malt mill rollers -- surfacing?

[chicagojimmyjames]

OK friends, I need some input here....

my next homebrewery project is going to be a malt crusher. I searched this site but didn't come up with anything...

I like the adjustable wooden box idea, seen here:
http://hbd.org/cdp/millc/mill_cd1.htm

but I like the wide rollers http://www.intothefray.org/brew/grainmill.htm

My question is this:

If I go with concrete rollers, what's the best way to add a bit of "tooth" to the surface?

 

[BBL_Brewer]

If you've got an angle grinder (hand grinder) you could cut some semi-shallow grooves longwise on the rollers. I believe they sell masonry cutting wheels that would work. If not, the cutting wheels made for metal would probably get the job done since you don't need to cut very deep. Pretty simple solution and should add enough bite to pull the grain in nicely.

 

[Lucky_Chicken]

What diameter rolls are you thinking? If the rolls are big enough you shouldnt need any roughness on the surface.

 

[Catt22]

What diameter rolls are you thinking? If the rolls are big enough you shouldnt need any roughness on the surface.

This is correct. No need to knurl the face of the rollers if the rollers have a large diameter. The smooth rollers are also much less likely to tear up the grain husks. The downside is that the larger rollers will require more force to operate. The same for wide rollers. Load up the full length of large diameter, wide rollers and it will be a bear to turn.

 

[chicagojimmyjames]

I was thinking of a 3" or 4" diameter, as in the website example with the concrete cast in a piece of PVC drain pipe.

I have an angle grinder, but I was just worried about taking off too much and making grooves. I guess concrete is cheap enough that I can make a few test rollers.

And yes, heavy and hard to turn -- I will motorize. I have several old 1/2 hp motors laying around. I'm going to build a box for it anyway to keep the dust inside.

Thanks for the advice, guys. I'll post some pictures when I get started.

 

[Hang Glider]

any way to embed cheesecloth in the outside diameter during the pour? that might leave behind a nice toothiness. I envision removing the cheesecloth after drying, but not sure how - some kind of acid, maybe...

 

[DrJerryrigger]

If your going with concrete there will be a bit of bight to them naturally. Maybe going with a coarse sand addition would help, or even dusting your mold with sand per casting. Also how you make your mold will make a difference in texture. You could also scratch at it with a nail after it's mostly cured, but still fully wet.
But assuming your making your rollers on the large side: It doesn't really matter, and getting a really smooth surface may be better for adjustments.

Cool project, hope you post pics of the construction!

 

[DrJerryrigger]

any way to embed cheesecloth in the outside diameter during the pour? that might leave behind a nice toothiness. I envision removing the cheesecloth after drying, but not sure how - some kind of acid, maybe...

Fire is good for that. Just dry it slowly first, oven at 250F for 5hr, then you can heat it to 500F to burn out the cloth, or just use a blow torch. If you didn't dry it, it could crack from steam trying to escape too fast.

 

[DrJerryrigger]

I was thinking of a 3" or 4" diameter, as in the website example with the concrete cast in a piece of PVC drain pipe.

I have an angle grinder, but I was just worried about taking off too much and making grooves. I guess concrete is cheap enough that I can make a few test rollers.

And yes, heavy and hard to turn -- I will motorize. I have several old 1/2 hp motors laying around. I'm going to build a box for it anyway to keep the dust inside.

Thanks for the advice, guys. I'll post some pictures when I get started.

Sorry to make three posts on this in a row. But I'm really exited about this mill, and may make one similar (as it's really cheap).
I was thinking, since your casting cement already, a hand powered one with a really big fly wheel would be nice, just get it going and let it ride.
The hardest thing to do as I see it, is to get the center pins in the rollers in the center. Let us know how that goes, and how well it comes out.

 

[Catt22]

Fire is good for that. Just dry it slowly first, oven at 250F for 5hr, then you can heat it to 500F to burn out the cloth, or just use a blow torch. If you didn't dry it, it could crack from steam trying to escape too fast.

This is really bad advice. Firing green concrete will cause it to disintegrate. Would be much better to allow it to cure as slowly as possible at a high humidity level and @ 80*F or so. Once the concrete has set (maybe 6-8 hours or so), you could submerge the rollers in a bucket of water for the ultimate in curing conditions. The concrete will continue to gain strength for several weeks and beyond.

 

[chicagojimmyjames]

Great input, guys.

I had thought of using cheesecloth or some rubber with a pattern... the trick would be to glue it (spray adhesive, I suppose) to the inside of the drain pipe. Tricky, but not impossible. I wasn't too worried about getting it off again when the roller comes out of the cast... I'm sure something would do the trick. (but no, I won't overheat uncured concrete.)

I had also thought about the flywheel, as I wouldn't want the mill to jam when first starting it up.. I thought I would put a door / hatch of some sort on my hopper so that I could measure the grain, but then not let it fall towards the mill until the wheels are up to speed.

