Jump to content
Jody Kruskal

Why are the holes extended?

Recommended Posts

Just now, Sprunghub said:

In support of the idea that it is a form of rudimentary porting and helping air-flow to the larger reed chambers, is it the case that Jeffries action boards - by the standards of the time - are thicker than some ( most ) Makers and may have benefited from this small modification.  From my very limited experience inside Concertina's it seems to me they may have used a heavier grade of material.

 

If 'porting' was generally beneficial to airflow, why not do the same thing to every hole?

Share this post


Link to post
Share on other sites
Posted (edited)

 

Quote

It would be interesting to get Geoff Crabb's take.  He is our strongest existing link to the Crabb/Jeffries tradition.

 

He gave his take on the thread linked above, it does, however, seem the attachment was removed. Perhaps some saved it?

Edited by Peter Laban

Share this post


Link to post
Share on other sites
Posted (edited)
2 hours ago, Peter Laban said:

 

 

He gave his take on the thread linked above, it does, however, seem the attachment was removed. Perhaps some saved it?

 

I did - but I'm a bit hesitant to stick it here without Geoff agreeing to it first? (I just ask myself why it has been deleted and perhaps we should ask him to re-post it) Send me a PM if you are desperate to see it...

 

Adrian

 

 

Edited by adrian brown
  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)

As mentioned, this is often done in woodwind instruments as well.

 

I make a particular kind of woodwind, where almost all of the holes are internally chamfered. Doing so has two effects:

 

-chamfering internally raises the pitch of the note without increasing the functional hole size. This is important for ergonomic purposes. Sometimes a hole diameter can be too large for average or small fingers to cover comfortably, so one chamfers the 'undercut' of the hole in varying amounts until the note is in tune and it will keep the hole much smaller than if chamfering was not used

 

-the more you chamfer, the more material you are removing, and by effect you are slightly increasing the chambers volume (size). There is a fine balance between chamfering too much and lowering the entire pitch/chamber of the instrument, and too little and having poor ergonomics. Sometimes if the instruments base pitch is too sharp, adding deep chamfers too all the finger holes will reduce it's overall pitch enough to bring it into tune

 

This makes me wonder. Was the purpose of adding these chamfers in the concertina to increase the overall volume (dimensions, not audible volume) of the corresponding chamber? Usually you see makers wanting to reduce the size of a reed chamber to improve response (though that's untrue on some instruments with tapered reed pans). Thoughts?

Edited by Oberon

Share this post


Link to post
Share on other sites
Posted (edited)
20 hours ago, Jody Kruskal said:

Wait a minute, could the cut-aways be merely to align the holes better to the chambers?

 

My thought is, to squeeze in everything on 38+ button instruments, the holes, buttons pads and levers have an ideal spacing which does not quite match the ideal reed and chamber spacing, more easily achieved on 30- button instruments. The hole extentions could be just to make these two systems achieve a better fit by slanting the holes to better match thier corresponding chambers.

 

This seems to me the most plausible answer, yet. Can anybody confirm or refute that it is only present on instruments with more than 30 buttons?

Edited by David Barnert
Too many commas

Share this post


Link to post
Share on other sites

David

 

Here's my review that I did in 2013:

"I’ve taken a look at a number of concertinas from different makers including Shakespeare, Crabb, Dipper, Jeffries, Shakespeare and Wheatstone.  The sample is small and may not be completely representative; I have no pictures of large Crabbs for example.  Only the Jeffries has the scalloping to the woodwork around the underside of the pad-hole and this can occur on the left or right hand and in reed positions around the action including the perimeter reeds as well as the “inner” reeds.  The scalloping is in locations where the reed is surface mounted screwed in position as well as in a dovetail-routed slot) and is in locations where the pad is on directly on the face woodwork as well as on top of the action board (where the pad-hole “chamber” is deeper.

"This makes it appear as thought the scalloping is somewhat random rather than as part of a well thought out scheme to improve the acoustics.  My first thought was that the scallops were to channel the airflow from the pad location to the optimal place on the reed, but the geometry doesn’t support this hypothesis.

