Reed Block "bridge"

[96Bass]

What is the purpose of the metal "bridge" between the reed blocks? On my 4 reed non-cassotto Beltuna,
there is one of these bridges connected to all four reed blocks.

 

[Dingo40]

What is the purpose of the metal "bridge" between the reed blocks?

Keeping things together ?

 

[Plinky]

High 96 bass ,they are Transit bolts, shipping bolts like on washing machines so the drum dosent move around in transit
Only kidding !!!!!
Had one on a meloeon I think its intended to add ,stability rigidity,less vibration wobble
But I forgot to put mine back and I don't think it made any real difference,but it may have a completely different purpose
I sold the box and I've got it in a tin somewhere

 

[jozz]

What is the purpose of the metal "bridge" between the reed blocks? On my 4 reed non-cassotto Beltuna,
there is one of these bridges connected to all four reed blocks.

to avoid unwanted vibration / resonance
should help on boxes with tight tremolo and keep a stable tuning

 

[boxplayer4000]

They reduce the energy of the vibrating reeds being absorbed by the reed blocks and instead turn that energy into sound.
It may also be the reason that some Hohner accordions had their treble reed blocks made in two parts but still had the metal ties fitted.

 

[dak]

What is the purpose of the metal "bridge" between the reed blocks? On my 4 reed non-cassotto Beltuna,
there is one of these bridges connected to all four reed blocks.

Gives reeds on different reed blocks a better chance to synchronize rather than show a real slow beating. Also (already said) increases the stiffness of the reed block against vibrating under forces from the reed plate: that kind of vibration loses energy a lot more than the bending back and forth of the elastic steel reed. That kind of energy loss not just affects brilliance but also pitch.

 

[Plinky]

Gives reeds on different reed blocks a better chance to synchronize rather than show a real slow beating. Also (already said) increases the stiffness of the reed block against vibrating under forces from the reed plate: that kind of vibration loses energy a lot more than the bending back and forth of the elastic steel reed. That kind of energy loss not just affects brilliance but also pitch.

dak thats Interesting,why not a full length ?or 3 at the ends and middle?

 

[debra]

The bridge is intended to reduce each individual block's tendency to vibrate with the notes on it being played. By locking two (or three) reed blocks together that vibration is reduced. It rarely has any effect on "synchronization" as Dak mentions because in many cases the blocks that are locked together do not share the same notes. In a 2+2 accordion (2 reeds in cassotto and 2 outside) one block will have the M reed outside of cassotto and the H reed of the same notes, and the other block again has the non-cassotto M reed and H reed, but for the other half of the notes.
The reed blocks vibration causes a slight change in frequency, so it is important to have the bridge in place when tuning is measured. (Oops, so much for people who believe you can measure tuning by just placing a reed block on a tuning table... think again.)
Some older accordions also have a "clamp" that presses down on the reed blocks in cassotto. But I have not seen that in accordions from the most recent few decades. It must not have mattered enough to be worth the trouble. Perhaps for the same reason many recent accordions also no longer have the bridge.

 

[Ventura]

if a "bridge" were intended to function like a Violin soundpost
(to pass vibrations through to other sections of the instrument)
then it would need to be substantial, hard and dense.. those
little aluminum strips don't have that, therefore i vote for
the stiffening and helping to hold it tight in place when shipped kind of reasons

 

[jozz]

therefore i vote for the stiffening and helping to hold it tight in place when shipped kind of reasons

it's not - it's very much sound related
a box builder that I know well, even has developed different shapes of bridges (mostly bent wire) - to support the sound he is aiming for

 

[Ventura]

ahh, but there is the rub

for what you say to be possible, it would be necessary for the area the vibrations are
sent TO to be RESONANT

there are no resonant, sprung energy radiating things in an accordion,
except for the reeds, as the rigid body and chambers are for shaping soundwaves..
and tone control by absorption of some frequencies ?
(doubtful absorption is at a meaningful level unless you add that felt stuff
people tak about stuffing under the grill)

some of the pre-war accordions had large tin plates under the keybed
and some people felt they were damn bright but even that could not
create or delete frequencies, merely direct them in a different way
so things would sound (to the squeezers ear) brighter bu dispersing the
highly directional higher frequencies in a wider pattern than modern boxes

the nice vibrations we feel from the body sometimes when rocking out
are just extra energy being dissipated, the accordion body is not a speaker
in any way, shape, or form that i can imagine, so i still vote for nada

 

[dak]

dak thats Interesting,why not a full length ?or 3 at the ends and middle?

