Lachenal Lever Problem

[Anglo-Irishman]

Friends,

 

I've had some trouble with two notes on my Lachenal 48-button Crane lately. Specifically, the G and D on the two buttons (one directly over the other) that lie in the centre of the RH keyboard. When I press the G (the outer of the two) and inadvertently just touch the D, the D note sounds weakly, but perceptibly, especially on the press.

 

A further symptom is that these two buttons at rest are slightly lower than the others.

 

Suspecting a weak spring or a bent lever, I opened the action box, and behold! the two offending buttons were now level with all the others! And the spring pressure was also the same. So something must be inhibiting the upward travel of the buttons when the action box is closed. But there was no foreign body or unevenness to be seen on the inside of the end.

 

After a couple of vain attempts to bend the levers into shape, I found the cause:

 

On these two buttons only, the levers do not run straight from the button through the pivot to the pad. The section between the button and the pivot takes a sideways curve around some other button. (Button, pivot and pad are, however, in a staight line.) And the (hooked, not riveted) levers of the offending buttons had rotated slightly round their axis, so that the curve was now sideways and slightly up. And this curved section was touching the inside of the end plate!

 

I rotated them back, but they resumed their rotation after a few presses, and the fault returned.

 

Then I noticed that the springs of these levers came to bear on the curved section, which is off the lever axis, thus exerting a rotating moment. The spring of the D lever was unusual in that its upper prong was longer than the lower, placing the upper hook on the curved section of the lever. I replaced this spring with one that had equal prongs (and a bit more force, because its point of application was now closer to the pivot), and the problem was solved. The G lever was less serious, and a slight adjustment of the bend was enough to get the spring to engage the straight section of the lever.

 

The question that troubles me is, was this "asymmetrical" spring the original, or had some repairer inserted it, perhaps to increase the button/pad pressure, not thinking of the possible side-effect?

 

Any views?

 

Cheers,

John

Edited May 8, 2013 by Anglo-Irishman

[Geoff Wooff]

 

 

The question that troubles me is, was this "asymmetrical" spring the original, or had some repairer inserted it, perhaps to increase the button/pad pressure, not thinking of the possible side-effect?

 

Any views?

 

Cheers,

John

So John,

it is one of these two cases ? If the asymmetrical spring was original then the effect of this might have been extra wear on the pivot which gradually allowed the lever to arc upwards .

 

If the offending spring was replaced by a repairer then this points to a careless approach of someone who does not play the Crane. I have noticed that several Maccanns which have been in my hands lately have been 'restored' to working order but not really 'playing order'. It s not until one starts playing an instrument more fully that some problems might present themselves.

 

The third and perhaps blameless case would be a spring replacement by a previous owner who did not take into account the effect of sideways pressure on the lever and pivot, but again this ought to have been picked up during a routine service if you had purchased your Crane through one of the current Dealers!

 

I might sight the case of one beautifull Maccann that I worked on last year, which had been purchased restored... this instrument had quite a few very poor springs , some of safety pin quality, dubious tuning and valve problems.. although it was shinny and glorious to view....

Edited May 8, 2013 by Geoff Wooff

[Anglo-Irishman]

 

 

it is one of these two cases ? If the asymmetrical spring was original then the effect of this might have been extra wear on the pivot which gradually allowed the lever to arc upwards .

 

...

 

The third and perhaps blameless case would be a spring replacement by a previous owner who did not take into account the effect of sideways pressure on the lever and pivot, but again this ought to have been picked up during a routine service if you had purchased your Crane through one of the current Dealers!

Geoff,

Thanks for the expert reply!

 

Could be a bit of both of the above, I suppose.

I did buy the concertina "through one of the current dealers," but the fault didn't emerge until I'd been playing it for over a year. So it could have been a previous owner or careless restorer who inserted the asymmetrical spring, and a functional test at the dealers - even by a Crane player - wouldn't have detected that a fault would occur over time.

 

The other thought that crossed my mind was whether the spring is original, and these simpler Lachenal Cranes have a design error. The curve in the lever is necessary to get it past the other buttons, and would be harmless, as long as button, pivot, pad and point of application of the spring force are in a straight line. Perhaps the last condition was overlooked.

 

Have any other Lachenal Crane owners had this problem?

 

Cheers,

John

[Chris Ghent]

I recently found this same issue fixing an edeophone. The springs had been fitted in the same place as yours, at the point furthest from a straight line between the button and the pivot on levers which deviated to go around another button. The levers had worn themselves and the pivot until the levers were on quite an angle and inclined to jam down. I was disappointed to find it was the original installation point for the spring, as there were no other holes in the action board for a spring. This is a truly superb instrument in all other respects.

[Greg Jowaisas]

The 4-5 48b Cranes I've refurbished seem to have more than their share of problems with the action on the RH side highest notes. Several of the levers follow the circuitous path from button to pad as described and several levers are extremely short.

Repositioning of the springs or replacement of a worn pivot post seem to be the cure but often accompanied with a seemingly inordinate amount of perseverance and patience!

