Sizing Standard For Valves?

[Oberon]

I know the common suggestion for sizing valves is to measure the previous existing valves, but is there a generally accepted standard for valve length for a given instrument?
Ive got a friend with a Wheatstone treble EC, 48 keys, with absolutely no valves on its 96 reeds (barring those few very high reeds which wouldnt have valves anyway). Someone began a project but never finished, it seems. All pads are present, but it is sadly barren of valves.

I assume I could use my digital caliper to measure from maybe 4 or 5mm beyond the base of the slot (where the old glue would be) and extend it a few millimeters beyond the opposing side for a valve that would be long enough to not be sucked in/stuck and function freely, but I wonder if there is a standard sizing chart somewhere that Ive never been able to find. Concertina Connection sells valves of all sizes, as well as two different thicknesses, so I could probably approximate with the calipers and select the appropriate length.

When folks have discussed valve length before, Id noticed its commonly stated that valve lengths vary from make to make, but surely wheatstone had a standard they used, lachenal as well, considering they manufactured thousands of instruments. 
Thoughts?

[Theo]

More important than valve length is the thickness/flexibility/ springiness of the valve that determines how for the valve opens and how efficiently it closes.   After 15+ years working as a repairer I've learned that getting valves right is the most critical part of concertina repair if you want the reeds to give of their best.  As an example I've just done some work on an Aeola tenor treble that came in sounding dull and lifeless.  It was re-valved about 15 years ago (not by me) and the valve material was just too heavy.  After replacing all the old valves the instrument is transformed with the bright and responsive character that you would expect from an Aeola. 

[Oberon]

Theo,

 

Valve quality and thickness, shape, etc, does seem to be a very nuanced subject. Those factors appear to affect quickness of playing, harmonic content, and the dynamics heavily for sure, and I look forward to learning much more about the very really and very severe effect valves have on a concertinas playability. One thing I'd noticed on my own instrument is that the valves are quite thin, leading to mant popping/slapping sounds and the occasional warble or jump in volume, but in general there seems to be a great level of volume dynamics available to me and higher harmonic values than my previous instruments. 

 

But in regards to size standards, is there a chart or picture or table illustrating valve sizes for a given reed? I'm sure the thickness and taper of the cross section of the leather is incredibly important, as well as grain direction, but is there a basic standard I can work off so I can order in some valves from CC or concertina spares or will I be better off ordering valve leather and manually cut 96 reeds by hand and shape them for my friends box? It's a beat up old tutor model and he just wants it running in some way shape or form

[Theo]

Concertina connection show their valve sizes here: http://www.concertinaconnection.com/valves.htm.  If you look at your reed pan you may be able to see the glue mark where each valve was attached which will let you work out the extra length needed at the base, then allow 1 to 2mm overlap at the tip.  Order 10% more vales that you need to give yourself some flexibility.

[Dana Johnson]

On 2/6/2020 at 3:54 PM, Oberon said:

will I be better off ordering valve leather and manually cut 96 reeds by hand and shape them for my friends box? It's a beat up old tutor model and he just wants it running in some way shape or form

Buying valves will be cheaper than buying valve leather, if there is any real agreement on what that is.  When I started looking into it 30 years ago, “cabretta” ( a variety of hair sheep )was what people mentioned.  But finding that in the various thicknesses was not easy.  I have since settled on Columbia Organ Leathers  Chrome Pneumatic Leather (cpl). They also sell cabretta in various thicknesses, but I prefer the cpl after comparing them.  Even so that is generally too soft as sold so I wet it and let it dry flat on glass which  restores some stiffness.  Then when you cut valves you need to orient the length in the direction of least stretch which is where you get the best spring back.  Valves cut the other way will be much floppier.  The leather is not tapered in thickness, but usually is wider at the base than the tip which improves the lifting characteristics of the valve..  Generally thick or stiff valves dull the sound while thin brighten up to the point of no valve.  Too limp and the valves, especially longer ones, will not close as rapidly when the pressure is released which will increase valve “slap” as the valves are sucked closed on the bellows reversal.

   The difficulty with buying precut valves is that you don’t really know how or where on the skin they were cut.  Hopefully the sellers are experienced and grade their valves accordingly.

[Don Taylor]

1 hour ago, Dana Johnson said:

Even so that is generally too soft as sold so I wet it and let it dry flat on glass which  restores some stiffness

So, would this technique work to restore old, curling valves back into useful life?