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Author Topic: Adding Stops/Couplers et al  (Read 2501 times)

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Gena Crisman

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Adding Stops/Couplers et al
« on: October 09, 2018, 06:14:00 PM »

Hello, as per the title, I'm curious about Stops and Couplers, so, after searching around for a few days and finding little functional information, I've made a post. A lot of information I have has been gleaned from pictures, in particular those that were shared in this thread, this post specifically.

I imagine we're all familiar with the external function of registers/stops; you push a button or move a plunger up/down and it turns off some of the reeds in the instrument.

Usually a slide with holes/blocked off areas moves in and out of alignment with holes in the fondo/reed block. Sometimes this is moved manually, with a direct physical connection, or mechanically, with springs and levers (I guess?)

However, this means that the part of the mechanism that you interact with is on the 'outside' of the instrument, and the part that stops the reeds from playing is on the 'inside' of the instrument. This means the mechanical connection must travel through the barrier separating the two sides.

So uh, I guess how does that work? Are the holes just a really tight tolerance? Are there any particular things one is supposed to do to mitigate issues in that regard?

I'm also quite unsure the mechanics of how mechanical coupler switches actually work, and am very interested in reading more about them. However, I have no leads on what the school of engineering related to it would be called to search out more information.

I ask because a) I'm inquisitive and b) I'm considering my options for adding a Thirds stop to a Black Pearl 2 that I own. First concern: The thirds do seemingly all share plates with one another, so a stop slide should be fine on that front. Second concern: because of the giant fundamental reed block next to it, there should be plenty of clearance to do things underneath the chord reed block that might raise it up, as there's no chance of the melody and bass chord blocks touching one another. Other instruments may have issues.

I believe that, principally, the standard process would be to

1) Remove the existing padding from the fondo
2) Create a sandwich of thin pieces of wood or metal, with a slidable filling, to prevent direct pressure from the block (once secured) on the slide
3) Restore the reed block mounting points (presumably a very fiddly step)
4) Put a new layer of padding on the top of the sandwich
5) Mechanically link the slide to an external plunger, which will involve putting a hole in the case and probably removing part of the bellows frame end so that there's space for that.
6) (I presume) fine tune the reeds as they'll have been pushed 1-2 mm farther away by the slide mechanism
7) ????

Are there other concerns of which I am not aware? It sounds quite involved but not implausible as something a dedicated individual could do themselves. I have other... strange ideas, but, I think I should first try to understand the reality of how existing solutions would work, and ideally test on an instrument that isn't my main instrument.
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Theo

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Re: Adding Stops/Couplers et al
« Reply #1 on: October 09, 2018, 06:20:08 PM »

Adding a thirds stop can be even simpler.  (1) no need to remove the gasket (padding)   (2)  no need to make a sandwich, just one layer works well. thats how most Italin made thirds stop work.

Other things to check"

(1) all the thirds reed plates are on one side of the block, move them if not.
(2) the reed plates are spaced far enough apart so that the sliding register plate can park the holes in between the reed vents.

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Gena Crisman

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Re: Adding Stops/Couplers et al
« Reply #2 on: October 09, 2018, 07:04:07 PM »

Well, that's interesting information! Just having the slide held in place by the reed block would be simpler. However, well, I'll attach a photo and see if that works (if not, it can be found here) - attached ought to be a photo of the present state of the bass end.

The thirds are all on the one side, the side with the 4 holes (it seems anyway) - they're the top side as viewed of the trio of air holes, so, there doesn't appear to be any obvious issue there which would require them to be moved. Also, there is clearly plenty of space for the parking of said holes, so, those (very valid) concerns are alleviated in this case. I am kind of surprised that that is the situation, but, there you go.

But, so, you'll have to help me a little here. When you say there's no need to remove the gasket, are we saying one could build a slide mechanism floating on top of the gasket, effectively placing the physical slide on the reed block side of the equation, but, just clamped in place via the reed block fixing down mechanism? That would be much simpler, but... I haven't seen that. I guess I got stuck thinking the gasket would have to be in a particular place but... there's really no reason for that to be the case I suppose, it just needs to be part of the clamping mechanism and anything that will transfer the pressure could be added in between the block and the gasket, right?

