Budget Stir Plate Build

[HisDudeness]

Thought I would have a go at making a stir plate as I have been culturing a few strains of yeast recently and hopefully it will help with that process.

Going for ultra low expenditure on this one so mainly used scavenged bits to build it. Bought the case fan, magnets and stir bar which totalled about £8, if you have an old PC lying around you could easily scavenge the first 2 as well.

The rare earth magnet poles are on the flat faces so I had to put 2 on end to end to get a North South face centred on the hub. Superglue and a bit of wiggling to get it spinning true and your ready to go.

 

[HisDudeness]

The magnets sit a bit proud of the fan casing so added some ply offcuts to the corners to act as spacers.

 

[HisDudeness]

Removed the PC connector from the fan cable and added a 1k potentiometer in series to the + lead for speed control and a 2.1mm dc connector socket at the end. This means I can use an old 12V PSU I had spare. The yellow lead is not used. I might add an ON/OFF switch later if I get round to it.

 

[HisDudeness]

Made the case out of some old 3mm ply and some scrap pine, feel free to mock my feeble woodwork skills! The top is 21cm sq and the sides are 4cm high.

 

[HisDudeness]

When the lid is fitted mark the centre on the inside and then fit the fan (magnet facing up!), I just used woodglue for this to keep the top free of screws/bolts.

This is as far as I got last night as the glue needed to set, will finish it off and test tonight hopefully....

 

[Chippy_Tea]

Great post HD, i think another member made one similar not long ago.

 

[HisDudeness]

Thanks Chippy, I just found this post http://www.thehomebrewforum.co.uk/showthread.php?t=28945
mine is definitely the ghetto version compared to the one in this thread! :lol:

 

[McMullan]

The way to go, HD. That looks very similar to my v1. What I found was that the strong magnets interfered with the fan starting to spin. I had to manually start it off. Seemed to get worse over time. But it done the job. Still working on v2, which has a stand off (short length of 32mm plastic tube) putting a little distance between the magnets and the fan motor. No more jump starts required and more control over the speed :thumb:

 

[HisDudeness]

Mine does start up ok but wont run at particularly low speeds probably for the same reason. Hopefully it wont deteriorate too much. Will see how it goes and may add spacers for magnets as well if required

 

[McMullan]

Here's my recent test run:

 

[HisDudeness]

Oooooooh nice gotta love a good vortex!

 

[McMullan]

Oooooooh nice gotta love a good vortex!

I call it 'Dorothy' It hypnotised my 6 year old son. I had to slap him round face to bring him out of it :-o

 

[HisDudeness]

I call it 'Dorothy' It hypnotised my 6 year old son. I had to slap him round face to bring him out of it :-o

:lol::thumb:

 

[HisDudeness]

Finished it up just now, wiring run in to case and controls mounted on front with nice retro toggle switch and speed control! Quick test with stirrer on top and it all seems to function well

 

[HisDudeness]

Used a big measuring jug to test with water and although the stirrer was a bit unstable due to the thickness of the jugs base it span and I got a vortex!!!
And yes I did then spend a fair bit of time playing with my new water tornado! :lol:

 

[HisDudeness]

Might put a coat of varnish on box to protect from inevitable spillages but otherwise job done:mrgreen:

 

[Chippy_Tea]

For forum member who may not like to ask could you explain its purpose.

 

[HisDudeness]

For forum member who may not like to ask could you explain its purpose.

Good point chippy, this is used for keeping yeast starters in constant motion to speed up growth and maximise number of active yeast cells by increasing oxygenation of the wort and preventing early flocculation.

 

[Chippy_Tea]

And of course it loook the business when doing its thing. :wink:

 

[McMullan]

For forum member who may not like to ask could you explain its purpose.

It's used for hydrated yeast (e.g. liquid and slopes/slants). It helps oxygenate starter wort. Yeast demand oxygen for efficient growth. Some argue against this, but ignore them. They're being too selective (biased towards fermentation) to appreciate the yeast for what it is and where it's from (wild relatives survive on tree bark, fruits, etc. and are exposed to AIR). The stir plate keeps the yeast cells suspended in the starter wort where nutrients are freely available. This is IMPORTANT. We often buy or have stored yeast in a 'sick' state of health (liquid, slurry, etc.) and they need to be nourished to recover, but might not have the capacity to suspend themselves (healthy yeast can, quite impressively too). And we need to build up/grow the population. Keeping them suspended in starter wort allows individual cells to get access to the required nutrients. The idea is to get as many cells as possible to recover to build a healthy (vigorous) population that guarantees a successful fermentation, after all the brew day effort. It's cheap to make and has been tested independently by millions of brews the world over. It works. Make one. Now!