DIY Turbo Oven Drum Roaster - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
MerlinWerks

#11: Post by MerlinWerks » Jul 10, 2015, 9:27 pm

Very cool build...

Some random ideas for you:

For insulation you could get some of THIS. Then for starters encase it in a couple of layers of heavy duty aluminum foil to contain any loose fibers and wrap it around the pot. You'll most likely want to find something a little tougher than foil eventually, once on the pot maybe a wrap of aluminum flashing would do the trick.

To reduce volume you could go to a restaurant supply store and and find a pot lid or pizza pan that fits inside the pot. Run some bolts through it vertically to act as standoffs from the bottom to within a couple of inches of the bottom of the drum. Then insulate under that.

I was working on a SC/TO type roaster, but then went with a BM/HG that you can see HERE. But I always thought it would be feasible to remove the TO and fashion a metal disc with a hole in the middle to accommodate a heat gun while still retaining the glass lid for viewing...

Good Luck!!

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dominico
Team HB

#12: Post by dominico » Jul 16, 2015, 3:39 am

Thanks for the suggestions on the insulation, that's going to be my next "enhancement".

I tried a roast preheating it first, but it didn't actually improve the times any, so I'm looking forward to seeing what improvements in roast times if any the insulation will do for me.

Here's the video I was supposed to post last week:
http://bit.ly/29dgjDW
Il caffè è un piacere, se non è buono che piacere è?

MerlinWerks

#13: Post by MerlinWerks » Jul 16, 2015, 10:31 pm

Nice, coming along. I definitely think some insulation will help, as well as reducing the volume of the chamber with a false bottom.

Another source for insulation: http://www.amazon.com/gp/product/B00GT5 ... 1F3P3N2M7T

Some silcone tubing,slit and ran around the perimeter of the top of the pot will help to seal some heat in as well: https://www.brewhardware.com/product_p/ ... ng12id.htm

I think some pillow block bearings would be a nice addition, if not eventually necessary. Something similar to this: http://www.amazon.com/Spyraflo-Housing- ... ow+bearing

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dominico
Team HB

#14: Post by dominico » Jul 19, 2015, 5:22 am

So I put in a "false bottom" of insulation wrapped in aluminum foil. The roast times did get shorter, but only by a few minutes, I still have 20 minutes to full city+. I'm starting to suspect that this may be an airflow problem. There is basically no airflow within the roaster, nowhere for the air to escape, could this account for they 12+ minute drying time I am seeing? What should I do, install a hatch?

Image
http://bit.ly/29dgjDW
Il caffè è un piacere, se non è buono che piacere è?

MerlinWerks

#15: Post by MerlinWerks » Jul 19, 2015, 10:39 pm

That would probably help. If you look at my roaster that I linked to above you can see how i did the exhaust port. I believe it works well in that application because I have two chambers. The inner bread bucket and then the chamber that it fits in to. During a roast the chaff blows out and over the inner chamber and settles in the outer, most of the material stays in the outer chamber and very little makes it out the exhaust port. Not sure how it would work with your setup, but i think it would certainly be worth a try.

Depending on the velocity of the TO fan the chaff may be heavy enough simply settle in the pot. I'd try a 1" - 1 1/2" hole about 1/3 of the way up from the bottom of pot. Then try a stainless mesh strainer over the hole to contain any chaff that blows out. I set a small cake pan under the port and then hang a SS mesh sink strainer over the port to knock down the little bit that comes out the port in to the pan. You'll just have to try it and see where you end up, the hole would be simple enough to seal if it doesn't work out...

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dominico
Team HB

#16: Post by dominico » Jul 19, 2015, 10:43 pm

Thanks for the advice,

I'm going to rig something up this week.
http://bit.ly/29dgjDW
Il caffè è un piacere, se non è buono che piacere è?

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ripcityman

#17: Post by ripcityman » Jul 28, 2015, 12:43 am

You may be under powered (heat) based on 22 min roast time, but the drying phase means what? Cooling? If thats what you mean, cooling should be accomplished ASAP. If you aim a large fan at that wire mesh colander and agitate the beans with your hands they will cool in 1 to 2
minutes.

Simple aluminum screen door material stretched over a wooden frame.

Image

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Almico
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#18: Post by Almico » Jul 28, 2015, 7:37 am

I've been down the road of turbo oven roasting quite a bit. Here was my first project. There are tons of helpful tips there from those that have gone before.

New to coffee roasting and H-B

I found that to do a pound of beans I needed both heat sources: the upper turbo oven as well as the lower heating element from the Stir Crazy. I ran the lower element off a variac so I could control the heat. With this set up I could roast 1-1/2lb of beans in 13 minutes and got a very even roast and even tied for first place in an H-B roasting contest last year.

When I tried upgrading the capacity to 2-3-4 pounds I ran into trouble. This was part of that journey:

Upgrading Turbo roaster for more capacity

I used a pot similar to your set up, still with heat on the bottom and top. The turbo oven alone just did not provide enough heat. It was not an airflow issue since the TO has an intake as well as an exhaust and circulates hot air quite well. It's just a matter of available heat energy to properly roast 1# plus of coffee.

The problem I found with the upgrade pot method is that although I could generate enough heat, the 500* ET was transferred right to the pot and made it very dangerous for handling after the roast. Getting the beans out fast and cooled before they baked was a hazardous challenge. I severely underestimated the heat energy required to roast coffee and how precarious handling that amount of heat was.

