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View Thread » BUILDING A ROASTER » Fluidbed Roaster
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Brewer to Roaster..blower question...
oldgearhead wrote:
Things are moving right along on this project. I only need to receive three parts and drill 3 holes before I start testing. Here is a copy of my final (120 VAC version) bill of material:

+ 1 - Bloomfield 8773 (Junk) Coffee Brewer
+ 1 - Wooden box 30’x18”x13”
+ 4 - 2.5” Castors
+ 4 feet of 2” Schedule 40 PVC pipe
+ 1 - 3 inch Schedule 40 PVC flange
+ 1 - 3 inch-to-two inch Schedule 40 PVC adapter
+ 8 feet of 2.5” flex hose
+ 1 - 2” Schedule 40 PVC ‘T’, for bean-evac-to quart jar
+ 2 - Two inch Schedule 40 PVC couplers
+ 1 - 1-1/2 HP spa blower (booted)
+ 6 - ‘T’ nuts (10-24)
+ 2 - 1” x 3” piano hinges
+ 1 lot machine screws, washers, and nuts
+ 1 - 12”x 1.5” Chrome sink drain extension
+ 1 - 3.5” Stainless steel cocktail shaker
+ 1 - Master HAS-043K heat gun element
+ 1 lot Permatex Red silicone
+ 1 lot hookup wire
+ 1 - 14/3 Power cord
+ 1 - 7.75” piece of 35 mm DIN rail
+ 10 - 8 mm DIN terminals
+ 1 - Ice cube relay & socket
+ 1- Nema 4x Enclosure 9”x 7” x 4”
+ 1 - Extech VFL PID Controller
+ 1 - Tyco 50A SSR
+ 1 - Brew switch (momentary rocker)
+ 1 - Heater stop switch (momentary N.C. push button)
+ 1 - Corning bread tube (3.75” x 14”)
+ 1 - 3” x 3” Aluminum turbo hose coupler
+ 1 - Zach & Dani chaff screen and baffle-type separator
+ 3 - Very nice RC parts, custom built by DJA
+ 1 - Lot of silicone o-rings
+ 1 - Box of Band-Aids
___ 1 - Tyco 30A circuit breaker
___ 3 - DIN Ground terminals
___ 1 - Green Pilot light
___ 1 - Main switch (maintained rocker)
___ 1 - Dayton 4X796B motor speed controller
___ 1 - Shop vac hose and wand assembly (1.25 inch) for bean-evac-to-quart jar



I'm replicating your build,specifically the heater manifold. I'm trying to locate the cocktail shaker, do you have the make and model of the shaker you used?

No model number available its a 3.5" diameter stainless from Target

No oil on my beans...
allenb wrote:
It's great to hear that recirc is possible without having to use an industrial high temp blower.


Oldgearhead, if the temps for the blower are getting a bit high or you want more, you may also be able to create a basic venturi by injecting you hot air from the blower / heater into a T piece with the return from the top of the roast chamber, similar to the way I inject cold air to cool my exhaust.

Similar to this but instead the LHS would be hot air from the blower / heater and the top would be from the RC.
Imclaren - The unit has been in use for 8 months now, and
the four 1/4" bleed holes located between the blower outlet and the heater inlet have done the job, so far. I don't know how much the motor will take but its been getting along fine with 150F inlet temperatures. (I know the PVC doesn't like 165F)

When the motor fails I'll just 'pop' in a new one, because this one had seen several hours of hot tub abuse before I
rescued it. I mainly bought it for the rubber boot motor housing.

No oil on my beans...
no problem, glad it is working for you.

best regards

We had a few days of unseasonably warm ambient temperatures in March. My roaster has a sliding door that has four, ambient temperature, positions: 40F, 50F, 60F, & 70F.
I was half-way through a roast when I realized it was 80F and I had the door set for 40F. A quick check of inlet air temperature indicated it was at 185F! After the roast completed, I took the pipe apart and inspected it. I found no signs of any problems. However, I though it might be a good idea to do a bit of research. I read 11 MSDS about PVC pipe and here is what I found:
1) Lowest combustion temperature I found was 730F (388C). Some of the sheets stated 849F (454C) for combustion, but I think this referred to ‘flash over’. (When PVC is burning it emits toxic gas)

2) Melting point - 284F (140C)

3) Deflection - 167F (75C)