Why not have it both ways?



Now in the treble, I have to grant Paul that "sympathetic vibration" is definitely not an issue addressed by the bridges in this accordion's treble side: on the reed blocks, there are markings indicating the reed groups. If we go from 1 to 6, we have:
1: M- M
2: M+ M+
3: M M-
4: M- M
5: M+ L
6: L L

Now the only reeds that could synchronize in this arrangement would be L with M (half blocks with the same name don't carry the same pitches) and there is no bridge for that: the L reeds in the déclassement are only connected to M+ . Now on this instrument you can throttle the tremolo reeds to make them more susceptible to cozying up to the normal reeds. But for this intent, you'd need a 2–3 bridge and also a 4–5 bridge. So clearly that hasn't been the purpose.

Each M- already shares a reed block with its M, but the M+ aren't as tighly engaged. The first M+ is bridged to its M, the others are entirely disconnected.

 

[Ventura]

now THOSE reedblock "bridges" look substantial enough to
actually pass vibration energy across and through

 

[dak]

now THOSE reedblock "bridges" look substantial enough to
actually pass vibration energy across and through

Well, there are the small bridges in the treble. The big bridge in the bass actually needs to be substantial since it is also the counterpiece to the internal bellows lock (the long bar across the treble locks into it, it's not connected to the treble reed bars). That bridge is across the melody bass reed blocks (the low bass reed block is unconnected).

So they have the same kind of resistance in the reedblocks across the button rows. But the treble setup does not connect the M from all button rows. So in the end, not much of a theory is corroborated in this instrument apart from Paul's "provide additional stiffness".

I could imagine that an isolated reedblock being stored sideways tends to press significantly into the gasket on its underside. Using the links would stop this kind of asymmetric load on the gasket: the combined foot breadth is much larger.

When setting down the instrument on its feet a bit too vigorously, the links also would confine the torsion able to act on a single reed block base.

So maybe it is not a measure for the sake of the sound but for mechanical robustness.

 

[Ventura]

was this the thinking of people like Morino, that it was worth trying
to figure out ways to keep that pressure even across the entire reedblock
base to enhance long term stability, and to minimize the affects of shock

incremental almost tiny improvements were once a part of the DNA of
the greats i think.. now they spend their time on solenoids and such..
are any accordion shop masters still steeped in the old traditions i wonder ?

well the more and more you guys show us pics of the insides of your Morino's
the more admiration i have for the guy who came before Gola

 

[dak]

was this the thinking of people like Morino, that it was worth trying
to figure out ways to keep that pressure even across the entire reedblock
base to enhance long term stability, and to minimize the affects of shock

Morino was a learnt carpenter. And he worked as an independent accordion builder in Geneva long before he had to accept Hohner's offer. So he really had hands-on experience with building individual instruments and solving problems coming with their construction and with the materials used in the process.

Here is a bit of memorabilia about an instrument he designed and built for Jeanne "Mimi" Thöni who was piano accordion player. So her father Maurice Thöni (CBA player himself) who needed to have her play free bass in a family ensemble, consigned an instrument with Morino that had two additional button rows in a piano arrangement, probably with low notes low in the instrument and with one row for the white keys and one row (interrupted appropriately) for the white keys, letting her retain similar left hand fingering she was used to from playing the piano.

French was the communication language between Morino and Thöni (my French is really lousy, so even the typewriter transcript is at best moderately helpful to me). Most of the correspondence between the two is in some boxes in the Harmonikamuseum in Trossingen. At some point of time I need to get there with someone versed in French and ask to be allowed to search for traces of how my own instrument fits into the story.

 

[Ikesaccordions]

The bridges stabilize the position of the blocks. They help press the blocks flat onto the fondo, and may make warping of the wood less likely. Whether they add any sonority is debatable.
The wood is less likely to warp if no air gets under it. The leather surface is also protected from air damage.

 

[Pipemajor]

A very interesting discussion.
I wonder if it would help to add these bridges to an accordion which doesn't have them.
I don't suppose it would do any harm.