When you say one layer, do you mean, no static flat plate of 'bread' at all? Or, just 1 'slice', ie, Fondo, Gasket, Bread, Slider/Filling, Reed block? I.. should probably draw a diagram at this point.

I should also ask, are there material concerns such as friction etc? I've seen both wood and metal slides. Presumably friction is both bad (hard to move) and good (stays in place). I've heard of magnets to help a low friction slide stay in place but, I'm not sure how to avoid having a high friction slide.
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Theo

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Re: Adding Stops/Couplers et al
« Reply #3 on: October 09, 2018, 07:13:24 PM »

Your reedblock looks ok for fitting a slide.  The slide does indeed just run directly between the base of the block and the gasket.  When these are factory fitted the block has a shallow channel routed into the lower face of the block. When retro-fitting you can glue the same material on either side to form a channel.  I’ve usually used 1mm aircraft ply to make the slide.
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Theo Gibb - Gateshead UK

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Rees

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Re: Adding Stops/Couplers et al
« Reply #4 on: October 09, 2018, 07:26:25 PM »

I've retro fitted a thirds stop to many Italian boxes. I always rout a 1.5mm deep channel in the reedblock then make a 1.5mm plywood slide to fit.
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Rees Wesson (accordion builder and mechanic)
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Gena Crisman

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Re: Adding Stops/Couplers et al
« Reply #5 on: October 09, 2018, 07:47:01 PM »

Well, huh, yeah, ok then. I guess I have another project to work on. I think I may have access to the right kind of equipment to shave the reed block down, but, being that I'm a bit of an amateur in this regard, I assume I should do my best to make sure anything I do can be undone.

Given the above, for double confidence, I disabled those reeds by sticking a bit of card over them temporarily, and ran the instrument through a spectrum analyser. Output is attached, and shows that it is indeed all the thirds that are disabled. I could have done the reverse and just used a tuner I guess but I also wanted to hear what it sounded like (weird!).

Am I correct that adding something in as a spacer, rather than shaving down the block to fit one, would affect the tuning? I have a layout tweak on my agenda sometime soon that I feel is outside of my experience level to do, and while I think I could do the work discussed here myself, I'm not confident I could also retune the chords competently if they are likely to drift. So, it'd be helpful to know if you would expect that kind of change, so I can kinda plan things to pan out, I guess.

And, do you really just put a hole through the side and a metal rod through it, and that's fine? It seems like it shouldn't be fine, for some reason...
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Theo

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Re: Adding Stops/Couplers et al
« Reply #6 on: October 09, 2018, 08:41:46 PM »

If the holes in your register slide don’t obstruct the vents in the reed block, and if you only add a mm under the block then any tuning change will be hard to detect.
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Rees

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Re: Adding Stops/Couplers et al
« Reply #7 on: October 09, 2018, 10:14:34 PM »

"And, do you really just put a hole through the side and a metal rod through it, and that's fine? It seems like it shouldn't be fine, for some reason..."

Yes, absolutely fine, there are four on a one-row four stop melodeon, so it definitely works. I have drilled holes in many a Castagnari :)
My method. Glue block of wood (stopblock) to stop slide. This is a shear joint so drill shallow "grip" holes in both plywood slide and stopblock, lightly sand off burrs. Use Araldite not wood glue. Don't clamp!
Fit stop slide in place under reedblock (channel already cut).
Make a temporary woodblock that fits dreckly between the top of the reedblock and the bottom of the stopblock jamming it against the top of the instrument casing.
Drill a pilot hole for the stoprod thread through the casing and through the stopblock.
Remove temporary woodblock, reedblock and slides.
Drill casing to diameter of stoprod. Make sure the rod is a snug fit in the hole and try to drill the hole at 90 degrees.  :-\
If you wish to get a bit nerdy, bush the holes with Teflon, a la Doug Briggs (hero :)  )
Re-assemble and screw the damn thing home.


« Last Edit: October 09, 2018, 10:20:32 PM by Rees »
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Rees Wesson (accordion builder and mechanic)
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Eshed

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Re: Adding Stops/Couplers et al
« Reply #8 on: October 09, 2018, 10:56:04 PM »

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Gena Crisman

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Re: Adding Stops/Couplers et al
« Reply #9 on: October 11, 2018, 06:26:32 AM »

A bunch of info here as well: http://forum.melodeon.net/index.php/topic,7527.0.html

Thanks for this!

