Talk to Todd at Flying Goat in Healdsburg, CA. I saw their Kestral this summer. Very effecient, but more of a Fluid Bed then fluid/drum hybrid like they say. My favorite feature was the weigh out cart with vacuum lift attachment. Way cool. I wonder if they'd retro fit one for a Proby.
I roasted on one for a couple of years at Taylor Maid Farms. My roast times were around 13 to 14 minutes and I could adjust the flame just like on a Probat. The construction is all stainless steel...and so is the cooling tray, which is actually not that great. It holds onto the heat especially on hot days.
Otherwise I loved working on it, and while some can taste the trace difference between iron drum and stainless as well as the end result of convection vs. radiant heat transfer, I did not find it an issue.
Still had great crema on espresso...all cupped out well against something like the Probat.
(TMF had a Probat hooked up as they launched the Kestrel and did copious cupping between the two...brought in industry "experts" an you know, did it up good)
Take a look at them, they are well worth the "green" effort you'll be making and the coffee will not suffer for it.
In November I installed the new Revelation roaster from US Roaster Corp. It's an alternative to the Kestral; I bought it because it was much more economical (in terms of purchase price at least). Mine is the only one in existence right now, but Dan Joliff is building more. I'm still learning the ropes but I do like it. Mine is a 12-kilo all electric because I have no gas service. I was apprehensive, but it's working out well.
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