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Author Topic: Thirds Pullstop on Hohner Corso/Corona/Club models … ie with 4-note chord block  (Read 1719 times)

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Microbot

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Hi Theo, Clive and all,

Following Sir John’s adventure into getting a Corona 3R and his last posting in which he laments the lack of a thirds pullstop, I was prompted to post this thread.

I’ve been fitting pullstops to remove the thirds from the chords in standard Hohners for some time. These are boxes such as pokerworks/ericas/pressedwoods with simple triad chords. It’s not a difficult job and requires slider+rails+block+stop and reorganization of the reeds to get the thirds on a single plate.

More problematic has always been the possibility of a pullstop to remove the thirds in Hohners with 4-note chords – as found in the Corso, Corona 3R and many Club Models. These models have 4-notes chords with Fundamental+third+fifth+fundamental(high). These instruments also have linked basses where the bass button picks out the 2 fundamental reeds from the chords, and plays these with the profound/bassoon basses… thus giving you a 4-reed bass.

The problem with a third’s pullstop on these models is that the holes on the chord block are so close together that there is NO position where a slider can sit, without blocking off an aperture…. (see 1st photo below) In other words … if you have a slider that removes the thirds, how can you then reposition/move the slider to get all 4 reeds sounding?

The solution I came up with (I don’t know if this is original) is to create a hole in the chamber wall between the two opposing reeds that play the fundamental notes in the chord block. You can then have a slider that blocks off the third and – when moved – blocks off one of the fundamental reeds. HOWEVER, this latter fundamental reed continues to play since it has airflow through the chamber aperture. I chose the high (small) fundamental reed to be the one blocked off … since it requires less airflow … and so that reed basically ’slaves’ off the opposing fundamental reed chamber when it is blocked off.

And it all works a treat!

Below are photos of work done on a Club IV for Matthew Hodgskiss, with two bass pullstops. One pullstop removes the thirds as discussed above, the other removes the fundamental bass. The latter bass pullstop required separating off the chambers of the bassoon and profound basses … then slider/rails/block and pullstop as usual.

Cheers!

Mike R
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John MacKenzie (Cugiok)

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Thanks Mike, very interesting indeed. Unfortunately, I also have a Club IV  ;)
Given me something to think about.

Sir John
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: Hohner Club Modell 1. Bb/Eb, de-clubbed : Early Hohner Pressed Wood A/D : 1930's Varnished wood G/C:  Hohner Erika C/F: Bandoneon tuned D/G Pressed wood: Koch F/Bb; G/C Pre Corso

rees

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Fair play Mike, you're not just a pretty face  (:)
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Rees Wesson (accordion builder and mechanic)
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diatonix

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It is quite possible to build in a slider that only removes/activates the thirds, without affecting other notes, even in a Corso. The solution is very simple and consists of 4 short sliders, linked together to make its business end  look like an E with 4 arms. Once the pull/push thirds are on the same frame and the necessary modifications to the base of the block have been made, the slider doesn't move sideways but up and down, opening and closing only the 4 relevant holes.
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rees

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I can't quite picture that. Please explain further. Thanks.
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Rees Wesson (accordion builder and mechanic)
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Microbot

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Hi Rees and Diatonix,

I  think I understand  what Diatonix is describing. When considering designs, I pictured exactly the same mechanism … a sort of “4-pronged E slider” that inserts from the side (rather than along the length of the block). This would indeed cut out the aperture with the third reedplate, and not affect any other aperture.

But I was concerned about an effective mechanism to actually operate such a ‘sideways-slider’… where would the pull-stop be situated and how would the slider operate?

You wouldn’t want a pullstop sticking out of the front of the instrument near the bass buttons! If you had a pullstop at the top/end of the instrument, you would then need a pivot mechanism to operate the sideways movement of the slider. Also, if you had a fraction of difference in the resistance of each of the 4 slider-prongs, it would tend to make the pullstop mechanism twist/snag to one side or the other. This is something you avoid with a single slider operating along the length of the block.

But Diatonix is right … it’s a neat solution and if anyone has actually installed such a pullstop, I’d love details/photo of the operating mechanism!

Cheers

Mike R
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diatonix

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I'm grateful that you came to my rescue here, Mike. When English is not one's first language it's not always so easy to explain such technical matters in an understandable fashion... Anyway, you are right, that's exactly what I had in mind. In my case I made a pivot mechanism with a switch sticking out near the air button, very similar to the one I use on my own boxes. Next time I'll try and remember to take some photos.
« Last Edit: August 01, 2016, 09:27:46 AM by diatonix »
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Microbot

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Well done Diatonix! Very neat!

...that arrangement also has the advantage of being operable from near the air-button ... my design works fine ... yours has clear advantages!

Who has that box? Was it a Corso or another model?

cheers

Mike R
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diatonix

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It was a Corso (property of one of my customers). While still being made in Germany it was certainly the most successful model of all times, at least here in Norway.
« Last Edit: August 01, 2016, 10:10:03 AM by diatonix »
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Microbot

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yes, Corsos are indeed great boxes...

Bravo!

Mike R
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John MacKenzie (Cugiok)

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Still quite a few around on German EBay, and at good prices too.


Sir John
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: Hohner Club Modell 1. Bb/Eb, de-clubbed : Early Hohner Pressed Wood A/D : 1930's Varnished wood G/C:  Hohner Erika C/F: Bandoneon tuned D/G Pressed wood: Koch F/Bb; G/C Pre Corso
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