I’ve spent a lot of time researching and building a couple motorized mills so I thought I’d give something back to the forum with this thread on my latest build.
A little background … I had been brewing all-grain for about 10 years relying on my LHBS to grind my grain. Once you decide to grind your own, you’ll never go back. The rationale could be the topic of another thread. Anyways, I started with a Barley Crusher mill and a hand drill. After a couple years, I fully motorized it with a gear motor. I followed almost exactly the instructions on Sam’s Wortomatic (http://www.wortomatic.com/articles/Sam's-Motorized-Grain-Mill
). These are great instructions and much more detailed than I’m going to provide below. I understand the used gear motors on surpluscenter.com are now hard to find. Anyways, I had this set-up for a couple years and it served me well.
Like my homebrew hobby in general, I was compelled to “take it to the next level” whether that really made any sense at all. I wanted a better crush (with 3 rollers) and more speedy throughput so I went with the Monster Mill MM3-2.0 (3 rollers, 2” diameter). At first I tried to power it with the gear motor from my previous set-up, but no way … not nearly enough power. It stalled with any small amount of grain in the hopper.
I spent a long time on the Internet trying to find the right motor set-up. I found that all-in-one gear motors (like above set-up) either have too little power for this big a mill or spin too slowly. Regular AC motors typically spin at 1725 RPM which is too fast. Ideal speed is 100-200 RPM. The old school way to drop the RPMs is with a belt and pulleys where ratio of pulley diameters is around 10:1. I didn’t want to do this … too dangerous and makes the design for the stand too complicated. My solution … 1725 RPM AC motor with 10:1 worm gear reducer which drops RPMs at mill to 172.5 RPM.
So, here it is … how to build a larger, more powerful motorized grain mill than any sane homebrewer needs to have. In terms of equipment, I spared little expense. In terms of a fancy stand or cart, I went fairly simple. My description is heavy on the component specifics (which I spent most of my time sourcing) and light on the build details (since it’s pretty simple and I literally only spent a ½ day building it).
Components (cost excludes shipping and handling):
- MM3-2.0 Mill (3 rollers, 2” diameter) with Hardened 1144 Steel Rollers (http://www.monsterbrewinghardware.com/mm-320.html) - $344
- MM-H1 Hopper Only (http://www.monsterbrewinghardware.com/basehopper.html) - $30
- MM-EXT Hopper Extension (http://www.monsterbrewinghardware.com/basehopper.html) - $25
- 10-2373 1 HP 1725 RPM 115/230 VAC Motor (http://www.surpluscenter.com/item.asp?catname=&qty=1&item=10-2373) - $147
- 13-175-10-L-56C 10:1 RA Gear Reducer 1.57 HP 56C Left Output (http://www.surpluscenter.com/item.asp?catname=&qty=1&item=13-175-10-L-56C) - $131
- 6408K14 Flexible Spider Shaft Coupling Hub (aka Lovejoy Coupler), 1/2" Bore, 2-7/64" OD, with Keyway (http://www.mcmaster.com/nav/enter.asp?partnum=6408K14) - $7
- 6408K14 Flexible Spider Shaft Coupling Hub (aka Lovejoy Coupler), 7/8" Bore, 2-7/64" OD, with Keyway (http://www.mcmaster.com/nav/enter.asp?partnum=6408K14) - $7
- 6408K75 Buna-N Spider for 2-7/64" Outside Diameter, Flexible Spider Shaft Coupling Hub (http://www.mcmaster.com/nav/enter.asp?partnum=6408K75) - $5
- 7065K21 Manual Reversing Motor Switch, 1-PH, Maintained, Indoor Enclosure (http://www.mcmaster.com/nav/enter.asp?partnum=7065K21) - $40
- 4x 801.842.41 Godmorgon Stainless Steel Legs (http://www.ikea.com/us/en/catalog/products/80184241/) - $40
- Laminated Pine Panel (Home Depot) - ~$25
- Pine 1”x4” (Home Depot) - ~$5?
- Pine ¾”x¾” (Home Depot) - ~$3? (I had some lying around)
- Short Piece of Redwood 2”x4” – ~$5? (I had some lying around)
- Simpson galvanized steel splices plates (Home Depot) - ~$5?
- Misc. bolts, wood screws, and wood glue - ~$10?
- Wood stain and polyurethane - ~$20 (I had some lying around)
- 2’ of 4 conductor wire in braided steel conduit - ~$10
- 2x electrical clamp connections - ~$1
- Heavy duty electrical cord - ~$5
Some commentary on components … the mill isn’t cheap, but is top notch, super beefy, and you’re not going to do much better on cost or quality unless you’re a machinist and have lots of time to kill. The hopper is also very well designed and built. Unlike the mill, I don’t think you could do better for the price even if you worked in a sheet metal shop. The motor and gear reducer were also not inexpensive which is mostly due to my impatience. They’re reasonably priced for being new. If you had more patience, you could probably find something cheaper used on Craiglist or eBay. The reversing switch is a little overkill (you almost don’t need a switch), but it’s really cool looking. The legs from Ikea were a great find. Based on the way I built the table (see below), they’re adjustable so the table height is can be made the exact height of a standard, food grade 6 gallon bucket (like most homebrewers use for their grain). Last, I didn’t list every nut and bolt used. They’re mostly self-explanatory and a true DIYer has a drawer full of all sizes in their garage.
