Lachenal Cranked Arms

[d.elliott]

A feature of the lachenal design is that the arms pivot through a slot or appeture in their respective pivot posts. Due to the layout of the action, some arms can be heavily cranked to be able to fit around other keys and arms in the action. This cranking of the arms means that there is a perpetual twisting force on the arm every time the key is pressed and a reverse twist as the pad comes back to rest on release of the key.

 

Eventually both the appeture and the arm wear on their flanks and several effects are noticeable:

 

1. the key height drops,

 

2. the pad is difficult to line up over the pad hole

 

3. the pad lifts at an angle

 

4. the key action is less than smooth.

 

 

On arms which are not bent about in this way, (i.e. are in a straight line between key and pad), this does not occur.

 

I have tried various solutions and work-arounds over the years. There are two problems: the worn arm and the worn pivot post.

 

So, What do others do???????

 

Dave

[d.elliott]

Yet again I am disappointed at the lack of response to more technical subjects

 

What's up Chaps, are we all stuck for words, or are we only able, or prepared to discuss the simpler (public domain) service repairs?

 

In private correspondance Geoff Crabb has given me his view. Thanks Geoff

 

In the past I have tried:

 

+ Side shimming with brass after filing the appeture square,

 

+ I have tried depositing solder onto the worn arm and dressing that flat.

 

+I have pinched an unworn pivot post from an unplayed position that utilises a straight arm and swapped them over.

 

Recently I met with Colin Dipper who asked me a question (perhaps a probing test...???)

 

' Which would I rather have: an Edeophone or an Aeloa of similar outward specification?'

 

I said the Aeola because the Edeophones has this cranked arm and eventual wear as an OE design fault. Eventually the Edeophone would fail in this mode.. I seem to remember a smile and a nod. I know Colin replaces the arm assembly with a riveted one.

 

Not every one has the workshop capability to make and fit entire new arms, so

 

What does the Team Think?? or have we all gone home for Christmas

 

Dave

[David Barnert]

I'd love to give you an answer, but I've got a Wheatstone, and haven't spent much time poking around in Lachenals.

[nils]

Hi Dave,

 

some years ago I had that problem on an extended treble edeophone and exchanged two posts. That worked quite well and was easy to do. The short arm of the top didn't cause any problems with the worn out post.

 

Nils

[Henrik Müller]

A feature of the lachenal design is that the arms pivot through a slot or appeture in their respective pivot posts. ...

...

...

So, What do others do???????

 

Dave

I've never given it a thought, but looking into an Edeophone wreck of mine, I see the problem.

I would probably sit down and replicate a new arm and a new post - replace the whole thing. A tedious*) job, and in the long run it doesn't fix the problem (which is the design) but I guess it takes a fair amount of time to wear down that much. If "keeping the original design" isn't too important, a (new) arm rivetted to a post would be better?

 

/Henrik

 

*) I am at the moment sawing away on my 28 individual-size arms of 1mm brass plate - I am now very sure I know the meaning of the word "tedious"

[Pete Dickey]

Since you demand a reply Dave, I feel that the only proper answer to the problem over the long term is the examination and rearranging of the layout of the mechanism if possible.

 

I would not be losing too much time giving it a lot of thought as I would commission Geoff Crabb to redesign the layout as he appears to be brilliant at that sort of thing (sort of like he is brilliant at most concertina-related things ).

 

So there is your answer, post it to Geoff

[d.elliott]

Posting a worn arm assembly to geoff would be an abdication, no disrespect to Geoff!

 

I get several of these situations in a year (of various degrees), and remember I service an repair, not manufacture and re-design. So I need a good working solution

 

For vey bad instances I have been able to re-create the worn arm out of reclaimed parts from a scrapper, and also use reclaimed posts.

 

My objective is to come up with a good and effective repair technique reclaiming original parts as possible.

 

My next experiment is to solder a thin piece of brass shim on the worn flank of the arm and then to dress out the worn side of the pivot post appeture to both accomodate the increased thiuckness of the arm, and to thus loose its worn profile at the same time.

 

I would also like to see this forum re-energised and get some of the original interaction going again, or do we need to bring back Jim's friend from Scandinavia...... can't remember his name, designed an ergonomic spell checker or something.

 

Meanwhile, add the check of 'action wear' to your mental checklist when buying Lachenal English instruments, particularly costly Edeophones........

 

Dave

[JimLucas]

Meanwhile, add the check of 'action wear' to your mental checklist when buying Lachenal English instruments, particularly costly Edeophones........

Your problem is one I haven't had to deal with, but you've worked on far more instruments than I have. Something similar, though, was when I had to replace the lever on a Jeffries anglo's air button. That wasn't due to any twisting motion; it was straight and simple wear. It was a rivetted action, but apparently the button had been used so much and so heavily that the rivet had eaten a hole almost twice its diameter in the lever where it passed through.

[Pete Dickey]

Posting a worn arm assembly to geoff would be an abdication, no disrespect to Geoff!

 

I get several of these situations in a year (of various degrees), and remember I service an repair, not manufacture and re-design. So I need a good working solution

 

For vey bad instances I have been able to re-create the worn arm out of reclaimed parts from a scrapper, and also use reclaimed posts.

 

My objective is to come up with a good and effective repair technique reclaiming original parts as possible.

 

My next experiment is to solder a thin piece of brass shim on the worn flank of the arm and then to dress out the worn side of the pivot post appeture to both accomodate the increased thiuckness of the arm, and to thus loose its worn profile at the same time.

 

I would also like to see this forum re-energised and get some of the original interaction going again, or do we need to bring back Jim's friend from Scandinavia...... can't remember his name, designed an ergonomic spell checker or something.

