maintenance for brass reeds

[Wolf Molkentin]

37 minutes ago, wunks said:

Aside from the metallurgical considerations above, is it possible that when playing you subconsciously settle in to a generally uniform attack whereas the less frequently visited lower register requires a slightly different focus to sound well?  Put another way, are these reed anomalies an artifact of a some what "one size fits all" approach?.......?

 

I don't think so - there are some reeds which will just "breathe" (without the tone, or the reed just starting to vibrate), which I can voluntarily (re-) produce at any time, but not twice or thrice in one go. There are - soundwise - adjacent reeds, or even the resp. push or pull reed, which wouldn't "do" that. I'm aware of this all being, as we would say in Germany, complaining on a high level...

 

As an aside, only my model 24 would clearly outperform any instrument I ever played re responsiveness of the reeds, even at very low pressure (apart from the higher range where valves may be too thick). My TT Aeola has a unique voicing, which I really like, but as well no "breathing" at low pressure.

[Wolf Molkentin]

I'd like to emphasise that the suboptimal setting is clearly visible, and that from my experience, mainly with steel reeds but as well some or the smaller brass reeds of this instrument, almost certainly could be improved (the "breathing" wouold disappear, the response would be better than before). It's only that I'm afraid I could prompt a reed to break, or develop a crack by forcing it beyond its given flexibility.

[d.elliott]

Wolf,

 

What you describe about the lower end of the range is, alas, very common in softer metalled reed tongues, however to get a particular frequency there is a ratio between the 'spring' stiffness in the area of flexing, and the moment of mass of the end of the spring. The spring in this case being the reed tongue. The geometry of the reed tongue (length & width) is set by the reed frame, which is controlled by the chamber size, which is controlled by size of the reed pan, which is a function of bellows frame size.

 

Back to the spring idea. the material 'brass' has a lower stiffness than say steel, so to get enough stiffness it has to be thicker, hence stubbier and I think, less responsive. Add to that the greater area in the clearances around the larger reed tongue, plus what ever voicing gap you optimise on and the reeds air efficiency drops comparative to a mid or upper range reed of the same material. Another factor may well be that for a constant bellows pressure the velocity of air flow will be lower the larger the reeds so it need more bellows force to compensate with the risk of stalling the reed.  A steel reed in the same reed frame in the same instrument will operate differently, it will need to be thinned more to flex and will be correspondingly well, springier. 

 

What do I do? well there is only so much. I confess I have experimented with deliberately weakened (for tone) steel reed substitutes, with some success. However, I do my best to ensure the best chamber air tightness, roughing the gaskets etc. If there is a problem, I adopt the reed profile  used on the big reed instruments, which I suspect focuses the area of flexing of the tongue , balancing the rate air escape along the reed flanks, I try to get away with the lowest voice gap as possible and often rely on vibration in play to optimise the gap over time. 

 

If all else fails I go back to my steel reeded instrument. Sixty years ago I was in the Wolf Cubs, part of the Boy Scout Movement, I am minded of their motto 'Do Your Best'.

 

Dave

[ttonon]

1 hour ago, d.elliott said:

Another factor may well be that for a constant bellows pressure the velocity of air flow will be lower the larger the reeds

This is incorrect.  The air flow velocity is a function of only bellows pressure, not flow area.  The Bernoulli Equation, V = (2*Pb/Rho)^0.5, shows it, with V velocity, Pb bellows pressure, Rho air density.  Physically, it means that specific potential energy (pressure) converts to specific kinetic energy (V^2), intrinsic properties of the fluid, nothing to do with geometry.  Remarkably simple.  

Best regards,

Tom

[Wolf Molkentin]

David, thank you so much once again, this is very helpful for me to better understand the character of "my" brass reeds.

 

2 hours ago, d.elliott said:

I try to get away with the lowest voice gap as possible and often rely on vibration in play to optimise the gap over time. 

 

I was hoping for the latter to happen, but am sure there's room for improving (lowering) the gap on those reeds which are audibly "breathing" before sounding at lower pressure (albeit loudness and tone leave nothing to be desired as soon as they're actually responding).

 

If I'm getting right what you're saying, you would encourage me to cautiously bend the reeds, without being all too afraid of causing a crack or breaking?

 

All the best - ?

[Don Taylor]

This is a suggestion/question completely out of left field:

 

Is it feasible to adjust the reed plate rather than the reed itself in order to reduce the gap?

 

Maybe by a little bit of thin glue or varnish, or very thin metalized tape on the end of the plate? 

 

I also recall reading somewhere that harmonica fettlers bevel or emboss their reed plates in order to improve response time:

 

 

I have often wondered if embossing would cure leaky Lachenal reeds.

 

Warning.  I have not had my first cup of coffee this morning so these suggestions need to to be validated by someone who knows what they are talking about!

Edited June 24, 2019 by Don Taylor

[d.elliott]

Tom,

 

perhaps I should have said the air pressure would decay faster requiring more effort given the larger air escapement area around a bigger reed tongue, affecting response issues,

 

Wolf

Every time you bend the reed tongue to adjust it, you are taking it through it's elastic limit, altering the stress make up across the reeds section. yes there is a risk of failure, how remote is anyone's guess. what is true is that you are probably going to flatted the reed's pitch by a few cents. If you are going down the route of profiling, then check the tuning of the reed outside the instrument fist, you may need to do a bit of gentle filing before re-assembly. Of course, filing the reed can cause the reed to distort and bend into the reed frame vent. you will then need to bend it back to profile again. If you bend the reed back to profile again then be warned this action may affect pitch again and so on an nauseam. 

 

To me,  I have to ask, are you chasing a level of perfection which these reeds cannot deliver? Please just consider if harm can result? 

 

Tom,

to clarify why my policy to hand work brass for reed tongue stock, you called it artisan work, (I think in the UK in Engineering circles that term is reserved for baker's of bread and the like, the highest engineering plaudit is that of 'master craftsman', in the steelworks it was a millwright, but putting that aside). You talk about the industrialised perspective. Remember that I repair and overhaul, I make enough stock for one or two reeds at a time, one to be  a spare in case I screw the first up. The need can occur once or twice a year or not at all for two or three years. For me my process works. However, usually I can get a substitute brass reed assembly, if only to rob it of it's tongue and fit that tongue to the original reed frame.

 

Dave