Fabric covered bellows

[Tiposx]

(I moved this discussion here from another topic)

Some time ago I made a set of anglo bellows for a vegan musician, from a synthetic material called Kraftex, which was technically a paper product. I had a set of Flying Duck vegan bellows, so I cribbed the late Paul Harvey's design from that.

His design used a full sheet of Kraftex in a tubular form with just one long glued joint. The bellows cards were made of very thin plywood.

After a lot of expermentation i chose heat-cured leather glue to attach the ply, and to join the paper together. The Kraftex was pretty stiff, and the traditional method of constructing bellows would not work. This was because the paper was more rigid than leather, and also stiffer than the cotton board cards.

I made separate pieces of Kraftex to attach the bellows to the frames. Thus three pieces in all. This gave nice proportions, but Paul Harvey's slightly larger single piece bellows were a better design. His were completely leak proof.

When the bellows were first compressed the gussets popped outwards, as on the Duckling.

My bellows were attached to vintage  bellows frames, Jones I think, which of course contained chamois leather and hide glue. So not completely vegan.

The bellows turned out quite well, and were destined to be used by students, possibly also vegans.

I don't know how they stood up to repeated use, but they seemed quite tough.

Petsonally I will continue with card and leather.

 

[genepinefield]

I thought all the pieces would be made from Kraftex, just the Gusset pieces, and the other pieces would be in the traditional ribbon or trapezoid shape.

[Tiposx]

Hi Genepinefield

I found that the Kraftex was too stiff to replace the leather. Also it needed quite a large glued area to make strong joints.

[Lappy]

…nice work Sir!

 I wonder if rip stop nylon fabric would work. Kite makers use it. 

[Tiposx]

It would be flexible. But I don't know if it would hold the pressurised air, or glue to itself.

 

[Steve Schulteis]

I gave this style of construction a go for my current MIDI prototype, but instead of Kraftex, I used Tyvek. I found this to work reasonably well, and I think it would function for an acoustic instrument. We'll see how it holds up over time. I used 1070D, but Tyvek comes in a number of thicknesses and styles, including a non-creasing fabric type that might be interesting to try.

 

I laser-cut the cards from 2-ply museum board, leaving little tabs to hold them together in four larger sheets. My plan was to use a roller to apply glue (I used Jade R, since I had some around) and stick an entire sheet of cards to the Tyvek all at once. In practice, the connecting tabs were too thin, and a lot of the cards came apart after they were wet with glue. Having tried it once, I'm not convinced this would actually save much time even if it went as I intended. Next time I'll probably try cutting pairs of connected cards with small spacer tabs at the edges to help place the adjacent cards.

 

Once the cards were glued down, I glued on an additional strip of Tyvek to complete the underside of the hinges. Again, I'm not sure this actually saves a substantial amount of time over doing them individually.

 

The end frames are 3d printed from PLA. After fitting them inside the Tyvek tube, I used CA glue to secure them.

 

 

[Kevin Knippa]

Some Tyvek-type products are more "air-tight" than others. The original Tyvek resists the passage of air but is not air-tight. For a conventional (acoustic) concertina something like Dupont Airguard might work as a bellows skin/fabric.

 

[Steve Schulteis]

On 3/15/2025 at 11:06 PM, Kevin Knippa said:

Some Tyvek-type products are more "air-tight" than others. The original Tyvek resists the passage of air but is not air-tight. For a conventional (acoustic) concertina something like Dupont Airguard might work as a bellows skin/fabric.

 

While a more specialized material could perform better, I don't think it's necessary to use a special kind of Tyvek to get usable results. The Tyvek I used may be air-permeable, but forcing air through it quickly is a different matter. I recorded another demo with my bellows' ends sealed better, and I'd say it's functional. It's clearly nowhere near as good as my Edgley, but that's asking a lot for a first-time, experimental construction, single-day project.

 

Edited Sunday at 03:36 AM by Steve Schulteis

[Roger Hare]

> While a more specialized material could perform better, I don't think it's necessary to use a special kind of Tyvek to get usable results etc...

 

Nice demonstration!!!

 

I couldn't resist the temptation to try this myself. I used 4 instruments:

 

Vintage Lachenal (5-fold)

Marcus Hybrid (7-fold)

Wolverton 'real' instrument (7-fold)

Flying Duck 'Duckling' (6-fold Kraftex)

 

I didn't actually get a stop watch on it, but I saw pretty much the same as in your video clip.

 

The Duckling performed pretty much the same as your prototype - maybe a little better.

 

Bearing in mind the fact that your demonstration model was a quick prototype, I think you may well be 'on to something' here? Nice!

 

I am now off to a well-deserved breakfast...

Edited Sunday at 04:57 AM by Roger Hare