 

Meanwhile, add the check of 'action wear' to your mental checklist when buying Lachenal English instruments, particularly costly Edeophones........

 

Dave

 

 

I was thinking more along the lines of the whole action board not just the lever.

 

Seriously though Dave, if it isn't possible to swap a few reeds around to end up with straighter levers, would this not be a suitable case for changing both the lever AND post to a rivetted action along the lines of Wim Wakker's action? Easily bought, or made for that matter. That should get rid of the twisting of the the lever with its consequent problems.

[Robin Madge]

Quote "It was a rivetted action, but apparently the button had been used so much and so heavily that the rivet had eaten a hole almost twice its diameter in the lever where it passed through."

 

I've had a lever actually break because the hole has eaten its way right through to the edge! I made a quick fix replacement from a spectacle side arm.

I'm not fond of rivets myself as i dont like something that cannot be taken apart without having a replacement rivet ready to reaasemble it. I have used rods with washers soldered on as a rivet replacement but would probably use a brass nut and bolt with a hardwearing tube around the thread if I had to do it again.

 

Robin Madge

[tony]

Yet again I am disappointed at the lack of response to more technical subjects

 

What's up Chaps, are we all stuck for words, or are we only able, or prepared to discuss the simpler (public domain) service repairs?

 

In private correspondance Geoff Crabb has given me his view. Thanks Geoff

 

In the past I have tried:

 

+ Side shimming with brass after filing the appeture square,

 

+ I have tried depositing solder onto the worn arm and dressing that flat.

 

+I have pinched an unworn pivot post from an unplayed position that utilises a straight arm and swapped them over.

 

Recently I met with Colin Dipper who asked me a question (perhaps a probing test...???)

 

' Which would I rather have: an Edeophone or an Aeloa of similar outward specification?'

 

I said the Aeola because the Edeophones has this cranked arm and eventual wear as an OE design fault. Eventually the Edeophone would fail in this mode.. I seem to remember a smile and a nod. I know Colin replaces the arm assembly with a riveted one.

 

Not every one has the workshop capability to make and fit entire new arms, so

 

What does the Team Think?? or have we all gone home for Christmas

 

Dave

 

Dave,

 

I've been thinking about this one and although I have not had to deal with this situation my engineering experience suggests the following:

 

At first sight one would think that the button, fulcrum and pad should be in a straight line irrespective of how many angles there may be in the rod. However it is my opinion that it is the location of the spring that presents the problem. If the button, return spring and fulcrum are in a straight line then as soon as one begins to press the button the pressure on the pad ceases to have any effect since it is lifted clear of the action board. If the button, return spring and fulcrum are NOT in a straight line then when one presses the button against the pressure of the spring the rod will not lift the pad clear and one side of pad will remain in contact with the action board for some time before it is lifted clear. But what is worse is when the button is released, the side of the pad will contact the action board too soon and put pressure on the side of the rod and fulcrum causing premature wear.

 

The solution would seem to be to relocate the spring and if necessary re-form that part of the rod between the button and fulcrum so that the spring pressure is acting in line with these two (if this is possible). Depending on the amount of wear you may find it is not necessary to re-build the worn parts.

 

Edited to add:

 

One more thought, if you do re-form the rod it would be a good idea to make the center of the three contact points (namely the spring) stand higher, with respect to the action board, than the other two.

Edited December 9, 2005 by tony

[Frank Edgley]

If I remember correctly, the problem with some of these solutions is the lack of room there is to work with. A traditional riveted action may work, but straightening the arm, A Wakker-type mechanism etc. may not be possible because it just might not work. As to completely redesigning the layout, it is easier said than done, and would be too expensive from a time/labour factor, even if it would be possible. The old concertina designers did an impressive job fitting so many notes into such a small box.

[Greg Jowaisas]

Dave,

 

I wonder if the "Edgley two spring method" might not help. Frank has a clever way of using two springs to stabilize his hook and arm type action. The result is a stable pivot point with little of the typical Lachenal wobble. Frank's concertina action is smooth, quiet and has a light touch, surprising in a hook and arm arrangement.

 

It might be a long lasting solution once the worn componants are replaced or repaired.

 

Greg

[tony]

Frank,

 

I wasn't suggesting the rod should be straightened, only that the three contact points should be lined-up (if there is room). It shouldn’t matter how many angles there are in the rod.

[Frank Edgley]

Tony,

I think my comments were in response to Pete's suggestion:

"Seriously though Dave, if it isn't possible to swap a few reeds around to end up with straighter levers, would this not be a suitable case for changing both the lever AND post to a rivetted action along the lines of Wim Wakker's action?"

[tony]

Sorry Frank, just not paying enough attention.

[Frank Edgley]

No problem. I agree with your comments about the three points.

[d.elliott]

Sorry I have been off line for a while!

 

I lean towards Frank's view that the designers of the Edeophone did a superb job, and that messing about with the layout or wholesale re-configuration is a nonsense, I also tend to feel that the edeophone man cranked action arms out of good need rather than for fun.

 

The edeophone is english system 48 or 56 keys, 24 or 28 action sets per side, not like the 10 or 15 of the more usual anglo configurations, space is an issue! and probably the root cause.

 

Usually its mainly one side of the lever arm that seems to wear the most and by soldering a thin brass shim onto that side and by dressing the pivot post appeture, it is possible to re-life the action arm (on bad cases), but this is a remedy to 're-life', not to 'eliminate' the problem. The wear will start again.

 

Someone mentioned spring position, next time I get a cranked arm proble I shall assess this as an option!

 

Dave