Roller Mill

I made my own grain mill. If you are not a homebrewer you probably won't understand.

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Blow by Blow

/!\ I have done a bit of reading but other than that I am flying by the seat of my pants - ie copy the design at your peril.

We have:

  1. 1 metre of 5/8" bright steel for the roller axles. $8 at the Steel Shop, Bayswater.
  2. A metre or so of jarrah which happens to be about 68x68mm. $10 at Mathews Timber, Nunawading.
  3. 4 sealed bearings, 12mm ID and 32mm OD. $24 at CBC bearings Mt Waverley.
  4. Something for the end plates. I picked up some 1/2" plate aluminium offcuts from Challenge Metals in Bayswater for about $5.
  5. Some 12mm round steel rod to hold it all together $3
  6. Misc nuts and bolts.

It will also need a hopper but I'll worry about that later.

First rip the jarah block down the full length.

Some people have suggested that jarrah won't be tough enough, my feeling is that it will be but hey, if it doesn't then I will replace it with something else. In fact just recently I noticed that the local scrap yard (Challenge Metals, Bayswater) had some aluminium rollers about 42mm in diameter. They looked like they came from some kind of conveyor belt and I picked up two for $16.

Then route grooves to fit the square rod. You need to take a bit of care setting up your router so the fit is not too sloppy. I will glue it anyway but Araldite could turn out to be the most expensive bit if there is lots of space to fill.

I didn't have exactly the right size router bit so I had to make two passes. You want to make sure that the second pass of the wood is feeding against the rotation of the router bit otherwise there is a risk the router will tear the wood right out of your hand (or worse).

I first thought about using round bright steel and boring a hole down the long axis of the jarah. Unfortunately I don't have the means to bore this hole.

Now I have turned the ends of the axles to take the bearings.

The rollers are all good to glue as far as I can tell.

And thanks to all those helpful folk who pointed out that it will perform better with round rollers. I would like to know if any of them have actually tried square rollers.

After gluing with epoxy and waiting a couple of days, I finally got off my arse and made the rollers round. That should improve the efficiency somewhat.

Now we are starting to get down to the business end. Actually there is still quite a bit of work to do which I can't really finish until I get my 4 jaw chuck fitted. Hopefully that is not too far away.

Uncle Al (actually my wife's uncle, just turned 80) did me a big favour and made the adapter plate for the 4 jaw chuck.

Now I have the 4 jaw chuck I can make the holes where the bearings fit. This is the fixed roller. The other roller will be slightly more complicated since I need a means for adjusting the gap.

The aluminium is from a scrapyard in Bayswater (Challenge Metals) who have lots of useful stuff, most metals are around $5-7 per kg. I paid $5 for the end plates in total.

The bearing fits ok.

The roller fits! Furthermore it turns freely.

I need to get this thing happening, down to two kegs now and drinkin'.

This is the eccentric arrangement for adjusting the gap between the rollers. This view is the inside of the end plate. I will probably use a grub screw to keep the eccentrics in place, however once it is all in place everything fits together pretty tightly.

The outside of the end plate with the rollers in place.

The rollers here are just sitting in the end plates. The rollers appear to be quite parallel and true.

I just need to bung everything together and add a hopper - there is still a bit to go. I plan to power it initially with a power drill.

For better or worse, it was at this stage that I bought the grain for my next brew, uncracked. Will the wooden rollers stand up to the grain? Will I ever finish the bastard?

Now we are getting somewhere, this is a top view with the end plates held in place by the 12mm bars in each corner.

A better view of the construction.

I made a last minute addition to the design, an o-ring to drive the "lazy" roller. I had to machine a groove in the roller to prevent the o-ring wandering around.

Test Grind

The first grain (malted wheat) that I put though it. Eureka!! This is a test grind, I only used a teaspoon or so of malt. I initially set the gap by eye and after I did this I checked the gap with a feeler gauge and it was quite a bit smaller than 0.8mm, probably something like 0.6mm. I set it to 0.8mm (maybe still a little close) and crushed a bit more.

There appears to be some slippage, I still have some work to do (not the least of which is the construction of a hopper) but I am confident that one way or another I can crush some grain.

After milling over 100 kg of grain, I noticed my efficiency dropping off, the last batch it dropped dramatically, from 85% down to 66% and when I measured the gap it was out to 1.4 mm. I am not sure of the reasons for this, it is due to either wear or shrinkage, probably the former. It is most likely from me disassembling then reassembling it without too much care or maybe backlash in the adjust mechanism. It is now back to 0.9 mm and working fine.

Brew Day

Comes a time when you need to pause from the never ending equipment modifications and brew some beer.

As I mentioned earlier, I had bought the grain and I was well under half my beer storage capacity.

I started brew day without a hopper, I had come up with a design while laying in bed and had the timber kicking around in the garage. I was keen to give it a whirl before HBS closing time (1pm on Saturday in these parts) in case it just wasn't going to work. A fairly simple design and a couple of hours later I was ready to go.

It just sits on top of the mill, with some slots to prevent it sliding all over the place. The mill definitely needs to be fixed to a heavy bench - holding it with one hand while cranking with the other resulted in some skun knuckles.

You can see that I was hand cranking it. I started out using a power drill, it turned it fine but I found at the faster speeds there was more tendency to slip and the grain just buffed the rollers. I achieved better throughput cranking it by hand. Later on I tried the drill and it seemed to work quite a bit better.

So for next time I need to make a handle.

At first not much happened. I fiddled around with the roller gap and there seemed to be a magic setting where it would really pull grain through well.

Some crush from an APA recipe. The husks seem to be flattened but intact. At the time of this picture I had brewed fewer than 10 AG batches and the only comparison I have is what I get pre crushed from the HBS. I only ran it through the mill a single time.

This is the grain bill for the APA I am brewing (see Allgrain #2). With all the stuffing around, it probably took me half an hour to grind this. When it is all bolted down, gap adjusted right and a decent crank handle I reckon I could do it in 10 minutes or less. If it grips better as it ages then the power drill will make short work of a batch of grain.

For this brew I batch sparged in a rectangular cooler. I achieved 90% efficiency, see also Allgrain #2 for the low down.

This is the complete box and dice. The hopper just sits on top, the base is quite heavy and additionally has a flange which I clamp to a solid bench. Last time I used this setup, I cranked 5kg grain in 6 minutes by hand. The torque required is quite high and using a power drill would pose some problems with overheating and speed control (slow is good). It really pulls the grain through the gap.

This is what the rollers look like after a few batches. Some of the malt has embedded in the grain but there is no real sign of wear on the surface of wood. You can see the two o-rings which drive the passive roller. Without these o-rings the mill doesn't work very well.

Here is 5.6kg of grain I milled in just over 4 minutes by hand. I need to work on my fitness a bit.

paul sorenson

RollerMill (last edited 2006-06-29 17:59:36 by PaulSorenson)