So, I've worked out basically the following.

First of all, there's actually a bunch of clearance between the bass and treble reed blocks (at least 4 mm) so, I could probably put a bunch of stops everywhere, if I wanted to. I guess if I'm doing a thirds stop I might as well consider a low fundamental stop, too.

I really appreciate the information that's been shared already, but, I do have an issue that I don't think anyone has yet alluded to a solution for yet.

With the way the reed blocks mount currently, there's kinda a lot of material in the way of any mechanism. Currently, metal tabs are screwed, with a single screw, into a block of wood (block A), and these apply pressure on the edge of the reed blocks to hold then in place. These are long metal clips, like this

Past this block, there is another block (block B). At first glance this exists for the bellows clip screw to fix into, but, I believe is actually there to provide space past the separating wall for the rotella bolt to advance into. This block B is probably larger than it needs to be, but I don't think it is a big factor.

The bellows frame also extends into this part of the instrument, and when attached the gap between the bellows frame and the barrier wall measures around 8 or 9 mm, so some amount of the frame may need to be removed.

So, if the slide must extend out past the foot print of the reed block in order to be connected, there appears to be a puzzle laid out in terms of exposing enough slide in the right place to attach a stop rod to it, while also being able to secure the reed blocks in place at the same time. I've attached a photograph of the area in question and tried to annotate it showing the wingspan of the metal plates.

Due to the amount of material I believe I would need to remove, the answer that I would think to go with would be to attempt to separate Block A from the instrument entirely (I guess it's hide glued in, so, warm + moisure + pallet knite?) and then create a new clamping system that allows a clear path for a slide mechanism beneath it. The other end of the block is held in with a clamp like this - my inclination though is to produce a solution that offers a similar clamping force to the existing one. Is any of that a sane course of action? Clearly this is an issue that would be confronted fairly frequently, so, am I missing a, let's say, more trivial solution?

I have some 1mm thick PETG plastic sheeting that I intend to make some test slides with to see how that goes. I have no idea if that's a terrible idea since I've never read of anyone using plastic, so, I guess maybe I'll find out? (Reasoning is that it's super cheap and I have a bunch)
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Rees

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Re: Adding Stops/Couplers et al
« Reply #10 on: October 11, 2018, 09:23:37 AM »

Ah yes, you do have rather a lot of timber in the way so surgery will be required. You are, however, on the right track.
Plastic slides are fine, Weltmeister have been using them for years.
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Rees Wesson (accordion builder and mechanic)
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Steve_freereeder

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Re: Adding Stops/Couplers et al
« Reply #11 on: October 11, 2018, 09:52:02 AM »

Not sure if this helps, but here is a photo of the interior of a Castagnari Laura. The top end of the instrument is to the left.

The photo shows the clamping arrangements for the reed blocks and the exposed portion of the aluminium slider which passes beneath the thirds reeds in the chords reed block, and which has vent cutouts to open/close air flow into the reed chambers. The upper reed block is for the chords; the lower block for the basses.

The left-hand end of the slider is not visible in the photo but it is glued to a small block of wood which, in turn, has the shaft of the external thirds 'mushroom' stop screwed into it.

As you can see, the LH reed block clamps are screwed into a rectangular wood block. The block and the line of the clamp are both offset slightly to allow space for the slider. There is no bass fundamental stop on this particular instrument but if one were to be fitted, a similar off-set would be required on the bass reed block clamp.

From your photo, it would seem that the clamping arrangements are the opposite way round: the top end of the instrument is to the right and this end also has the flat clamping plates. You would need to modify your wood block 'A' and cut a shallow channel for the slider to run in, and also modify block 'B' or drill through it for a slider stop shaft.

It might also be worth investigating whether the clamping plates could feasibly be swapped from one end to the other, so you have the flat plate at the other end of the reed block, as in the Castagnari photo. This would then allow you to have a smaller wood block 'A' which might give you more working room to install your slider (not sure about that though - would need to see the whole bass-end interior).