"In size order, here are the instruments I've seen with scallops

30 key C Jeffries in C/G - scallop to right hand top row little finger - one of the smallest reeds

30 key C Jeffries in F/C - scallop to left hand middle row little finger - lowest "F"

39 key C Jeffries in Bb/F - scallop to left hand thumb drone

39 key C Jeffries in C/G (may have been converted from a Bb/F) - scallops to right hand, 5 locations around the perimeter and inner

39 key C Jeffries in C/G - scallops to left and right hand locations (not the same as the concertina above so no consistency)

45 key C Jeffries in G/D - scallops to left and right hand

50 key C Jeffries in Ab/Eb - scallops to left hand inner and perimeter reeds

50 key Jeffries Bros Duet - scallops to left and right hand inner reeds"

So in conclusion, it's not just the larger instruments, it's not just the lowest or the highest reeds and it's not just the surface mounted reeds.  The "scalloping" is mostly running vertically, but sometimes is directed towards the root of the reed and sometimes towards the tip and in one concertina the scallop runs at 90 or even 45 degrees to the reed's long axis

 

Alex West

Share this post


Link to post
Share on other sites
Posted (edited)

I just now opened up my 50-button Jeffries Duet, and the five inboard reeds on the right side are all "ported". Same for the left side, the five inboard reeds, plus four of the outside reeds also have that ported bevel. And the air hole on the right side is also beveled but only on one side.

 

The bevels do not appear to be "after market" additions, so I'm thinking it must have something to with fine-tuning the air flow, like the motorcycle example.

 

Gary

IMG_0588-2.jpg

Edited by gcoover

Share this post


Link to post
Share on other sites
Posted (edited)

What effect does increasing the hole size for a pad have on the playing characteristics of its note? Typically these holes are round and can only be a certain usually round size in order to fit the profile of a reed chamber as well as for applying even and consistent pressure, no? As I said before, in ocarinas, chamfering a hole causes the pitch to rise for that corresponding note. By removing material around the hole without increasing the pad contact areas diameter, there may be some effect that helps with pitch balance or something. 

Considering the chamber cant be made larger due to the tight and precise quarters of a reedpan, chamfering may be a way to get chamber volume that you would be lacking in particular areas. I imagine it must be incredibly awkward to try to make a chamber in the middle our out areas larger without having to make severe modifications to neighboring reed chambers and overall dimensions of the reedpan.

 

I also know that in my experience of 22 years of making ocarinas that the response time of a hole that has been chamfered is indistinguishable from those that have not. The only thing that changes is pitch, but of course, the ocarina may have some different properties in terms of physics here 

 

If someone wants to try it, one way to figure this out would be to fill in the area of the chamfer, making it the same as the other 'normal' holes, with a temporary and removable material and record the pitch change. That would be risky for sure, but I bet something changes.

Edited by Oberon

Share this post


Link to post
Share on other sites

Perhaps a clue and/or more confusion;

I just opened up my JD 50 button which is a close match for Gary's and perhaps the one Alex examined as well.  On the left hand,  all the inboard 5 (lower) notes are chamfered plus the low C#  which has an outlying chamber with it's button at the far lower left in the low note row.  All these are heavily weighted at the tip except the D which is in the center of the inboard notes and has more room to extend towards the point of the hexagon.  On the right hand the inboard 5 notes all have the chamfer but none other.  None are weighted.

Share this post


Link to post
Share on other sites
12 hours ago, Alex West said:

 

So in conclusion, it's not just the larger instruments, it's not just the lowest or the highest reeds and it's not just the surface mounted reeds.  The "scalloping" is mostly running vertically, but sometimes is directed towards the root of the reed and sometimes towards the tip and in one concertina the scallop runs at 90 or even 45 degrees to the reed's long axis

 

Alex West

 

Just to be clear on a couple of points - has anybody seen this done on a concertina by another maker than the Jeffries family?  And has anyone seen inboard chambers on Jeffries concertinas without it? If so, are they on the right or left side?

 

 

What strikes me about the scalloping is just how similar it looks in all the photos (and in all the instances I've seen personally). Clean and decisively cut with sharp tool(s), it looks the work of somebody who knew what they were doing and went about it in an efficient manner, rather than a later, perhaps hesitant modification by a repairer.

 

 

Adrian

 

 

Share this post


Link to post
Share on other sites

Adrian

 

I've not seen this on any concertina other than a Jeffries.  On my Jeffries Duet, two of the inboard reed locations on the right hand side show no scalloping and none of the perimeter locations (both sides) are scalloped so mine is unlike Gary's.  On One of the 39 button Jeffries, the scalloping is with the reed longitude and is fairly crude, on the other, it's at 90 degrees.  The 45 key and 50 key anglos and the Jeffries Duet are similarly neat, but inconsistent as to which reeds - both locations and right or left - are scalloped or not.

 

I've looked over Geoff Crabb's paper on suggested explanations - he offers 4 - and they all sound credible but because of the inconsistent nature of the location, orientation and execution, I find it hard to see that there's one logical reason - either for mechanical or acoustic purposes

 

There's got to be a PhD thesis in there somewhere!

 

Alex West

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...