Posted Tue Feb 5, 2013, 3:51pm Subject: New drive for CO roaster
So, I have finished reworking the drive mechanism for my roaster. Formerly driven by a bread machine drive, it spun at about 250 rpm which was doing a little more than "stirring" the beans. After giving the issue some thought and looking at prices of windshield wiper and power window motors, I decided to try modding a power screwdriver. The local big box had a 6V unit powered by AA batteries, so it was simple to convert it to run off of an adapter. It remains to be seen how the screwdriver holds up to 15-20 min drive sessions, but at less than $9 new, I'm not worried.
Posted Tue Feb 5, 2013, 5:54pm Subject: Re: New drive for CO roaster
Window motors as well as power screwdrivers are generally not considered constant-duty motors. It is why I recommend the windshield wiper motors considering that you can walk into a pick-n-pull yard and get them fairly cheap. it will be interesting to see how long the B+D driver lasts.
Snaxx Senior Member Joined: 11 Dec 2008 Posts: 174 Location: Northeast Michigan, LP Expertise: I love coffee
Grinder: Capresso Infinity burr Drip: Technivorm Moccamaster Roaster: I Roast2
Posted Tue Feb 5, 2013, 7:12pm Subject: Re: New drive for CO roaster
I wouldn't think those B-D power drivers are designed to run for more than a minute before needing a rest. If and when it finally destroys itself, you might want to consider looking at the selection of gearmotors from Burdens Surplus. Many of the cheaper motors are listed as intermittent duty, but intermittent duty cycle in most of these would certainly be more that the duty cycle of an AA battery powered driver. Some are even 120 volt, so you wouldn't meed an adapter.
Posted Tue Feb 5, 2013, 9:00pm Subject: Re: New drive for CO roaster
Yeah, I agree that its more of an experiment in misuse and abuse than a long term solution. I am running it at 5V even though it is a 6V (4XAA) driver. Being a DC motor, that might cause it to run a little cooler, i.e last longer. The stir mechanism puts almost no load on it, especially considering it's intended use. It has now survived 2 roasts, and I will probably be roasting at least twice a week, so we'll have to see how long it will go! Hopefully it will give me enough time to locate a windshield wiper motor on the cheap. I had also considered using a variable speed power drill, but 1) it also is not designed for constant use, although it could do much better than the screwdriver with better brushes and cooling. 2) It is more difficult to mount and getting it turning at 60 rpm is difficult as it is at the bottom end of the RPM range.
Windshield wiper motors are probably the best fit: designed to run for hours at a time, and at different voltages, and the RPM range is right too.
I'll have to check out Burdens, thanks for the tip!
farmroast Senior Member Joined: 13 Jul 2006 Posts: 1,449 Location: Amherst MA. Expertise: Professional
Espresso: Strega,Cremina, MCAL... Grinder: Majors, Dienes Vac Pot: Hellem10 Drip: CCD, and more Roaster: 1kg. DreamRoast
Posted Wed Feb 6, 2013, 7:45am Subject: Re: New drive for CO roaster
I like the variable speed control gearhead motors by Oriental Motors. They are expensive retail/new but sets can be very commonly found like new or new old stock on ebay for cheap (approx. $35.- $100. set). They offer different wattage sizes and different gearhead ratios. I have some extras but just moved and they are still buried in my storage unit.
Posted Thu Feb 7, 2013, 8:17pm Subject: Re: New drive for CO roaster
Thanks for all the advice (and good humor)! I just ordered a couple of Brevel 95 RPM 36 VDC gearmotors from Surplus Center (Burdens) Their customer service says that the motors will run on 6-36 VDC, so just about any spare adapter I have laying around that has a decent current rating should suffice. The 5/16" gear shaft will be easy to adapt to mate with my pan drive, which is a 5/16" SS Allen bolt that takes a 1/4 allen hex. Now I need to look up some schematics for PWMs.... although 95 RPM might be about perfect. I'm guessing that 12-15 VDC should spin it a bit slower.
Ed, since you weighed in here, I wanted to ask you about your chaff collector - I cut a 1/8"X 3/4" "S" slot for chaff collection, but haven't seen a mass exodus of chaff through the slot. Perhaps the Dreamroast's higher spin rates are what help push the chaff out? I get about 1/4 of the chaff out of the pan, and rest stays in. It really isn't a big issue as my cooler deals with the rest. With my shallower depth (3 in), the higher spin rate of the breadmachine was bouncing beans so violently that they were getting stuck up in the GG heat shield.
I started with a thin super cheapo ss stock pot from Dollar General and cut it down to the right height for the bean whirling action, then fashioned a new lip for the GG to sit on. I assumed the bottom of the pot needed to be square to control the bean action. Never tried anything curved or slanted.
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