Turbo Oven Question (as in in a/an UFO/TO)

[CAGurl]

 I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.

Susan

 That's the correct way but what mods have you decided to do?

Dan Brewer

Oh, that.....hmmmm....
I'm not altogether sure yet, but I want to see if I can get into that cavity to look around before I start sourcing parts.

My primary ideas (none is original) are to disconnect the thermostat, make the fan run independently of the heater, and wire in an infinite switch to control the heat ramp up.

[peter]

 I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.

Susan

 That's the correct way but what mods have you decided to do?

Dan Brewer

Oh, that.....hmmmm....
I'm not altogether sure yet, but I want to see if I can get into that cavity to look around before I start sourcing parts.

My primary ideas (none is original) are to disconnect the thermostat, make the fan run independently of the heater, and wire in an infinite switch to control the heat ramp up.

Wondering what you mean by that.

Like I hinted at earlier, the split-wire/variac setup would be neat.  But if you're going to be close to the roaster and can bear the thought of adjusting the temp dial from time to time, none of that is necessary and the stock thermostat will serve you just fine.

[J.Jirehs Roaster]

the first thing I would test is if the fan turns off when you lift the handle or if only the heat turns off when you lift the handle.. if only the heat you don't need to split the heat and fan unless you are going to PID or milowidget it.. and for the short times I turn mine off with the handle the fan could turn off and it would probably not make a difference... I just turn the heat knob all the way up and watch the temps on a separate thermometer...

[CAGurl]

An "infinite switch" is what is behind the knob on an electric switch and controls the power to the coil and so controls the heat.

The fan is currently controlled by the handle along with the heat.  AND, since eventually I'm sure I would want to Milowidget the thing, now is as good a time as any to split those two.

And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops.  It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process. 

Susan

[J.Jirehs Roaster]

An "infinite switch" is what is behind the knob on an electric switch and controls the power to the coil and so controls the heat.

The fan is currently controlled by the handle along with the heat.  AND, since eventually I'm sure I would want to Milowidget the thing, now is as good a time as any to split those two.

And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops.  It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process. 

Susan

Hmm..  if yours drops temp as soon as you lift the handle than your fan is probably turning off... mine actually climbs temp a little when I lift the handle.. (probably the fan speeds up because the heater is not drawing so much power)  if you decide to crack it open it will be pretty clear what wires go to the fan.. I put those wires on a new power chord and closed it up...

I pre-heat to 400 then dump in my beans... maybe burp the top if the temp is getting to 300 before 3 minutes then at 350 deg I will lift the handle for 20 to 30 sec. / then 20 to 30 sec. on... etc to slow down for caramel zone slowing down for 1st crack is trickier.. depends on the bean and were I want the roast to go.. but the on/off is more like 15 on and 10 off  not 20 or 30 sec.. you have to watch the rate of temp climb.. and turn the heat back on before it stops climbing or your temp may drop before it climbs again..  (on a really good day it can become almost trance like, but that is not always a good thing)

[peter]

And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops.  It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process.  

Susan

That does not concur with my experience whatsoever.  You may be using very small batches, but even at that, there should be some 'momentum' in the bean mass.  With 8oz. (or my usual 14oz.), if I run it up to say 350 and turn the heat off, it will continue to climb to about 365, all on its own.  That's why, if I want to hold it in the mid 350's for caramelization, I shut it down in the low 340's.  Maybe you are leaking lots of air, letting too much heat out.

[grinderz]

My experience is the same as Peter's. I wonder perhaps if your temperature probe isn't down in the bean mass enough?

[peter]

My experience is the same as Peter's. I wonder perhaps if your temperature probe isn't down in the bean mass enough?

I was going to ask Susan that, but forgot.  Please tell us how you are monitoring your temps.

[CAGurl]

Given your questions and answers, I will try a few more roasts later today and see if I can answer your (and my) questions better.  

I don't think I'm losing heat because I have the foil wrapped around the roaster between the UFO and the aluminum spacer.

Here are pictures of my three roasts from day before yesterday and also of the probe set-up.   I see that the probe might be problematic, but I doubt if I can get it any more "in the bean mass" without increasing the bean mass to a higher quantity of beans that I want/need.....Maybe what I need is something to corral the beans into a narrower radius....

Susan

[mp]

Susan ... you should check out how Peter has changed the wires turning the beans.  Quite a clever idea.  Follow the SC/TO thread.

 

[Alan]

For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat.  I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while.  My thermocoupler will note little to no decrease in temp if first crack is cracking away.  In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward.  I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass.  As a reference I start hearing FC around 270-280*f.

[J.Jirehs Roaster]

For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat.  I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while.  My thermocoupler will note little to no decrease in temp if first crack is cracking away.  In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward.  I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass.  As a reference I start hearing FC around 270-280*f.

WOW?!?!  my probe is basically the same as peter's and I am at 385F to 405F for 1st crack... but I suppose the numbers are not as important as the roast curve you use the numbers to duplicate...

[Gime2much]

  I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass.  As a reference I start hearing FC around 270-280*f.

 Mine also. Using a 20ga K-type thermocouple & Fluke.

Dan Brewer

[CAGurl]

For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat.  I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while.  My thermocoupler will note little to no decrease in temp if first crack is cracking away.  In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward.  I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass.  As a reference I start hearing FC around 270-280*f.

WOW?!?!  my probe is basically the same as peter's and I am at 385F to 405F for 1st crack... but I suppose the numbers are not as important as the roast curve you use the numbers to duplicate...

I'm soooooo glad you said that, because my temp reading is usually around 410 when I am hearing FC.   But, my probe (as you can see in the picture previously in this thread) is all the way to the center of the UFO and probably just at the top of the bean mass.  Probe placement obviously matters, but that's a huge difference.....


Susan