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A while back a certain forum member introduced me to Coffee Snobs and the KKTO design, so I thought Id have a go at making one myself. Heres a run-down of the parts and construction:
Motor-drive Base
The drive is provided by the pedestal fans oscillator gearbox. This contains two gears driven by a worm on the motors shaft. The gear driven directly by the worm turns at about 30 RPM, with more than enough torque to spin 600g of green beans in the pot as a single mass. This is the gear that houses the disengaging mechanism that pokes through the top of the motor housing on the original pedestal fan. The round-headed hex-drive bolt is a perfect replacement for the disengaging mechanism, once it is cut to length and the plastic "bearings" are removed from the plastic housing. This is glued into place to provide a hex-drive to an appropriately shaped stub of melamine chopstick. The chopstick must also be glued, otherwise it has a tendency to pop out under load, but can be removed easily for replacement. An 8cm computer fan was butchered and stuck onto the other end of the motors shaft to provide some of the airflow that the motor would have enjoyed in its original deployment.
The motor assembly is mounted onto a 300x300 sheet of MDF, which forms the removable base of an MDF box. A small hole is cut in one side of the box to accommodate the computer fan, and a larger hole in the opposite side permits operator access for the purposes of lifting up the drive shaft to attach the agitator, and electrocution. By which I mean to say: this is a home-made, mains-voltage appliance, lacking some of the polish and safety features of commercial offerings - the motor body is earthed and everything else on the inside is at-least single-insulated, but I dont recommend anyone stick their hand inside it while its plugged in.
The MDF sheet with the motor attached fits inside the bottom of the base, and rests against a couple of strips of pine running along opposite sides of the box. It is screwed to these strips rather than nailed/glued in place, so that it may be removed easily for maintenance. The top of the box is slightly recessed to accommodate the floor tile, with the sides of the box protecting the fragile edges of the tile. The tile isnt strictly necessary (the bottom of the pot never gets all that hot), but provides a durable, non-staining surface for the pot to rest on.
The drive extension bar runs through a hole in the top of the MDF box and the tile, and is driven at the bottom by the square end of the chopstick stub. The chopstick probably isnt needed for heat-resistance, but given that everything else in the power-train is glued or otherwise rigidly locked in place, Im hoping it will break before worse things happen (like the worm drive stripping the main gear).
Roaster
The fibreglass blanket is wrapped around for insulation (mostly to stop me from idiotically grabbing bits of steel at 250°C). The spark plug lead was slit lengthwise and the outer sheath removed. The outer sheath slips onto the top of the pasta pot to provide an interface to the glass of the turbo oven, and the core sits in the gap between the two parts of the pot to help seal and keep everything steady.
The top (hex-drive) half of the socket has a slit cut in it to accommodate the mild steel agitator, and the agitator has a notch cut in the bottom to accommodate the bottom (square-drive) half of the socket, such that the mild steel sits about 1mm off the base of the pot when the socket is sitting in place. The two are assembled and welded, and the mild steel twisted along its length such that the ends of the agitator have a leading edge at the bottom, angled at almost 45° from vertical.
6 vertical chaff slots are cut in the inner pot and levered open, narrow at the bottom where the beans are, and wider at the top where a lot of large bits of chaff spin around. The turbo-oven spins the chaff counter-clockwise, so the slots are bent open in such a way that they guide the chaff out, while keeping the clockwise-moving beans (mostly) in.
Thats about it
except for all the trials and tribulations along the way, like the version of the agitator made from 10mm rod - which made for some very uneven roasts.
All in all, given the price, Im pretty damn happy with the results
Ill post a shot of the next roast here as soon as its done.
Attached images:[list][*]The finished base.[*]The roaster, complete.[*]The inside, showing the chaff slots and the original version of the agitator.[*]The inside, showing the chaff slots and the original version of the agitator, covered in beans, not working very well.
