bellows-msg - 10/2/10

Medieval bellows for metalworking and kitchen fires.

NOTE: See also the files: blacksmithing-msg, blksm-anvils-msg, casting-msg, blksm-forges-msg, blksm-welding-msg, bladesmithing-msg, charcoal-msg.

************************************************************************
NOTICE -

This file is a collection of various messages having a common theme that I  have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org

I  have done  a limited amount  of  editing. Messages having to do  with separate topics  were sometimes split into different files and sometimes extraneous information was removed. For instance, the  message IDs  were removed to save space and remove clutter.

The comments made in these messages are not necessarily my viewpoints. I make  no claims  as  to the accuracy  of  the information  given  by the individual authors.

Please  respect the time  and  efforts of  those who have written  these messages. The  copyright status  of these messages  is  unclear  at this time. If  information  is  published  from  these  messages, please give credit to the originator(s).

Thank you,
    Mark S. Harris                  AKA:  THLord Stefan li Rous
                                          Stefan at florilegium.org
************************************************************************

Date: Tue, 15 Oct 1996 07:29:43 -0700 (PDT)
To: markh at risc.sps.mot.com
Subject: Re: bellows for casting
Newsgroups: rec.org.sca

>I have done most of my pewter casting at home with an electric 
>melting pot. Recently I tried to do some casting over a hardwood
>charcoal fire at an event. Unfortunately, I could not get the pewter 
>hot enough to cast cleanly. So I want to make myself a period style
>bellows.

M'lord, I'm a bit concerned here.  Plain charcoal, without forced draft
will get up around 1200 degrees F.  Hot enough to melt plain aluminum in
small sections (like scraps from soft drink cans).  For pewter you're
talking temperatures in the 500-600 degree range.

If you blow charcoal, you can easily reach temperatures where brass and
bronze liquify (1800-2000 degrees F).  With a bit of insulation and a
large mass, you can get iron casting temps (3200 F).

I suspect that there is something else happening if you can't get your
pewter hot enough to flow.  What kind of melting pot are you using, and
what type of pewter are you using?  Also, how are you supporting the pot
over the fire?  Distance from fire?  Size of fire?

I've found that the size of a charcoal fire is critical.  For example,
if I have a crucible of about 5" diameter, I can just barely get enough
heat to melt brass.  It won't retain enough heat to pour reliably.  I
need to get to an 8" hemisphere to contain enough fuel to reach and
maintain a decent temperature with the best charcoal.  Briquettes are
almost a total waste, unless you have a huge pile of them.

At any rate, if you have a charcoal fire about 10" across and about 3"
deep, I'd expect you to be able to melt over a pound of pewter in a 16
guage steel pot and get it much hotter than you should.  (Ever tried a
wood splinter as a temperature guage?  It starts to darken around 500
degrees.  If it chars in 5 seconds, you're ready to pour)

>Does anyone have any books they can recommend to me for this. I
>would like a good secondary source that shows a cross-section
>of the bellows and preferably discusses the materials used.

Don't have the author with me at work, but the book "The Blacksmith:
Ironworker and Farrier" shows how to construct a double chamber bellows.
If you want documentation of this bellows, "De Re Metallica" gives an
explanation, and also shows single action bellows and how they are
built.  I can get you better information if you need.
 
>Or can anyone recommend some good period paintings or woodcuts
>that show bellows.
>
>I would prefer info on the two chamber versions that allow a
>continuous flow, but I'll take what I can get.
>
>Or has anyone built such an item?

Yep.  Been there.  Done that.

I'd suggest just a small, hand-held, single acting bellows for your
application.  They're really handy when building a fire, too!  A couple
of puffs and you can really get things going.

If you want the big, double-acting type, you're going to find yourself
wanting to get more involved fairly fast.  Brass/bronze casting comes up
pretty fast when you've got the technology just waiting to be used.

Best primary sources for metalworking and fire stuff:
Birungoccio's "Pirotechnica" and "De Re Metallica"

Careful.  This way can lead to madness! <manic laughter>

Morgan de Comyn
Piper and Blacksmith to Clan Hubert
-- 
morganh at teleport.COM  


From: WISH at uriacc.uri.edu (Peter Rose)
Newsgroups: rec.org.sca
Subject: Re: bellows for casting
Date: Wed, 16 Oct 96 16:42:53 EDT
Organization: University of Rhode Island

>hot enough to cast cleanly. So I want to make myself a period style
>bellows.
 
I'm pretty sure Theopholis describes bellows,
but the basic idea is that you have a box with flap-valves
and boards on a leather bag.   I, (Designing from scratch)
would do something like:
             +===================     Where P is a pipe,
         ====[           \            [ and == are wooden parts,
 PPPPPPPP[1 f]     2      \           f is a flap of leather,
         ====[           f]           and \ and / are parts of the
             +===================     leather bag forming chamber 2.
 
When you lift the top handle, the leather flap in the solid box [1]
is sucked shut against a board w/a hole in it, at f.  at the same
time, the flap in chamber 2, which is made of a leather bag with a
board on top and bottom, is sucked open, allowing the bag to fill.
When you push DOWN,  the flap in 2 is forced shut, and the one in
1 is forced open.   If you want a 2-bag system,
you put another bag on top of the moving board, with another
valved hole into the box 1.  The board on top of this second bag
needs to be fixed in place against something.  Only the center
board should move.


