Furnace Build.

HOW TO BUILD YOUR OWN FURNACE

The whole project is actually about tacit skill. The fact that we know more than we can say. 
Many years ago I worked for a few months as a plumber in a large housing estate. We worked in teams of 5 and specialised in one day central heating installations. I worked in a team that generally finished the job by 2pm each day (we were paid by the job not by the hour). As the junior member it was my job to hang the radiators on the walls. On my 1st day, the forman found me measuring up with a tape and a level, as I was taught during my apprenticeship. He took them off me and told me that he would sack me if he saw me with them again. I thought this was unprofessional and shoddy until he demonstrated how he wanted the job done. He placed each radiator on the floor at the points where they would be fitted. He drew a pencil line across the top of the rads and then pulled the top away from the wall, noting where the brackets would be, and drew 2 vertical lines at those points. Where the 2 lines crossed would be the place where 2 holes would be drilled. Once this was done, the bracket would be placed in position and the lower screw hole could be marked and drilled.
This meant that instead of the job taking 4 hours or so, I could have all the rads on the wall in less than an hour.
It also eliminated the risk of holes being slightly out, causing instability problems and making the radiator uneven. As the radiator was related to the floor in each case, they always looked level to the eye and were always the same distance from the ground which corresponded to the distance between the top of the bracket to the top of the radiator.
Far from being unprofessional and shoddy, this method was far more efficient and always looked good because it was installed using the components and the immediate environment as integral units of measurement. This is a local system utilising tacit skill and knowledge, developed by craftsmen in their working environment, and is a great example of reflective rationality. The way I was taught during my apprenticeship, developed outside of the local environment and handed down in the form of instruction and training is an example of technical rationality, societies preferred mode of thinking since the industrial revolution (You can find my paper on reflective and technical rationality on the Plymouth College of Art Making Futures website).

What follows here, via a facebook page, will be a collection of images showing how a simple 25kg furnace can be constructed using its components as integral units of measurement. The first vital component is the crucible, and each part of the furnace is designed around that. Once we have the crucible, we can estimate the size of the combustion chamber allowing for 6 or 7 inches of ceramic fibre in the walls. Luckily, using the LJ1 R2 crucible ( Dyson Precision Ceramics - now owned by Magma), a standard oil drum is pretty much perfect. The base is measured using standard insulation bricks plus 3 mm on each edge to allow for angle iron to be positioned at each corner. Their are no dimensions on drawings here because none are needed.  The size of the bricks are used as units of measurement which means that no bricks need to be cut at the base of the furnace. Once we put the bricks on the floor, we simply measure them and add 3mm to each edge to find the size of the metal baseplate.
So from the size of the crucible, we get the size of the combustion chamber. From this we find the size of the brick base, which in turn gives us the size of the metal baseplate.
This results in a design for a furnace which is incredibly simple to construct.

 

 The only bricks that need cutting are placed inside the square base to support the combustion chamber (under the ceramic fibre ring). Once the furnace is constructed, silica sand is poured into the base to protect the insulating bricks when a crucible fails. I have had one complete run out and turned off the furnace immediately. Breaking up the glass with a hammer drill, I took out the glass and added a little more sand without damage to the brick base.
Even if there is major damage, the brickwork in the whole base can be replaced for about £60.

For detailed images of how to build a furnace, go to  http://www.facebook.com/Bobtoo2012
Don't forget to read the H&S info on this blog and ask me for the manual. I should state that you must use the combustion system specified for this model and have a qualified engineer issue a gas safe certificate before it is commissioned.

2 comments:

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  2. Man, creating that furnace seems like a tough job! That must be an interesting experience. Is that the finished product? The design looks nice; you did a good job creating it.

    Darryl Iorio

    ReplyDelete