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Can we talk ........ motors?
Beaner
HI folks, long time since I posted and I have a question about a motor.

I was browsing Grainger online catalog and came across a AC/DC speed control.

http://www.graing...Pid=search

It states: For Universal Brush Type AC/DC Motors, 115 Volts, 60 Hz, 20 to 100 Percent, Dial.

Just what exactly is a AC/DC motor or is it saying it will control either an AC or DC motor, which doesn't make sense to me.

I'm going to try my hand at a BM roaster build and will use a little different approach to it than the usual designs (I seem to like to do things the hard way).
I was thinking I wanted to slow down the speed of the BM motor but seems the only way of doing that to a AC motor with starter capacitor is to vary the AC frequency. Something I don't want to get into for now so I'll try using the default speed of the BM motor.

If I get my design actually built I'll post a few pics, they should be good for a few laughs.

And speaking of motors, I was wondering if I could get a few links to suppliers that some of you have used to get gear motors. I used to have those links but didn't keep them when I upgraded to Win7. :|
.
.
Off the motor topic for a sec. KK posted a pic of a drum and it's vanes in this HR thread:

http://forum.home...post_16440

The drum looks like it has an inner lining of some other metal. I'm wondering what the lining is and why it was used. Also wondering how the chaff is extracted from that drum.

Thanks for any feedback.
 
Beaner
I think I found one of the links by searching Yahoo surplus gear motors:

https://www.surpl...m/home.asp
 
Koffee Kosmo

Quote

Off the motor topic for a sec. KK posted a pic of a drum and it's vanes in this HR thread:
http://forum.home...post_16440

The drum looks like it has an inner lining of some other metal. I'm wondering what the lining is and why it was used. Also wondering how the chaff is extracted from that drum.


Yes Beaner & welcome back

With regards to the link - that photo is of a drum roaster

With regards to your BM project
I have developed a kit roaster that can be used with different heat sources
Heat gun or Turbo Oven

We use a 12 volt square drive motor in a base hub
The base hub is reversible so the end user can use any number of baking pans to roast coffee, nuts ect

All the info drawings & component parts photos is on the Koffee Kosmo Site
koffeekosmo.com.au

KK
Edited by Koffee Kosmo on 08/04/2010 1:04 AM
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Beaner
KK, I know of your roaster as I've been to your website and have read posts relating to it on various forums. It's a nice setup but I want to see how my BM design will work. It might flop or it might work but I wanna know. :)

And yeah, I know that linked pic is a drum roaster and is why I asked about the lining and chaf removal from it. I mean, how is chaf removed from a solid drum if there are no holes or slots drilled/cut in it.
 
Ringo
Most solid drums have an opening on the top of the front plate, the air is sucked through this opening bringing the chaff with it, if you change a gate the airflow is blocked and the green beans can drop into the drum. The bottom hole in the picture is for dumping the beans.
Ringo attached the following image:
home.jpg

Edited by Ringo on 08/04/2010 11:05 AM
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
Dan
An AC/DC motor is a motor that can operate on either AC or DC (using the appropriate voltage, of course). They always have brushes.

An AC/DC motor controller will control the above motor, and perhaps some DC motors, but never an AC motor.

I am not that familiar with Bread Machine conversions. But, for drum roasters, most people just chose a single speed motor since drum speed is not critical as long as it isn't too slow or too fast. For most home roasting applications, anything from 25rpm to 75rpm will work, with 50-60rpm being very common.

To get these slow speeds the motor needs to be geared down. The simple way is to just install a gearmotor. These are motors that have a gearbox attached directly to the motor shaft. They are compact and easy to install since they are direct drive to your drum and can support one end of your drum.

www.surpluscenter.com and www.grainger.com and the most common sources of gearmotors for hobbyists.
 
Beaner
I probably shouldn't have mixed in the drum question with the motor question. It might imply I was thinking of using the BM motor with a drum roaster.

I am strictly working on the BM design right now and will be using the BM motor. As I said before, I would prefer to slow the rpm down but I'm sure it will be ok.
I won't start building the drum roaster until I'm satisfied with a BM setup.
.
.
Ringo, I've seen the exhaust pipe connected to the front faceplate on carious drum roasters but wasn't sure if it was also used for chaf extraction.
.
.
Dan, thanks for shedding some light on the AC/DC motor. I know the type of motors that are being used for home built drum roasters due to all of the great info provided on HR forums. I could swear there were a couple other motor sources mentioned in past threads but can't remember them. I've looked at Grainger's motors but they are pricey and limited in the low rpm gear motor selections.

