Repairing an old Curtini CBA

[niels]

Hi all
Parallel to MilkoTVs thread ..
As I would like to learn how to repair an accordion i got myself an old Curtini CBA as classroom material

As far as I can see now there are two jobs to be done.
First is replacing the felt+leather underneath the pallets. The stuff that is there now is completely desintegrating.


The other job is a crack in the housing by the bottom plate. That job is for later in autumn/winter. By Christmas I hope to have the thing fixed
Any progress will be documented here. Tips and advice are very welcome

 

[debra]

If the felt+leather comes off easily and the pallets lift high enough (which by the looks of this accordion may well be the case) then you can get the old disintegrated stuff off, maybe sand down any left-over residu and just glue on new felt+leather. You can buy the leather+felt pads from Carini (carinidena.it) pre-cut for a standard 2-voice pallet. Glue on with (preferably water-resistent) white glue.
A crack is a different (more difficult) matter to deal with. Fixing the crack itself is usually a matter of prying it open a bit more, pour some good wood glue in the crack (I always use Titebond III) and then clamp the parts together. The difficult part is repairing the celluloid, which requires having some new black celluloid at hand. You dissolve the celluloid in a bit of (pure) acetone until it becomes a paste. You can then smear that into the crack. Wait 24 hours, then sand. If needed, repeat. When you have a smooth (but dull) result, polish to make the surface shine again.

 

[niels]

thanks Debra! I hope to get the pallets done without having to take the keyboard mechanism apart. Maybe take the pallets off, don't know yet.
When on a holiday in Sweden I got a piece of felt/leather from Karlsson, so I think next job is to cut that to fitting pieces.

The crack is an interesting one. Working with celluloid, eager to try it

 

[niels]

I have decided to go the remove-the-pallets way for refreshing the felt+leather. These are fixed with wax. The first one has come off easily with some heat and patience.
Will have to learn how to apply wax later on.
Those black strips on top, I will try to preserve them but they may tear. It looks like they are bellows tape material. Is this standard accordion shop stuff ? Could cut some myself I suppose?

 

[debra]

I have decided to go the remove-the-pallets way for refreshing the felt+leather. These are fixed with wax. The first one has come off easily with some heat and patience.
Will have to learn how to apply wax later on.
Those black strips on top, I will try to preserve them but they may tear. It looks like they are bellows tape material. Is this standard accordion shop stuff ? Could cut some myself I suppose?
...

The Italians use a half-moon "spoon" for applying wax, which is probably not so easy for a beginner. But some time ago I got a great tip to use a pilette. You can suck up a small amount from your pot with melted wax and apply it carefully without spilling. Touch up is with a soldering gun at medium heat (not full heat to melt solder).
The black strips are indeed bellows tape. Many new accordions nowadays come without such tape. It serves no real purpose other than looking decorative and maybe slowing down the process of the wax drying out over several decades.

 

[niels]

Thank you Debra.

Do you mean one of these for applying wax?



I try and keep the strips. They look nice; and on that first pallet I took off, the wax was still fresh maybe because of the strip

 

[debra]

Thank you Debra.

Do you mean one of these for applying wax?



I try and keep the strips. They look nice; and on that first pallet I took off, the wax was still fresh maybe because of the strip

Yes, but I use a somewhat larger version (you find many different ones on Amazon for instance). You want one without the "bubble-like" end that makes it hard to aim precisely. You want a narrow end.

 

[KiwiSqueezer]

Paul De Bra wrote: 'The black strips are indeed bellows tape'.

Thank you for that! The pix show that to be true. I've been looking for leathercloth for just that purpose, here in NZ, for weeks, without success. Another example of NZ Unobtainium... And all the time, I had a roll of bellows tape in store - hiding in plain sight!

Regarding cracked wood: I've got a bee in my bonnet about PVA adhesives and their too-widespread application. They are unarguably excellent adhesives, in the right application, but have two (actually more, but not relevant here) disadvantages. Firstly, they perform poorly if asked to fill gaps - ideally, the joint needs to be clamped tightly. Secondly, they creep, so a stressed joint will move, given time. For this reason, they are not used where the wooden joint design relies on the strength of the adhesive, so highly-stressed joints in chairs won't be glued with PVA. In, say, a pegged mortice and tenon joint, or a dovetail joint, where the joint design is strong without adhesive, they are fine - if you can work quickly enough: the open time afforded by PVA is short. Epoxy is a good adhesive for open cracks in timber: it has good gap-filling properties, doesn't creep, and is strong. If the crack cannot be easily closed, it may indicate that the timber has warped, thus, even if the joint can be sprung closed by clamping, it may open again because of the adhesive creeping under stress. Further tips: slow-curing epoxy is stronger than the 5-minute stuff; attempting to lower the viscosity of the stuff, for instance with acetone, results in a weaker cure, but gentle warmth works well.

 

[debra]

...
Regarding cracked wood: I've got a bee in my bonnet about PVA adhesives and their too-widespread application. They are unarguably excellent adhesives, in the right application, but have two (actually more, but not relevant here) disadvantages. ...

