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Radiant Roaster MKII |
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This
roaster is the second generation of an experimental coffee roaster using
direct radiant energy rather than the usual convection/conduction or air-bean
conduction of commercial and home roasters. |
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The roaster drum is stainless
steel, 8 inches diameter x 8 inches deep. Controls are for heater power,
heat ON/OFF, and drum rotation (CW / OFF / CCW). |
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The front
of the drum doesn’t rotate, and opens to dump the beans into the
cooling tray. Drum rotation is electrically reversed to dump the beans, using
spiral vanes mounted inside the drum. |
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In these views the drum is removed
to show the heater mounting. The heater elements are placed over the centre
of the bean mass. |
The
shield over the reflectors keeps the beans off the top of the reflectors during roasting. |
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There are
two 500 Watt halogen lamps providing the heat – these are fitted with
parabolic reflectors to maximise the heat transfer to the beans. About 90% of
the energy is emitted as near-infrared = heat. |
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Power to the DC reversible drum
motor comes from a 2.5 Amp switched-mode plug-pack. The heater control is a heavy-duty
triac lamp-dimmer using an 8-amp TRIAC (capable of controlling loads of
2kWatt at 230 Volt). |
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The interior
of the drum. Everything in here is stainless (vane, nuts, bolts, washers,
wires, etc). The
tumbling/sliding motion of the beans tends to keep the drum reasonably clean
of oils and buildup. |
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Beans are loaded into the drum via
the chute, which also acts as the smoke vent and viewing window (no shortage of light to see
what’s happening to the beans!). An externally-ducted extractor
with flexible duct is attached to the top bar of the roaster during roasting,
especially for darker roasts. |
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Both
Lamps at very low power (left) – and high!!
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Beans are
cooled in a stainless sieve with air being drawn upwards by an
externally-ducted fan. This also clears and expels the last of the chaff from
the beans. I store my roasted coffee in the vented bags that I get from my
(coffee roaster) green beans supplier.
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