Radiant Roaster MKII




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.





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).



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.



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.



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.




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).



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.




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.




Both Lamps at very low power (left) – and high!!



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.