Double (not Great) bellows

[Nick]

My travelling setup forge is an old Buffalo forge with a large ratchet and flywheel blower driven by a tiller. It works all right for the small ren faires I've been doing, but I want a more authentic setup. As part of that I'm planning on replicating the rest of the Mastermyr tools and making better garb, but I'd like a more authentic forge, too.

A friend of mine is making a small double chambered bellows, but he recreates the early to mid 16th century. I'm more interested in the 14th century, and as far as I know that's before the introduction of the D.C.B. I've seen recreations of Viking forges with two single chamber bellows, pumped by hand. But, I've seen some later medieval illustrations (see below) that show what looks like a lever system so that the smith can pump the bellows one handed, just like the great bellows. The thing I wonder about with a two bellows setup, though, is that when one bellows blows out, the other is sucking in. Is this a problem, or something not to worry about?

[Finnr]

Both those illuminations are new to me. I am only familiar with the double bellows being used by an apprentice while the master forges. But then My time period is closer to the Mastermyr period. I do tenth century Norse.
Finnr

[irnsrgn]

Pardon me for saying so, but those pictures look like an artists rendition of a smithy, not an actual drawing of the setup. Single chamber bellows are possible you just need a very flexible flap valve at the outlet for the intake stroke.

[Sam Salvati]

It looks simple, probably weighted on top so when you pull the top or bottom up by the handle, it pushes air in.

[HWooldridge]

Our local group restored a 15th century Spanish blacksmith shop at Mission Espada in San Antonio. I was not directly involved in building but have seen their pair of single accordion-style bellows in operation. It takes two people to work this setup, with the helper pumping first one bellows and then the other while the smith does the forging. There is a simple valve in the back and another at the nozzle of each bellows - the rear closes on the pump stroke while the front one opens then vice-versa on the reverse stroke. The forge goes "chuff-chuff" while in operation so it is not a continuous blast but will get plenty hot to weld - the tuyere blows down from the side into a small duck's nest that holds the fuel. In accordance with the period, our members use lump charcoal at public demonstrations.

I'll see if one of our members has any pictures - better than typing 1000 more words...;-)

[Archie Zietman]

until about 15th C. as far as I know it was just two big single bellows, which works fine. All of the illuminations and drawing from 15th C. back have double bellowses in them, great bellows weren't invented yet. I'm going to try and dig up some photos of a very good medieval setup I saw pictures of once.
two single bellows either weighted, or with something that when one goes up the other goes down would be great. I'll think up how it would work, I've seen a few great setups with two alternating single bellowses, worked by pulling a chain which emptied one, then when the other one went down the first filled with air again so that when you pulled the chain again it would be full. You could get a very good continuous stream with it, just have to remember and sketch it up. I'll sleep on it (the design).
Good Luck,
Merry Being,
Archie

ask around on armourarchive.org forums, they do a lot of pre-15thC. viking and norman type stuff and some people there could help I'm sure.

[jake2431]

I've got an idea in my head of how continuous airflow may have been achieved by looking at these photos. It does was Archie was writing about and could have definitely been made during you ideal period. It is hard to tell exactly how the ones in the pictures work, but I will try to explain my idea.

I agree with AMan that it was most likely weighted. The green organic shapes on top if the bellows in the first picture could be weights (but that's just a guess). Anyway, you could make a wooden frame with a bellows on each side of wooden board that acts as a "seesaw" that, on the raised side, extends the lung to its maximum capacity, while the other lung expels air due to the weight on it. Now, in my idea one of the bellows would have more weight than the other, so that when you let go of the lever that you are working the bellows below the lever (the one with the most weight) will expel its air and it must have enough weight lift the opposite bellows to it's full capacity. When you pull on your lever, you will be lifting the heavier weighted bellows. You will also need some simple valves, but I'm not sure what was available in this period. If you are interested in the idea and would like a visual aide to see how it is build, I will draw one up. But if this seems like a bad idea to you, I don't want to take the time. But that' the basic idea for "Jake's Pre-D.C.B Late Medieval Continuous Flow Dual Seesaw-Bellows"! :-)

Seems like it would work, but I may have missed something, as I just thought it up. Oh, plus there may be a better way, but this seems pretty easy.

[Nick]

Pardon me for saying so, but those pictures look like an artists rendition of a smithy, not an actual drawing of the setup.