 

[chicagojimmyjames]

A few other thoughts...

If I build the frame for the rollers out of plywood, what's a good way to reduce friction where the roller pin goes through the outer box wall? A bit of PVC pipe or copper pipe might do the trick, but I'd love a more professional idea if anyone has one.

I'm about to head over to the store and price some materials. Maybe black pipe is the easiest way to go...

 

[DrJerryrigger]

This is really bad advice. Firing green concrete will cause it to disintegrate. Would be much better to allow it to cure as slowly as possible at a high humidity level and @ 80*F or so. Once the concrete has set (maybe 6-8 hours or so), you could submerge the rollers in a bucket of water for the ultimate in curing conditions. The concrete will continue to gain strength for several weeks and beyond.

Well yeah, it clearly need to fully cure before any drying should be attempted, I thought that was just common knowledge.

 

[DrJerryrigger]

A few other thoughts...

If I build the frame for the rollers out of plywood, what's a good way to reduce friction where the roller pin goes through the outer box wall? A bit of PVC pipe or copper pipe might do the trick, but I'd love a more professional idea if anyone has one.

I'm about to head over to the store and price some materials. Maybe black pipe is the easiest way to go...

The position of the rollers matters a lot, so just some PVC as a bearing may not work so well. Any give in the bearing will mean the wheel could shift when in use.
I think your best bet would be to buy an appropriately sized sleeve bearing or ball bearing for each connection. Ideally; the bearings would be attached to the box in a very ridged way giving less than .005" of play, with one side having adjustable mounting.

 

[martinworswick]

as has been said previously 4inch rollers would have more than enough friction to bite the grain

i made a similar mill but i filled steel tubes with concrete
https://www.homebrewtalk.com/f51/my-concrete-steel-3-roller-mill-217600/
it crushes 15lb grain in under 30 secs

 

[DrJerryrigger]

as has been said previously 4inch rollers would have more than enough friction to bite the grain

i made a similar mill but i filled steel tubes with concrete
https://www.homebrewtalk.com/f51/my-concrete-steel-3-roller-mill-217600/
it crushes 15lb grain in under 30 secs

Holy cow, that thing could take off your arm! I like the idea of steel on the outside, I might have to go that way myself.
I see you had problems getting the axle centered. Any suggestions to how you could have done that better the first time around? I was thinking three long set screws on each side (tapped into the outer pipe) to center it, then pour.

 

[chicagojimmyjames]

Now that's what I'm talkin' about!!!

 

[martinworswick]

that could work, the way i did it was to cut a circular groove into a piece of plywood the same size as the steel, i used a router and a circle jig to do this,the problem came when i enlarged the hole at the centre of the ply to take the shaft,
the drill bit i initially used was 5mm,i left this in the timber and rotated the router around it,i then redrilled the hole to 20mm to take the shaft,i though it would centre itself accurately enough in the initial 5 mm hole but it must have drifted off centre slightly hence the problem. follow that? i'm not sure i explained that very well.
i figured if i ever did it again i would do the same but make the full sized centre hole initially and remake the jig to rotate around the actual shaft i was using with hopefully greater accuracy.

i'm sure someone else would have ideas on how to achieve this,suggestions?

 

[DrJerryrigger]

Yes, I could follow that. I don't think I'll attempt that way myself, as I'm a better metal worker than wood worker (though I'm lacking both kinds of tools).

 

[chicagojimmyjames]

I think I got it. You used a piece of wood at either end of the tube to center the axle, right?

Next time you might try this first... .... and then add the center hole. The nail hole from making the circle on the table saw tells you where your center spot is.

 

[martinworswick]

I think I got it. You used a piece of wood at either end of the tube to center the axle, right?

Next time you might try this first...http://www.youtube.com/watch?v=Wxbzrf4z_cg .... and then add the center hole. The nail hole from making the circle on the table saw tells you where your center spot is.

he really should wear some hearing protection:cross:

same principal but different tool, my problem came when enlarging the nail hole to the shaft/spindle size,if you had a drill press you could probably eliminate the problem or gradually enlarging the hole would probably work but i went from 3/16 to a 3/4 auger bit and it must have just wobbled slightly.

 

[chicagojimmyjames]

Ok, got it.

Another way to avoid that problem would be to use some squares to hold the metal rod when the concrete is setting up. A "speed" square might be good enough, with some zip ties, or I would recommend the magnetic squares used for welding. Not expensive and very useful. They'll hold both pieces nicely, and still easily allow minor adjustments. It wouldn't matter if your jig was slightly larger than anticipated.

... but I've always been a "measure once, cut twice" kind of guy. When I make my rollers, I think it'll take a little more accuracy than I normally can muster...

