Motor size for a monster mill?

I'm thinking of purchasing the MM3 1.5" roller, any opinions on that mill would be great. I'm looking at a geared motor that is rated at 40 inch pounds of torque and 178RPM, is that enough power? Thanks for any info.

Monster mills are pretty hefty. 40lbs might be on the low end. If you already have the motor give it a go, but if you are looking at purchasing I would definitely go with a higher torque. Especially if you plan on adding any pulleys to drive it or brew with wheat and rye.

40 is probably not good enough. Especially for the 3 roller.

I got a 1725 1/3 HP motor and a 10:1 gear reducer. That gives me 100 in-lb torque which is plenty. My 3/8" drill was itself almost not good enough and started smoking towards the end of the grain bill. The last thing I want to do is go thru spending and mounting to end up with not quite enough power.

Fred said questionable on the 40 in-lb. I asked. He thinks at least 50 and up.

I love my MM3 so far.

I looked around for a gear reduced motor for a while that could be mounted vertically so I could mount it in the same orientation/footprint as the mill + hopper (behind it). I couldn't find one (used, surplus). I even looked into buying a special bracket from (say) Boston gear to mount a surplus gearbox from them and it was itself like $70. So I found the sweetest gearbox by chance. I'm very happy with it. The Groschopp RA40.

http://www.groschopp.com/Products/G...htAngleRAGearboxesNEMA/tabid/269/Default.aspx

and also sold on ebay under the username: iowabarns

It was $99 + like $15 for the shaft (which is removable). The thing is aluminum and is like 5 lbs. There are mounting holes in every direction. I just mounted it upright and it's working great.

That way I was able to find a 1/3 HP GE motor for $40 on ebay. So, plus the Lovejoy coupler ($15) the whole thing was like $150ish. Gear reducing motors are going for about that much used themselves.

It worked out much better for me this way.

FYI- Fred recommends 175 RPM more so than say 233 (which is what I asked cause I had the option of getting a 7.5:1 gearbox).

Thanks for the info, I'll look into what you did. I don't have a motor yet, so this is good info.

Yeah- best price on a gearbox I'm seeing on ebay is like $60-$90 and that doesn't usually include vertical mounting like I said. If you didnt' want to do this you could find one for ~$60 or so used. My design's most important concern was being low profile. If you were making your own mounting table, you may not care to mount vertically and some other way is fine.

The weight concern was also an issue for me so I'm glad the gearbox is like 5 lb. The motor on the other hand is very heavy.

You could do with a 1/4 HP 1725 rpm, but 1/6 or less is pushing too little power.

Do u have any pictures of your setup?

Here's a quick and dirty for ya.

I plan on posting my own thread when I mount it into my table. You can see the slide out drawer track already on the wood.

This whole thing is quite heavy already. I'd hate to have a 25 lb gearbox on there rather than the 5 lb Groschopp.

And, the motor just "BARELY" fits behind the hopper. If I were Fred I would have made the shafts just another 1/2" longer than they are. But is works well, no issues.

I'll repost here with a link to my thread when I make it so you don't miss it.

To me, even though this is more money, it sure beats a pulley system. I'm OCD about low profile design though (apartment brewer).

I have a 1/2 HP cap start...I'm scared of it, I think if a finger got fed into it it wouldn't cease up until around the elbow . A little more power is better than a little less so you don't have to worry about it stalling if you start it with the hopper fully loaded. That gearbox is nice though. I made a cube that contains the the motor, pulley system, hopper, and MM3 in as a compact area as I could muster.

Any pictures of your grain mill?

flyguy340 said:

Any pictures of your grain mill?

Click to expand...

If that is to me I will see what I can do for pics in a few weeks when I get back from Alaska.

Bensiff said:

I have a 1/2 HP cap start...I'm scared of it, I think if a finger got fed into it it wouldn't cease up until around the elbow . A little more power is better than a little less so you don't have to worry about it stalling if you start it with the hopper fully loaded. That gearbox is nice though. I made a cube that contains the the motor, pulley system, hopper, and MM3 in as a compact area as I could muster.

Click to expand...

I'm pretty sure you wouldn't want to get your arm caught in my 1/3 HP either. I can't slow it down at all by squeezing the lovejoy coupler with my fingers. For geeks sake, your 1/2 HP motor would yield 151 in-lb torque in my setup.

Here's a helpful link from Groschopp for those calculations:

http://www.groschopp.com/Portals/0/Marketing/NEMA 60 hz Data Specs.pdf

SankePankey said:

I'm pretty sure you wouldn't want to get your arm caught in my 1/3 HP either. I can't slow it down at all by squeezing the lovejoy coupler with my fingers. For geeks sake, your 1/2 HP motor would yield 151 in-lb torque in my setup.

Here's a helpful link from Groschopp for those calculations:

http://www.groschopp.com/Portals/0/Marketing/NEMA 60 hz Data Specs.pdf

Click to expand...

Wow, you simultaneously appeased my inner geek and laziness...awesome thanks.

Sorry to resurrect and ancient thread, but I'm new to this concept and SankePankey seems to have gotten the exact result I'm after (I'm also an apartment brewer with limited space).

My mill is the MM3 1.5": http://www.monsterbrewinghardware.com/mm-3.html. The motor I'm about to get (I don't have the manufacturer/model number yet) is 1/2 inch keyed shaft, 1/4 horsepower 1725 RPM.

