Bellows Card Depth

[alex_holden]

What are your thoughts on bellows card depth? All the standard-size vintage instruments I've worked on and all the bellows I've so far made myself had 1" deep cards, though I have seen bigger instruments with deeper cards and smaller instruments with shallower cards.

 

I've heard that Jeffries sometimes used 1 1/4" deep cards on a 6" hex frame. How well does that work, and are there good reasons to stick to the standard 1" instead? Has anyone tried going deeper than 1 1/4" on a 6 1/4" wide instrument?

 

As I understand it, the advantage of using deeper cards is it allows the bellows to open further, increasing the capacity for the same number of folds. The disadvantage is it makes the valley hinge narrower and thus weaker. The gussets would have to be larger too, which might lead to some problems.

 

Is the number of sides a factor? I.e. do bellows with more sides need to have shallower cards to get the same strength/stability as bellows with fewer sides?

[Jake Middleton-Metcalfe]

The measurement I have observed on jeffries cards was 1" and 1/8th" or something near 28mm. The benefits of folds deeper than 1" which was standard on Wheatstone and Lachenal instruments is something which experts seem to disagree on. The argument against is:  the bellows are able to extend further but the deeper folds mean there is a smaller volume of air inside. In such a case you would have a bellows that comes out further but does not actually have any more air inside. But others believe that the deeper folds do give you more air. I have been told conflicting things on the subject.

 

If anyone could mathematically or otherwise calculate weather a 6" wide 7 fold bellows with 1" deep folds has more or less air inside than a 6"wide bellows with 1" and 1/8th" bellows I would be very interested to hear what the answer would be. I was thinking about building a deep fold jig at one point but am unsure if I should bother. 

 

alternatively: build one of each and fill them both with water and see which holds more ?

 

 

[Wolf Molkentin]

I reckon the amount of air inside a closed bellows might be less, but not so re the capacity of a fully opened one. What matters should be the difference/amount of air which can be moved by a complete push or pull move, shouldn't it? So, mathematically deeper cards should be an improvement, possibly with the downside of more movement being required for a certain portion of air?

 

Apart from that, I can't judge on issues re the construction as mentioned by Alex.

 

Best wishes - ?

[Takayuki YAGI]

I cannot measure actual card size from outside of the bellows, but Frank Edgley instrument has deeper bellows than Lachenals here.

[Chris Ghent]

My recollection of measuring Jeffries a long time ago was they were more like 30mm. I pulled back from that depth some time ago because instruments I had played with shallower folds seemed inherently more stable.  I ended up at 27mm and they do seem less floppy.

[Jake Middleton-Metcalfe]

Playing dynamics certainly are important as well, maybe this is why jeffries bellows tend to be a bit 'heavy duty' looking. If they were more fine they might have been somewhat unstable with that depth of fold

 

[Little John]

I've done some (literally) back-of-an-envelope calculations. I simplified the arithmetic a bit and made some assumptions. Principally I assumed a 6 1/4" instrument would have bellows measuring 6" AF, and that the folds opened to 90 degrees. On this basis, and starting from a card depth of 1", increasing to 1 1/8" gives 9.3% more air and increasing to 1 1/4" gives 18% more air.

 

However, leaving the card depth at 1" but increasing the fold opening to 110 degrees gives a 20.5% increase in air; while increasing card depth to 1 1/8" and the fold opening of 110 degrees gives a whopping 32% increase in air.

 

Don't take these figures as gospel. Someone else might like to do more accurate calculations, but I'm pretty confident of the trend they show. Taken together with the comments about stability it would seem best to put effort into increasing the opening rather than the card depth.

 

How reasonable is that 90 degree assumption? From the sample of five available to me three didn't quite make it to 90 degrees and one made it to 102. The real exception was my 1934 Crabb, which opens to about 114 degrees. Maybe that's why I've never found it short of wind, despite having only 6-fold bellows.

[alex_holden]

10 hours ago, Little John said:

How reasonable is that 90 degree assumption? From the sample of five available to me three didn't quite make it to 90 degrees and one made it to 102. The real exception was my 1934 Crabb, which opens to about 114 degrees. Maybe that's why I've never found it short of wind, despite having only 6-fold bellows.

 

Thanks John! Prompted by an email discussion with John a few weeks ago, I had a go at building a set of bellows that could open wider than 90º without compromising their ability to close fully. I didn't manage the 114º of the Crabb, but they do open comfortably to about 104º, or a little more if you stretch them (I suspect they might get somewhat looser when they have been broken in for 84 years or so).

 

It sounds like it is worth also adding slightly more depth to the cards, e.g. Chris's 27mm is about 1 1/16". I wonder what is physically happening to cause bellows with deeper cards to feel 'floppier' and if there are things we could do to mitigate the effect, e.g. by using stiffer card.

 

Perhaps the type of instrument/style of playing has some bearing on matters too - e.g. a duet player who uses a lot of fat bass chords might want more lung capacity whereas an ITM anglo player might care most about rapid reversals.

 

I'm still curious about the number of sides thing. Do vintage Edeophones have 1" deep cards?

[DDF]

2 hours ago, alex_holden said:

 

Thanks John! Prompted by an email discussion with John a few weeks ago, I had a go at building a set of bellows that could open wider than 90º without compromising their ability to close fully. I didn't manage the 114º of the Crabb, but they do open comfortably to about 104º, or a little more if you stretch them (I suspect they might get somewhat looser when they have been broken in for 84 years or so).

