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Correct Glues To Use


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#37 Dave Prebble

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Posted 02 January 2004 - 11:33 AM

Although the jokes are getting "tacky.........


Not to mention my enduring 'pearls of wisdom' ;)

Dave

Greg, do let us have some feedback on how you get on with your project and feel free to shout up if you get stuck....... :ph34r:

#38 Dave Prebble

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Posted 02 January 2004 - 04:48 PM

Hi Greg,

Just a couple of afterthoughts:
While bearing in mind Dave E's comment about sufficient thickness of the leather, do be aware that Chamois leather skins can wary quite widely in thickness from one part of the skin to another. Take good care to select an area of the skin with even and sufficient thickness throughout and cut all your partition seals from there.

Another ommission in my earlier post....take care not to stretch the partition seals as you glue them on. Chamois stretches easily and could lead to uneven thicknesses.

As Dave mentions, do try to ensure a good snug fit but never force things along. The beauty of using an unglued skirt is that' if compaction does occur over time causing leakage, you can easily make very fine adjustments by shimming out under the skirt using paper strips.

As an additional measure to help with the safe removal and replacement of the reed pans, a one off application of a little French Chalk to the new linings will greatly ease the passage of the pans.

Regards

Dave

Edited by Dave Prebble, 02 January 2004 - 04:51 PM.


#39 Pete Dickey

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Posted 03 January 2004 - 02:04 PM

Hi Daves P and E

Count me in when you meet for that pint of PVA. I want to bear witness to the discussions.

Dave P - just to pick up one point re: the fit of the chamois to the face of action box. You mention shimming out the chamois as necessary to improve the fit. My question is what is the best way of checking the fit - if you were for example using a sheet of glass over the bellows end? How would you mark those parts of the chamois that needed adjustment or conversely those parts that were making a proper contact? If machining you could use "Engineer's Blue" but this clearly is out of the question with the chamois. Or do you feel that it is adequate to just estimate the fit by eye?

Cheers
Pete

#40 Dave Prebble

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Posted 03 January 2004 - 08:33 PM

Hi Pete,
I’m sure you would be most welcome. Being a bit of a traditionalist I expect yours will be a pint of ‘Newcastle Brown Gum’ and a ‘Scotch’ chaser ? :D

As regards sealing I think we are a little at cross-purposes here.
The shimming I mentioned goes behind the chamois seal that you see on the inner faces of the bellows end frame when the pan is removed. Shimming behind this inner piece, which I call a ‘skirt’ when it is loose, will effect a tighter seal on the edges of the reed pan itself and on the ends of the partitions.
On many old concertinas, however this skirt is actually glued to the inner face of the bellows frame.
Having said that, I have unglued and shimmed behind such a seal in order to marry up bellows and reed pans from two scrap instruments…Ah! The wonders of reversible glues! :lol: :lol: :lol:

As regards the partition seals that mate to the action box, the key points to consider when renewing them are:
- With the old seals removed and the old glue residues cleaned off, place the pan face down on a flat surface and check for any significant warping by trying to rock it.
- Ensure even thickness (and texture/density) of the new seal material and take care not to ‘thin’ it by stretching while ‘placing’ it.
If you get the above right, you should have no problems obtaining a good seal.
In effect you are starting with a flat surface and adding the same thickness throughout.... result = flat surface
After all, the whole idea of the chamois seals is to take up and allow for any minor irregularities between the mating surfaces.
Do remember, only a very light application of glue is required. Too much and it will soak into the seal and harden to create ‘high spots’ and possible leakage. Just place each section onto the glue as gently as possible and then invert and gently press down each new seal on a flat surface is to ensure even glue distribution. When you think about it, these seals are held in compression and the only requirement of the glue is to stop them falling off when the instrument is stripped down for repair or maintenance.

Though I have heard of a sheet of glass being used in this way, I have never tried it myself. The only way I can see that it would be of any use is if one could visually judge (thriugh the glass) how compressed a section of chamois seal is when say finger force is applied; air leakage being, of course, invisible. I have just tried it out using an old reed pan with well bedded in seals and could determine no visual differences.. I can however imagine that with well textured and, as yet uncompressed, new seal material, some differences might be visible.
I would love to hear from anyone who uses the ‘glass trick’ to useful effect.
I suspect it may be of some use when building new instruments or compensating for warped reed pans but my feeling is that under normal repair circumstances, the guidelines set out in the various postings in this thread should suffice to give good results.

The above ‘general guidelines’ will of course only hold true if the reed pan is free of significant warping.

Hmmm……I feel a 'warped reed pan' thread coming on…. :)

Regards

Dave

#41 goran rahm

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Posted 04 January 2004 - 03:51 AM

As the chamois sealing between reed pan and action board ( particularly between reed chambers and board) has come up ....I just would like to add an un-orthodox idea wondering if anyone else has had the same thought?:

It really can be a tricky matter to get the chamber sealings tight, some wharping of the reed pan is not uncommon, getting the (often loose) pieces holding the reed pan in place in the frame also somewhat vague.... in all not very secure conditons for getting it tight.

A technically and practically easier,cheaper and more reliable way to seal it all up is not using any strips on the reed chambers at all (or leaving them as is if not perfect)!
....just using one (not glued/fixated) common gasket sheet (open for the pad holes) covering it all up in one piece. There are lots of cheap suitable materials for the purpose today that did not exist before....
You may have to change it now and then like any other machinery gaskets, but so what? If cheap and easy to make...
Of course since we may be traditional 'purists' some of us...maybe not so attractive...but still..there is NO alterations of 'original conditions' and NO risk for accidental mishaps....

Goran Rahm

#42 Clive Thorne

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Posted 04 January 2004 - 08:16 AM

Goran,

I like that idea in princible, after all your replacing about 40 pieces of leather with one large piece (of leather or other material). As you say, I suspect many traditionalists might object if it were applied to old instruments, but there wouldn't be that problem with new instruments.

My main concern would be whether that large area of soft material in the reed chamber would deaden the tone of the instrument? Of course, according to the individual's taste, this might be seen as a good thing or a bad thing.

It probably needs someone to try it out.

Clive.

PS: A happy and prosperous New Year to everybody at C.Net.

Edited by Clive Thorne, 04 January 2004 - 08:17 AM.


#43 d.elliott

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Posted 04 January 2004 - 02:16 PM

Dave P & Pete,

Newcastle 'Brown Gum', 'Scotch' Chasers,

So.........

I suppose that PVA is Particularly Vile Ale,

actualy we are all close enough together to meet for a pint, perhaps a bit of bonding? (probably supping sump oil, knowing you Dave)

Dave E

#44 d.elliott

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Posted 04 January 2004 - 02:23 PM

Glass in hand, not for beverage.

. I have used plate glass to check/ judge the seal on the bellows frame edge gasket. Simply by pressing the open end of the bellows onto the glass and lifting by the opposite sealed end of the instrument and judging the degree of suction. It was all too imprecise to be useful but when you get a good seal then the bellows really stick.

Dave

#45 goran rahm

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Posted 04 January 2004 - 08:10 PM

Clive:"My main concern would be whether that large area of soft material in the reed chamber would deaden the tone of the instrument? Of course, according to the individual's taste, this might be seen as a good thing or a bad thing."

Goran:I haven't tried to measure an effect but I've tried a couple of gasket materials and subjectively found no difference. You know there have been lab tests using *very* different materials (wood,metal,plastics...)for reed chambers and action boards on accordions with no detectable differences either....
I once tried covering the entire space underneath the endplates with asphalt sheet which hardly had any effect..."Baffles", fretwork and filtering covers have greater influence on tone.

Goran




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