Large valves

[Robin Harrison]

Just opened up a Lachenal tenor, in response to another thread, and noticed something interesting.

    The large valves on the non-chambered side seem to be held in place with bent brads/pins (don't know the correct name)

    Or were  brads/pins at one stage much longer and have fractured ? seems odd so many have fractured neatly at the same place. .......see image where valves have been replaced with much shorter ones.

    And why on the non-chambered side only ?

    Any ideas ?

Robin

 

Edited November 21, 2018 by Robin Harrison
Clarity

[Theo]

They were longer and have broken off.  You can see the line on the valve where they were.  They serve to limit how far the valve can open in the same way as the valve pins on the chamber side.

[Robin Harrison]

Tx Theo..........funny that so many have broken off; wrong material, I guess.

Robin

[Lofty]

8 minutes ago, Robin Harrison said:

Tx Theo..........funny that so many have broken off; wrong material, I guess.

Robin

It seems more likely to me that they have been deliberately broken or cut off. I don’t suppose they would move enough for metal fatigue to have set in.

 

Perhaps whoever replaced some of the valves did it: you can see that some of the replacements are shorter at their fixed ends. Maybe the person who did it didn’t know what they were or found it difficult to fit new valves under them.

 

Steve

Edited November 22, 2018 by Lofty

[Theo]

The broken off wires are often get weakened by corrosion and break off.   Possibly some of the chemicals in the leather speed up the corrosion.  I have successfully replaced such large valves with leather valves designed for bass accordion reeds.  These are usually fitted with a "helper spring" which serve a similar purpose.  Examples shown here

Edited November 22, 2018 by Theo

[d.elliott]

What you have is valve springs which are fitted to the non-chamber side of double action baritone and bass instruments. I have never seen them corrode through, and I suspect these (from what I can see of the spring stubs, have been clipped off. Usually they are made of brass wire, although I us phosphor-bronze spring wire. Their purpose is to emulate one of the functions of the valve pins in the chambers in that they force to valve to open progressively and prevent the long valve from opening too far whilst enabling the valve leather to be chosen from stock which is sufficiently supple to permit playing on the widest dynamic range possible.

 

I have seen accordion valves with 'helpers' but I prefer to make the instrument work as designed. Valve springs are easy to make, cheap to fit, and can bring a sluggish baritone back to life.

 

Dave

[Wolf Molkentin]

David, just to reassure my understanding: „helper springs“ are rather flexible and just stiffen the valve, whereas valve springs are  being bent to a certain degree to set the maximal opening angle?

 

Best wishes - ?

[d.elliott]

Helpers springs are something invented to go on accordion valves, some of the accordion reeded hybrid concertinas have inherited this feature, yes they are weak, some times added to vinyl(?) valve backers. The helpers are permanently engaged with the valve, trying to hold the valve closed, and thus return the valve to it's closed position. Dare I say that there are pictures of 'proper' concertina valve springs in the Concertina Maintenance manual. The concertina valve springs are not there to add resistance to air flow, or to hold the valve closed, they are stood off from the valve  back and act as much as a restrainer limiting overall valve opening distance. The are usually shaped to make sure that the curvature of the valve is progressive along the valve length forming a natural shape where no part of the valve is taking all the bend.  This way, there is a minimum of resistance to air flow, and the valve shape is controlled making it more reactive to changes in air direction..

 

Dave