB

Re: Morgenstern & Kotrade piano action - 10/12/19 09:44 PM

Sorry, I cannot figure out what those things are supposed to do.
Posted By: Chernobieff Piano

Re: Morgenstern & Kotrade piano action - 10/12/19 10:26 PM

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
Posted By: MilePost51

Re: Morgenstern & Kotrade piano action - 10/13/19 12:08 AM

I agree with Chris.
If everything is well regulated and the piano is being played in a normal manner things would look much different.
Posted By: ulrichg

Re: Morgenstern & Kotrade piano action - 10/13/19 06:44 AM

Yes, that's what I wrote

But without proper regulation nothing will work evently
Posted By: P W Grey

Re: Morgenstern & Kotrade piano action - 10/13/19 01:04 PM

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
Posted By: Craig Hair

Re: Morgenstern & Kotrade piano action - 10/13/19 01:26 PM

It prevents the action from collapsing if backcheck fails.

Craig
Posted By: Ed Sutton

Re: Morgenstern & Kotrade piano action - 10/13/19 02:06 PM

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.
Posted By: Gene Nelson

Re: Morgenstern & Kotrade piano action - 10/13/19 02:43 PM

I’d try taking up some of that lost motion and bending the wire.
Posted By: Ed McMorrow, RPT

Re: Morgenstern & Kotrade piano action - 10/13/19 03:28 PM

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.
Posted By: Chris Leslie

Re: Morgenstern & Kotrade piano action - 10/13/19 08:11 PM

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.
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