Therefore, keeping it in the 150F - 165F range is a good idea….

oldgearhead attached the following image:

No oil on my beans...
More info: When PVC burns it releases chlorine, which instantly combines with the hydrogen and moisture in the air to form hydrochloric acid fumes.
I guess if it works don’t fix it... This month, July, marks the first anniversary for this coffee roaster. It has successfully completed 150 pounds of green beans without any problems. I was planning to tear down the vacuum motor, inlet and outlet tubing, and check motor brushes and etc. However, after checking a couple of sections of inlet tubing (PVC pipe), I’ve decided to just keep roasting. The first year design changes and maintenance were:

Because the ‘baffle separator’ was only 50% effective I had to vacuum one-half of the chaff from the top of the roasted beans. So I removed the chaff collector and simply vacuum all of the chaff from the top of the beans. You see, all of the chaff ‘sticks’ to the 30 mesh screen and stays inside the roasting chamber, so a couple of ‘taps’ to the screen and it all drops and is easily removed after cooling and before evacuating the roasted beans.

Sound - I added pyramid waffle sound insulation to several areas of the roaster and ‘cracks’ are now very easy to hear. Actually that was a major accomplishment because my 71 year-old ears were ‘pounded’ from years of completive clay target shooting. My first attempt caused my temperature controller to overheat and ‘blink’ a few protests, but I rearranged the insulation and it’s happy now.

Maintenance has been very easy. I vacuum both screens after each roast and wash the roasting chamber and the screens with soap and water every six months. When I roast ‘dry/natural process’ beans I also need to vacuum the air-mixing chamber area of the roaster. But with ‘wet process’ all is very clean.

I’m pretty sure the vacuum motor will need to be replaced some day because it had seen several hours of hot tub use before I purchased it, but it should be an easy swap. The heater element is still working perfectly and I have a spare, but it won’t be as easy as the motor.

Summary - If you are like me and never go very far into second crack, recycling 50% of the RC air is simple and rewarding.
oldgearhead attached the following image:

No oil on my beans...
Can you hear the ‘cracks’?

I’ve spent the last few days thinking about ways to decrease the ‘noise’ level of the vacuum motor’s air inlet. My hearing has been dulled by both age and thousands of rounds of 12 gauge shots fired after fleeing clay pigeons. Therefore, it’s a bit difficult, but not impossible, to hear the ‘cracks’.

So how loud is my roaster? I dumped in 450 grams of greens and starting measuring, (‘C’ weight/slow):
T= 0min. _ 81 db
T= 3min. _ 71 db
T= 6min. _ 73 db
T= 9min. _ 73 db

Next, I got to wondering if a 40 micron, sintered bronze, pneumatic silencer would decrease the sound level. So I got one and ran a couple of more tests:
1) 450 grams of spouting, green, coffee beans, with my usual 120 mesh screen in place = 81 db/ 80 volts/ 4.3 amps.
2) 450 grams of spouting, green, coffee, beans, with a bronze silencer in place of the 120 mesh screen = 74 db/ 110 volts/ 7.2 amps.
Conclusion - A reduction of 7 db is pretty significant, but I would have to replace my DC drive (its max is only 90 volts) and the vacuum motor is working much harder at over 7 amps.

But, how much difference is there at the T=8min point in a roast when the cracks can be heard and the blower is turned down? I checked, and its 69 db with the bronze silencer and 73 db with the 120 mesh screen.

The 4 db is not a bad improvement especially because ‘bean noise’ seems to overcome the vacuum intake noise with the silencer. I’ll probably try a roast or two with my variable-autotransformer before jumping to a 130 volt drive. Do you think the vacuum motor’s life will be decreased?
oldgearhead attached the following image:

No oil on my beans...
If you are working on the cold inlet, you could make a higher flow 'muffler' with some egg carton like foam, couple of 90deg changes I suspect would soak up a lot of the noise.

I know just putting some cardboard around help mine a lot, by the time i put the panels on the outside with some foam to soak up a bit of noise, it should be a lot quieter.


oldgearhead wrote:

Do you think the vacuum motor’s life will be decreased?

I thought I saw your ametek part# somewhere....but I can't find it.