That's one of the challenges of interpreting medieval art. There can be an incredible amount of detail at times, but the way in which it's portrayed (perspective, arrangement, etc) can make figuring it out harder.

The first drawing seems to have a more detailed blower, but it's obscured by the forge. The second clearly shows the bellows but it's more representative than detailed. Still, they both show the bellows attached to ropes on a handle.

Jake, I think I understand what you're saying. The green things in image #1 could be weights. They're absent in #2, but like I said it's more representative. I've found a few pictures of blacksmiths from the period, but not many good ones of forges. They seem to be more common in the later 15th and 16th centuries (I've got a copy of De Re Metallica, it's got a great period exploded view of a great bellows). When I'm in Leeds I'll see what I can dig up.

[jake2431]

Sounds good. Let me know what you find. I am actually really interested in this period also, as well as the later late-middle ages. My interest in blacksmithing actually stems from my interest in medieval/renaissance European history.

[jake2431]

Also, medieval artist try to do pretty detailed pieces. The only thing that should be missing from the images are details that the artist may not have grasped and perspective. Artist of that period hadn't yet obtained a proper understanding of three dimensional space. In essence, there was no perspective. That is why the images appear so flat, and why it is so hard to recreate something seen in the images. You can't really tell what the equipment is doing without it's placement in the room in three dimensions. However, examining the images suggest that it is possible that they could have been using some seesaw type system, and I believe that the bellows setup in the two images is far to similar for it not to be a basic rendering of that particular period setup.

[Archie Zietman]

Okay, I think I have figured out a design, thinking along the same seesaw pronciples. I'll just draw it up and then post it.

Here is the design, hopefully it makes sense. :D

[Wayne]

I use a pair of single action bellows when I am doing my medieval demonstrations, what I have found so far roughly runs as follows - two single action bellows worked by hand from the rear are good for Roman and Dark age.
Two single action bellows operated by the crank mechanism are good for medieval and upto about 1550 period when you start to get illustrations of double action bellows from german illustrations.
For VERY late medieval - early Tudor the book De Re Metallica by Agricola has very good instructions and sketches of the construction of single action bellows.
On my own set up the bellows are weighted with stones with the bellows furthest away from me being just slightly heavier to help on the up stroke of the lever.
The main pivot bar of the crank has to be angled - higher at the back than the front, I will have to measure mine as I cannot remember if the angle of the bar matches the angle of the top board of the bellows when they are half inflated or fully inflated, this angle is needed because of the twisting effect you get as the crank pivots.
I original thought this angle was only shown by the artist in an attempt to show as much detail as possible, but I found out the hard way it really is needed.
If I can figure out or someone can point out how to post pictures I will send some of my set up.

[Nick]

Wayne, I'd love to see pictures of the setup! Do you have a digital camera or know someone who does and can upload them? If so, and the pictures are on your computer, click the "manage attachements" button below the reply window and you can load the picture. Otherwise, upload it to Photobucket and you can then post the URL here (posting it with will post the picture here directly.)

[Wayne]

Ok,
If this works,, here is a shot of my medieval forge. With this set up I can cover most of the middle ages, by attaching my double action bellows I can cover from mid 1500's through to 1800's and by replacing the woden set up with my metal set up I can cover the Victorian to almost the present day.

[Wayne]

Oop's,
Not quite right but you should see what I mean

[jake2431]

If I'm not mistaken, Wayne, that first image is exactly what Nick is looking for, and what is pretty much happening in the medieval artwork.

[Nick]

Wayne, that's exactly what I've been looking for, thank you! When you said the pivot bar has to be angled, are you refering to the bar I've marked in blue? Also, if that's the case, is the pump lever attached to the crossbar and the pivot bar, or is it just resting on the pivot bar?

What's the bronze colored thing on top of the bellows nozzle? Is it just a weight to keep things from shifting? What kind of valves do the bellows have, and do you get a continuous airflow or puffs?

Lots of questions, but this is the first time I've seen this kind of setup recreated!

[jake2431]

Very cool! I can't wait to understand exactly what is going on as well.

