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Brews & Views Bulletin Board Service * Brews and Views Archive 2004 * January 9, 2004 * Torque & gear motors for motorizing mill < Previous Next >

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Cabonation problems.Jon Meeker12-19-03  01:51 am
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Bob McCouch (68.32.206.76)
Posted on Wednesday, December 17, 2003 - 01:35 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Hey all,
I have an Automatic/St. Pats mill. I've been using a drill to run it, but I yearn for a more permanent solution.

I've decided that messing with sheaves and high-RPM motors and aligning belts probably isn't my best option, so I'd like to use a gear motor. My problem is that I'm having trouble figuring out how much torque I need.

I know that using a pair of sheaves to gear down a motor to a mill multiplies the torque, and I remember from a past life as a car nut that horsepower, torque, and RPM are all inseparably linked. Does the HP rating of the motor matter, or is tq the only important number? I don't know how much of either is enough...

Does anyone here use a gear motor, and if so, how much torque does it have? I don't even have a "feel" for lb-in of torque, I'm used to lb-ft from the car stuff.

Here's a few of the motors I'm looking at. NAYYY with any of these sites, and if anyone else knows of other good surplus suppliers, I'm all ears:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_Code=TM93MTR2471&Category_Code=MTR

http://www.sciplus.com/category.cfm?subsection=18&category=169

http://www.surpluscenter.com/item.asp?UID=2003121619051643&item=5-1141&catname=electric (I'm thinking of the "Beefy Bodine motor")

The last one is about the speed I want and looks like it would work nicely, but is 34 in-lb enough to run a mill with 6" rollers? The middle one has much more tq (too much?), but it doesn't come with the caps so that's more I'd need to find before it's useful to me.

Any help on this topic would be greatly appreciated. I've already seen the pages by Mike Dixon and another gentleman about motorizing mills, but those are using high RPM AC motors and gearing them down with belts. Not very applicable to what I'm trying to determine.

Thanks!
 

Rob Beck (65.64.101.200)
Posted on Wednesday, December 17, 2003 - 01:57 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Bob, I use a Dayton gearmotor that is 1/15th horsepower and is 61 in./lb. of torque and I have not had any problems in terms of power or torque.
E-bay might be another place to look. Something else to consider is the diameter of the shafts on the gearmotor and the mill. I ended up using a spider type coupling because my shafts were different diameters. You might also want to consider some sort of break-away between the shafts in case you get a rock in your grain because sometimes that can ruin your rollers.
Rob
Kansas City
 

danno (63.224.226.20)
Posted on Wednesday, December 17, 2003 - 11:27 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Rob, does your motor start up with grain in the hopper? That's the defining torque for me.

Bob, go to http://www.oregonbrewcrew.com and look for the gadgets page for my gear motor run Automatic mill. Mine is under powered as it explains on the web page.

The first two are intermittent duty motors so be carefull there. 34 in-lbs is on the light side of what I consider necessary but then with that speed, you might be ok. I have not determined the minimum amount of torque needed but I know that 20 in-lb is too little.
 

Rob Beck (65.64.101.200)
Posted on Thursday, December 18, 2003 - 12:39 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

danno, Yes it will start with the hopper full of grain (even wheat malt)

Bob, Another thought; maybe you could call the manufacturer of the mill directly and ask them about torque requirements. I'm using a Schmidling 2 roller mill with both rollers driven and I don't really know how it compares to the Automatic.
Rob
 

Ken Anderson (24.55.255.75)
Posted on Thursday, December 18, 2003 - 03:45 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

You might be able to hang a small pail off the handle, and then see how much water you need to add before she breaks loose and sends the grain through the crusher. Of course, you'll only see a quarter turn, but it's enough to let you know the starting torque requirement. Multiply the weight of the water (plus pail) times the length of the handle.
Ken
 

Bob McCouch (199.21.28.225)
Posted on Thursday, December 18, 2003 - 03:06 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ken- I was thinking about some experiment like that, but I was thinking I'd need to get a torque wrench to test it, which would be more expensive than just trying a couple motors... Remind me of what lenth I'm interested in on the handle. Is it the distance than the handle travels during its movement (ie, 1/4 * Circumference of handle swing, assuming 1/4 turn movement), or is it the length of the handle arm from the pivot point on the mill's axle to the pail?

Danno- Great page, thanks! After using your motor for a while, does 20 in-lb work other than starting with a full hopper? Frankly, I have no problem starting the motor and then filling the hopper, the concern would be what happens if it does stall at some point...

Rob- Thanks for the comments. I was figuring I would need a spider coupling anyway to compensate for misalignment and such. They're only a few bucks from McMaster-Carr. Where did you find your 61 in-lb Dayton?
 

