Bellows card…and construction.

[RogerT]

I know it’s an old question, but is there a suitable card material (and advisory thickness) available in the UK for making bellows?

I think some makers create their own composites..but are there any 'over the counter' cards that would do the job?

in one thread on c.net Presspahn card is suggested..it’s obtainable in the UK in varying thicknesses. I think it needs to be at least 1mm thick..?

And on construction itself..the faces are all hinged with glued tape (and leather binding). I assume this is because folds would be too stiff? 
Accordion bellows are made from strips of folded card, plus corner gussets (and metal corners etc). Probably the cheaper (for instance Stagi) concertina bellows are made this way?..I don’t have one to hand to check to see if they are or not. 

Finally, some makers use an armature/jig to form the bellows, with forms for the folds, whereas some do not..they just used a hexagonal armature to suspend the bellows (I have one like this).

in this video of APJames making a concertina he uses a complicated looking jig. But how does he remove it once the bellows are formed? I assume he unscrews the metal plates and removes the central ply forms…does anyone know? You see the jig from around 2 mins (if lower the vid speed you can see it in reasonable detail).

 

[Steve Schulteis]

I have a bunch of presspahn for this purpose, but I haven't built an actual bellows with it yet - that project has been sitting on the backburner. It does look promising from the testing I did, but it doesn't hold up to moisture well, and that may or may not be an issue during construction. I ordered grade K, 0.8mm thick.  My write-up of the materials I tested is here: 

 

[RogerT]

Ah..yes..I remember your post now. I will have another look at it. Thanks

[Steve Schulteis]

Alex Holden has a better depiction of the style of bellows jig you mentioned: https://www.holdenconcertinas.com/tuning-bellows/ His blog and Instagram (as well as his posts here) are great resources. You've got the right idea - the sides of the jig can be detached from the its core, which slides out, allowing the six fold forms to be removed one at a time.

[alex_holden]

Bear in mind that I don't use that collapsible bellows jig any more. I now make a much simpler style of jig that supports the sides on pairs of wooden dowels. It can accommodate any number of folds and it only takes an hour to make a new pair of end boards for a different width or number of sides. The threaded rod in the middle isn't strictly necessary if the dowels are a tight fit.

 

 

 

[Seth Swingle]

What a beautiful, genius rig, Alex! As with all great ideas, one thinks, "how come I didn't think of that?"

[Ken_Coles]

5 hours ago, Seth Swingle said:

What a beautiful, genius rig, Alex! As with all great ideas, one thinks, "how come I didn't think of that?"

 

Easy: You have to be clever, like Alex! Me, I must have other talents.

 

Ken

[gcoover]

And look out the window - it's propane-powered! 

[RogerT]

Alex, did you find the original jig, with forms for the folds, an unnecessary complication? I’ve looked at you Insta posts (now following). Having the frames fixed to the jig must be crucial? To get the spacing properly set?

 

[alex_holden]

12 hours ago, Seth Swingle said:

What a beautiful, genius rig, Alex! As with all great ideas, one thinks, "how come I didn't think of that?"

 

After the first few sets of bellows I assembled with the complicated collapsible jig, I built several sets without a jig. It's possible but more difficult, and I spent a lot of time thinking "this is awkward, surely there's a better way". I originally made the two end boards and the central rod as a way to stretch out a set of bellows after manufacture (as part of the breaking-in process), before I thought of adding dowels to support the valleys and using it earlier in the process as an assembly jig.

[alex_holden]

12 minutes ago, RogerT said:

Alex, did you find the original jig, with forms for the folds, an unnecessary complication? I’ve looked at you Insta posts (now following). Having the frames fixed to the jig must be crucial? To get the spacing properly set?

 

 

The original complicated jigs took me a few days of work each to make. I made two because my first instrument had four sides and my second had six. When my third instrument had eight sides I couldn't be bothered making another complicated jig and, for a while, I made my bellows with no jig at all. With my instruments all being bespoke I have probably made about ten different sizes/shapes of bellows so far and I expect that trend to continue. I now feel the simple dowel jigs are a reasonable compromise between speed of manufacture and ease of use. If I was running a production line that was constantly making identical bellows every day then a more complicated jig might be worth the effort.

 

It does help to attach the bellows frames to the end boards so they don't flop around during assembly. It's a bit hard to explain but the spacing sort of works itself out if the core is the right size and you set the distance between the ends such that the valleys are loosely resting on the core.

 

The difficult part has to do with the difference in depth between the inner cards and the end cards which gives you the inset - I've got that wrong more than once. It's a good idea to take the bellows off the jig and check they look and move as they should after attaching the linen hinges but before attaching any leather parts.

[Łukasz Martynowicz]

9 hours ago, alex_holden said:

 

The original complicated jigs took me a few days of work each to make. I made two because my first instrument had four sides and my second had six. When my third instrument had eight sides I couldn't be bothered making another complicated jig and, for a while, I made my bellows with no jig at all. With my instruments all being bespoke I have probably made about ten different sizes/shapes of bellows so far and I expect that trend to continue. I now feel the simple dowel jigs are a reasonable compromise between speed of manufacture and ease of use. If I was running a production line that was constantly making identical bellows every day then a more complicated jig might be worth the effort.

 

It does help to attach the bellows frames to the end boards so they don't flop around during assembly. It's a bit hard to explain but the spacing sort of works itself out if the core is the right size and you set the distance between the ends such that the valleys are loosely resting on the core.

 

The difficult part has to do with the difference in depth between the inner cards and the end cards which gives you the inset - I've got that wrong more than once. It's a good idea to take the bellows off the jig and check they look and move as they should after attaching the linen hinges but before attaching any leather parts.

Exactly my experience with making bellows that are attached to the frames - you only need the jig size to be exact and frames mounted dead center - folds space out evenly by themselves. I used simple octagonal prism cut from MDF. I can’t be sure, but I suppose that „Wakker bellows” are made with similar „freeform” setups.