From: william thomas powers <powers at cis.ohio-state.edu>
Date: Sun, 20 Oct 1996 15:34:08 -0400
Subject: Re: bellows for casting
Newsgroups: rec.org.sca
Organization: The Ohio State University, Department of Computer and Information
 Science

>Greetings from Stefan li Rous,
>
>Does anyone have any books they can recommend to me for this. I
>would like a good secondary source that shows a cross-section
>of the bellows and preferably discusses the materials used.
>
>Or can anyone recommend some good period paintings or woodcuts
>that show bellows.
>
>I would prefer info on the two chamber versions that allow a
>continuous flow, but I'll take what I can get.
>
>Or has anyone built such an item?

Good Lord Stefan;  RUN to a copy of "De Re Metallica" by Agricola,
Dover has reprinted the Herbert Hoover translation.

In it you will find pictures and instructions on building a period
"double acting" bellows "like goldsmiths use"  I believe it is at 
least in the chapter on assaying furnaces and such.  Materials used:
leather, wood, nails.

Note from my bellows experiences please make sure that your nozzle
incorporates a check valve so you don't end up sucking flames or coals
into the bellows---this is really needed for single action bellows;
since double acting should always be venting through the nozzle and never
filling.

wilelm the smith who brought DRM to Jakarta with him and read several hundred
pages.


Date: Fri, 10 Jan 1997 16:42:35 -1000
To: markh at risc.sps.mot.com (Mark S. Harris)
From: Robin Hayes <rhayes at powerup.com.au>
Subject: Re: Charcoal Burners

>In article rhayes at powerup.com.au (Robin Hayes) wrote:
><snip>
>> ~~~~~
>> Traditional crafts in Britan
>> A Readers Digest Publication (Bl**dy hell!!!)
>
>Why do you say this?          ^^^^^^^^^^^^^^

In Australia, RD does not have a reputation for quality. This book, though
is superb. Produced in England.
<SNIP>
>Thanks. this is one of the items I am looking for. I want to make a
>medieval bellows and have a few drawings but the more the better.

Somewhere I have a book on that...

Found it!
The Blacksmith - Ironworker & Farrier
Aldren A. Watson 1977-1990
W W Norton & Co
ISBN 0-393-30683-6

The book talks a lot about New England.

On P129-P146 Chapter 11,
There are full drawings and plans to make a 19C (similar to period style)
double chamber bellows about 4 1/2 ft long and 3 ft in diameter, including
how to mount the pole lever.

On P153 , There are some details about charcoal burning.

Robin
pereant omnes ignavi seque stuprent
rhayes at powerup.com.au  http://www.powerup.com.au/~rhayes/


Date: Wed, 25 Feb 1998 11:16:26 -0500
From: "Gedney, Jeff" <Gedney.J at phd.com>
Subject: RE: SC - kitchen kits (long)

One of the oldest bellows that I have seen is a "Bag" bellows:
A largish sack of leather shaped a lot like a rectangular handbag, with
two rods instead of a clasp affair at the top and a tube to the fire.
Lay it down, grab the rods in both hands, and pull them apart, lift them
up and close them to capture air, then push the rods down to express the
air from the bag, then repeat the cycle.
Very simple, no valves needed.
I have seen examples similar to this in reconstructions of Bronze Age
sites.
Keep in mind that this was used in the early and middle Bronze Age, not
the Medieval Period. And, because there is little efficiency,  the
technique required a lot of relatively rapid pumping to fire the
charcoal to the temperature needed to reduce and smelt tin and copper
ores.
IMHO, Regarding materials for making a bellows for cooking, while it
would be nice to have "airtight" leather and joinery, I doubt that it is
needed,  because even if there is 50% of leakage of air, still that 50 %
delivered is enough to stoke the fire.  I think that with lower
temperature smelting of metals, as well, efficiency is nice, but not
necessary.

        <snip>
> Actually I believe it is a little more complex than this. I have been
> doing some looking into bellows since I would like to create one for
> the pewter casting I do. Even in the simpler ones, you will want a
> one way valve, which can easily be done with leather.

That depends entirely on how you input the air. True, if the bellows
were to use a pump type of arrangement, like you see in modern bellows,
then you are right, but if you use a scoop type of air capture, like
above, then this is not true.
If you are using the "pump" type, then use at least two valves, one at
input, to prevent captured air escaping out the intake, and one at the
outlet, to prevent the bellows from drawing in hot air and smoke from
the fire.

> The more
> sophisticated bellows had two chambers. One was emptying while the
> other was filling. This gives a continuous blast of air. However, this
> may be less important for cooking fires.
        <Snip>
Multichambered bellows used a barrier between partitions with another
valve, and depended on a steady pressure, usually by applying weights,
to make a steady stream. Examples of this can still be seen in various
reconstructions of old Blacksmiths shops all over the US.