[Wayne]

Hi nick,
Thats right, I call it the pivot bar as every thing runs off of it.
The pivot, crossbar and lever are all fixed - imagine a crucifix with one end of the pump lever attached just short of the right arm. You then cross the lever over the pivot until the handle is in a comfortable position for you and then it is fixed where crosses. On my early version I used to lash it in place but it has a tendency to work loose as the day progresses so now I fix it in place with screws sunk in and the hole closed with a small dowel pin to hide it.
On the underside of each bellow there is a hole about 4'' square. this hole is closed with a square of plywood about 6''square, on the underside of the plywood I have glued suede leather which has about a 7'' square and this helps to seal the hole.The hinges for the flaps are leather also.
There is a flap of suede leather pinned to the top of the bellows where the air comes out - it is hidden inside the metal cones and is there as a precaution which so far has not been needed. to give you an idea of scale the bellows without counting the metal nozzles or the small handle where the ropes attach are 40''long 18'' at the widest point and open up to 20'' if I made any more I would probably make them slightly longer and deeper but not wider to give me a slightly larger air flow, with a little practice you can get a near continous air flow going with the air stopping only as long as it takes to change the stroke.
This forge will happily handle up to 1''square and will burn charcoal,coal or coke without problems and I can fire weld on it.
To hold the bellows to the frame there are metal brackets on the frame under which the bellows sit on - two under each bellows and I put a couple of screws into the underside of the bellows to fix them - not terribly authentic but the public cannot see them.
All of the frame is held together by mortice joints and knock out pegs.
Remove the coals, lift out the fire pot and the floor tiles lining it ( a friend is a potter and makes copies of medieval floor tiles) just a single layer suffice for me .
Lift out the metal sheet the firepot sits on - this in turn sits on four pieces of angle iron around the edges of the frame.Lift off the hood, knock out the pegs and it all the forge and frame breaks down.1 front,2 sides,1back, 2 bellows supports,2 cross braces for same,1 rear frame,1hood and 1 pivot/crank.
The wattle and daub effect is what you guys call hybrid adobe or papercrete -70 parts pulped paper,10 parts sand,10 parts soil and 10 parts cement ( the measurements do not have to be exact) there are several sites that tell you how to make it. Put it onto the frame and let it dry, it is flexible, fire retardent,waterproof and (fairly) light weight. The unfinished hood is deliberate it shows the public the construction and helps dissipate the heat away form the canvas.
The bronze coloured thing is actually my medieval drinking mug.
I hope this helps
Wayne

[Wayne]

Nick,
Forgot to mention, if you are coming over to leeds and plan to hit the royal armouries give them a call first as tucked out of sight they have a first rate reference library which is or at least was when I last went open to the public ( but they tend not to tell people this fact), but you would need to find out the opening times and days. They also have a photocopier there and for the price of the paper are not to adverse to assorted tomes falling on to it.

[Nick]

Drinking mug, got it

Thanks for all the info, it'll be very helpful when I build my setup. It'll be a while because of school, but I like to plan ahead a little.

I'll be in Leeds for a year or more for graduate school, at least one of my classes is going to be in the Royal Armouries. I'll be there for medieval history, and my main focus is the armour and metalwork of the Middle Ages, so I hope to plumb the depths of their library and archives!

I just remembered a couple other illustrations, these are woodcuts from the 15th and 16th century.

[ThomasPowers]

When I built my Y1K bellows I did not include a nozzle check valve as Theophilus did not mention them for his metalworking bellows but did for the organ bellows. "Divers Arts", Theophilus; c1120 AD

I learned that alternating the pumping just right would keep small bits of hot coals from being drawn into the bellows. The biggest problem being that you have to stairstep their inflation every time you start from zero; not hard to learn to do.

I also leaned that leaving an airgap between the nozzles and the tuyere pipe about the diameter of the tuyere pipe helped---this has been seen in pre 1000 CE excavations and was though to be an attempt to entrain more air---like an aspirated propane burner does. Calculations indicated that it didn't work well for that.

Well it worked a treat to keep hot coals from being sucked into the bellows and I have informed Rehder author of "Mastery and Uses of Fire in Antiquity" of this other use for it. (book contains a "foolproof" small bloomery plans!)

Medieval and renaissance art can be quite accurate or woefully inaccurate depending on the artist, time/place and what they were trying to accomplish.
Remember that while the illustrators *may* have the originals to work from they don't *know* blacksmithing and so important details may get left out or be skewed.

I am currently working on a 1570's camp kitchen based on representations of one in a book written by one of the Pope's cooks around then. Items are missing/inaccurate and sometimes escher-ized to show details. Mine will not be "exactly" like the drawing---mine will actually *work*!