Reed slot stepped profile

[4to5to6]

I was checking a 1955 Wheatstone Aeola EC tonight and noticed the reed shoe slots are stepped instead of tapered. The step looks milled versus an angle created by a file.  I’m trying to visualize how a stepped reed slot versus an angled reed slot would affect the tone, dynamics, air flow, etc.  Photo attached.  
 

Any thoughts?

 

.

Edited July 30, 2023 by 4to5to6

[4to5to6]

Looked at more of the LH side tonight.  All the reed shoes are stepped like this except for a few of the lowest ones which are filed in the traditional way.

Edited July 30, 2023 by 4to5to6

[alex_holden]

I suspect they did it as a way to save on labour cost. Hand-filing the vent relief to the top face is quite time-consuming. My guess is it may result in less dynamic range.

[Clive Thorne]

Would it start to sound at a lower pressure perhaps?  it is milled away so much that perhaps the effect would be as if the shoe were shallower.

Edited July 19, 2023 by Clive Thorne

[alex_holden]

12 hours ago, Clive Thorne said:

Would it start to sound at a lower pressure perhaps?  it is milled away so much that perhaps the effect would be as if the shoe were shallower.

 

I don't think so. My guess is that instead of a gradual rise in volume as you increase pressure you would get low volume (tongue vibrating in the parallel region above the step), then a jump to moderate volume (as the tongue goes past the milled step), then it would kind of run out of steam and not get much louder.

[d.elliott]

What material is the reed frame? It looks steel?

[4to5to6]

Reed frames are made from punched out aluminum. All frames are the same thickness at 0.075” except Low F and F# which are slightly thicker.  It is a 1955 64B BT model 16, Low baritone F to high treble C with middle C on the LH side, 8-3/4” ATF EE Aeola.  Every vent relief is step milled like the photo except for the low F and F# which are filled on an angle in the traditional way.

Edited July 20, 2023 by 4to5to6

[Clive Thorne]

9 hours ago, alex_holden said:

 

I don't think so. My guess is that instead of a gradual rise in volume as you increase pressure you would get low volume (tongue vibrating in the parallel region above the step), then a jump to moderate volume (as the tongue goes past the milled step), then it would kind of run out of steam and not get much louder.

You could well be right, I was only guessing. What we really need is someone to make two reed assemblies identical except in the way the "Relief" is done, and then try them side by side.

 

Do you know anybody with the requisite skills, Alex? 🙂🙂🙂

[d.elliott]

I don't think that the brass reed frame vents had their taper filled on, it was part of the punching process (becking in forging parlance). This also went for the dovetail taper on the outside of the frame. Brass is fairly malleable so this would have been no big issue. I wonder if Aluminium had a tendency to tear in punching? and what you have is a work around. 

 

I also note that the 'step has been filled by means of some form of fusion or weld? Perhaps TIG? This may have been an attempt to form some sort of taper rather than just a female corner. (can you say female these days?)

[Clive Thorne]

42 minutes ago, d.elliott said:

I also note that the 'step has been filled by means of some form of fusion or weld? Perhaps TIG? This may have been an attempt to form some sort of taper rather than just a female corner. (can you say female these days?)

I had put that look on the side down to poor feed & speed, a knackered cutter, or simply insufficient rigidity in the machine or clamping.  The smooth bit at the end possible having been finished with a burr?

 

Edited July 20, 2023 by Clive Thorne

[4to5to6]

A couple of additional photos… two different reefs.

[gcoover]

Since it looks a bit handmade, maybe it is someone's attempt at trying to create a quicker reed response, but being especially careful to avoid and not mess up the actual opening at the reed tongue?

 

Gary

[d.elliott]

On 7/20/2023 at 8:54 PM, Clive Thorne said:

I had put that look on the side down to poor feed & speed, a knackered cutter, or simply insufficient rigidity in the machine or clamping.  The smooth bit at the end possible having been finished with a burr?

 

Clive,

 

Looked too smooth for chatter marking, but Fusion processes would have caused twisting or pinching in the vent.

[Jake Middleton-Metcalfe]

Geoff crabb did a document about this process wheatstone used a while ago where it was described as a cost cutting approach wheatstone tried at one point. It was something c.wheatstone and co did or had made on purpose and not a later mod according to the document. 

 

Edited July 24, 2023 by Jake Middleton-Metcalfe

[4to5to6]

58 minutes ago, Jake Middleton-Metcalfe said:

Geoff crabb did a document about this process wheatstone used a while ago where it was described as a cost cutting approach wheatstone tried at one point. It was something c.wheatstone and co did or had made on purpose and not a later mod according to the document.

 

it would be interesting to see when this document was written.  I’ll look around for it. Thanks.

[Jake Middleton-Metcalfe]

31 minutes ago, 4to5to6 said:

it would be interesting to see when this document was written.  I’ll look around for it. Thanks.

Here is a link to the thread with the document Geoff wrote, it's quite an interesting read. https://www.concertina.net/forums/index.php?/topic/20077-post-wwii-wheatstone-reed-pans/#comment-187627

 

Document downloadable from Geoff's post on the thread at the bottom of the page

Edited July 24, 2023 by Jake Middleton-Metcalfe

[4to5to6]

Very good…

 

Non-traditional Concertina Reed Types.  
1950’s Wheatstone Surface mounted.

Geoffrey Crabb, 2013

 

very interesting.  While the 1955 BT in the OP does not have the reeds surface mounted like the article, I would agree with the description that the slot is first milled out then completed in a punch press to save time compared to creating a traditional drafted slot.  This is perhaps a transitional instrument.

 

I went ahead and did a study on this 1955 instrument by entering about 20 different measurements into a spreadsheet for each reed, pad, hole, tongue thicknesses, etc. so I can compare the graphs.  The reed scaling is not terrible. It follows a predictable exponential curve.  There are a few inconsistencies but nothing absolutely horrid.  
 

In spite of the partially milled then punched reed vents and aluminum shoes, the dynamics are not bad.  Overall it’s not a terrible BT Aeola although not stellar from a musical expression point of view but this may change as it is played-in more.  

Thanks for all the help.

.

Edited July 25, 2023 by 4to5to6

[Little John]

On 7/25/2023 at 6:46 AM, 4to5to6 said:

The reed scaling is not terrible. It follows a predictable exponential curve.

 

Somewhat off topic, but as I recall the frequency of a cantilever is inversely proportional to the square of its length, so an inverse square curve is what you might hope to see. In practice you don't get that as it makes the lower reeds too long to be practical.