 

It sounds like it is worth also adding slightly more depth to the cards, e.g. Chris's 27mm is about 1 1/16". I wonder what is physically happening to cause bellows with deeper cards to feel 'floppier' and if there are things we could do to mitigate the effect, e.g. by using stiffer card.

 

Perhaps the type of instrument/style of playing has some bearing on matters too - e.g. a duet player who uses a lot of fat bass chords might want more lung capacity whereas an ITM anglo player might care most about rapid reversals.

 

I'm still curious about the number of sides thing. Do vintage Edeophones have 1" deep cards? 

I just measured the card in a 12 sided Lachenal bellows from around 1910 and they are 1".David.

[Little John]

3 hours ago, alex_holden said:

 

It sounds like it is worth also adding slightly more depth to the cards, e.g. Chris's 27mm is about 1 1/16".

 

 

This is, coincidentally, the size of the cards on the Crabb. It would give less than 5% extra air over 1" cards, but for no real cost. Add bellows that extend to 100 degrees and you get 10% more air over 1"/90. 110 degrees look like the goal to me, and if you've already got 104 from virgin bellows you're probably almost there.

 

Incidentally, I've added another one to my sample set - a Wheatstone baritone, circa 1900, with 1" cards and opening to 97 degrees.

Edited September 6, 2018 by Little John

[alex_holden]

21 hours ago, DDF said:

I just measured the card in a 12 sided Lachenal bellows from around 1910 and they are 1".David.

 

Thanks David!

[Jake Middleton-Metcalfe]

There is sometimes a downside to bellows which extend over 90 degrees though - I am not certain that any of these bellows were ever designed to do that (though maybe some were I don't know), though I can be certain that sometimes such extension is actually caused actually by internal de-lamination of the bellows cards at certain points in a complex way - be cautious with bellows that can do this. 

 

A Crabb concertina which opens to 114 degrees was mentioned. Perhaps Geoffrey Crabb might know - did crabb ever design their bellows to extend beyond 90 degrees?

[alex_holden]

52 minutes ago, Jake Middleton-Metcalfe said:

There is sometimes a downside to bellows which extend over 90 degrees though - I am not certain that any of these bellows were ever designed to do that (though maybe some were I don't know), though I can be certain that sometimes such extension is actually caused actually by internal de-lamination of the bellows cards at certain points in a complex way - be cautious with bellows that can do this. 

 

A Crabb concertina which opens to 114 degrees was mentioned. Perhaps Geoffrey Crabb might know - did crabb ever design their bellows to extend beyond 90 degrees?

 

I've worked on John's Crabb and the bellows are in remarkably good condition. One card had delaminated slightly and I successfully glued it back together.

[Jake Middleton-Metcalfe]

On 9/8/2018 at 6:09 PM, alex_holden said:

 

I've worked on John's Crabb and the bellows are in remarkably good condition. One card had delaminated slightly and I successfully glued it back together.

 

I see, very interesting, I never knew any bellows were made in this way. Good insight

[David Hornett]

Quote

 

My bellows cards on the 51/2 inch instruments are 30mm deep. I have never really given much thought to depth other than the extra extension one gets on a 7 fold bellows, the Tassey Tigers have  28 cm extension, or if one counts from bottom of frame to bottom of frame with the bellows open, the bellows are 32 cm long.  They don't feel floppy,  but then my bellows only open to 75 - 80 degrees which would help with rigidity I suspect.

 

David

[Little John]

1 hour ago, David Hornett said:

My bellows cards on the 51/2 inch instruments are 30mm deep. I have never really given much thought to depth other than the extra extension one gets on a 7 fold bellows, the Tassey Tigers have  28 cm extension, or if one counts from bottom of frame to bottom of frame with the bellows open, the bellows are 32 cm long.  They don't feel floppy,  but then my bellows only open to 75 - 80 degrees which would help with rigidity I suspect.

 

David

 

David - based on your figures I calculate these bellows open to about 83 degrees.

 

LJ

[David Hornett]

Yes, David,

 

With a bit of pressure on the new bellows they possibly would open 83 degrees.

 

On my first few concertinas I had wider angles, 120 degrees, with 11/4 inch cards, aiming for max. air (It is easy to widen the angle on the jig I use, simply slip card under the bellows so raise the gullies before adding the gussets) but as Chris observed, they did become 'floppy', and because they opened the extra width, the outer leather banding would crinkle when fully extended and look unsightly, so since I've stuck to about 80 degrees with 1 1/2 inch card. If an instrument seals nicely how often does one need all that extra air? And if ever you do, then 8 fold bellows take minimal extra effort to craft, although add a little extra weight.

[alex_holden]

I didn't notice any less stability from my latest set that opens to about 104º than my earlier ones that stopped at less than 90º. All of them have had 1" cards. I suspect with wider opening bellows and an efficient instrument, many players would be happy with six folds. Dropping a fold results in a smaller, lighter, cheaper instrument. (Incidentally, I notice that Dipper's standard and professional models have six folds.) The ridges do wrinkle slightly when you fully open them, but then so do my knees and that doesn't bother me either. ?