Design Progression
        The design for this project started out extremely broad and ambitious, and eventually settled on a very modest fabrication. More information on its original goals is outlined in the "Background" section.
         As discussed in the "Challenges" section, in order for this solution to work it must be affordable to switch from heating oil to wood, at first this end was approached by designing as cheap of a wood furnace as possible, however this design was abandoned and a feeder system was designed and built (see "Challenges" for further explanation)​.
The first way to reduce the cost was by substituting a much cheaper material, and manufacturing the bricks ourselves by the method shown on the right.
Perlite, a kind of very light rock, is mixed with refractory cement and then cast into trapezoid blocks, which were then to form the body of the stove.
This design was abandoned when considering its structural integrity- Perlite/cement is an excellent high temperature insulator, but it is not very strong, and portions of the (heat exchanger) design shown on the right are very thin, and would be subject to crumble.​​
Next the design looked to incorporate a cheap containment component, and galvanized steel transh cans were initially chosen, because their economy of scale and simple design makes them very affordable.
A number of designs followed, some using air coming up from below, others down from above, and in one case up and then back down.​
Responding to this concern the next iteration of design was made with steel pipe in mind. Some advise was given that a copper tube heat exchanger would quickly corrode in the presence of high heat and combustion products, and so a fire-tube heat exchanger was to be used (representation shown left, tubes full of hot exhaust inside a larger tube full of water).
Unfortunately when prices for the pipes needed for this design were checked, they far exceeded the budget of the project, and since affordability was the primary concern, these designs too were abandonned.
The strategy of using pre-fabricated components was carried forward, and a barrel grill smoker was purchased from home depot and the design moved forward into fabrication.
In the image to the left the barrel is shown as a horizontal rectangle- this is the heat exchanger chamber with a spacer in the middle and rows of pancake coils wrapped around it. One pancake coil is shown in the image to the right, with the spacer again shown shaded in the middle.
The challenge here was integrating the fabricated components (the combustion chamber and ducts) with the
 barrel smoker. While the challenges could have been troubleshot, this process would have been arduous, and instead the project refocused on the feeding system for a pellet stove.
The image to the left now shows the full set up of a calibration experiment. After a few iterations were tested this design for a feed auger was chosen, with an auger drawing pellets out of a side hole cut in a wood pellet hopper.
The experiment sought to measure the precision of this system by applying a known voltage to the drill motor for a set duration of time. The pellets dispensed during this time period would then be collected and weighed with the scale shown on the right side of the picture. The hope was that with this simple and cheap feeding system a reliable and repeatable feed rate would be possible, however the power supply was not capable of providing the needed current to the motor, and this experiment was not able to go forward.