It was an odd experience listening for first crack when the noise of the tumbling beans stopped. The drum's square drive hole was rounded out after about 2 years of service. I decided to continue the roast by manually turning the drum with a metal rod. The oven door was opened and the drum was pushed around the spit rod to mix the beans for about 5 seconds every 20 seconds or so. I had to return to full heat to counter the effect of the frequent door opening. First crack proceeded "normally" and after a minute of quiet time there was increased smoke and the roast was dumped. The roast level was city, lighter than my intended city+. In addition to the expected flavors there was a nice vanilla taste. No off flavors were found. This was the best of 6 roasts for this Panama coffee. The effective drum rotation was far slower than my normal 50 rpm and maybe slower than the original 3 rpm rotisserie drive. So there is a possibility that fast drum speed is not necessary. This will be my next experiment, the effect of slow vs. fast drum speed. I already have the dc drive in place so next will be a series of roasts at maximum and minimum drum speeds, probably 50 and 5 rpm. Results in a month or so. --
Sounds like an awesome roast! IIRC, the faster drum speed is recommended only so that the motor is strong enough to withstand the drag of a heavy drum. Power is more important than speed, and the slower rotisserie motors usually don't have the strength to keep a heavy drum turning... On 8/17/06, Ken Mary wrote: <Snip> -- Regards, Brett Mason HomeRoast Zassman
Ken, I wonder if you can emulate the off-axis rotation of the GeneCafe? Rig your spit to go through at an angle - the higher the better as long as yo= u have clearance for the drum to turn. You probably don't even need to cha= nge your vane set up to get good mixing at slow rotations - the end-to-end 's= loshing' seems to really help the beans mix. <Snip> <Snip> er <Snip> <Snip> <Snip> <Snip> te <Snip> <Snip> nd. <Snip> be <Snip> ty <Snip> the <Snip> <Snip> ably <Snip> Enjoy! Steve :->http://www.cafepress.com/stevespics<- My little store of Impressionist">http://www.svandyke.com<- My simple websitehttp://www.cafepress.com/stevespics<- My little store of Impressionist & Special Event photography
Gears- The cheapest motor to manufacture that has useful power is the two pole, shaded pole induction motor. Like the more powerful PSC motor, it generates heat in operation. Two pole construction means the armatures always spin in the range of 1600- 1750 rpm shaft speed. Happily, that's way too fast to spin a rotisserie. A gearbox is used to divide the speed and multiply the torque. You can find surplus gearmotors online using the Google web browser. Instead of trying to reinvent the wheel, why not just get a drive setup that's already researched and available, from RLK of RKDrums? Lowe's was recommended on this list as a source of useful potisserie drives. Funny thing- I was prowling around their gas BBQ's and accessories, and asked to see their strongest drive with a 3/8ths inch square shaft. He pointed it out , and asked, "What are you going to be roasting with that?" "Coffee- I've got an 8 inch dia X 12 inch [RK] drum, and modifying a BBQ for a coffee roaster. Sir, you've never had coffee as good as fresh roasted-" I happened to see him again about a month ago, and you know the rest of the story!! He and his wife vacation in Hawaii. I don't know the details, but apparently he has never done any other than Kona roasting, only in his gas BBQ drum roaster! "I roast Kona too-" "Real Kona? Where do you get the beans?" And you know that one, too... Cheers -RayO, aka Opa! What's in your roaster?
<Snip> IMO the Genecafe design has less to do with roasting coffee better and more to do with adding a "coolness" factor. End to end mixing does not have to be emphasized if the heat distribution to the drum is correct. There is or used to be an industrial solids blender/dryer that had an off axis design with two unequal volumes. This prevented size segregation that sometimes occurs in a cylinder due to "overmixing". --
<Snip> I already use a dc gearmotor which gives me a variable drum speed of 5 to 50 rpm. And very energy efficient, it consumes a measured 3 watts at 50 rpm under load. My drum is small and does not need anything more powerful. I always assumed but never proved to myself that a higher drum speed is better. There is one definite advantage to high speed in dislodging the silverskins from the beans. "Rotisserie drives were too slow" was my opinion when starting drum roasting. And there was some proof in better tasting coffee at the higher speed in those initial roasts. But that was 2 years ago. I do expect the result of my experiment to yield a taste that is different at high vs low rpm but maybe not better. --