Author Topic: creating a curd stirrer  (Read 473 times)

Offline steffb503

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creating a curd stirrer
« on: April 25, 2014, 03:53:49 PM »
I would love some feedback on this. I am going to have a curd stirrer made. I am not exactly sure how I want it though.
I have a micro dairy vat with a central agitator. I was going to utilize that central shaft to turn something. There in lies my problem. I see a lot of them that look a lot like curd cutters spinning on a agitator. My thought was to have rods coming off the central shaft outward to move through the curds. My thought was it should be like fingers? Am I thinking this wrong?
What would you want in a curd stirrer?


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Offline WovenMeadows

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Re: creating a curd stirrer
« Reply #1 on: April 25, 2014, 05:20:31 PM »
The one's I've seen on commercial vats do seem to look like that - sort of like rakes extending from the center. The fingers would be slightly curved, or just angled, to gently scoop up the curds keeping them moving and not settling. It would sort of mimic the action of one's own hand.
This is for one of Frank Kipe's vats?

Offline steffb503

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Re: creating a curd stirrer
« Reply #2 on: April 26, 2014, 05:44:54 AM »
Yes Franks vat.
I was thinking straight from the center shaft so that the bottom one would ride almost the bottom of the vat.
Do you have one of his vats?

Offline Tomer1

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Re: creating a curd stirrer
« Reply #3 on: April 26, 2014, 06:53:52 AM »
Share your design when your done.  I finally got a geared motor (4rpm) for my 30L vat but I still havent figured out what Im gone use as a stirer.
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Offline WovenMeadows

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Re: creating a curd stirrer
« Reply #4 on: April 26, 2014, 07:48:25 AM »
Yes Franks vat.
I was thinking straight from the center shaft so that the bottom one would ride almost the bottom of the vat.
Do you have one of his vats?

I was planning on getting one of the MicroDairy Designs vats, but just after we got our loan approval, there was a goat dairy having a going-out auction and picked up a 75 gallon Fromagex vat instead (for an awesome price!). I will probably still get the MDD packager though.


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Offline CheeseDoc

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Re: creating a curd stirrer
« Reply #5 on: April 26, 2014, 01:48:59 PM »
I make 4 and 8 gallon test batches of cheese as a fairly serious hobby.  As we all know, standing over a pot stirring for many hours gets pretty tedious after a while.  It also gives me a sore back.  I've been working on a "Cheese Machine."  Basically, it's a store-bought stock pot with removable stirring and heating features. Everything is operated by a laptop computer and custom built controller.  My Cheese Machine measures temperature and pH.  It turns the heat and stirring mechanism on and off under the control of a "recipe." I write text-based, step by step instructions to control the vat and to signal me when I need to do things like add cultures, or cut the curd.  It constantly displays things like: vat temperature, vat pH, heater on or off, stirrer on or off, lists of ingredients, the current step in the "recipe, the time until the next step, and so on.  Everything works beyond my expectations.  The temperature control is outstanding (within a degree) and I never miss a step; the Cheese Machine alerts me whenever I need to do something.  The quality and consistency of my cheeses has taken a very positive turn.  I'm particularly pleased with how well the Cheese Machine carries out temperature ramps--something very difficult to do well on the stovetop.

However, there is one feature that still isn't up to snuff.  I've been tinkering with the stirring mechanism for a while, hoping to get it working as well as hand stirring.  I use a slow turning motor originally designed to turn an auger that moves wood chips into a home wood stove.  It's cheap, easily replaced and has enough torque to move through curds.  The motor is mounted on a cross bracket that straddles the top of the pot and nestles into the pot's handles.  Gravity holds it in place.  It never moves during use.  For the stirrer itself, I pieced together sections of food grade stainless pipe fittings for the vertical shaft and horizontal arms (tees, crosses, and nipples.)  I used standard Teflon tape to seal the joints where the various pieces attach together.  If you decide to do this, I'd recommend using the type of threads that increase slightly in diameter as they get farther from the end of the fitting.  This insures a very tight fit and makes sure no water gets inside the stirrer.  I didn't want to worry about bacteria growing inside the stirrer and eventually contaminating the cheese.  I had to custom make a connecting rod to go between the uppermost tee fitting and the motor's drive shaft.  This is just a short length of stainless rod into which I cut threads matching the stainless fitting on one end.  Finally, there is a coupler that attaches the unthreaded end of the connecting rod to the shaft of the motor.  The coupler tightens with several hex screws.  Eventually, I'd like to replace this coupler with a magnetic coupler that allows the stirrer to stop turning if something solid (like a stirring spoon) accidentally falls in the vat. It would also allow the stirrer to be easily and quickly removed from the stirring assembly without needing to use tools.  I typically remove the stirrer from the motor assembly and put it in the dishwasher to clean.

The stirrer does a great job stirring the milk before the rennet is added.  Wherever I measure the temperature anywhere in the vat, the milk is at pretty much the same temperature, whether I'm on a step where the temp is held constant or on a step where I'm slowly ramping the temperature over time. This alone has made my efforts worthwhile since these steps can go on for over an hour.