So the issues I see with your design are:

1) generating enough heat to roast 1# of beans in 12-14 minutes. I don't think the TO will get hot enough to do it by itself in a pot that size. You are losing a lot of heat through the pot. And If you do get enough heat, that pot will be scorching hot. You can get insulation wrap from wood stove stores that could be used to surround the entire pot. That could work, but would be awkward.

2) How are you getting the beans out quickly? You can't scoop them out of the drum; that would take too long. You can dump them into the pot and then invert the pot, but that means handling a 500* pot with 435* beans inside and a stirring motor attached. Not fun.

3) The built-in thermostat on the TO is useless for roasting high quality coffee. I found it had over 75* swings from on to off. In other words if I dialed the thermostat to 450*, it would kick off at 475* and then not come back on until the temperature went down to 375*. This could be a large part of your longer roast times. You need a PID to control temperature within 1-2*.

What worked with my first set up is that I got convection heat from the top and conduction heat from the bottom. It took an hour or so to get the stirring wire to work properly, but once I did, I was off to the races. That roaster worked perfectly for over a year until I ditched the DIY upgrade and purchased a commercial roaster. It broke my heart to have to disassemble the TO/SC and repurpose the PID and variac. A lot of good times were had designing that machine.

yalcinclk

#19: Post by yalcinclk » Jul 28, 2015, 8:30 am

Hello Dominic, you may try a turbo oven with two heating elements one in up and one in down for better heating and more isolation because of its design. That way you may expedite the roasting time. Coincidentally, I ordered the same drum (it is on the way) and plan to buy a 320 C capacity mini turbo oven and modify by drilling one side to attach a motor or drill. Will share my experience.

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dominico
Team HB

#20: Post by dominico » Jul 28, 2015, 12:01 pm

Hey guys, thanks for the continued support and ideas! I took this roaster to CoffeeCon Chicago this last weekend to participate in the home roasting area. We were roasting coffee all day and it gave me the opportunity to experiment with a lot of the parameters.
By the end of the day I had roast times down to less than 17 minutes.

I haven't posted pictures yet, but I made two smallish opening and closing airflow doors on either side of the pot just above the insulated bottom to experiment with the air flow.
We found this didn't seem to have a measurable effect on the roast time other than they give me a greater degree of temperature control. It was also suggested I could re-purpose one of the doors as a heat gun entry point to help the Turbo Oven along, so I might try that out at some point.

What we did discover is that I hadn't been preheating hot enough. I now let the pot internals get much hotter before dumping in the beans and they make it through the green and yellow drying stages much quicker now, lowering the overall roast time. I got the chance however to meet in person another_jim at the event and he said that the length of drying time didn't have that much effect on the taste compared to the roast profile once the beans truly start roasting.

I also talked with him about charge size in a convection style roaster, and I decided that until I either experiment with more insulation or add a second heat source I will lower the batch size to 12 oz. That combined with a thorough preheat brought me down into normalish roasting times.

I got to talk through a lot of fun ideas for insulating the rest of the pot, a couple of which I will prototype.

Also of lesser note, the ice cream maker motor effectively died on me, so I replaced it with my variable speed drill and quick adjust hose clamp.
ripcityman wrote:the drying phase means what? Cooling? If thats what you mean, cooling should be accomplished ASAP.
Almico wrote: 2) How are you getting the beans out quickly? You can't scoop them out of the drum; that would take too long. You can dump them into the pot and then invert the pot, but that means handling a 500* pot with 435* beans inside and a stirring motor attached. Not fun.
Regarding the questions I have gotten about cooling. I can get the beans cooled to room temp in about a minute. My procedure is as follows:
Put on heavy work gloves (done during the last minute of actual roasting)
Take the Turbo Roaster top off <1 sec
Dump the pot upside down with the drum still closed to drop out all the chaff that collected at the bottom ~4 sec
Reconnect the drum to the motor ~5 sec
Blast the beans with a leaf blower while they are tumbling around in the drum ~45 sec.

By now they are cool and I can dump them out at my leisure.
ripcityman wrote:If you aim a large fan at that wire mesh colander and agitate the beans with your hands they will cool in 1 to 2
minutes.
Simple aluminum screen door material stretched over a wooden frame.
That's a neat build, how do you handle chaff?
Almico wrote:I've been down the road of turbo oven roasting quite a bit. Here was my first project. There are tons of helpful tips there from those that have gone before.

New to coffee roasting and H-B
...
Upgrading Turbo roaster for more capacity
Thanks for the links, I'm always looking for more inspiration
Almico wrote: When I tried upgrading the capacity to 2-3-4 pounds I ran into trouble. This was part of that journey:
Yeah, with this design I was mainly going for something in the 3/4 lb to lb range. I figure in order to be able to do bigger batch sized than that I would have to do a grill roaster project. I've already started collecting the parts for it.
Almico wrote:The built-in thermostat on the TO is useless for roasting high quality coffee.
I completely agree. I now just set mine to the max and I am using my little doors to get a finer control over the heat. Not very high tech but effective.

I'll post some pics of my "air/heat control" doors, and then probably do another video at some point in the future.
I've got 12 oz in 17min by now, so I could probably do 10 oz in 14min or so. I'll test that out.
I'd like to see if I can actually get this thing to do 14 oz in 15 minutes, but if not, I'm pretty happy with where I've gotten it to so far.
http://bit.ly/29dgjDW
Il caffè è un piacere, se non è buono che piacere è?