- Assemble gear reducer to motor. I configured mine to have the gear reducer hang off the motor where the motor is mounted to the table. You can do it the other way around where the motor hangs off the gear reducer. You’ll have to think about the spacers needed line up the gear reducer shaft to the mill shaft (described below). I intentionally wanted to put spacers under the motor so I would not have to put spacers under the mill which I thought would be more complicated.
- Lay out mill (without hopper) and motor (with gear reducer) on laminated pine panel to determine lay-out and overall size.
- Cut laminated pine panel to size. I went with 23”x31”. This is really the structure of the mill stand. You need something pretty stiff and strong to hold the weight of the mill/motor/gear reducer and give the mill base some rigidity. I wouldn’t go with anything thinner or wimpier than laminated pine.
- Very precisely mark outline and opening for mill base. From outline and opening, measure and mark holes for mounting mill.
- Carefully cut mill opening and drill holes for mill mounting bolts.
- Mount mill will bolts a little loose. Since bolt holes through wood base are very close to mill opening, I reinforced with Simpson splice plates on the bottom side of the wood. That essentially sandwiches the wood panel between the Simpson plates and the mill end blocks.
- Squeeze end blocks of mill together so blocks and rollers are tight, everything is square without rollers being cocked, and tighten mill mounting bolts.
- Assemble Lovejoy couplers to mill and motor. Motor has a key-way. However, mill just has a flat. I was concerned about slippage of the coupler so I used a Dremel to grind a shallow hole in the mill shaft that the Lovejoy coupler set screw would go down in to.
- Now it’s time to mount the motor (and attached gear reducer). Line up the shafts and measure the gap under the motor. I neatly ripped some short pieces of 2”x4” as spacers. I went a little on the thin side and used washers to finely adjust the height.
- Drill mounting holes through 2”x4” spacers and pine laminated panel. I oversize the holes a bit so I could make some adjustments.
- Carefully line up gear reducer shaft to mill shaft (with Lovejoy coupler installed). They don’t have to be perfect (which is the point of the flexible Lovejoy coupler), but they should be as perfectly aligned as your eye can get them. Shim motor and slide around until the shafts are aligned and tighten down the motor mounting bolts with enough torque so the motor isn’t going to slide around. Make sure to use washers and lock washers.
- Mount 1”x4”s on bottom side of panel along two edges in opposite direction of panel grain. I buttered these up with wood glue, used short wood screws to fasten, and cleaned up the glue squeeze out. These boards give the panel more strength in the direction opposite the grain. They also give the screws for the table legs more meat to grab in to (see below).
- Mount ¾”x¾” trim wood pieces to bottom of panel around the mill opening. These help guide and position the bucket under the center of the mill. Use a bucket to trace a circle around the mill opening and attached the trim pieces just outside this circle (leaving a little gap so you don’t have a tight fit). You’ll likely have to predrill these so they don’t split when you screw them down.
- At this point I disassembled all the metal stuff, sanded the wood, applied some stain, and then applied a couple coats of polyurethane. If you’re impatient like I am, you can use a heat gun (or hair dryer) between coats of stain and poly to speed it along. After my 2nd coat of poly and heat gun, I took a short break for lunch and a beer and the poly was hard enough when I was done to continue working.
- Wire motor to switch and switch to electrical cord. This took a little head scratching on my part, but I figured it out eventually. It helps to draw up a wiring diagram. If enough people reply and ask for one, I can recreate it. To make it reversible, you have to use four conductor wire (black/white/red/green) and use the metal flexible conduit as ground. Honestly, the mill has never bound up and I never have had to reverse it so this feature isn’t really necessary.
- Mount switch to pine laminated panel.
- Mount Ikea legs to bottom of panel into 1”x4”s with screws long enough to go as deep as possible without poking out the top.
- Roller spacing can only be measured with the hopper removed so I took the extra step of measuring and scribing marks on the side of the mill for different roller spacings. Spacing can be measured with feeler gauges (find them at an auto parts store). I put a mark on the adjuster knobs (one on each side of mill) and then made 12:00 to be my nominal 0.035” spacing. I then marked off 0.002” increments wider and narrower in each direction. Make sure you also mark which way is wider and narrower on each side of the mill as they’re in opposite directions.
- Assemble and mount hopper to mill.
- Monster mill recommends running some grain through the mill to remove any dirt or metal burrs (and then throwing out grain of course). Think of this as your test drive.
- Relax and have a homebrew!!
Some commentary on construction … like I mentioned before, I put my money and focus on the equipment and didn’t go real fancy on the table. I made it look nice (it matches the dark woods and stainless steel in the rest of my brewery), but it’s mostly function over form. There’s lots of other posts with elegantly built or creatively sourced cabinets, carts, stands, etc.. Also, I didn’t provide any dimensions. Hopefully you can get the overall idea from the pictures. I did measure when I built it (i.e. I didn’t slap it together), but didn’t keep notes afterwards. It’s mostly an exercise in picking the size you want and carefully aligning and laying things out.
This mill rocks! It plows thru 30+ lbs of grain in just a minute or two. It’s big, beefy, and overpowered. Throwing the red lever on the control box is blast (you’ll know what I mean after you’ve built yours).
Anyways, I hope this was helpful. The parts cost a few bucks. You could do a little better on the motor and gear reduce with some patient eBay hunting. Construction should take less than a day.