I made a mill

[n87]

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[Matplat]

As I understand it, you can't slow down AC motors with a speed controller as the current draw goes up and it overheats.

Is there anyone here that can confirm or reject my claim above?

 

[Ducatiboy stu]

Yeah I would need a smaller pulley than what I already have on the motor... at the moment it is 1 1/2" on the motor and 14" on the roller I think 1 1/4" is the smallest you can get, which gets me down to 250rpm... but I think I may do that as well as halve the motor speed...

You probably want to get it to around 150rpm on the roller. remembering that larger rollers will have a faster surface speed compared to smaller rollers at the same rpm

 

[Mardoo]

Is there anyone here that can confirm or reject my claim above?

I can't, but variable speed electric drills come to mind. Are those DC motors with a transformer?

 

[Dave70]

Is there anyone here that can confirm or reject my claim above?

This was possible with about every power drill I've ever owned. You varied the chuck speed according to how far you depressed the trigger.
Some even had dials that would govern how fast the motor spun. I actually have a 5" grinder (GMC, 4 years of abuse and counting?!.) with the same feature.
So based on purely anecdotal, sample size of one observation, yes it's possible. Probably not optimal however. Pretty sure most stationary electric motors would be manufactured to run at a certain RPM and current for a reason.

 

[Matplat]

Yeah, I'm going to flog the motor from a small drill press.

Drill presses seem to go cheaper second hand than the motors that run them.... pool pumps can be had for even less, but they all seem to have the 2800rpm motors that I am already using.

 

[wide eyed and legless]

Have a look on eBay. (speed controller)

 

[TheWiggman]

Most large AC motors run based on line frequency and number of poles. Here's a reference as an example - http://www.engineeringtoolbox.com/synchronous-motor-frequency-speed-d_649.html
If it's an induction motor, your motor will have the number of poles written on it as well as run speed. To vary the speed you either need to change the number of poles (i.e. buy a new motor) or alter the line frequency using a VVVF drive or similar. If you have a brushed universal motor on the other hand the speed can be controlled much the same as an electric drill using the appropriate controller.

Agree with the above posters, with rollers at that diameter and speed it would be absolutely rip-tearing through that malt with reckless abandon. Large diameter rolls is a good thing but you really need to slow it down. Look into a lower speed motor or controller if you can. Otherwise, add an extra shaft for the pulleys for an extra reduction. And a cage to ensure fingers remain on the ends of you palms.

 

[Matplat]

Afternoon all, so i got a motor from a drill press second hand which has cut the speed in half so theoretically I should now be running at 150rpm, but I don't have a strobe to confirm this... anyway here is 100g of grain that I put through it at 1.5mm gap, I think it looks pretty good but could possibly close the gap a bit. The proof will be in the brewing, but I've got to make a hopper first

 

[mash head]

Looking good, you can get a cheap rev counter off ebay with a magnet pickup if you need. I put one on my harvester thrasher when the original cable drive rev counter was going to cost heaps to replace. Make sure you are not getting any whole grains getting through as the grain size on some malts can vary a lot.

 

[Matplat]

Yeah good idea but I don't think I'm that bothered about knowing the exact rpm, as long as I can get good efficiency...

I was thinking about doing a few mini-mashes on the stove to evaluate efficiency at different gap settings, however that would be BIAB whereas my brew system is 1v malt pipe. Is the main consequence of milling too fine getting a stuck mash? I'm sure tannin extraction would also become an issue at some point also, but would you run into a stuck mash first?

 

[wynnum1]

Getting a stuck mash would be ok if doing tests to evaluate need to test until it fails.

 

[dannymars]

I found that the bigW malt pipe is fairly prone to stuck mashes, mine is anyway.

 

[Matplat]

Cut some more holes dude, last brew my LBP couldn't barely keep up with the flow through the grain bed...

 

[Matplat]

So just did the first brew last night with the gap set at 1.4mm with rollers at calculated 150rpm. I did an American wheat 50:50 pale and wheat. 5kg of grain crushed in 2-3 mins max, and I hit 75% eff so I'm stoked.

 

[Benn]

Good work Matplat :beer:

 

[Ben1]

Out of curiosity, what was your eff before matplat?

 

[Matplat]

Last few brews were 70, 65, 58 in chronological order, but has been as high as 80. I set my recipes at 70, consistency is my main problem, however the beer still tastes good!

Achieving 75 this time round wasn't necessarily a step up, simply that I was expecting less while fine tuning the mill.

 

[Hpal]

I made one years ago & power it with a windscreen wiper motor
Not sure of the speed but pretty slow

Might be an option for you to try

Forget my gap but its large 1.4mm ? 50mm rollers

Here's mine http://cdn.aussiehomebrewer.com/uploads/albums/gallery/album_1215/gallery_26644_1215_249415.jpg
Powered with a wiper motor, slow but steady, 65mm rollers and I've set gap at 1.6mm, any smaller is too fine.
Good work on the mill mate, looks great! http://cdn.aussiehomebrewer.com/uploads/albums/gallery/album_1215/gallery_26644_1215_658805.jpg

 

[Matplat]

Wow, 1.6mm! I think that the optimum gap size depends alot on the size of the knurl on the rollers. Looks like off-the-shelf mills have a much coarser knurl. If I were to set the gap at 1mm as it seems alot of people do, I would end up with flour.