A month or so
back, I had a go at making a machete out of an old truck
spring... The results were far better than what I expected, so my buddy -
Bob, & I decided to turn our attention towards a dedicated wood/charcoal
fired forge.
The Master-Blaster
Melt Furnace is certainly up to the task of doubling as a forge, but this
unit will be Bob's when done, and serve as yet another
"Proof-of-concept" project largely for us both to develop better fabrication
skills and prove-out a "Homebrew Refractory" recipe that will be used
in a similar project over the next year.
The lawn mower is
pulled from the pile-o-mowers behind the foundry, while the tall galvanized tank
was recovered from the demolition of the barn
last summer (2008).
There is one
cracked tire, so we opted to replace all four with the sturdiest tires we could
find...
In anticipation
of well over 10 times the weight of the motor that was removed, I opted to
secure the adjustable metal work such that the deck is as level as can be
expected and marginally more sturdy...
As it turns out
this is a lost cause, as the assembled and tested unit has the wheels splaying
outward after moving the forge 10 or 15ft.
Bob will look for
a few lengths of 1/2" solid rod and some heavy metal wheels over the next
couple of weeks.
The tank is
chopped and grinded, welded and re-welded to form the "Stubby Tank"
pictured below.
The sizing was
chosen to fit nicely on the mower deck.
A line of masking
tape scribed the lid at about the 1/3 to 1/4 mark of the tanks horizontal
orientation.
The lid is
liberated from the base by an angle grinder fitted with a "Walter
Zip-Cut" - the official cutting disc of theworkshop.ca.
The tank is
secured to the deck with 4 (four) chunks of angle-iron. Both the deck and tank
are meticulously prepped for welding...
The lid is
secured with hinges at the back, a snappy looking rebar handle and a length of
chain to support the lid in the "Open" position.
A considerable
amount of thought was put into getting the "Slant" of the tank assy
such that the lid would open fully without stressing the hinges too much, while
retaining ease of operation and stylish good looks...
Although the
concave end-plates will likely hold the refractory in place we did have concerns
that if the lid did "Slam-Shut" a few times that the entire mass would
fall out.
To that end, the
mat of "Corn-Crib" wire was tediously welded into place... If this
still proves to be a "Failure-Point", then a series of holes will be
drilled and a similar wire mat will be laced through the holes for an even more
secure retention scheme.
The pipe that
runs along the base of the tank is the Tuyere, or air-supply line to the
"Fire-Trough".
We even went so
far as to measure the cross-sectional diameter of the tuyere and calculate the
diameter of 5 evenly spaced air-nozzles, such that there is a Balanced flow of
air.
Of the many
"Refractory Recipes" that Bob & I reviewed, all pointed to
Portland cement and Dolomitic Lime.
Other's referred
to a measure of Ceramic Grog...
The Grog is
simply a inert filler that has a measure of heat tolerance. In our case I opted
to use a complete set of "Earthen Ware" plates & bowls that were
glazed & fired.
As well as a
bucket of ceramic tile cuttings from a bathroom renovation project last year.
The ceramic
rubble is reduced over a period of approx 3 (three) 8 hr days in the cement
mixer, aided by the 20lb metal weight that was tumbling along.
The finished
ceramic filler is screened through this 1/4" wire mesh.
This is a very laborious
task and may not be essential, regardless, I can't bring myself to simply dump
the plates and tile material given the total energy embodied in their
manufacture and the fact that they are already in my possession.
The images below
are to an ingredient that never appeared in any of the refractory formulas we
reviewed, but was inspired by my scholastic endeavors several years ago as I
pursued my "Foundryman's Ticket".
I've been
accumulating bins of Aluminum Dross/Slag from the foundry and finally have a
chance to use it.
The basic premise
is that Aluminum when oxidized during the melting process, forms a slag that
chemically is expressed as Al2O3
In this state the
resultant "Alumina" is no longer a metal, but rather a Ceramic, and
the Aluminum/Oxygen bonds are so strong that the compound requires approx twice
as much heat to break them which equates to 2,300F to 2,500F of heat absorption.
(For
a more detailed discussion of Alumina and ceramic/clay based refractory
properties see this
link...)
So the basic
recipe is;
1 Part Lime
1 Part Portland
Cement
2 Parts Screened
Sand
1 Part Powdered
Alumina
1 Part Ceramic
Filler
We added water
very carefully with considerable mixing by hand to achieve a consistency of
adhesion just past the "Crumbly Phase", the batches mixed were
"Trowel Tested" for surface finish properties, and "Ball-Form
Tested" ...
The forge
assembly had to balanced on a set of cinder-blocks to create a pair of
semi-level molds...
The surfaces are
trowelled flat, and the refractory is carefully worked down through the wire
mesh.
The finished
forge is left to cure of a full week...
The wood form was
easily knocked out, and the resultant Fire-trough with tuyere looks excellent!
With the shape of
the inner chamber now defined, we cut a simple exhaust port on the front end.
An old blower is
recycled (for a 3rd-time) for the forge, and is re-wired with a GFI protected
line-cord.
As I'm but a
simple dirt farmer, with no state sanctioned licensure with regard to electrical
devices, the GFI was included for fear that the metal blower electrify the
entire forge and pose a safety hazard if used on damp ground, or left out in the
rain while plugged in.
My personal
Attorney & Advisor would be proud, but read the disclaimer
just the same...
Here Bob is
kindling the first stirring of life in the Baby...
As an
aside, I can only imagine Bob's pride, as just last week his 2nd grand
daughter was born... And now this!!!
Please don't
email me about how inappropriate the comparison is, I fully realize most men
will never build a Forge, while grand children are born everyday...
The refractory
held up perfectly and has started to assume the snow-white coloration that is
characteristic of the commercial refractory's that I'd worked with twice in the
past.
Once the forge
was completely fired (no longer seeping steam out of edges), Bob wanted to
anneal his blade.
The idea was that
we would throw in the blade, fire the blower for a 10 minutes or so, to build-up
some heat, and then leave the blade in the ashes and embers to slowly cool over
night.
Perhaps we lost
track of time as we were entranced by the bluish purple flame coming from the
exhaust port...
Or we were so
busy congratulating each other on our apparent success, nonetheless, the blower
ran too long and we were in for quite the surprise.
The forge was
measured on a whim with the foundry Pyrometer, we watched the temperature
steadily climb, when it hit 1,600F we immediately knew the blade was in grave
danger, and rushed to it's aid, but we were too late...
The high carbon
spring steel of the blade was no match for the aggressive oxidization of the
air-nozzles, as the metal melted and had a clean hole blown right through the
blade.
A
failure???
No way!!!
The blower can
always be turned down, while a forge that can never reach an adequate working
temperature is as useful as a water tank welded to a lawnmower and filled with
concrete.
The implications
are tremendous, this forge can easily double as a small melting furnace exactly
as it sits for Aluminum and copper based alloys. And this opens the door to cast
alloy handles and fastening hardware for knives beyond the original function of
heating the steel to the point that it can be worked.
The link below is
to a short video that wraps up 4 (four) Saturdays of work, in just under 10
minutes...