I use PVA (white glue) for only one application: keeping the felt+leather glued to the wooden pallets.
For serious wood glue Titebond III (Ultimate Wood Glue) is very strong and I believe it is now also used in (some) accordion factories instead of the smelly bone glue that was used in the past.

 

[KiwiSqueezer]

PVA adhesives, of which Titebond III is one, are indeed 'strong', in that, under sufficient stress, the substrate will usually fail before the glue line does. But dimensional stability is also required. This can be a problem if the joint is under even mild, prolonged stress, even for 'strong' and modified PVAs: they creep, including the Titebond family. In continually-stressed glue joints - say a 'glu-lam' beam, laminated furniture, or in stringed instruments, PVA should not be used. Resorcinol is favoured for laminates, in industry. Now, whether creep is a problem in practice obviously depends on a lot of things, some of which are controllable and predictable: for non-critical applications, the abundant evidence of its widespread use suggests PVA is probably OK.

 

[niels]

Getting underway with removing the pallets. Using a thin hobby knife and a hot iron to warm the knife up against.

Just an observation.... The wax inside the pallets seems to have been held in place on the front side. Maybe by a partially glued on black strip? Going to give that a try later on in the phase of rewaxing.

 

[oldbayan]

I use wax sticks and a hot wax stylus, similar to a soldering iron.

 

[KiwiSqueezer]

niels said: 'Just an observation.... The wax inside the pallets seems to have been held in place on the front side. Maybe by a partially glued on black strip?'

That's my assumption too - make a 'bucket', into which the wax can be poured. Regret it's only an assumption - not knowledge... When the time comes, I'll do what you suggest.

 

[niels]

I use wax sticks and a hot wax stylus, similar to a soldering iron.

Thanks for this, oldbayan
I may go pay a visit to a gentleman I know who had an accordion shop for decades but has now retired. Hopefully he will be so kind as to teach me in person.

 

[niels]

That's my assumption too - make a 'bucket', into which the wax can be poured. Regret it's only an assumption - not knowledge... When the time comes, I'll do what you suggest.

KiwiSqueezer, whatever happens in the wax stage, I will make some pictures and a description Hopefully sometime in coming weeks.

 

[niels]

PVA adhesives, of which Titebond III is one, are indeed 'strong', in that, under sufficient stress, the substrate will usually fail before the glue line does. But dimensional stability is also required. This can be a problem if the joint is under even mild, prolonged stress, even for 'strong' and modified PVAs: they creep, including the Titebond family. In continually-stressed glue joints - say a 'glu-lam' beam, laminated furniture, or in stringed instruments, PVA should not be used. Resorcinol is favoured for laminates, in industry. Now, whether creep is a problem in practice obviously depends on a lot of things, some of which are controllable and predictable: for non-critical applications, the abundant evidence of its widespread use suggests PVA is probably OK.

when the time comes for repairing the crack in the bass half I hope you will take notice and have some expert advice

 

[niels]

Pallets removed, quick job, these can easily be wriggled off with a bit of warmth and care.
Removed old felt, some pulverized, some stonified. There is a fine fabric glued to the underside of the pallet. Cleaned it up as well as possible. Roughed it up a bit for better glueing later on.
Now cleaning out the inside of the pallets. A very small screwdriver, 2.5 mm blade, fits the gap perfectly.
Beginning to understand how a dentist could find his job satisfying

 

[niels]

progress report…
cut out 43 pieces of felt+leather. Thickness is 4mm as advised by Karlsson.
glued them to the pallets using white woodglue.
put the pallets in position to see if they run free and cover the register gaps.

challenges were
cutting the felt to exact size. I used a heavy metal ruler and a sharp hobbyknife but still some turned out a bit large or small. Hopefully there is margin for such minimal errors. I found using an actual pallet as a measuring stick worked well.
glueing without getting glue on my fingers and other places it shouldn’t be. My way was to apply the glue with a slender metal tool used for shaping clay, dip that in the glue, and when applying the glue keep the felt between fingernails so as not to get the stuff on my fingers.
focus… after about 20 pallets I found myself holding a piece of felt+leather with glue on the leather side

Will probably shave off some of the felt that is sticking out.

All in all it was quite doable so far, not as complicated as I had imagined, since the keyboard mechanism has stayed intact.

What is next? learning about wax for fixing the pallets; maybe adjust the height of the keys. I hope to get advice and instructions for this in real life...

 

[KiwiSqueezer]

Niels, have you found the 'Accordion Revival' web site? George Bachich provides a wealth of advice there about setting up keyboards (and most other things, too). Much better than 'Accordion Repairs Made Easy' or 'The Ins and Outs of the Accordion', both of which can be found as downloadable .pdf files, if you search hard enough, and take the risk of downloading possibly copyrighted material.

 

[niels]

Thanks Kiwisqueezer. I know the Accordion Revival site and also Accordion Repairs made easy, but not The ins and outs of the Accordion. Will see if I can find that one .