Anyway, can you capture a vacuum pressure reading infront of the fan?
At least for me, that would offer some indication of how hard it is working, and how much cooling air it is getting.
Scott -It's a two-stage, flow through, #116671-50. What's an air-watt (321)? I don't have a vacuum gage, but maybe I can find one. I think the motor is rated near 100/100 (
oldgearhead attached the following image:

No oil on my beans...
Airwatts are kinda the 'smoke and mirrors' of the central vac sales world. It does offer some insight into performance, but it's not exact by any stretch.

I'll see if that part # comes up on the ametek site. The site was inop yesterday.

Does it sound like the RPM has ramped up alot?
(in relation to the power you're giving it)
No, rpm seems to increase only slightly.
I think I'm going to do a heat-rise check next.

I keep hearing my departed father saying: "If it works, don't fix it"
No oil on my beans...
I tend to agree. It sounds like that filter doesn't offer too much restriction. ....let 'er rip! -Scott
The unit is still running just fine.
Here's a couple of notes:
1) Noise - I added extra pyramid foam in a couple of spots and the 'cracks' are now very easy to hear. I'm not using the bronze muffler.

2) The 40 mesh and the 120 mesh screens still have the chaff under control, and another tear down of the blower indicates very little accumulation. The 160°F inlet air temperature doesn't seem to bother the blower either.

3) Here is a photo of the air-mixing box. The 'ambient' door is shown at the 40°F setting. The door is raised when the garage is warmer. I did have it a bit lower last winter when it was below 40°F in the garage for a few roasts. The idea is to maintain an inlet air temperature between
150°F and 160°F.
oldgearhead attached the following image:

No oil on my beans...
Two years ago this week I started roasting coffee with this fine machine.
It has performed flawlessly (after a couple of rough starts). I have replaced no parts! The old, used, Ametek/Lamb, two-stage, flow-through, blower (removed from a Sundance spa) seems to thrive on 150°F intake air. Furthermore, two screens easily control and contain the chaff.

I roast an average of four, 440 gram batches of wet-processed green coffee per week. Batch size is 440 gram so it fits in a one-quart Mason jar. I use mostly wet-processed greens so I don't have to clean-up. Roast times are in the 11-14 minute range, and I usually stop before second-crack.

This spring, I did make a modification to the top of the RC. I made the coarse screen (Wal-Mart sink strainer), three-inch extension, and the silicone seals, into one assembly. This mod makes working with the RC faster and easier.

Happy 4th to all my friends at/on HomeRoasters dot org!
oldgearhead attached the following image:

Edited by oldgearhead on 07/04/2013 06:46
No oil on my beans...
Just a note about fluid-bed roaster control:
For most of the first two years of my roaster's life, I adjusted the
% on time of the SSR during each roast (note, measured watts at 119VAC):
1) Drying = 70%/ 1075Watts/ 500°F
2) Ramp-to-first-crack = 90%/ 1389watts/ 650°F
3) Finish = 80%/ 1234watts/ 610°F

However, this summer and fall I have not been doing that. Instead I have been setting the % on-time based on the bean I'm roasting, and only adjusting the blower during each roast. The beans in the RC seem to respond quicker to air flow changes than to heater element changes.
In other words:
__Decaf (low test weight) = 70%/ 1075watts/ 500°F
__Decaf & Brazil (normal test weight) = 75%/ 1150watts/ 550°F
__SHG = 80%/ 1234watts/620°F

My set-up probably has more inertia than non-recycling roasters. However, maybe not so much. I turn down the air-flow at 3,6,& 7 minutes and turn it back up during a strong first crack..Try it!
oldgearhead attached the following image:

No oil on my beans...
I member just asked me for more detail about the bean evac.
The only thing I posted was a short video of me 'fumbling' around with it
a couple of years ago. I think that is post 113 in this thread.

What I use is called a 'J-tube' in the grain industry. Vacuum is applied at the
two-inch yellow fitting (I can use either my shop vac or the roaster's air intake). There is a 40 mesh screen inside the white PVC tee fitting, located in the 'red tape' area. I believe the rule for a 'J-tube' is the suction line should be a larger diameter than the material line.

The white PVC fitting fits inside the neck of a Mason jar and the black wand goes into the beans.
oldgearhead attached the following image:

No oil on my beans...
The roaster has ran perfectly for for 3 years now with no failures!
Bean count around 1800 pounds (green).

I've roasted in ambient temperatures ranging from 15°F to 95°F.

The only issue has been with a couple of dry process beans that produce large size chaff, I must roast smaller load sizes...
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