Anyway, the Laura photo might help you as an example of how it is done on Castagnari instruments.
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Rees

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Re: Adding Stops/Couplers et al
« Reply #12 on: October 11, 2018, 09:55:00 AM »

Thanks Steve, that saves me opening up a Castagnari :)
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Rees Wesson (accordion builder and mechanic)
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Lester

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Re: Adding Stops/Couplers et al
« Reply #13 on: October 11, 2018, 10:46:18 AM »

This is the coupler I have fitted for thirds on my Pressed Wood


https://photos.app.goo.gl/8ADDHyU5WzibeXtg7
The block that holds the reed block in place had to be cut in half and the chord side removed and notched so the the slide could pass under it. It was the refitted (glued and screwed) and modified to place a clamp for the reed block which used to slide under rather tan be clamped.

https://photos.app.goo.gl/wXeNuyxkJjnT9rbo9
Reed block in place to show block clamps.

Can do better photos etc when not in a holiday cottage in Norfolk

Rees

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Re: Adding Stops/Couplers et al
« Reply #14 on: October 11, 2018, 06:37:33 PM »

Clever design, Lester.
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Rees Wesson (accordion builder and mechanic)
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Gena Crisman

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Re: Adding Stops/Couplers et al
« Reply #15 on: October 11, 2018, 07:03:55 PM »

Steve and Lester, the photos posted help a lot, I don't have access to any instruments with slides and I have been able to find surprisingly few pictures showing the mounting solutions in use & what sensible options look like.

It might also be worth investigating whether the clamping plates could feasibly be swapped from one end to the other, so you have the flat plate at the other end of the reed block, as in the Castagnari photo. This would then allow you to have a smaller wood block 'A' which might give you more working room to install your slider (not sure about that though - would need to see the whole bass-end interior).

You are correct that the clamps are currently the other way up in my instrument vs the Laura. I've investigated simply swapping them from end to end, and good news, I can absolutely reverse the mounting solutions. I guess drilling a small hole into the reed block to allow swapping them over is of little consequence, so, a solution like that shown in the Laura is likely the route I shall take, as if I make a complete mess of everything else, the reed block could still be perfectly clamped in place with the remaining material.

I believe my plan then would be to first reverse the mounts, and see how far over I can comfortably offset the thinner sort. If I establish this, then I can consider simply removing parts of Block A entirely. My preference is to try and avoid having to remove, work on, and then reglue any parts as I have no experience with hide glue and I know there are reasons not to use eg PVA. So, my plan would be to do the work in situe by using eg a hand drill with depth indicator to gently make most of the cuts across the block, finish the cut with a small file or blade, and then remove the offending sections via detaching their glue.

If I make a slide that just runs underneath just the set of holes I wish to block, I'll need my slide to serpentine from the 'inside' side of the reed blocks to the outside. I noted though that Lester's slide appears to run the whole width of the reed block. I imagine that increases the friction somewhat and most importantly increases the risk of the slide being able to move left to right out of alignment if you don't have enough going on to prevent that from happening, which is an issue I may run into.

So, I believe I have a plan:

A) Relocate the mounting hardware to a more convenient orientation and check that the reed blocks don't fall off. Also order some Stop plungers.

B) Use a scanner/copier to produce an orthogonal projection of the instrument and reed blocks and spec out my slides and work out what looks it would make sense and will actually be able to move enough to do the job. I suspect the holes in the blocks and the holes in the fondo are out of alignment so pick one of those to match up with I guess.

C) Try to actually make the slides out of the material I've considered and see if it works or if it's garbage.

D) If successful, believe in myself enough to remove parts of wood from my expensive instrument and test fit the slides, see if they work etc by manually moving them up and down with the instrument open, then reassemble play etc.

E) If successful, Drill holes in to my melodeon... presumably while screaming? Then put the Stop rods through them.

I will update with any progress, pictures or diagrams etc as I generate them. Thank you for the guidance & sharing of experience.
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Re: Adding Stops/Couplers et al
« Reply #16 on: October 11, 2018, 09:00:56 PM »

"Drill holes in to my melodeon... presumably while screaming?"


You're a better man than I am, Gunga Din!

