Well, I sure hope someone is learning something from my experiments besides me. Yesterday I rebuilt the stirrer, reassembled it with hi temp silicon rubber and started to cut a hole in the Pyrex lid with my Dremel. Well I was taking it easy, very much aware that Pyrex does not necessarily like having holes cut in it, and after a half hour or so I just had to get a cup of coffee! I put the GG down on the bench gently and left. When I returned all the Pyrex had spider webbed. Looked like a broken windshield! Someday I will learn about leaving from what I am doing in the middle. :-( So I looked in my 'spare parts' and came up with a Plexiglass convection oven top. Unfortunately, the GG is the only one I have over 1400 watts, so I adapted this plastic unit to fit the GG heater assembly with my Dremel. Also cut another hole in the top and mounted a 750 Watt heating coil in it, bent so that it almost touches the bottom of the GG. Plenty of clearance for beans underneath :-) Today all the red silicon had cured so I had to test it. First I plugged the heaters into my 20 yr old 15 amp circuit and let it heat up. Now 1440 for the GG and 750 for the auxiliary should have popped that circuit breaker, but it did not. Perhaps I should have an electrician look at it, or maybe these wattages are over rated, but the circuit handled it fine. I had not yet thrown out the beans from yesterday, so I just tried my first roast with the new set up with those. Not sure whether to pre heat or not, I decided to warm it up to 270 before I added the beans. The stirrer held together fine, and the temp first dropped to 160, then started to climb. 300F in under 2 minutes, and first crack in under 5 minutes! I should mention that when it got to 400F I turned off the auxiliary heater. This did not seem to matter, at 430 I started pulsing the main heater, but the temp still continued to rise. At 440 F I turned off the heaters and the temp still shot up. In less than 7 minutes total the TC read 454, and second crack was well under way, big time! I had to take the top off and cool it with the hair dryer to avoid another meltdown. It seems to me that the heating coils must be well over 400, and still give residual heat even though they are turned off. So, I need to turn them off sooner, or pulse both of them. Looks like it is controllable and can roast some great coffee. Will try that this afternoon. PeterZ Reporting the news on coffee roasting, here in LHC.
Monster Garage has little to offer the list that we don't already get from our more adventurous members! Carry on! Brett On Wed, 09 Mar 2005 12:02:51 -0700, petzul wrote: <Snip> -- Regards, Brett Mason HomeRoast __]_ _(( )_ Please don't spill the coffee!
Sometime around 11:02 3/9/2005, petzul typed: <Snip> Have you tried drilling with an abrasive bit with the Pyrex in water? Keeps it cool and should let you drill it right out in a minute or two. You can't use a spiral cut bit though, just flings the water out. <Snip> -- John Nanci AlChemist at large Zen Roasting , Blending & Espresso pulling by Gestalthttp://www.dreamsandbones.net/blog/http://www.chocolatealchemy.com/
<Snip> If the beans can see the heating element, they may be getting overheated. I am not familiar with the physical size of the heater, but it may still radiate a lot of heat after it is turned off. You should be switching the heat earlier, or raising the heat in steps from the start so you have better control. For example, preheat and load the beans, then try to stabilize at an intermediate temperature. Now since the roaster is under control, you can gradually raise the temperature until you reach the roast degree that you want. In my drum roasts, I am now setting the first control point at 380 F which is just short of first crack. After waiting at 380 to allow drying and bean to bean equalizing, I can very easily control the ramp through first and up to second. --
Thanks Ken for your input on this, and your other contributions to the list. The beans do 'see' the element, and I am afraid they are getting overheated, they have a burnt taste (yuck). In the GG the heater is 'hidden' behind a grill, and just the hot air gets to the beans. Back to square one again. The other problem with the aux heater, it kind of melted my hi temp plastic convection oven top! That may contribute to bad bean taste also... again yuk. AT any rate, I have decided that I do not need an auxiliary heater unless I can shield it. When I checked it with the pyrometer it easily gets to 800F, but not to red heat. Still a bit much for plastic. Also the plastic convection oven is not very good for temps I am likely to hit in biasing for a fast rise time to 300F. The thermostat in the convection oven shows internal temp of the GG up over 500F at the end of the roast ( I took the stop off the thermostat so I could crank it up). Next step is an aluminum plate on the top of the chamber (nothing too serious, a serving tray) to mount the GG in; more insulation, and I would like some kind of a window so I can see what is happening. Although a window is not really necessary. Sound and smell works pretty good for me at this stage. How long does it take you to do your drum roasts? How big a batch can you do? PeterZ Need to fix this soon, almost out of roasted beans.. here in LHC. Ken Mary wrote: <Snip>