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Home Brew Forums > Home Brewing Beer > Equipment/Sanitation > Motor size (HP) for grain mill?
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Old 02-13-2012, 01:36 AM   #1
atomicjoe23
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Default Motor size (HP) for grain mill?

What size motor would you guys recommend for motorizing a grain mill?

I plan on a 110V TEFC motor, but I was unsure on HP rating. . .I know more is better, but I didn't want to go overboard.

I plan on milling 50 lb. bags of grain at a time. . .the rollers are gonna be 1.5"-2" solid stainless steel 10.5" long (10.5" is the actual length of the portion doing the milling. . .the OAL of the roller will be longer due to the support shaft on one side and the drive shaft on the input side) and I plan on driving both rollers through a set of gears.

Thanks!

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Old 02-13-2012, 12:17 PM   #2
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At least 60+ in-Lb torque at whatever your speed, but 175 RPM is a sweet spot.

Mine is a 1725 RPM 1/3 HP that gives me 100 in-Lb torque at 172 RPM with aid of a 10:1 ratio gearbox (reducer). This is an easy motor to find on ebay.

So, I'd not go any less than 1/4 HP, to directly answer your question.

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Old 02-16-2012, 01:07 AM   #3
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Would 3/4 HP be overkill?

I'm planning on milling grain a 50 lb. bag at a time.

Thanks. . .also I saw that the MaltMill was set to run at 400 RPM when motorized (3.3 seconds for 1 lb. of grain); is the 175 better? Any other suggestions?

I.e. are smooth rollers more desirable than knurled rollers? Spacing between rollers (I saw the Malt Mill was set for 0.045" between the rollers)?

Thanks!

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Old 02-16-2012, 01:31 AM   #4
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It only draws the torque it needs.

Knurled rollers are needed on smaller diameter bars to grab the grains. A large diameter smooth roller is more ideal.

I'd have to look on the gap. I think that is pretty standard as shipped on mills. Most tighten it up from there.

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Old 02-16-2012, 03:36 AM   #5
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I was planning on 1.5" rollers 10.5" long out of SS. . .I was going to try smooth rollers initially just because knurling is one extra step in the machining process that if unecessary I would prefer not to do, plus it's quite a bit of effort to get all the little metal shavings out of the knurls after machining to make sure there are none left to make there way into the crushed grain.

I was planning on both rollers being driven rollers (1.25:1 gear ratio between the gears) as well instead of a driven roller and an idler roller.

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Old 02-16-2012, 03:50 AM   #6
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Considering the issues many report with 1.5" diameter knurled rollers, I suspect 1.5" diameter rollers are too thin to go smooth. The only attempts at smooth rollers I've seen in the forums were much bigger - like 4" diameter or larger.

Curious about that gearing between the rollers. Are you saying one roller will spin faster than the other?

Cheers!

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Old 02-16-2012, 04:32 AM   #7
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I second that 1.5 is likely too small for smooth.

I prefer the idle roller over 2 driven. If a rock or similar is in the grain then it has a lot better chance of not being forced through. With 3/4 you might do some damage.

Yuri-rage built a mill. Have you found his thread? Might help you avoid some of his pitfalls. One was too small of motor for his rollers if I remember. You should be covered there.

Bits of ss in the grist shouldn't be a problem. Just clean off any machining oil.

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Old 02-17-2012, 04:13 AM   #8
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Thanks for the tips guys. . .I don't spend much time on this forum so I haven't seen Yuri-Rage's mill thread, but I will look for it tonight, thanks for pointing me in that direction.

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Old 02-17-2012, 04:21 AM   #9
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Is this the thread you are referring to?

http://www.homebrewtalk.com/f51/diy-...i-mill-210443/

I also found a thread on roller diameter effect, but I haven't read it yet. . .will be reading it tonight.

Thanks again!

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Old 02-17-2012, 05:15 AM   #10
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OK. . .I should have checked that thread first, that was not the grain mill thread, that was an actual CNC mill. . .

. . .but I think I found it this time; I'm starting it now. . .

http://www.homebrewtalk.com/f11/diy-grain-mill-12858/

The roller diameter issue makes sense to me; I will have to modify my CTC mounting distance and size of gears, but that's no big deal since I haven't actually started making any parts yet (guess it's a good thing I was busy today because I intended to start making parts if I had time).

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