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#19 Dana Johnson

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Posted 05 June 2017 - 04:59 PM

Just picked up om this thread, its about valves for big reeds?
 
I do a lot of work with Baritones, having re-valved no less than three in the last six weeks. 
 
I have also been offered half strained  leather for hand cut valves, indeed I took a delivery of half strained leather pre-cut standard valves. Half strained is just too stiff and inflexible for standard valves, and not much better for hand cuts. I rejected several £100's of valves back to the supplier who sent a load of samples of alternatives, none of which I was really happy with. (I suspect we are using the same supplier Alex,) The original leather I used to get was was Mordant sheep.
 
On big reed instruments I have seen synthetic valves, which were less than successful when playing pianissimo. Thin rubber insertion which had the same problem but just killed all resonance.  I have also seen valves glued together full length. Valves with another valve as a part length backer. all of which lacked play sensitivity.  
 
The trick is in valve springs, I use the same spring wire as a coil action springs from, and fit them in a similar way to the heavier OEM valve springs. but at a shallower angle to that the maximum opening is about 50% more than the valve pin height in the mating chamber. In the chambers valves are constrained by two or three pins, usually positioned to restrict the valve on opening so it can fall back or be easily drawn down by airflow to cover the reed pan vent. The valve spring is there for the same purpose, not the same way as an accordion valve vire works.
 
Hope this helps
 
Dave

Curious as to what "half strained" means, also the "mordant" in mordant sheep, revolving around getting darker colors. All I've found was that a number of different chemicals (acids etc.) were used as a mordant in tanning sheep leather. Living in a different part of the world, many of these once common terms have faded. I have a fantastic book called "fortunes in formulas" that is full of old chemical names. You have to work to figure out what they are referring to. Hint, if you break your meerschaum pipe, glue it back together with garlic juice!
Dana

Edited by Dana Johnson, 05 June 2017 - 05:00 PM.


#20 alex_holden

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Posted 06 June 2017 - 12:16 AM

Curious as to what "half strained" means,


I wondered this too, so I asked the valve supplier. They replied that it is just what their leather supplier calls it. I later found a passage in an old book that mentioned straining as a process that makes leather stiffer (it didn't say what this involved), so half strained is stiffer than unstrained but not as stiff as strained.

#21 Chris Ghent

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Posted 06 June 2017 - 06:03 AM

I looked for a definition also, found a similar one or perhaps the same https://books.google...leather&f=false



#22 Chris Ghent

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Posted 06 June 2017 - 06:07 AM

Mmm, maybe this is a clue https://link.springe...A:1004725922870



#23 d.elliott

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Posted 06 June 2017 - 08:32 AM

Thanks Dave. The valves I've had problems with aren't very low: the lowest is C below middle C. I'm working on getting hold of some appropriate leather so I can try cutting my own.

If I'm following you correctly, on very low reeds you put valve springs on the bottom of the reed pan to prevent the bottom valves opening too far, in the same way as the chamber pins restrict the opening of the top valves.

 

in essence, you are correct, the springs are on the non chambered side of the reed pan. The shape of the spring and how it contacts with, or not, with the root of the valve is also important. it is not enough to fit a single 'bridge' restraint towards the valve tip, any more than only one valve pin in the chamber. The springs shape the valves as well as restraining them.

 

i have fitted valve springs to long series reeded trebles before now, never mind tenor trebles and baritones. Anything from middle 'C#' or below is a possible candidate. the original heavy wire worked, but I find lighter wire makes the valve more responsive

 

Dave



#24 d.elliott

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Posted 06 June 2017 - 08:33 AM

Mmm, maybe this is a clue https://link.springe...A:1004725922870

I also looked into this, and got the same sort of references and comments



#25 Don Taylor

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Posted 06 June 2017 - 08:51 AM

Thanks Dave. The valves I've had problems with aren't very low: the lowest is C below middle C. I'm working on getting hold of some appropriate leather so I can try cutting my own.
If I'm following you correctly, on very low reeds you put valve springs on the bottom of the reed pan to prevent the bottom valves opening too far, in the same way as the chamber pins restrict the opening of the top valves.

 
in essence, you are correct, the springs are on the non chambered side of the reed pan. The shape of the spring and how it contacts with, or not, with the root of the valve is also important. it is not enough to fit a single 'bridge' restraint towards the valve tip, any more than only one valve pin in the chamber. The springs shape the valves as well as restraining them.
 
i have fitted valve springs to long series reeded trebles before now, never mind tenor trebles and baritones. Anything from middle 'C#' or below is a possible candidate. the original heavy wire worked, but I find lighter wire makes the valve more responsive
 
Dave

I would really like to see a picture of this.

Don.

#26 Dana Johnson

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Posted 06 June 2017 - 05:39 PM

Sounds like the strain drying process is a bit like tensilized Mylar, where it is stretched to align the polymer molecules to the point where there is no stretch left. Leather being a fibrous material whose fibers are free to move across each other when wet, would also align with the same treatment, and would have no great desire to return to unaligned form even if re wet, since the collagen has no shape bias that I am aware of, unlike a rubber band, whose molecular bonds are distorted by stretching, generating a return force when tension is released. This may augment the natural grain of the leather, or provide more area that is with the grain than just along the spine and half way down each side.
The biggest problem I've found is getting the valve density low enough while maintaining enough spring. Most of the leather I've found is either to dense, which provides good spring, but is too easily pulled by gravity under it's own weight, or has too much inertia. Less dense leather is usually too floppy with little spring. I think the main problem is that no leather suppliers make or condition leather for valves. Even basically good leather has been either under tumbled, or over tumbled. I think it is a worthwhile thing to figure out how to reprocess the stuff ourselves to get what we need.
Btw, heating chrome tanned leather a bit isn't too bad for it, but vegetable tanned leather will shrink and try to thicken. Can't remember what the reaction is called, but putting a piece of leather into boiling water is a sure test for whether something is vegetable or chrome tanned.
Dana

#27 Robin Harrison

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Posted 06 June 2017 - 09:18 PM

Has any one else been dying to make a pun about mordant sheep or is it just me ?

    Anyway, I hope I sleep well tonight or I'll be counting..........etc 






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