Tedrow Bellows construction Page TWO

Tedrow Concertinas

Mark a line the width of the rabbet, are you with me?
Walk off the six side......or eight.....or whatever.  You will get the EXACT fit.  (unless you are not paying attention)

a 55 degree angle works for a six sided concertina......

hmm, now I get it....
Do you recognize the trapezoid in this picture?

Split that pencil line with your bandsaw....no excuses for a bad bit.

Cut just shy of the edges......you will need that little piece of matboard for a while.
Note how completely flat this closes.....without effort at all and flat as a pancake. (flatter!)

Yet, with ease opens 180 degrees

Glue linen to the edge of the bellows
Very pretty I think.

Let me stop right now and tell you where I figured this out.

Several years ago........................

I was pretending to listen to the sermon while seated comfortably at church.  Spiritually,  I was  many miles away in my shop.   Admit it, you have done this too.

It there occured to me this basic idea might work.  It did, sort of.  After many attempts and refinements I had a functional bellows.  It took a couple years to hammer out the little details, glues, clamps moisture content, rabbet joints.

I did most of that pretending to listen to the sermon as well.  

Now, I did confess this to my preacher and thank him mightily for the inspiration and the comfortable seat in the sanctuary.

He said that perhaps it was some kind of divine inspiration, I like to think so.

thank you Robert Montgomery!

A good fit, indeed!
Securely glued now

Trim the corners as close as you wish, but I would leave just a hair there.
This is always a satisfying moment.......unless I did a sloppy job.

Rubber bands help keep the free ends together for the next operation
 Rubber band in place in the valley

100 % cotton cut on the bias into 5/8" strips
 Time to get out the hide glue pot, plug it in and make a fresh batch of hide glue.  I have often kept my coffee warm in the same pot.

With tweezers, soak the cotton or lined strips in hide glue and use the tweezers to "squeegy" off most of the sticky viscous stuff......work briskly er the hide glue get too cold.
The strips of hide glue soaked lined goes around the exposed edges of the bellows cards.  This makes a very strong but flexible joint.  The hide glue shrinks a bit when dry and conforms nicely to the bellows cards.  This also makes a tough and durable foundation for the leather to be applied later.  One can put additional glue over hide glue with great success, not all glues will bond to a previously glued surface. (does that make sense?  I am not editing this page as you can no doubt tell)

cutting the linen on the bias helps make a smooth corner
When the linen is darn near dry....open the bellows to their natural extent.  We want to exercise the hide glue joint.  If you let it dry, the linen will rip.

Ok, let me explain an important point here.

Bellows are made up of two "planes",  one plane bisects  the outside edge, the other plane bisects the inside plane at the valley.  The two planes are connected via the lines formed by the edges of the trapeziods.  The outside plane is of a fixed dimension, the inside plane has a variable dimension. 

A properly made bellows will stop dead at the limit of extension.  If all the trapezoids are cut the same and all the glue joints are in the same relative position, you can feel the bellows come to its limit very clearly. 

This is a geometric fact (is that a term?)  If one had a bellows made of metal and hinged at the bellows card joints, it will extend to the same dimensions.

That does not mean you cannot defeat this by bending over over extending the cards.  Don't do that, you will destroy the inherent stability of the structure.

(the old sport of "drawing and quartering" comes to mind here....that activity will disrupt the integrity of the human body)

It is easy to feel this when the bellows in their "endoskeletal" phase....much harder to perceive when the bellows are covered with leather.....or are poorly aligned when they are glued up.

SO.....I make an assembly jig that has the outside diameter that matches the extended diameter of the inner plane.   (So I have a bunch of these jigs made up for each different size concertina.....I never said my method was slick or easy now did I?)

The leather work has to be completed with the bellows in their extended position.
Come on, you knew there had to be a jig involved here somewhere, didn't you?

Bellows shown here mounted on the assembly jig.  I wish you could feel the absolutely sturdy nature of this assembly at this point.

I use a chrome tanned leather....about .025" thick.  I have used thicker and thinner, I have used vegetable tanned goat, sheepskin, kangaroo, calfskin all with good results.
Paring and skiving is done with a Scharft-fix.......I do love this gadget.  Skiving by hand is very time consuming and usually not too accurate.  I need to cut the gussets, edge runs and endruns. 

Time for a pot of BOILING HOT water, rubber gloves, more glue and an old wool blend sock.
Glue applied to the gusset region.....don't be stingy with it either, ok?

I have lately been using  hide glue for most all of the bellows gluing.  Hide glue has  a character that makes it particlularly  useful for bellows making.   Properly used and applied, hide glue provides a much more flexible joint than a PVA glue.  This is because hide glue dries hard and will fracture into hundreds of tiny glue crystals each tenaciously holding fast upon flexing, while a PVA glue remains ever tough and stiff.  A bellows with hide glue joints will require less "break in" and will be more flexible than bellows make with other glues.

Gussets all laid out on the valleys
I am very serious about the rubber gloves and boiling water.  That was a nice sock at one time.

Press the gussets in place with a hot wool sock.  Wool blend will hold its shape, stays warm, will let you press into the gussets and will not wad up like a wet paper towel,  Cotton does not work well at all.
Gusset glued in

keep the leather down in the valley of sheepskin skiver.  The bottom of a chrome tanned leather glues up very nicely to the top of the skiver.
 This is a hot job in the summer, I'll tell you.

Lets clean up the wood before we glue the leather down.
edge runs and end run glued on.  Not too many picture here....too much glue on my hands to touch the camera.  I hope you get the idea.   Incidently, it take a bit of practice to apply the proper amount of glue to these strips.   I use the hot sock on all these pieces.

This is a nipping press, a bookbinders tool.  It works great for this purpose.  If you don't drill a smallhole in the bottom of the lower platen.....you will be very very sorry.  If you can't figure out why.........ask me.

Another shot.  I just like the looks of this. a man and his bellows.

Dye the valley black
I make these myself, one day I will show how.

a homemade hydraulic press and cutting die for the papers.
I glue the papers on with a dilute solution of PVA and water.  The papers are of 20lb weight stock

looks nice so far.
into the lacquer room for a light shot of a satin lacquer  that is my very exensive explosion proof exhaust fan you see in the background.

a view into the gaping maw of a Tedrow Bellows

I had this tool made for me in England.

Comments?  argh...... keep em!

Not at all, I am very interested in your opinions.  Kindly email me at hmi@scott.net

Bob Tedrow
Tedrow Concertinas
Homewood Music
205 879-4868