 

[DrJerryrigger]

The thing is you really do need them no more than 0.010" off, even that much would be bad, but it would work. To get that accurisy you need to be able to measure it's centeredness to 0.001" which is tricky in it's self with out all the right tools.

Bring them to center once made seems like a great option, which it what I'd do if I had metal working lathe.

 

[Catt22]

Well yeah, it clearly need to fully cure before any drying should be attempted, I thought that was just common knowledge.

Actually, no drying at all should be attempted. Concrete solidifies and hardens through a process called hydration. It does not harden through a drying out process. Exposing concrete to high temperatures in an oven or kiln will weaken, not strengthen it. Concrete continues to cure and gain strength for a very long time, as in years and years. Properly cured concrete will typically reach about 90% of it's maximum strength in 3-4 weeks, but will continue to gain strength for decades. Ideal curing conditions for concrete are cool temperatures and very high humidity. Again, applying heat to accelerate the curing process is not a good idea at all, even if it appears to be fully cured, which it won't be anytime soon.

 

[DrJerryrigger]

Actually, no drying at all should be attempted. Concrete solidifies and hardens through a process called hydration. It does not harden through a drying out process. Exposing concrete to high temperatures in an oven or kiln will weaken, not strengthen it. Concrete continues to cure and gain strength for a very long time, as in years and years. Properly cured concrete will typically reach about 90% of it's maximum strength in 3-4 weeks, but will continue to gain strength for decades. Ideal curing conditions for concrete are cool temperatures and very high humidity.

We're not building a bridge here, a few weeks of curing is more than enough, particularly with quick fixing cements.

Again, applying heat to accelerate the curing process is not a good idea at all, even if it appears to be fully cured, which it won't be anytime soon.

Applying heat would be to dry it. Drying and curing are completely different. The drying stops the curing posses (as you've said a few times now), but there are applications where you need dry cement, which can be done by carefully heating it after it has cured to desired hardness.

 

[Catt22]

We're not building a bridge here, a few weeks of curing is more than enough, particularly with quick fixing cements.


Applying heat would be to dry it. Drying and curing are completely different. The drying stops the curing posses (as you've said a few times now), but there are applications where you need dry cement, which can be done by carefully heating it after it has cured to desired hardness.

Yes, a slow, humid and cool curing time for a few weeks, as in 21-28 days to reach approximately 90% of the mix design ultimate strength. I think I already said that. You are again correct. It's a grain mill, not a bridge. Don't know how you ever got the notion that this thread was about bridge building.

Why the hell would you want to stop the curing process? That makes no sense at all. There are no applications that I am aware of where you would want to dry cement. Got a link perhaps? Also, it's not cement, it's concrete. Cement is but one component of concrete. The others would be coarse aggegate, fine aggragate and water in various proportions, ideally in compliance with an engineered mix design. Additional additives are often used, but those are the primary components of concrete.

I continue to maintain that applying heat is a bad idea. There is no benefit to be had and it will likely damage the end product. Slow, cool and humid will give the best results.

 

[DrJerryrigger]

Yes, a slow, humid and cool curing time for a few weeks, as in 21-28 days to reach approximately 90% of the mix design ultimate strength. I think I already said that. You are again correct. It's a grain mill, not a bridge. Don't know how you ever got the notion that this thread was about bridge building.

My point is that max strength is not needed at all for this application, 50% would likely be more than enough, though 80-90% would be better (as it's quite attainable).

Why the hell would you want to stop the curing process? That makes no sense at all. There are no applications that I am aware of where you would want to dry cement. Got a link perhaps? Also, it's not cement, it's concrete. Cement is but one component of concrete. The others would be coarse aggegate, fine aggragate and water in various proportions, ideally in compliance with an engineered mix design. Additional additives are often used, but those are the primary components of concrete.

To remove cheese cloth via burning, which doesn't seem like it's necessary after all, but that was (I thought) clearly the only reason I gave directions on drying concrete.
The link in the original post described using just cement, not concrete.
There are many applications where drying is necessary. Cement floors for example, before putting down plastic tiles, must be dried to an appropriate level. My experience is more with refractory cements. When your final product is used at 3000F you need to dry it properly. Normal cements will not hold up to temps above about 900F, but the same drying proses can be used (after curing).

I continue to maintain that applying heat is a bad idea. There is no benefit to be had and it will likely damage the end product. Slow, cool and humid will give the best results.

There are only benefits for applications where you need dry cement.

 

[GNBrews]

Drying, then heating concrete to a point where anything would burn out of it would reduce its strength considerably. The surface would be chalky and crumby, and would likely wear quickly when used to mill grain. As Catt was saying, it needs to be in a hydrated form in order to retain its strength. Heating it to dehydrate it or burn something from it would be a bad idea.

As a refractory material, you're not worried so much about its strength but rather its insulation value and melting point. I realize that a lot of "backyard metal-casting" mixes use a bit of portland cement, but as you know, it's not the ideal material for the job.