Greg

Edited May 8, 2013 by Greg Jowaisas

[Theo]

The same problem often crops up on 56 key treble Lachenal ECs where there is one lever on each side that is seriously offset and tends tilt sideways as a result of wear. Replacing it with a riveted lever is a good solution.

Edited May 8, 2013 by Theo

[d.elliott]

What we are talking about here is 'cranked arm syndrome' and it is the result of an arm being cranked or bent around other keys.This causes the key, the pivot and the pad centre to not lie in a straight line, and the arm itself is certainly not to following a straight path between the three points. The outcome is that the pad force and key forces are applied with a twisting action around the pivot post as well as the rocking action. This causes the lever to gain flank wear and the 'window' of the pivot post to wear on the vertical sides of the opening. the wear patterns send both the lever and the pivot post window rhomboidal.

 

The increases clearances, the lever tips with the twisting action. The pad then takes a slicing action onto the pad hole, the key starts to sit out of vertical dropping the key height and the vicious circle kicks in, the more wear, the worse it gets, the more corner contact in the pivot/ arm interface. The more point contact, the faster the wear, and the worse it all gets.

 

1. one quick and easy solution, but not necessary a full solution is to take out the existing pivot post and simply turn it round thus taking out say 25 to 30% of the wear.

 

2. The next solution is to get a pivot post from a scrapper which is not worn, this halves the problem

 

3. The next solution is to change the pivot post and change the lever arm too, if you can get a lever arm of the right length.

 

4. The next solution is to open up the pivot window by filling out the wear, then file the flanks of the lever arm to get rid of the wear there too, then shim the newly widened gap with brass shim, catching it onto the arm flank with a touch of solder.

 

I have used all these techniques in different circumstances, often number 2. above is all it needs, especially if the new pivot's window is on the narrow side; so you can thin the arm at the pivot point eliminating more wear, as you make the arm fit the post window.

 

regards

 

Dave

[Anglo-Irishman]

What we are talking about here is 'cranked arm syndrome' and it is the result of an arm being cranked or bent around other keys.This causes the key, the pivot and the pad centre to not lie in a straight line, and the arm itself is certainly not to following a straight path between the three points. The outcome is that the pad force and key forces are applied with a twisting action around the pivot post as well as the rocking action. This causes the lever to gain flank wear and the 'window' of the pivot post to wear on the vertical sides of the opening. the wear patterns send both the lever and the pivot post window rhomboidal.

 

Dave,

 

Thanks for putting a name to the malady! I always feel better when the doctor can put a name to what I've got.

 

In this case, the button, pivot and pad centre are in a straight line - it's just the point on which the spring acts that is off centre. This opens up the additional therapy of moving the spring to a slightly less "cranked" position. But I'll bear your other cures in mind if the problem recurs.

 

Cheers,

John

[d.elliott]

John,

 

In this case the resultant issues are the same,including the wear between pivot post and lever arm flanks, I would certainly try taking, if you can and as you suggest, the spring to a different position, but this will not address existing wear, so please try replacing or at least turning the pivot post as well.

 

best wishes

 

Dave

[RAc]

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Edited March 4, 2016 by RAc

[d.elliott]

All ideas are good ones, however the issue is one of forces being transmitted around corners, causing rotational couples and the wear has already taken place.

 

Dave

[alex_holden]

Here's a blog post about how I solved this problem:

http://alex-holden.livejournal.com/275201.html

[Chris Ghent]

Lovely work and lovely photos too..!

 

I fixed a couple of these recently by cutting out new levers which were slightly oversize in both thickness and height. The increase in height meant the new lever passed across the worn spot in the pivot. There was enough height in the pivot slot to allow this. The increased thickness meant I could custom file the lever to a nice clearance in the sides of the slot. Finding a better place for the spring might mean it never has to be done again.

[RAc]

Here's a blog post about how I solved this problem:

http://alex-holden.livejournal.com/275201.html

Excellent work, thanks for sharing, Alex!

[alex_holden]

Thanks! I recently got a set of camera bellows specifically for taking close-up photos of this sort of intricate work.

 

Chris, I also considered making the lever taller before deciding to make the pivot thicker instead. My idea had been to silver-solder a fin to the bottom of the existing lever, directly below the pivot point. Perhaps I will try out that solution instead the next time I come across this problem!

[Syncopepper]

I have had this problem with my 56 key Lachenal extended treble and have nursed it along by messing with the spring.

 

In leu of replacement parts I wonder if swapping the offending pivot post with one from a straight levered high key seldom used might help?

 

Otherwise, as the instrument's original restorer when quiried did not want to replace the hook action with rivited unless for the entire 56 keys (very expensive), is there anyone in the states who does this kind of repair?

[alex_holden]

In leu of replacement parts I wonder if swapping the offending pivot post with one from a straight levered high key seldom used might help?

I think it would help, though it may not completely solve the problem because I found that the affected levers also had notches worn into their corners at the pivot point.

[RAc]

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Edited March 4, 2016 by RAc