Malt mill motor minimum torque

[Dodes]

Hi,
I know that this topic has been started numerous times. I've read plenty of them till now, but still doesn't have definitive answer.

I've malt mill (2 rollers) which I want to motorize and I'm searching for the right motor + gears. From this post [1] it looks like the computed minimum torque using this site [2] is 6.7 Nm (60 in-lb). This is "in match" with [3], where minimum is defined as 7.5 NM (66 in-lb).
But I was trying with my corded drill, which has torque of 7 Nm (62 in-lb), with Special B malt and with mill full before starting, it didn't even start the mill. With the empty mill, it has stuck.
Then I tried the cordless drill with the soft torque (definition at [4]) 11 Nm (97 in-lb) and it has behaved the same as corded drill.
With pale ale malt the corded drill wouldn't start with the full mill. The cordless would start even with the mill full, but it was so-so.

From this it looks like the minimum torque is a lot bigger than shown in the links I posted.

I'm thinking of buying the 0.55 kW, 1380 rpm AC motor with gear box/transmission (don't know the right word) with ratio 10:1, so the resulting RPM would be 138 with torque of 38 Nm (336 in-lb). But I want to be sure it is sufficient to even mill a harder malt and not to stuck.

Does anyone have a reliable source where the minimum torque is defined for the malt mill? Or is there a method to measuring the torque needed for my mill without using expensive tools?

Thank You very much

[1] - https://www.homebrewtalk.com/showpost.php?p=1339882&postcount=2
[2] - https://planetcalc.com/1908/
[3] - https://homebrew.stackexchange.com/...orque-is-required-to-operate-a-barley-crusher
[4] - https://www.bosch-professional.com/gb/en/community/category/soft-hard-torque/3977186-t

 

[Minky]

I use a Bodine gearmotor (42R4BFSI-5L) on my two-roller PhilMill II, and it works fine. The label specs indicate it is 1/8 HP with a 20:1 gear ratio, and puts out 54 in-lb at 85 RPM. The mill has never shown the slightest hesitation when started full.

I was initially hesitant to buy it, worried that 54 in-lb may not be enough, so I loaded my mill and, using an in-lb torque wrench, slowly applied pressure until the mill just started to turn. As I recall, I measured ~45 in-lb.

I still wasn't totally comfortable with a 9 in-lb cushion, but the price ($60) was so good, I pulled the trigger. So far, I'm happy.

 

[beergolf]

This is not the cheapest solution, but it is a great set up. Easy to configure and super powerful. I think it would grind rocks if i put them in the hopper. It is a Monster Mill MM2 Pro with the 2" rollers. I use the 180 rpm set up.

I load up the hopper and flip the swithch. There is not even the slightest bit of hesitation. Starts up just like it was an empty hopper.

https://www.allamericanaleworks.com/shop/grain-mill-motor-shaft-couplers-package/

Here is a pic of my set up.

 

[Dodes]

Hi,
thank you for reply for both of you.

Judging from both of your replies, it looks like the mine configuration should be more than OK.

beergolf, could you provide us a information about your motor and gear setup (HP, RPM, gear ratio, torque), please? Because there is no info on the link you posted.

Thank You

 

[Morrey]

Beergolf was helpful sending info when I built my grain mill with a MM3 mill and All American Ale Works 180 rpm motor. If I remember correctly this reduction steps down the rpm 10:1 which inversely steps up the torque proportionally. Like Beergolf says, this mill will grind rocks.

I had previously used a 10 amp corded DeWalt drill, and as you know by now, you need ample torque to power thru a grind with your rollers set up for a fine grist with a close gap.

 

[beergolf]

beergolf, could you provide us a information about your motor and gear setup (HP, RPM, gear ratio, torque), please? Because there is no info on the link you posted.

I think all that info is somewhere on the site. If it is not just email them. They were very responsive to any questions I had and replied quickly.

I do know that I have the 180 RPM version . it does have a 10:1 gear reducer to get to that speed. I would not worry too much about torque, there is way more than you need. Like I mentioned in my previous post, I can start it with a full hopper and it does not even think about hesitating. It just plows through the grain,even harder grains like rye and wheat.

Like I said. Not the cheapest, but definitely one of the best. I cheaped out on a previous set up that never was totally happy with. So it is cheaper in the long run to do it right the first time.

 

[Dodes]

I just look to the page once more and there is a manual which has the specifications needed.

So ti looks like it is 0.37 kW motor, with 1800 RPMs with gear ratio 10 or 7.5. With 10:1 ratio (180 RPM) it will have 19.6 NM (174 in-lb) torque.

So I think I too could go with 0.37 kW motor.

Thanks for the info once more

 

[Morrey]

Personally, I think the 180 rpm option is way fast enough for the average home brewer milling reasonable amounts of grains per batch. For a commercial operation, they likely need more speed to get the job done. The flip side of that gain is the reduction of torque, so 180 rpm is a very good choice for the average home user.

 

[IslandLizard]

Personally, I think the 180 rpm option is way fast enough for the average home brewer milling reasonable amounts of grains per batch. For a commercial operation, they likely need more speed to get the job done. The flip side of that gain is the reduction of torque, so 180 rpm is a very good choice for the average home user.

Exactly!
Somewhere in the past I've read to keep roller face speed under 15" per second for grain crushing. For a 1.5" roller mill that equates to 15 / (1.5 * 3.14) = 3.18 revolutions per second, or 3.18 * 60 = 191 rpm.

I think I keep my variable speed drill to around 130-150 rpm, but the gap is 0.032-0.034". Milling with narrower gaps benefit from lower speeds (but need more torque).