Ken Anderson (24.55.255.75)
Posted on Thursday, December 18, 2003 - 04:24 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Boy, a torque wrench might be the easy way to do this, if there was an easy way to attach it to the shaft. The pail thing would involve the length from shaft center to handle center, and in theory is only legit at the 3 o'clock position, but I would be happy with anything from 2 to 3 o'clock. About the coupling, I wonder if a guy could get away with a stubby piece of stiff hose, and two hose clamps?
Ken
 

danno (63.224.226.20)
Posted on Thursday, December 18, 2003 - 04:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Bob, as you know, the great thing about the Automatic mill is the ability to adjust it on the fly. If the mill stops more than a couple of times during milling, I'll open the gap one step. To get the mill running again, I just use pliers to turn the shaft. As soon as it breaks through the tough kernels, the motor drives it on it's own.

Over time, I have been able to find a setting that works well for specific grains. Wheat is the toughest (I haven't used rye yet) so I will generally use a smaller gap than for two row malt and then adjust it down for a second run through the mill. Cyrstal malt is tough so it works best mixed 50% with the two row.

The worst is the Marris Otter which always seems to have pebbles in it. I primarily use Golden Promise for English Ales because of the rock issue (its also a great malt) but GP is getting hard to find. Now, when the mill stalls while milling MO, I just open the gap wide, use the pliers to help start the mill and then start closing the gap down again in order to prevent damage to the rollers. Again, that's the great advantage to an Automatic Mill.

I do have a new motor that runs at 150 RPM and about 50 in-lbs of torque but haven't put much effort into making the change. Someday, I will build a mill box (my excuse to buy a router) and install the new motor.
 

Rob Beck (65.66.153.63)
Posted on Thursday, December 18, 2003 - 05:35 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I got it on e-bay for $40. Just type in gearmotor in the search box. You'll probably want to just look at the AC powered models. I first bought a DC powered one and then learned that it would cost too much to build the power supply. If you need a 90 watt DC, 100 RPM gearmotor, I can let you have it for $20 :)
Rob
 

Bob McCouch (199.21.28.21)
Posted on Thursday, December 18, 2003 - 05:37 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Danno-
I've yet to notice pebbles in my MO, but I'm just starting to get into my first sack of it. I sure like the resulting beer. When I mill, I usually measure out all my grain, mix it all up (small amounts of wheat included) and then run it through. I've found one gap setting that seems to provide a good crush across the board. Perhaps for a wheat beer I'd want to tighten down a little, my last wheat brew cost me about 5% eff., I think due to the mill gap being set for barley.

If you're able to run decently with 20 in-lb, I'm starting to think of something like this:

http://www.surpluscenter.com/item.asp?UID=2003121810481889&item=5-1404&catname=electric

I know it's rated "intermittent", but I'm planning to use it for about 5 minutes once a month! If that's not intermittent use, I don't know what is! (seriously, does anyone know what the duty cycle of such a motor is when classified this way?)

I want a reversable, since every mfgr seems to decide "CW" or "CCW" from a different viewpoint. ~100 RPM, and 40 in-lb, I'm thinking is probably sufficient based on your experiences. The only variable with this motor is the caps. I think that oval dealy on top is the cap, but I'm not sure and the listing doesn't state a need.

Ken- I was thinking that with equal shaft sizes, a piece of automotive fuel hose (thick, braid reinforced rubber) would work as a fine coupler. I'll probably be ending up with different shaft sizes though, so for $6-8 shipped, the spider coupling is probably just as easy as figuring out a solution myself. I've already got my hands full just trying to build a mill table!
 

danno (63.224.226.20)
Posted on Thursday, December 18, 2003 - 09:13 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Go to http://www.herbach.com and look for item TM01MTR4527. Now that's a motor! A bit expensive at $75 but its got 100 in/lb of torque at 151 RPM and is reversable. For $25 more, I think I'd go that route. Capacitors are cheap. Mine cost about $6.

Intermitent use will depend on speed. My sluggish 29 RPM motor requires about 20 min to crush 20 lbs. With yours at 100RPM, you should only see about 5 minutes of use. I like the way that the capacitor comes mounted. That will save another $10 for a wiring box and accessories.

There's also item 5-1356 at the same place that you linked to Bob. Again, more expensive and requires a cpacitor but continuous duty and brand new from a very reputable company, Bodine.

On the coupler, look at the lovejoy connector that I used. It was only about $15. You cna get them for matching up different shaft sizes.
 

Bob McCouch (68.32.206.76)
Posted on Friday, December 19, 2003 - 12:40 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

OK guys, I did some experimenting. The handle on my mill is 8.5" of "functional" length, and I rigged up a small container hanging off the handle that I could add pocket change to, in order to add weight.

The absolute minimum weight I needed to get the rollers to turn (full of MO barley) was 2.25 lbs, or just shy of 20 in-lb. -- Sound familiar, Danno? As I moved up to 3 lb of weight the motion got smoother, and with 4 lbs, the rollers met no real resistance regardless of gap setting. 4lbs * 8.5" = 34 in-lb of torque.

That says to me that the 51 in-lb of the motor you mention, danno, should be more than sufficient. The 40 in-lb I was looking at would probably work too, but really, for $30 is it worth it to cut corners?

Thanks for the help, everyone!
 

danno (63.224.226.20)
Posted on Friday, December 19, 2003 - 02:58 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Let me know how it works Bob, I may have to upgrade to that one and skip the lower powered one I bought (I can't remember what torque it had but I know it was more than my current one).

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