(No sexist or racial smears or slurs intended, so there's no need for any recriminations, thank you, Big Brother!) 
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Lester

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Re: Adding Stops/Couplers et al
« Reply #17 on: October 11, 2018, 09:02:09 PM »

I noted though that Lester's slide appears to run the whole width of the reed block. I imagine that increases the friction somewhat and most importantly increases the risk of the slide being able to move left to right out of alignment if you don't have enough going on to prevent that from happening, which is an issue I may run into.


The reason that the slide is the full width is because I was working with a hohner chord block which, even after some clever tuning stuff*, has the thirds reeds on alternating sides of the block.


   O  O O  O  O O
  O O  O  O O  O


*Hohner in their wisdom don't put the thirds for the pull and push on the same reed plates
eg G chord    G    B    D
     D chord    F#  A    D
So as a start it is necessary to do tuning wizardry to end up with

eg G chord    G    B    D
     D chord    A    F#  D

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Re: Adding Stops/Couplers et al
« Reply #18 on: October 12, 2018, 12:46:04 AM »

....If I make a slide that just runs underneath just the set of holes I wish to block, I'll need my slide to serpentine from the 'inside' side of the reed blocks to the outside. I noted though that Lester's slide appears to run the whole width of the reed block....

As Lester has explained, the thirds reeds in Hohners tend to be on both sides of the reed block.

However, on your Dino Baffetti instrument, in common with most Italian instruments, and as you have mentioned in your earlier post, the thirds reeds for both push and pull are on the same reed plates on one side of the reed block, so your slider doesn't need to be the full width, only half width, which makes the job easier.

As Theo mentioned earlier, you could use thin strips of 1 mm aircraft ply to form channel edges on the base of the reed block, each side of your thirds reeds for your slider to run in. You would also need to attach a similar strip of ply along the other edge of the reed block adjacent to the tonic/fifths vents, and short strips of ply transversely to isolate each pair of tonic/fifths, otherwise you will get leakage of air between those reed chambers of adjacent chords.
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Gena Crisman

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Re: Adding Stops/Couplers et al
« Reply #19 on: October 12, 2018, 03:06:22 AM »

A) Relocate the mounting hardware to a more convenient orientation and check that the reed blocks don't fall off. Also order some Stop plungers.

Stage A complete!

The larger metal clips were a direct translation from one side to the other. In order to fit the smaller clips to the other side, I decided that I would position them so they could mount into the original holes left by the larger clips, because from this position, when rotated ala Steve Freereeder's picture of the Laura, they would be well within the margins of where I expect to trim this block in the future - the margins informed from how close the existing holes were to the edges of the block. The different kinds of metal clips are of differing thickness, and as the main screws that secure the clips were identical at both ends, the holes in the wood were of different depths, so, one side was now too shallow. I measured 12mm depth for the original holes where the smaller clips had been, and used a hand drill to extend the existing holes on the top side of the instrument (noting that the pieces of wood were of the same size at either end). I attached the clips to these mounting points, and made pilot marks on the reed block - the smaller holes into the block take smaller screws, measured to 7mm deep so, I drilled them to that and then screwed the whole lot together to I guess little to no fanfare, but, I felt pretty good about it. Then, I took it apart one last time, rotated the mounts into the intended offset position, made even more holes (to the 12mm depth again) and put that all back together.

It currently seems stable and not like the reed blocks are being pulled at an angle or unevenly as things stand, so, I'll have a good play tomorrow and see if anything feels different, and then await the arrival of some new ink cartridges so that hopefully my scanner will stop being off limits as the part of it that is also a printer is constantly screeching until appropriate tribute is paid.

I should say, I noted Lester's slide construction being of full width mostly because I personally would actually find it easier to make a single, reed block footprint sized slide rather than several strips that must all have straight, parallel edges and interlock. Given the thirds and bass fundamentals are all located on the 'inside' side of my reed blocks, it would also perhaps simplify the construction if the whole thing can move, but, again really I'm keen to design to a scanned image rather than a measured copy as I don't have any good measuring tools, and the equipment is sadly out of action. I would love to know, how does your full width slide feel, Lester? Appreciably different or awkward in any way?
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