Okay People figure this one out. Some of you might remember I was working on an electric drum roaster I called Hot Mama because it was a hacked Betty Crocker rotisarie. Here is the problem. It takes 23 minutes to 1st crack. I preheat her, put he drum in, and within 3-4 minutes I'm pushing over 500, with a starting temp of 450. So why the @#$%^ @#$%^ does it take 23 minutes to first crack. I have a bbq T in the unit sitting close to the drum and below the center line. Ben |
In a message dated 8/1/2004 7:23:10 PM Eastern Daylight Time, btreichel writes: Okay People figure this one out. Some of you might remember I was working on an electric drum roaster I called Hot Mama because it was a hacked Betty Crocker rotisarie. Here is the problem. It takes 23 minutes to 1st crack. I preheat her, put he drum in, and within 3-4 minutes I'm pushing over 500, with a starting temp of 450. So why the @#$%^ @#$%^ does it take 23 minutes to first crack. I have a bbq T in the unit sitting close to the drum and below the center line. Ben Is your temperature gauge working? George |
GHHOLT wrote: <Snip> Yeah, calibrated too. -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |
she hates you Benny... face it, get over it and move on. ginny At 04:30 PM 8/1/2004, you wrote: <Snip> |
What's your batch size? I wonder if it would work with, say 10-20g of beans? Your "individual cup esspresso roaster" ;) I haven't had much luck with consumer rotisseries. I imagine the heat capacity is too small, but I really don't know for sure. I envision it as a creme brulee torch as opposed to a turkey fryer. They're both the same temp from burning propane, but the pocket torch would take forever to roast a turkey leg. I think Ginny's answer was more Ben-ificial, though. Bob C. rcantor |
Robert Cantor wrote: <Snip> 20 oz <Snip> I thought it might be also; but its wearing an R-13 blanket and I can raise the temp 30 degrees in one minute. <Snip> |
Ben As, probably, the only other person that has seen HM up close and personal ( ;-) ) maybe I can offer something. First, what is the present orientation of the heater WRT the drum? Did you ever get any type of convection working? jeff Ben Treichel wrote: <Snip> |
Jeffrey A. Bertoia wrote: <Snip> Moved underneath the drum like we talked about. <Snip> Yes, didn't seem to make any difference. Since you saw it I can get the temp to 550 and still go higher. Before the t-stat was keeping it cooler. Do you think that the thermometer might be reading high due to radiant heat. However, the bean mass is closer and should be effected in the same way. <Snip> |
20oz. is a pretty good size batch. I roast 500g in my weber at 515 deg. in about 17 minutes...maybe your 500 isn't a real 500 as the beans see it. Have you tried a smaller batch? Say 150g? jason --- Ben Treichel wrote: <Snip>http://sweetmarias.com/maillistinfo.html#personalsettings<Snip>">http://lists.sweetmarias.com/mailman/listinfo/homeroast<Snip>http://sweetmarias.com/maillistinfo.html#personalsettings<Snip> |
Ben, I'm no expert, engineer, or physicist. But I think there are different types of heat radiation, such as "radiant" verses "convection", or something like that. In any event, I bet you would get better results if you had a fan going to stir that hot air around, like in a convection oven. I'm thinking a gas grill might have a good bit of air flow inside due to the moving blades inside the drum as well as the rising heat from the burners. Sounds like somehow the drum is too "tight" or else it is somehow insulating the beans from the hot air outside the drum but inside the unit. Of course as Dennis Miller says, I could be completely wrong.. :) Allen am |
At 08:45 PM 8/1/2004 -0400, Jeffrey A. Bertoia wrote: > >Did you ever get any type of convection working? > Sorry I should learn to read the whole thread before replying.. :) Well hopefully I might add something small to the discussion. I often see shiny aluminum foil on foam board for homes which helps to reflect the radiant heat, just like the insulation covering the Apollo Lunar module. I'm wondering if the drums shiny surface might have the same effect? Maybe scratch it up and make it rough. I hear that if dust or paint or anything collects on the shiny insulation, it looses some of its heat reflection properties. How much I do not know. Does your drum happen to be really smooth or shiny? Allen am |