Brandu


Date: Thu, 26 Feb 1998 11:17:37 -0500
From: "Gedney, Jeff" <Gedney.J at phd.com>
Subject: RE: SC - bellows

> Brandu describes a simple bellows:
>
        <snip>

> ------
> I’m not sure of your description.  Is this a completely soft bag?
> No flat boards? I’m not sure how the rods are arranged. What do
> they do at the bag?
Completely soft bag. Laid on the ground.  hole in the bottom to which
the exit tube is attached.

The rods are to stiffen the "mouth" of the bag, and to serve as handles.

The bag has a rectangular opening, with the rods sewn in along two
opposite sides.
the action is as follows
Open the rods wide,
Raise rods to lift the opening off the ground. Bag is now roughly
vertical, and looks kind like a large empty purse.
Now swiftly clap the rods together to close the mouth, and trap the air
in the bag
Keeping the rods together, flatten the bag, to express the air out the
tube.
Repeat

> Can you point me toward any pictures of this type of bellows?
Not on the net. I'll try to find the source book at the library, but I
saw it a long time ago.

> I have seen examples similar to this in reconstructions of Bronze Age sites.
> Keep in mind that this was used in the early and middle Bronze Age,
> not the Medieval Period.
> ------
> Are you saying that these were not used in medieval times?  Or that
> you have just not seen any evidence of this?

Just that I have not seen evidence. Since it is an easy bellows to make
and transport, it is possible that is persisted well into period, just
like some low tech wood lathes did ( and still do ) in Egypt and the
Middle East.
But since that is pure conjecture, I did not feel comfortable without
the disclaimer.

> ------
        <snip>
> -------
> True. Or keep the snout away from the embers. This is one of the
> advantages of the dual chamber version. Since air is always
> being blown out through the nozzle, you don’t need the second valve.

And yet, the examples that I have seen (Like at Mystic) have the tip
valve.  Perhaps as a backup, or to prevent Backflow at the first pump (
where the bag is pulled open form a being completely deflated.  The
opening of the first chamber will tend to pull on the second chamber
because the air into the first chamber is partly restricted by the
intake valve. Since air is not being pulled through the barrier (because
of the second valve), the movable barrier will be pulled on by the
negative pressure in the first chamber. If no valve exists at the
output, then air ( and smoke and ashes ) may be drawn in to the second
chamber because of the resultant negative pressure from the pull on the
barrier between the chambers.
This backpressure in the second chamber will probably occur every time
the bellows is pumped from a fully deflated position
This can be minimized by good design, but no design can completely
eliminate this effect due to the slightly springy action of the leather,
to hold the plates of the bellows apart. You can see what I mean by
taking any bellows, and letting it come to deflate to a rest position,
then press on the bellows. Additional air will be expressed. This is due
to the natural stiffness of the leather, holding the plates of the
bellows slightly apart.

I do have some experience to support this. But I haven't made bellows
since Boy Scouts, and only have repaired the "constant flow" type, while
fixing an old organ for a friend. I cannot be considered an authority,
but I have done it with my own two hands.

Brandu


Subject: [Metallum_Lochac] Medieval bellows images
Date: Fri, 22 Feb 2008 23:49:16 +1100
From: Tyghra na Tintagel <tyghra at fastmail.com.au>
To: Metallum_Lochac <Metallum_Lochac at yahoogroups.com.au>

A good resource for the bellows makers amongst us...strangely I just
notice the Tinker's image in a book I have on the Luttrell Psalter, just
today.  It's under 14thC.

~ Tig
-------
I created a page of all the images of medieval bellows that I have found at:  

http://www.medievalocity.com/ImageDisp.asp?img=267
If you know of any other images or references let me know and I'll
include them.  I haven't put in De Re Metallica and Pyrotechnica yet.

Guillaume


From: Alex Haugland <ahauglan at gmail.com>
Date: May 13, 2009 3:09:01 PM CDT
To: pewterersguild at yahoogroups.com
Subject: Re: [pewterersguild] charcoal fire to melt pewter

If you're going to explore a route like this, why not look for a cheap set of fireplace bellows?  They're more period than the foot pumps and essentially work off the same principle, plus they aren't plastic, so there's less concern about heat exposure.  I've seen them at a range of stores in the past, including Wal-Mart.



--Alysaundre 

Weldon d'Ath
Barony of Adiantum, An Tir

Jim Fry wrote:
<<< Can anyone give us some tips on how to get a charcoal fire hot enough to melt a small iron frying pan of pewter? We want to demonstrate pewter casting at June Faire and plan to use charcoal in a brazier as the heat source but have not have much success getting it hot enough. What can we do to get the temperature up?

Red Bow and Madrun >>>

I just had a thought,...
I've seen small foot powered air pumps used to blow up air mattresses when back packing. I wonder how well that would work if you cut off the tip and stuck a piece of tube in it. Keep the pump out of sight under the table and run the metal tube into the fire pot. You could be hands free while "blowing" air into the fire, in order to increase the heat while casting. And you could lay another piece of tube on the table in order to demonstrate the old way of "bellowing".

<the end>
Edited by Mark S. Harris	bellows-msg	Page 8 of 8