Diagrams for CBA levers/wires/buttons?

[David Colpitts]

Hello, All.
I am a relative newcomer, and very curious about CBA mechanics. Is there a place/site/book I might see to get an idea about how the buttons' force goes through its path of levers/wires/pads/springs, etc? To be honest, I am thinking of making a conversion to CBA from a simple piano-style melodica, to get something like an "Accordina" but at low-cost DIY prices. Any suggestions will be appreciated! For the record, I have successfullly converted 5 or 6 keyboards to the (also isomorphic) Janko-style keyboard, but that just requred a little woodworking atop the extant keys. I suspect not so simple to get from piano-style to CBA, where identical notes end up diagonally displaced from each other, and not just horizontally/vertically, like the Janko.

 

[David Colpitts]

As so often happens, after I post a question I stumble upon some more information. Daddy Long Les of this forum posted some diagrams showing the relationship between a CBA layout and the piano equivalent, which gives me reason to believe it isn't going to be so tough to modify my little keyboards to CBA style.....looks like the same wooden overlays I use for the Janko conversions, but with different button arrangements for CBA. Might be my next "hobby-shopping" instrument! But, I'd still like to see any more technical pictures of the mechanism, as I asked for a little while ago. Thanks!

 

[debra]

The mechanics of a CBA accordion keyboard cannot be compared to the accordina. The accordion uses levers from key or button over a pivot point to an arm that lifts a pallet. An accordina just has a push button straight down to open a valve, and is held up using a simple spiral spring... Much simpler than the mechanism of the accordion. The 4 and 5 voice CBA has even added complexity to make the movement of the buttons on row 1 and 4 (and 2 and 5) similar, unlike what that movement would be if both buttons were simply fixed onto the same lever/arm.

 

[David Colpitts]

Thank you, debra. I guess I should ask, "is the arrangement of reeds inside a CBA completely linear in that from left to right (or is it right to left in a CBA?) all notes are "in order" like inside the melodica? And are the levers you mentioned bent every-which-way like some concertinas, to allow the buttons to be where they need be? I haven't found pictures of "the works" in a CBA, but I know they're out there.....And, as I said in my second post above, I am imagining a 3-row CBA could be an easy conversion from the melodicas. Here's a picture of one of my Janko melodica conversion, for reference.

 

[dak]

There is no one-size-fits all approach to CBA keyboards. Here are 2 different approaches to 4-reed instruments. The first is of the Morino Artiste family (to be more precise, the Artiste D series which fundamentally differs in the internals from the succeding N and S series). Here you can see a 3-row staggered arrangement of the pallets corresponding to the 3 button rows, with each reed set for a note being spread across 1½ reed blocks each for a total of 6 reed blocks (the pallets for the L reeds cannot be seen: they are separate round pallets in the gap behind the keyboard). All the levers are stamped from sheet metal and are straight.


Now contrast this with the following CBA that has 4 reed blocks in total, using alternating sets of pallets (similar to how a PA would do it, or even more like a native Jankö keyboard would do it). The straight correspondence of button row and pallet row is gone, and the lower density of the reed plates leads to increasingly crooked levers towards the ends of the button board that have a less direct feel than with the Morino. Even though the buttons take up more space than the reed blocks, it still manages to have dead buttons on both ends of the keyboard because the keyboard tray is similar in size to piano accordions with their lower note density.

So the geometry of mapping notes from the different rows to pallets and reed blocks is, like, totally different. The latter is more frequent with instruments that have a direct piano accordion cousin with similar geometry and possibly identical bass side. The straight correspondence of the former is more typical for "native" CBA instruments that have been designed in one piece not compatible with piano accordions.

With a melodica you'll have the slight complication compared to a piano that the key levers in a piano (and thus the black keys which are flush with them) are spaced with 12 identical spaces per octave while the white keys are spaced with 7 identical spaces per octave. In contrast on a melodica the black keys are centered between the white keys I think and do not have a grid separate from the white keys. So the mapping is slightly different than on a piano and may be slightly less suited to covering with a CBA gear that won't fit the black keys as perfectly.

 

[Siegmund]

Here a peek at the inside of a CBA keyboard (this one is 4 rows, by Mengascini), from the front and the back.

The good news is that the layout of the reeds is as regular as the layout of the keys -- 3 equal rows, every note a minor third apart, and no weird bent key arms near the pallets.

The bad news is that there's a coil spring underneath each individual lever, attached just behind the axis of rotation of each level, to pull the keys up/pallets shut, rather than the simpler type that lies underneath a PA key and pushes it upward. Further bad news is a bunch of fiddly little spacer bits along the axis of rotation, and as Paul already mentioned, some weirdness to make the 1st and 4th rows feel similar.

 

[debra]

Thank you, debra. I guess I should ask, "is the arrangement of reeds inside a CBA completely linear in that from left to right (or is it right to left in a CBA?) all notes are "in order" like inside the melodica? And are the levers you mentioned bent every-which-way like some concertinas, to allow the buttons to be where they need be? I haven't found pictures of "the works" in a CBA, but I know they're out there.....And, as I said in my second post above, I am imagining a 3-row CBA could be an easy conversion from the melodicas. Here's a picture of one of my Janko melodica conversion, for reference.

The reeds in a melodica are small, all on one long plate, and only one reed per note. So the reeds fit in a row. In an accordion there are separate reeds for push and pull and so they take up twice the amount of space and do not fit in a row. You need at least two rows of reeds (for instance one row for white keys and one for black keys) in order for the accordion to not become much larger than needed for its keyboard.
In an accordina you have separate reed plates for each note and there are again two rows, one on each side of the instrument. The first row of buttons uses reeds on one side, the third row reeds on the other side and the second row has its reeds distributed over both sides. The same is true for a CBA with pairs of reed blocks: First row go onto one reed block, Third row onto the second reed block, Second row has its reeds distributed over both blocks. Very large CBAs use triplets of reed blocks, one block for each row of buttons (and possibly another set of three blocks on a four voice instrument).