From what I'm reading here and on other threads, I should get a 10:1 gearbox. This http://www.groschopp.com/stp-online/ handy tool says I get 9.134 lbs of torque with just the motor, so the gearbox would bring this to 91.34 lbs, correct?

I think this is what I want: http://www.groschopp.com/data/Cad_Pdf/RP7300_2S.pdf and a LoveJoy coupler. The MM3 is a 3/8" keyed shaft, so I think this is the right one: http://cgi.ebay.com/CNC-Stepper-Motor-Lovejoy-Coupling-3-8-X-1-2-spider-/290424941328?pt=LH_DefaultDomain_0&hash=item439eaceb10

Does this look correct? Thanks in advance!

For the lovejoy coupler, it's just a matter of if it comes in sizes that you can use for the shafts you have. Otherwise there is no matter. I do remember getting the elastomer inside open jaw coupler (second strength) because it was rated for more torque (like the 100 in-lb I have). Oh, and my grosshopp has a 3/4" shaft, not 1/2".

A 10 to 1 gives you a redux of 10 to 1 in speed. Not sure if it's also necessarily 1 to 10 in torque increase. My 1/3 HP 1725 RPM motor gives me 100 in-lb. Might be more like 75 in lb for you which is still great. I don't know the math on that.

I was told by another forum member who wanted to do this that Grosshopp told him they weren't making the NEMA mount gearboxes anymore. You might want to call them to see if they're right for the motor you want. There isn't anything special about the Grosshopp compares to any other gear box except that it was mountable in a vertical position from the factory, so I could have the motor pointing up in the same orientation the hopper was. Most of them are mountable in a vertical position, but you usually have to buy a separate mounting bracket. Before I found the Grosshopp for $100, I was looking at a used Boston gear box and was gonna buy the bracket from them direct. It would have all been more than $100 and used for that matter. Also the Grosshopp is aluminum so was like 5 lb, which matters for my sliding shelf.

Also, if you are planning to do as I did with the vertical mounting, just really check your measurements. As you can see with mine, there is just about 1/4" in between the motor and the hopper. I did my measuring and in the end it was a little bit of a leap of faith that it would fit and work (as is most of my brew rig!). Since some of the parts are now changing from what I did, you might want to take out the graph paper, or what not, to make sure that you are doing the right thing. On mine, if the shaft were a 1/4" shorter or anything, it would have been a no go.

OK cool, thanks. So I've got the coupler nailed down but am still working on the gear reducer...Thanks for the input.

How about one of these for a gearbox? http://ondrives.us/gearboxes.htm

I went with the L090 love-joy couplers, got them at a reasonable price at amazon. I ordered a Groschopp reducer a few months ago, the guy on the phone said the stopped making them but had some leftovers they could sell. Give them a call, they may still have one left.

I'm running my MM3-2 with a 1/2HP, 1725rpm at 10:1 reduction. With this reduction on this motor it's darned near impossible to stop the rollers. A note on the couplers, if you can get slot the grain mill shaft that would be ideal (and get matching coupler). My coupler on the mill is secured by screw and the torque is deforming the shaft.

Here's a pic, the motor is an ebay special. It was intended for a industrial garage door, reversible too. Not that you can really do much with a reverse on a 3 roll mill when it jams up. I recommend replacing some of the factory screws with knob-screws so you can quickly take it apart on brew day w/o tools. Key for me are the roller spacing-adjustment screws and the bottom frame securing bolts. The monster mills like to be perfectly square and if they're a little off they can jam up.

(and i put a piece of silicon tubing between the hopper and the hopper extension. It keeps the noise down)

Great job Oustide. I like that mounting. I have virtually the same motor. Mine is a reversible 1/3 hp GE from the bay for $40. I thought about wiring it in so that I could reverse it, but didn't see the point.

Yes. My shaft got deformed a bit as well. Monster (Fred) says the shafts aren't really made for a lock screw (or whatever they're called). They are more for a drill chuck. You just have to take a metal file and widen one of the flats on the shaft to about twice it's width so that the lock-screw doesn't jump it and chew into the shaft. No big deal.

Also, the 'gotta be square' thing is so very right.

I've worked out most of the kinks on mine and I still think there is a little roughness in one of the shafts. The bottom roller makes a little noise when spun by hand. It spins well, but has a sound. If I don't fill the hopper more than 1/5 of the way, there isn't enough weight to prevent binding. If I fill it more, there is enough to keep the grind going till the end every time. I couldn't re-assemble it any squarer if I tried. Fill the hopper fuller- easy fix. Wish I knew why though.

Good idea on the thumb screws. I am hoping that when it never binds again, I don't have to open it up at all.

Thanks for the tip on the shaft deformation / filing. I'll definitely do that, the first time i used the setup the deformation was severe enough that i could not remove the lovejoy coupler and therefore could not fully take apart the mill. I had to whack it a few (many) times and that bent the shaft. Doh! Took me a couple of hours to straighten it out just so.

I forgot to mention that i put some PTFE/teflon washers on the rollers. Amazon is selling sheets of .015" x 6" x 12" for $7 or so. It's very easy to cut with scissors to any size. The two inch washers i made are keeping grain out of roller/frame gap, it's keeping some of the dust out of the bushings, and eliminates the roller/frame contact making it smoother and quieter (and making it last longer?) I tried a few standard/commercial washers from ebay but the .032 and .045 washers were too thick causing problems.

But it works: cantilevered it across the bottom of a shelf and the edge of a kitchen table to save space. Thanks so much for the pointers!

Hopefully the pic does it justice, this was a really complicated project for me.