Reed slot stepped profile

[4to5to6]

3 hours ago, Geoffrey Crabb said:

Apologies to those who have invited me by PM to take part in this discussion. 

But I don't think I am clever enough.😉

 

However, the attached from 2012 may be of interest.

Reed slotting and forging. GC 2012.doc 171 kB · 10 downloads

Awesome!  I now see how the punch forms the slopes.  Thanks.

 

[4to5to6]

To throw in something new here…  but closely related…. I’ve noticed that the edge of the tongue clamp in Wheatstone reeds is often not in line with the reed opening underneath the tongue.  Is there a possibility that this misalignment of the clamp at the pivot point is done on purpose to cancel some unwanted harmonics (in-harmonics)?

Edited August 3, 2023 by 4to5to6

[Jake Middleton-Metcalfe]

On 8/3/2023 at 8:09 PM, 4to5to6 said:

To throw in something new here…  but closely related…. I’ve noticed that the edge of the tongue clamp in Wheatstone reeds is often not in line with the reed opening underneath the tongue.  Is there a possibility that this misalignment of the clamp at the pivot point is done on purpose to cancel some unwanted harmonics (in-harmonics)?

I haven't heard of that as something someone would do on purpose, its probably just the drilling jig for the bolt holes in the reed frame was set up in a hurry or was a bit mis-aligned. It was just a simple little drilling jig that held the frame and clicked into two positions. Or maybe it got knocked half way through a batch or something like that. 

[Chris Ghent]

On 8/4/2023 at 5:09 AM, 4to5to6 said:

To throw in something new here…  but closely related…. I’ve noticed that the edge of the tongue clamp in Wheatstone reeds is often not in line with the reed opening underneath the tongue.  Is there a possibility that this misalignment of the clamp at the pivot point is done on purpose to cancel some unwanted harmonics (in-harmonics)?

Really good observation and question 4 (for short). A long time ago while playing with a ruler on the edge of a table  I realised when the ruler is pinned back from the edge of the table it makes a noise but none when the clamping is at the absolute edge. I also realised when the clamping is back from the edge the up amplitude and frequency must be different from the down amplitude and frequency because the ruler is longer in the up direction. What must this do to a) the tuning, b)the partials (harmonics) and c) the efficiency of the swinging action?

 

 

I decided to make the clamp edge and the frame slot edge as closely aligned as possible in the interests of efficiency. The inefficiency of having them misaligned comes from the energy in the tongue being absorbed by the frame when the tongue comes from the longer half cycle and hits the edge of the slot. 

 

More recently I have been wondering about the effect on harmonics of the combination of a longer half cycle and a shorter half cycle. I know its a small difference but it is a difference. I took apart a couple of Jeffries reeds I have lying around and the mismatch between the edge of the clamp and the end of the slot was large.
 

Inconsequential so disregarded, inattention to detail, or deliberate policy? Don’t know. 

Edited August 8, 2023 by Chris Ghent
Edited for stupidity

[David Hornett]

Hi Chris,

 

I also measured the few Jeffries reeds I have (Jeffries Bros, Praed St) for their alignment of saddle and shoe (reed pitch stamped as below):

 

B#3  shoe alignment in front of saddle 22mm

 

A# 4                                                          3 mm

 

G#5                                                           2 mm 

 

David

[Chris Ghent]

I think I’d better make one with a similar offset and compare the sound. 

[David Hornett]

Sorry, forgot to put the "." in front of the figures.  

 

The Indian stringed Tanpurra has a rounded nut, this helps generate its characteristic sound. As the string vibrates it is lengthened and shortened by where it grazes the nut in its vibration. (This is added to by placing a thin thread between the string and the nut so producing a buzz, made by the string's touching of the nut. The point of contact changes as the note dies.) With this in mind, a displacement of a reed's saddle in relation to the shoe could, maybe, change the sound, by producing a distinctive reed quality arising from any, otherwise imperceptible, buzz when the reed hits the overhang, shoe or saddle, in its swing; and also from the lengthening and shortening the reed in its swing .... maybe??