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Halogen Radiant Roaster
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Brainiac |
Posted on 08/21/2007 11:58 PM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Inside of drum. The main agitating vane is curved to speed up dumping of beans. I don?t know if more vanes would make any difference to the evenness of the roast? at present the motion of the bean mass under the radiant heat source is slide-and-tumble rather than continuous tumble, and I believe that provides the optimum heat transfer.
Brainiac attached the following image:
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Brainiac |
Posted on 08/22/2007 12:01 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The hole for the loading chute was cut in the door using a sheet metal nibbler. the chute itself is a circle of scrap stainless steel and is held in place with bent tabs.
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Brainiac |
Posted on 08/22/2007 12:03 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The door mounting allows accurate alignment of the door to the drum (the original plan was to use this mechanism to open the door for dumping the beans, but the top-mounted hinge and lock knob proved easier to use)
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Brainiac |
Posted on 08/22/2007 12:06 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Most of the weight of the drum (and beans) rides on a small ball bearing, shown here, mounted on the top of the door
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Brainiac |
Posted on 08/22/2007 12:07 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Bearing viewed from inside....
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Brainiac |
Posted on 08/22/2007 12:11 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The lamp holders are mounted on a bracket hand-fabricated from aluminium angle, fixed to the inside of the door
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Brainiac |
Posted on 08/22/2007 12:12 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Side view of the lamp mounting bracket and one of the reflectors
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Brainiac |
Posted on 08/22/2007 12:14 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
A shield over the reflectors prevents beans from lodging on top of the reflectors and burning
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Brainiac |
Posted on 08/22/2007 12:15 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Electrical connector inside the roast chamber is ceramic, cables are high-temperature insulated (but no asbestos, please!)
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Brainiac |
Posted on 08/22/2007 12:16 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Lock washers on all fasteners means no metal bits in your coffee. This is the shield over the reflectors.
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Brainiac |
Posted on 08/22/2007 12:19 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
I was lucky to find this surplus power supply housing. Everything fits in here with no awkward mounting jobs.
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Brainiac |
Posted on 08/22/2007 12:21 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
A wrecker?s yard provided the 12 volt motive power for the drum. This has a nylon gear, but temperature doesn?t seem to be an issue.
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Brainiac |
Posted on 08/22/2007 12:22 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Before we discuss electricals: I always run my projects through a residual-current device (sometimes called an earth-leakage circuit breaker). A potential lifesaver for all 230 Volt project work (110 might give you a buzz, but 230 will kill you!). I can?t stress this enough ? take care with electricity! |
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Brainiac |
Posted on 08/22/2007 12:23 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Circuit diagram:
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Brainiac |
Posted on 08/22/2007 12:26 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Power for the motor comes from a plug-pack power supply ( switched-mode for lots of current and light weight)
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Brainiac |
Posted on 08/22/2007 12:26 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The temperature control is a beefed-up lamp dimmer control (good for 2000 watt). DPDT switches (one ON/OFF/ON) rated for 230 Volts were used for lamp ON/OFF and drum rotation control |
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Brainiac |
Posted on 08/22/2007 12:28 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Electrics...
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Brainiac |
Posted on 08/22/2007 12:29 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
I used an IEC mains connector, as I have lots of computer power cables lying around, and it make the machine easier to store. Earth connection to the metal housing was a must.
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Brainiac |
Posted on 08/22/2007 12:30 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The lock knob for the door is placed on the left so that the action of tightening the knob also closes the door. The screw connector will eventually (probably) be replaced with mains-rated plug and socket setup
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Brainiac |
Posted on 08/22/2007 12:32 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The bottom support legs are a couple of shelf supports attached with machine screws.
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Brainiac |
Posted on 08/22/2007 12:34 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
Electrical wiring is protected by an aluminium cover strip which clips snugly over the main aluminium support beam
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Brainiac |
Posted on 08/22/2007 12:38 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
There was a question earlier about buildup on the lamps. I can confirm that not only is there no buildup on the lamps, there is none on the reflectors or the mounting bracket either. Obviously the temperature here is too high for deposits..:@
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Brainiac |
Posted on 08/22/2007 12:43 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The lamp dimmer controls from 0 to 100% power (this is lamp test at dim - can't look at the lamps at full noise!)B)
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Brainiac |
Posted on 08/22/2007 12:45 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
The end of the reflector shield is about a half-inch from the back of the drum. This view also shows the offset of the lamps, which covers the position of the bean mass as the drum rotates CW.
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Brainiac |
Posted on 08/22/2007 12:46 AM
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1/4 Pounder Posts: 89 Joined: July 27, 2007 |
A view of the heater assembly mounted, with drum removed
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