Specification of brass needed for replacing old Lachenal reed tongues

[Rod Pearce]

I had raised this post as a continuation of an earlier thread entitled Making A Brass Reed For An Antique English Concertina , but it has become overshadowed. So I am raising it as a new thread in its own right in the hope of attracting further responses.

 

I am interested in having a go at making some new brass reed tongues to replace several broken ones in a Lachenal 48 key English, but I don't know what specification of brass to use.

 

There are a number of UK suppliers of brass sheet on the internet, e.g.

 

https://www.metaloffcuts.co.uk/product/natural-brass-sheet/

 

but I would not know what proportions of copper / zinc would be suitable for concertina reed tongues. This website sells its sheets with the following specification , Grade CZ108 (Cross references UNS – C27200,  ISO – CuZn37,  EN – CW508L) also known as common brass and has a composition of 67% copper and 37% zinc ( I know the maths doesn't add up, but that is what it says).

 

Would this be suitable?

 

If you can offer any advice I would appreciate it.

 

Thanks, Rod

 

On 11/23/2021 at 11:24 AM, Chris Ghent said:

See if you can find a few old harmonium reeds and take the brass out of them. There will be someone in the UK who sells them. 

 

Chris, thank you for your earlier response . I will follow this up.

 

Edited November 26, 2021 by Rod Pearce
Spelling!

[Don Taylor]

I wonder if they even had classifications for brass in the 19th century?  Even if they did then do you suppose that the makers would tell what they used?

 

Maybe you are over-thinking this.  Those sheets of brass are cheap, just pick one and try it.

[d.elliott]

 

I use brass from a similar sort of source, I get twice the thickness that I think I will need then cold hammer it down to a thickness just enough above the thickness under the clamp, leaving enough stock to be able to dress underside of the tongue to be flat and smooth. This cold working hardens the brass. 

[Rod Pearce]

Don, Dave

 

Thanks for your replies. I will go with the source I have found and see how it goes

 

Regards

Rod

[Paul_Hardy]

You could try contacting Steve Dickinson (Wheatstone.co.uk), who possibly still has unused sheets of the original brass from the Lachenal factory! He replaced a fractured brass reed starting with sheet brass for me while I waited once - but it was the best part of twenty years ago. It was fascinating to watch him at work.

[Rod Pearce]

19 minutes ago, Paul_Hardy said:

You could try contacting Steve Dickinson (Wheatstone.co.uk), who possibly still has unused sheets of the original brass from the Lachenal factory!

 

Thanks , Paul.  Definitely worth a call to Steve.

 

Regards

Rod

[SteveS]

On 11/27/2021 at 10:37 AM, d.elliott said:

 

I use brass from a similar sort of source, I get twice the thickness that I think I will need then cold hammer it down to a thickness just enough above the thickness under the clamp, leaving enough stock to be able to dress underside of the tongue to be flat and smooth. This cold working hardens the brass. 

This is exactly what I did to make a new brass reed - cold hammered the brass sheet to work harden it. 

[Dissonance]

Are the reeds we are talking about really brass reeds? Could they be phosphor-bronze? 

Edited November 30, 2021 by Dissonance
Simplified the question

[Dana Johnson]

The old reeds were brass, but C510 Spring temper Phosphor bronze works fine and may have a longer lifespan since it is designed for springs.  It’s physical properties for reed making are very similar to “common” brass and won’t need work hardening since it is already rolled to the optimum temper.

[Dissonance]

So the consensus is likely that all the old reeds are brass that is work hardened to some extent. I made some replacement reeds out of both and had a much easier time getting the phosphor bronze to match the sound of the originals. 

[alex_holden]

I've seen some originals where the brass frames had oxidised to a dark brown/black, but the reed tongues were still a fairly bright yellow, which made me suspect they were different alloys. I don't know how long phosphor bronze has been available as a spring material.

[Theo]

Phosphor bronze has a distinctly pink colour, so if tongues were bright yellow then they are more likely to have been brass.  There are dozens of different brass alloys.  I have an Aeola from I think the 1920s which have non-ferrous reeds which have the pink colour that I associate with phosphor bronze.  It plays with the responsiveness and dynamic range that would normally be associated with the best steel reeds.

[Chris Ghent]

When brass looks pink it can mean it has been cleaned with citric acid. The acid leaches the zinc out of the brass and leaves a not quite copper colour. 

[Theo]

2 hours ago, Chris Ghent said:

When brass looks pink it can mean it has been cleaned with citric acid. The acid leaches the zinc out of the brass and leaves a not quite copper colour. 

Interesting, I didn’t know that.  I suspect it’s not a commonly used cleaning method for concertina repairers.  The reeds I mentioned earlier retain their pink colour when the surface is removed during the normal course of tuning.

[Rod Pearce]

On 11/27/2021 at 11:27 AM, Paul_Hardy said:

You could try contacting Steve Dickinson (Wheatstone.co.uk), who possibly still has unused sheets of the original brass from the Lachenal factory! He replaced a fractured brass reed starting with sheet brass for me while I waited once - but it was the best part of twenty years ago. It was fascinating to watch him at work.

 

On 11/27/2021 at 11:50 AM, Rod Pearce said:

 

Thanks , Paul.  Definitely worth a call to Steve.

 

Regards

Rod

Paul

 

I contacted Steve a while ago. He said he has no stock of brass for reed making.

 

He did offer some advice of what spec of material to use, together with a possible source. I am reluctant to 'publish' Steve's his comments for general viewing without his permission as it was a one to one conversation. However, if you feel you would like to know his comments then PM me and I will OK it with Steve first.

 

Rod

[d.elliott]

Theo,

 

if the reed tongues only have the coppery hue, then it is probably the reed tongue alloy, if the reed frames are also a bit pink then it is mist likely a chemical cleaning process.

[Theo]

It was just the reed tongues that had the pink colour.

[ttonon]

I'll give my two cents from an acoustic point of view.  The only material parameter governing the vibration of cantilevers is the ratio of Young's modulus to density.  In other words, all materials having that same ratio will vibrate in identical ways.  However, when we consider the acoustics of the air vibrations caused by those vibrations by the tongue of a free reed, there are other complications. 

Yet without anything else to go by, and to a first approximation, I'd look at this ratio in trying to guess what the acoustic properties will be for different materials.  That ratio for 1095 spring steel, the usual material used for tongues, hard tempered flat brass, and phosphor bronze is 2.78E8, 1.43E8, and 1.42E8, in English units of ft^2/sec^2.  And the corresponding ratios are 1.00, 0.51 and 0.51.

We often hear that brass tongue instruments sound softer or more mellow than steel tongue instruments, and so we might conclude that lower values of the ratio Young's Modulus to density lead to softer sounding reeds.  By this criterion, phosphor bronze tongues should have a sound similar to brass tongues.  

In the literature they state that phosphor bronze has resistance to fatigue, and my guess is that it's superior to brass in that regard.  The conclusion is thus that phosphor bronze might very well be a good choice for tongue material. 

Concerning fatigue, we often hear that brass tongues tend to break, and ten years ago, I did an analysis that explained why that's so.  I posted it on this site at
 
https://www.concertina.net/forums/index.php?/topic/14533-why-do-brass-tongues-break/#comment-138648

It's a long post and only those hard core techs will be interested, but be my guest.

Tom
www.bluesbox.biz