Btw, what are some thoughts on possibly using this next DC motor for a drum roaster....

I have a little electric scooter that my sister had bought for my nephews when they were young and she said I could have it since it's not used anymore. It uses two 12V DC batteries for total of 24V. Here is a link to the scooter:

http://www.extrem...cooter.htm

My thinking is that it only needs 24V for the max speed so why not hook up a 12V DC supply to it along with a potentiometer to adjust it to the speed I want. Seems I saw someone else mention using one of these motors on the CS forums.

Any reason come to mind that this wouldn't be feasable?
 
Koffee Kosmo

Quote

I am strictly working on the BM design right now and will be using the BM motor. As I said before, I would prefer to slow the rpm down but I'm sure it will be ok.
I won't start building the drum roaster until I'm satisfied with a BM setup.


I had this dilemma and found that mixing the beans instead of pushing is more important

See video of agitator test
http://www.youtub..._ewkisDF5o
KK

I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
Dan
I use Grainger AC reversible parallel gearmotors for work. The are flexible and have options that make them very attractive for a lot of applications. They are more expensive and powerful than a one or two pound drum roaster needs. For those, I use a lightweight shaded pole gearmotor such as the one below, about $60 new.

http://www.graing...Pid=search


 
Beaner
Found this 12V DC motor and it looks interesting but I am somewhat at a loss when it comes to torque specs. Based on the example applications it gives I don't know if it is viable as a small drum roaster motor.

http://www.robots...motor.html

Quoted spec: Rated torque: 254.8mN.m

Can one of you brainiacs explain in laymans terms how this can be related to how much mass or weight it can drive? Same goes with inch pounds and foot pounds.

Hypothetical example:

Say you have a 7in x 7in stainless steel drum and has 1lb beans in it, and it will be direct drive, i.e. no pulley, chain, etc. How much in.-lbs, ft.-lbs, is needed to drive that load?

If this has been covered in another thread somewhere I'd be happy to view that link.

Edit: Just did a forum search on "torque" and found one of the links I used to have from HR.

http://www.herbac...e_Code=HAR
Edited by Beaner on 08/04/2010 9:40 PM
 
Dan
I've posted this simple torque equation before, I should probably post it on the downloads page:

This equation calculates torque needed to turn a horizontal coffee roasting drum and includes a safety margin, too.

T = torque in in/lb
D = Drum diameter in inches
P = largest batch size in pounds

T = D/2 * P

For your drum that is:

T = 7/2*1 or 3.5 in/lbs = 395 mN-m

Considering that your motor is close, and there is a big safety factor in this estimate, and if that motor has a decent service factor, then it might work if it is well ventilated and given some time to cool off between roasts.

Technically, torque is pound force-inch or lbf-in, but Americans switch this around a lot.
 
Beaner
Thanks Dan, that's what I was looking for. But I must be missing something here on the conversion from in-lb to N-m.

Based on this chart I found:

UNITS of TORQUE SI English

1 N?m = 0.738 ft?lb 1 in?lb = 0.113 N?m
1 N?m = 0.113 in?lb 1 in?lb = 0.113 N?m
1 N?m = 141.61 in?oz 1 in?oz = 7.062E-03 N?m

Wouldn't our example be:

T = 7/2*1 or 3.5 in/lbs = .395 mN-m (3.5 x .113)

I'm usually wrong on this this stuff so what am I missing?
 
Dan
The little 'm' (em) means milli, or 1/1000.

.395 N-m = 395 mN-m ;)
 
Beaner
Ahh, see. I told ya I was missing something. I was wondering what that little m meant on the spec from the motor I linked.

Thanks.

Just hooked up that scooter motor to my ATX PS and at 12V it seemed like it was spinning at about 120 rpm. Not the motor itself but the cog wheel on the the axle.
The batteries are dead I think and is why I used the ATX PS. Gotta try and wire up the throttle control and test some volts/rpm just for grins. Just messing around with that scooter motor, when the time comes to build my "official" drum roaster I'll be using an appropriate motor.
 
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