However, the stirrer doesn't really stir the cut curds as well as I'd like. I still have to use a spoon to help out.   I was hoping the multiple sets of cross arms would provide sufficient agitation to keep the curds moving around the whey and also keep them from knitting together.  However, this doesn't happen with the current design.  The bottom-most arm either shoves the curd mass in front of it, or the curd mass slips between the two lowest arms. Either way the curds continue to knit together into a larger and larger mass.  My first tweak was to soldered sweeping blades (sort of like a fan blade) to the bottom most set of arms. The blades are soldered across the top of the arm all the way from the central shaft to the tip of the arm.  They are positioned facing forward and angled downward so they almost touch the bottom of the pot.  This had helped a little--it gets the curds off the bottom of the pot.  But it still doesn't do the job right.  Part of the problem is due to the nature of curds.  They start out very fragile.  They need a gentle touch in the first few minutes.  But as they lose whey and begin to firm they can stand a more vigorous stirring.  I have not found a shaft turning rate that is both gentle enough for newly cut curds, and vigorous enough to keep the curds continually separated.  Part of the problem is simply the way the curds are being agitated.  They are heavier than whey, so tend to quickly fall to the bottom of the pot.  They need to be lifted off the bottom and kept moving without being so bullied that they disintegrate.

At this point, I'm considering various tweaks.  One is to attach blades to all the arms.  I'm hoping that a curd swept off the bottom of the pot by the lowest arm will then be gently lifted higher and higher buy the arms above.  This could mimic the way a spoon stirs curds from the bottom of the pot toward the surface.  Another idea is to use a variable speed stirring motor that can treat freshly cut curds gently, but then pick up more and more speed as the curds firm.

Any ideas would be appreciated.  The Cheese Machine will never be like a bread machine or ice cream machine.  It will never be something you load up with ingredients, turn on, and walk away.  It will always require human intervention to carry out certain steps.  But, if the milk heating steps and the curd stirring steps can be automated, it would make cheese making a lot less tedious.  It would also enhance the ability replicate cheeses from one batch to the next.   

Offline steffb503

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Re: creating a curd stirrer
« Reply #6 on: April 27, 2014, 10:20:40 AM »
Can you post a pic?

Offline Alpkäserei

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Re: creating a curd stirrer
« Reply #7 on: April 28, 2014, 01:01:10 PM »
On the alp, we had a pretty simple curd stirrer.

The stirrer was sort of like a big propeller, so it kept the curd stirring all around, If you had say, a steel of aluminum fan blade

it was powered by a motor taken off an old car -a windshield wiper motor- So it had 2 settings for fast and slow. You had to get it started by pushing it, since it didn't have enough torque to self start, but after that it worked like a charm in 150 liters

Also, you have to put a fin on the side of the vat, a board or plate that sticks down in to break up the circular motion. that will keep the curd from sticking together

 
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Offline ArnaudForestier

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Re: creating a curd stirrer
« Reply #8 on: April 28, 2014, 04:18:12 PM »
On the alp, we had a pretty simple curd stirrer.

The stirrer was sort of like a big propeller, so it kept the curd stirring all around, If you had say, a steel of aluminum fan blade

it was powered by a motor taken off an old car -a windshield wiper motor- So it had 2 settings for fast and slow. You had to get it started by pushing it, since it didn't have enough torque to self start, but after that it worked like a charm in 150 liters

Also, you have to put a fin on the side of the vat, a board or plate that sticks down in to break up the circular motion. that will keep the curd from sticking together

That's ingenious, Alp.  What did you mount the motor on, just wood? 
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Offline Alpkäserei

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Re: creating a curd stirrer
« Reply #9 on: April 28, 2014, 07:29:32 PM »
It was mounted on a board. But it was a really nice board  ;)
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Offline ArnaudForestier

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Re: creating a curd stirrer
« Reply #10 on: April 28, 2014, 07:56:47 PM »
It was mounted on a board. But it was a really nice board  ;)

 ;D
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Offline steffb503

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Re: creating a curd stirrer
« Reply #11 on: April 29, 2014, 06:14:14 AM »
My vat has a motor for the agitator. I was planning to use that. I have been using the paddle that agitates the milk to pasteurize but being just a flat paddle it wads up the curd into one large mass and pushes that around.
I am hoping to come up with something that will move through the curds and keep them some what separate as it turns
I came up with this. What do you think? it would mount into my agitator motor.

Offline Alpkäserei

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Re: creating a curd stirrer
« Reply #12 on: April 29, 2014, 09:41:51 AM »
Have you tried simply placing a flow-breaker on the side of the vat?

This is just a flat surface that interrupts the circular flow of the stirring, creating turbulence and backflow which keeps the curd broken up better.

A simple solution that may work for you.
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Offline steffb503

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Re: creating a curd stirrer
« Reply #13 on: April 29, 2014, 09:58:55 AM »
not sure I know what that is can you explain a bit more

Offline Alpkäserei

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Re: creating a curd stirrer
« Reply #14 on: April 29, 2014, 10:09:30 AM »
Just take a flat surface -a board, a piece of metal, whatever you have- and attach it to the side of the vat at a right angle to the vat wall. It sticks down into the liquid a good ways, 6 inches or so depending on the size of your vat, and a good ways toward the center -4 inches maybe. But not far enough to interfere with the stirrer.

It's very simple.

SO then when the paddle spins the liquid and curd, it will hit against this stationary object, which disrupts the flow. The eddy created at that point agitates the curd, keeping it from sticking together.


if your paddle is flat, you may want to put the flow breaker at a slight angle to the vertical, so that it creates a slight up and down flow as well. This will help the curd to mix around.

We have an angled paddle and a board that sticks straight in.

It's easiest when the stirrer is a seperate device that the flow breaker is just a part of the whole assembly, like in thes pictures via google (I don't feel like going through my pictures right now):


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