End Warping

[jedderee]

I recently purchased my first concertina on ebay, labelled Cambells but I understand Cambell modified and relabeled other instruments, and it looks a lot like a Lachenal.

 

I'd hoped to buy a playable instrument but cursory inspection showed that it was not - even to my untrained eye the pads appeared worn, and there were what looked like insect eggs inside the instrument! Instead of doing the sensible thing and trying to return the concertina, I have since entered the world of concertina repair.

 

I feel quite pleased with the progress I've made so far, but one thing that took me a while to work out was why a few notes on the left end of the concertina continued to sound even after I had changed the pads. I tried putting tape over the holes and this solved the problem, but I could not find a reason the pads were not sealing. In the end I realised that, presumably due to warping (there are a few cracks in the fretwork) the end panel of the concertina was pressing down on the lever arms and causing the key pads to lift when the end was screwed down. For the moment I've managed to stop this by raising one edge with a double layer of cardboard, however this leaves a noticeable gap where the end is lifted up and does not seem to be a very elegant solution.

 

Has anyone else come across a similar problem while dealing with older concertinas? If so, what did you do? I imagine it would be possible to put a spacer all around the edge - has anyone done this, and if so what with/how?

 

Any input much appreciated!

[Dirge]

Have you checked the action height? It sounds as if lowering it a bit may be the fix.

[Theo]

Also check that the pivot posts for the levers are fully pushed home into the board. It is not unusual for some of them to come loose.

[Geoff Wooff]

Also check that the spacers, where the screws go through Under the hand rails are long enough. These sometimes have extra washers added, of paper, card board or leather to keep the ends from touching the levers.

 

Another method if the action is too high and the top ends of the levers are coming into contact with the fretted ends would be to add an extra 'sampa' those little discs of leather that sit on top of the pads... increasing the thickness of these will bring the action down without going to the bother of bending the levers.

[jedderee]

Thanks for the replies - I've reset the action height on all the keys as part of the work I've done so it is the same on all keys. Will check the other things you've pointed out and see where that gets me.

 

Edit- I've had a look and can't find any evidence the pivot posts have come out at all. Re-positioning the springs so they sat further along the arm seemed to help (I changed these and might not have got them in the perfect positions, especially a few I had to make a new hole for as the old spring snapped at the base during removal). I also took Geoff's advice and added an extra sampa to a few keys for the levers which were difficult to bend down. I've still got a bit of a leak through one pad but I repositioned it a little during the process so it might just need to re-bed itself. Can hear the air moving but it isn't sounding any reeds.

Edited June 7, 2013 by jedderee

[Geoff Wooff]

Sounds like you are getting there with your restoration !

 

Happy music.

[jedderee]

So that pad I thought was going to need to re-bed? I had the end off the concertina today to take a look at it and there is something very strange going on.

 

Now the note is sounding when I let the bellows drop (this started since I took the end off), and I cannot work out where the air is coming in from. It isn't through the pad - I confirmed this by putting some tape over the hole. The chamois round the reed looks like it's forming a good seal - another thing that makes me think it isn't the chamois is that there is an audible whistle of air moving, similar to that heard when the air release button is pressed (what I could hear before the read started sounding).

 

I've lost count of the number of times I've had the end on and off this afternoon trying to work out what's going on and it's getting me very frustrated. I'm hoping one of you experienced bods might recognise the symptoms and be able to tell me what is going on!

[Geoff Wooff]

If you feel that the fretted ends were warped then why not the Pad board too. I had this in one of my concertinas and air was passing across the top of the reed chamber wall and venting into the air release chamber and every time I released the air I got a note, a faint one which had me foxed for a while because it had the pitch of a reed that was on the opposite side (radially speaking) of the Pan...

 

Part of the cure for this was making sure that the Reedpan and the Pad board (action board) were mated together. If there is any simple warp in the wood, in the form or curvature, this usually occurs from left to right, as you look at the ends from the playing position; your wrists being bottom and finger tips point to top.. so the wood grain of the Reedpan and Pad board are both in line from top to bottom.

 

So, it is often that there is a small amount of curvature from left to right.. best if this is convex ie when you place a straight edge across the underside of the Pad board, (left to right) the centre of the board should be slightly higher than the edges... usually this is not the case if you have some inefficiency in the sealing department. Sometimes this warping can be quite a lot and concave but as long as it matches the the reedpan curvature it is OK... but what usually happens is that it does not match (quite) or this type of warping has made the top and bottom corners turn up their toes a little... then someone has tried to improve the seal by over tightening the end bolts and you get warps along the edges of the Pad board... put straight edge along the Under side of the padboard on the edges where it fits onto the end frame of the bellows... check also the straightness of the bellows frame.

 

Some Lachenals are made with the Padboard side walls stuck onto the outside of the hex shape and there can be a gap where the pièces have come unglued... air can escape there.

 

If the ends and the Reedpans are warped then either compensating Gaskets need to be made or the parts need to be flattened, either by Un-warping (steaming perhaps) or by grinding flat by some method like fixing a sheet of good Wet and dry paper to a flat surface with double sided tape and carefully sanding the offending surfaces... sometimes then requiring re-making the chamois gaskets.

 

Check also the fit in the bellows frame of the Reedpans and the state of the gaskets and the height of the support blocks to have everything in a good place for sealing..

 

Make really sure that you have found the cause of your leak before making irreversible changes.

Edited June 11, 2013 by Geoff Wooff

[d.elliott]

Can you advise: are we talking an anglo, or english system instrument?

 

Dave

[jedderee]

Sorry, I should have mentioned - it's a 20 key anglo.

[jedderee]

Oh dear - first of all, thank you all very much for your replies and help.

 

I'm a little embarrassed - it seems that when localising the source of the leak from the pitch of the reed that was sounding, I overlooked the fact there are a few buttons on the same end that sounds reeds of the same pitch! I'd been targeting the wrong pad. Ooops. The good news is, all sorted now, it was another matter of the fretwork compressing the lever arm, and solved by lowering the action a smidge.

 

I won't be making that mistake again!

[Frank Edgley]

I suspect that at least part of you problem may be due to the thickness of the replacement pads. If the are thinner than the original pads when new, the button end of the levers will raise up and contact the underside of the grill, not allowing the pad to come into full contact with the action board.

[jedderee]

Interesting comment - I would say however that if anything the replacement pads were thicker than the old ones. I did raise the action on most of the keys though, which is probably the source of the problem.

[d.elliott]

As a rough guide,

 

when the keys are pressed the distance from the top of the key to the top of the action box cover should be around 2mm or a bit over, the the travel of the key from un-pressed to fully depressed should be 3mm or 1/8th ins.If this is maintained then the key guide pegs should not bottom in their holes, there is usually room for 2 dampers, sometimes plus another, and the leather lever arm bead should not strike the underside of the action box cover. With these settings the pads should open enough to give full voice to the reeds with the action feeling positive and fast.

 

This is all independent of pad thickness as you set the action by bending the levers to suit the pads fitted. I do not subscribe, ever to compensating for pad thickness, or adjusting action height by packing up the arm end by adding extra dots to the top of the pads.

 

Dave