jason molinari wrote: <Snip> I was talking with Jeff B. about that also. Figure I'll try 10 oz and see how it works. <Snip> |
Allen Marsalis wrote: <Snip> Thats what I was thinking; but that s the reason I also moved the heater to the bottom, from the side. With the side mounted heater it seemed to make a lot more difference. <Snip> Actually, I was talking to Jeff B about surface area to bean mass, and the effects of heat transfer. Even though I'm getting good agitation, maybe most the the beans are buried to much of the time. Thats one of the reasons for trying a smaller load. My target load is 1 to 2 lbs. <Snip> -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |
Thermometer is reading direct heat and not the heat the beans are experiencing...or...the thermometer is wrong. I have used three on my grill, in different placements and they read as much as 200F different. ******************************* Ed Needham "To absurdity and beyond!" ed at homeroaster dot com ******************************* |
At 10:44 PM 8/1/2004 -0400, you wrote: <Snip> Seems like a heat transfer problem to me. I found that with 20 oz green in a solid drum in my 35,000 btu (10kW) bbq needed the temps adjacent to the outside of the drum at ~550F to get to first crack in <15minutes. You are probably using a perf drum. If you are relying on hot air alone to transfer the heat then you need a *lot* of hot air to do that as the drum presents a large surface area of beans to be heated. OTOH I watched the 'Joe Roaster' do a pound in < 20 mins a couple of times from a regular 120V, 15A circuit but I think there a lot of the heat is radiant. |
--- Ed Needham wrote: <Snip> Oh yeah, forgot to mention this. Try a different thermometer. I had one in my grill that was reading 50 degrees low, and all of my batches were going into the 23-25 minute range and i didn't know why! jason |
<Snip> You did not describe the drum design or rpm. If you are using the original 3 rpm motor, then that may be most of the problem. Reading the correct temperature is another problem when you have radiant heat. I suggest moving the thermometer above the drum so it does not see the heater. You may want to control the temperature such that there are no "long" heater on/off times. A variac or dimmer may be needed. In my toaster oven experience, manually switching the heat while controlling temp within +/- 2C with a quick reading t/c seemed to help. Controlling with the original thermostat at +/- 25C gave unpredictable first to second crack times. Allen mentioned the drum surface. I realized this on my very first roast with a drum made from aluminum flashing. After 30 minutes and no pops, the roast was ruined. So I put a few coats of high temp black paint on the drum. The next roast reached first in 6 minutes at 550F. Roughening the surface will not help, you need to change the emissivity with a coating of paint. -- |
What is her wattage and drum dimension? Sometime around 04:22 PM 8/1/2004, Ben Treichel typed: <Snip> -- John Nanci AlChemist at large Zen Roasting , Blending & Espresso pulling by Gestalthttp://www.dreamsandbones.net/blog/http://www.chocolatealchemy.com/ |
Johnny Kent wrote: <Snip> Yep. Makes sense. Not much contact roasting going on. <Snip> -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |
Ken Mary wrote: <Snip> Yes & no. I have always been able to get even roasts @ 3rpm. <Snip> Was thinking that. <Snip> I can hlod temp faily well with just the little bi-metalic. <Snip> -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |
AlChemist John wrote: <Snip> 1000 watts & 8" round. <Snip> |
You're not confusing potential with work, are you? -- Rick |
Rick, you always come through in the end... ginny At 02:37 PM 8/2/2004, you wrote: <Snip> |
Rick Farris wrote: <Snip> well sufficient potential should drive work, but ...... <Snip> -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |
I was just wondering about the internal impedance of your source... -- Rick |
Rick Farris wrote: <Snip> Well I normally try to keep my source centered and internal. That pretty much consumes my abilities; so the impedenece of the thing has to take care of itself. <Snip> -- Ben Treichel Program Manager S.E Michigan SwRI 248-232-7365 (o) 248-935-6845 (m) |