Author Topic: Torque  (Read 969 times)

Online morticaixavier

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Torque
« on: June 06, 2013, 12:20:07 PM »
So my 1 year old blade style coffee grinder broke the other day. The plastic bit that held the blade on to the drive shaft broke so the blade just fell right off. We got a nicer burr style grinder which is lovely and was on clearance so it was not too expensive.

But anyway the question around the house is 'what do we do with this perfectly good electric motor?'

I just started wondering if I could motorize my mill with it.

obviously it goes very fast, far more RPM than I actually need so I can gear it down with a larger pully on the grinder but will I have enough torque to actually grind grain?

Any engineers out there want to help a guy out? is torque a readily available piece of info available with the model number of the grinder or would I have to know the motor info itself?

Can I do the math to determine it from the voltage/wattage rating of the motor?

Does the ratio used to gear it down change the torque at all?

school me.
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Offline Slowbrew

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Re: Torque
« Reply #1 on: June 06, 2013, 12:27:38 PM »
I am definitely not an expert on gear drives but I can't imagine a realistic way to make the motor from my old blade grinder run a mill.  This is without any idea what your blade grinder actually looked like though, of course.   ;D

My old blade grinder was tiny.  The motor would fit in my hand and the drive shaft is about 2mm thick (tops).

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Offline redbeerman

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Re: Torque
« Reply #2 on: June 06, 2013, 12:35:28 PM »
The motor will be too small, even if attached to a gear drive to turn your mill.  If you have gear reduction the torque does increase, but it will take some b*lls to turn your mill with grain in it.  Don't know how many amps that little motor is, but I'm guess it's probably .01 or less, which at 120VAC is less than 1.2 watts or .0016 HP.  Even if you increase it 30 times through a gear drive, it ain't much.  Something like an old sewing machine motor would probably work.  I have a little motor I use to turn a valve on a piece of equipment that is a little over 2 watts and you can stop it with a pair of pliers.
« Last Edit: June 06, 2013, 12:41:21 PM by redbeerman »
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Offline AmandaK

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Re: Torque
« Reply #3 on: June 06, 2013, 12:40:42 PM »
The motor will be too small, even if attached to a gear drive to turn your mill.  If you have gear reduction the torque does increase, but it will take some b*lls to turn your mill with grain in it.  Don't know how many amps that little motor is, but I'm guess it's probably .1 or less, which at 120VAC is less than 12 watts or .016 HP.  Even if you increase it 30 times through a gear drive, it ain't much.  Something like an old sewing machine motor would probably work.

This is what I'm thinking as well. Do you have any specs on the motor or broken coffee grinder?
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Offline bunderbunder

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Re: Torque
« Reply #4 on: June 06, 2013, 01:07:41 PM »
Ours (cheap Krups model) is 200W.

Online morticaixavier

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Re: Torque
« Reply #5 on: June 06, 2013, 01:21:55 PM »
The motor will be too small, even if attached to a gear drive to turn your mill.  If you have gear reduction the torque does increase, but it will take some b*lls to turn your mill with grain in it.  Don't know how many amps that little motor is, but I'm guess it's probably .1 or less, which at 120VAC is less than 12 watts or .016 HP.  Even if you increase it 30 times through a gear drive, it ain't much.  Something like an old sewing machine motor would probably work.

This is what I'm thinking as well. Do you have any specs on the motor or broken coffee grinder?

Not yet. It's at home. I'll take a look and see what, if anything I can learn from the little sticker on the bottom.
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Offline klickitat jim

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Re: Torque
« Reply #6 on: June 06, 2013, 06:10:32 PM »
I'd be thinking pump not grinder

Offline hopfenundmalz

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Re: Torque
« Reply #7 on: June 06, 2013, 06:46:50 PM »
For motors you need to know the operating speed and the power. 200W is just over 1/4 HP, for example. A 1/2 HP corded drill will turn my mill, but sometimes has to be given a lot on the trigger to start milling, so starting torque/current is a consideration. Another consideration is the duty cycle the motor is designed for. You might burn out the coffee grinder motor working up a large batch of grain, while a 1/2 horse drill motor will keep going.

Search the nets and see what has been used.
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Offline yso191

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Re: Torque
« Reply #8 on: June 06, 2013, 11:09:41 PM »
After doing research I spent ~$100 on the motor to get this setup:


At 1/3 hp it runs at 1725 RPM, so I have a 14" sheave on it which makes the mill run at about 200 RPM, which is what my research says is in the range of what one wants.

I got mine new though these are very common motors which one can often get used.  I have heard of people scavenging them out of washing machines.  All that to say I seriously doubt that a coffee grinder will cut it.
Steve

Offline Slowbrew

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Re: Torque
« Reply #9 on: June 07, 2013, 04:21:00 AM »
Used motors are like rabbits.  I went 30 years without an old motor lying around.  One year I got one from my mother-in-law, which I used to motorize my mill.  By the end of the next year I had 3 sitting downstairs.  The first one must have been pregnant when I got it.   ;D

Actually, word got around that I was looking for 1/2hp, 1725rpm motor and people would drop them off at the house.  Then we cleaned out my Mom's house and found a couple more on shelves in the basement (Dad and Grandpa were both small time hoarders).  You might be amazed at how many are out there collecting dust.

Good luck with you project.

Paul
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