Motor-drive Base
- Sheet of MDF, 1200x600x16 - $16
- Floor tile, 300x300 - $1
- ¼" socket drive extension, 6" - $10
- Round-headed hex-drive bolt - $2.75 for 2
- Pedestal fan motor and oscillator gearbox - $0 (at the side of the road)
- Chopstick, screws, nails, glue, angle brackets, wood scraps, 8cm PC cooling fan - close to $0 (lying around)
The drive is provided by the pedestal fans oscillator gearbox. This contains two gears driven by a worm on the motors shaft. The gear driven directly by the worm turns at about 30 RPM, with more than enough torque to spin 600g of green beans in the pot as a single mass. This is the gear that houses the disengaging mechanism that pokes through the top of the motor housing on the original pedestal fan. The round-headed hex-drive bolt is a perfect replacement for the disengaging mechanism, once it is cut to length and the plastic "bearings" are removed from the plastic housing. This is glued into place to provide a hex-drive to an appropriately shaped stub of melamine chopstick. The chopstick must also be glued, otherwise it has a tendency to pop out under load, but can be removed easily for replacement. An 8cm computer fan was butchered and stuck onto the other end of the motors shaft to provide some of the airflow that the motor would have enjoyed in its original deployment.
The motor assembly is mounted onto a 300x300 sheet of MDF, which forms the removable base of an MDF box. A small hole is cut in one side of the box to accommodate the computer fan, and a larger hole in the opposite side permits operator access for the purposes of lifting up the drive shaft to attach the agitator, and electrocution. By which I mean to say: this is a home-made, mains-voltage appliance, lacking some of the polish and safety features of commercial offerings - the motor body is earthed and everything else on the inside is at-least single-insulated, but I dont recommend anyone stick their hand inside it while its plugged in.
The MDF sheet with the motor attached fits inside the bottom of the base, and rests against a couple of strips of pine running along opposite sides of the box. It is screwed to these strips rather than nailed/glued in place, so that it may be removed easily for maintenance. The top of the box is slightly recessed to accommodate the floor tile, with the sides of the box protecting the fragile edges of the tile. The tile isnt strictly necessary (the bottom of the pot never gets all that hot), but provides a durable, non-staining surface for the pot to rest on.
The drive extension bar runs through a hole in the top of the MDF box and the tile, and is driven at the bottom by the square end of the chopstick stub. The chopstick probably isnt needed for heat-resistance, but given that everything else in the power-train is glued or otherwise rigidly locked in place, Im hoping it will break before worse things happen (like the worm drive stripping the main gear).
Roaster
- Pasta pot - $50
- Turbo oven - $79
- Fibreglass blanket - $10
- Spark-plug lead - $5
- ¼" drive socket and mild steel, 180x25x3 - $0 (lying around)
The fibreglass blanket is wrapped around for insulation (mostly to stop me from idiotically grabbing bits of steel at 250°C). The spark plug lead was slit lengthwise and the outer sheath removed. The outer sheath slips onto the top of the pasta pot to provide an interface to the glass of the turbo oven, and the core sits in the gap between the two parts of the pot to help seal and keep everything steady.
The top (hex-drive) half of the socket has a slit cut in it to accommodate the mild steel agitator, and the agitator has a notch cut in the bottom to accommodate the bottom (square-drive) half of the socket, such that the mild steel sits about 1mm off the base of the pot when the socket is sitting in place. The two are assembled and welded, and the mild steel twisted along its length such that the ends of the agitator have a leading edge at the bottom, angled at almost 45° from vertical.
6 vertical chaff slots are cut in the inner pot and levered open, narrow at the bottom where the beans are, and wider at the top where a lot of large bits of chaff spin around. The turbo-oven spins the chaff counter-clockwise, so the slots are bent open in such a way that they guide the chaff out, while keeping the clockwise-moving beans (mostly) in.
Thats about it
except for all the trials and tribulations along the way, like the version of the agitator made from 10mm rod - which made for some very uneven roasts.All in all, given the price, Im pretty damn happy with the results
Ill post a shot of the next roast here as soon as its done.Attached images:[list][*]The finished base.[*]The roaster, complete.[*]The inside, showing the chaff slots and the original version of the agitator.[*]The inside, showing the chaff slots and the original version of the agitator, covered in beans, not working very well.
, nearly winter it wont be missed 
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