First outing for homemade stir plate

[Simonh82]

I've just cranked up my homemade stir plate for the first time to make a starter with Wibbler brewery yeast. It was also the first outing for one of the erlenmeyer conical flasks that I bought for this purpose.

I was pretty nervous putting the flask directly on my hob and heated it up very slowly and carefully but all was fine. Next time I'm going to just use boiling water to dissolve the DME in. I don't know why I forgot this time.

It's really nice boiling the wort in the same vessel I'm making the starter in as it reduces the chance of contamination.

Once I'd boiled it for 15 minutes I left it to cool for about half an hour. Once it had cooled down a bit I put it in the sink and added warmish water. When this bought the temperature down further I swapped the warm water for cool and continued the cooling till it was about 25°C. Again I was worried about cooling to quickly so may have been overly cautious but I didn't want a sink full of shattered flask.

Then it was on to the stir plate. I was concerned that the stir bar wouldn't stay in place when it was switched on but so far so good. I'd had quite a few problems getting the magnets centred and balanced when I was building it but I wonder if the more viscous liquid helps keep it on track.

I'm hoping it stays spinning all night and hopefully I'll have a cracking starter in a day or so.

 

[Simonh82]

Well at some point during the night the fan heated up enough to melt the glue that held the magnets on to the fan. I used a UHU water based glue which took ages to set and I'm regretting that now. I need to scrape it off and start again with some super glue or araldite.

For the moment I've stuck it back on and set it going again with strict instructions for my girlfriend to keep an eye on it. Still it was clearly fermenting away nicely by 7am this morning, which is pretty quick for a yeast that has been in the fridge for 3 months.

 

[MyQul]

This is why I'd never make a stir plate. My DIY skills are virtually non existant and I'd worry that I burn the whole of Peckham down in a massive electrical fire

 

[RichardM]

That looks good. I can see my next project coming. What did you use for a power supply and what value is the speed control pot?

 

[Dutto]

Well done!! :thumb: :thumb:

I used Araldite Rapide but found that the relatively slow setting speed allowed the magnets in the fan motor to drag the Stir Plate magnets out of position. I had to wedge the magnets in place with bits of plastic until the Araldite set.

The photograph is of the "finished" Stir Plate. It worked okay but at high speeds the stirrer magnet flew off before it pulled a satisfactory vortex.

Fortunately, a cheap Kindle cover came apart about a week later and two 2cm flat magnets fell out. They are magnetised on the flat sides rather than the ends so they gripped the two little magnets, increased the magnetism holding the stirrer and as a result the Stir Plate now works perfectly and will pull a vortex all the way down to the magnet itself.

I use an old 12v battery as a power source and I'm well pleased with the result for an outlay of about £15. :thumb:

 

[Simonh82]

I used a 12v DC power supply that I got off ebay for a few quid. I looked for an old phone charger but all mine were too low voltage.

Apparently the glue came unstuck yesterday whilst I was out at work so it sat for a few hours without being stirred. When I got home I clean off the old glue and used some superglue to stick it (and my fingers) together. Then I left it running for a few more hours.

I'm pretty pleased with the results actually. Given that it had two prolonged periods of interruption and was only going for about 24 hours, I got quite a bit of yeast from it.

I reckon I've got about 2 billion cells in the dense yeast layer at the bottom.

 

[MyQul]

stir plates are definately the bollards when it comes to yeast propogation

 

[GlentoranMark]

Can you buy a cheap version? The only stir plates I can find are laboratory ones £50+

I have an old PC I could take the fan out but I'd prefer to buy a ready made one for under £20 if possible.

 

[MyQul]

Can you buy a cheap version? The only stir plates I can find are laboratory ones �£50+

I have an old PC I could take the fan out but I'd prefer to buy a ready made one for under �£20 if possible.

I had a quick look on ebay and I couldnt find anything either.

If like me your DIY skills are **** and you cant make one yourself, a kindly forumite might make one for you for parts plus P&P?

 

[Soton]

Can you buy a cheap version? The only stir plates I can find are laboratory ones ��£50+

I have an old PC I could take the fan out but I'd prefer to buy a ready made one for under ��£20 if possible.

I have this one
http://www.ebay.co.uk/itm/262552237...49&var=561409351997&ssPageName=STRK:MEBIDX:IT
It works great and was about the cheapest I could find

And there is this
http://www.ebay.co.uk/itm/DIY-magne...3846b2c&pid=100005&rk=1&rkt=6&sd=262552237901
one but you might have to make a box for it

 

[serum]

From your pic it looks as though your magnets are too close together and that's why the bar didn't stay in place. If they're right next to each other it puts strain on the fan. I use a flat metal bar which the magnets stick to with a rubber spacer between them. Once i got the spacing right the fan spun much better and the bar stayed in place.

I'll try find you a link for the metal strips as they're really handy.

 

[GlentoranMark]

Thanks guys, on my last trip to Geterbrewed I actually bought a flask with the intention of building/ buying one.

 

[Simonh82]

From your pic it looks as though your magnets are too close together and that's why the bar didn't stay in place. If they're right next to each other it puts strain on the fan. I use a flat metal bar which the magnets stick to with a rubber spacer between them. Once i got the spacing right the fan spun much better and the bar stayed in place.

I'll try find you a link for the metal strips as they're really handy.

I did have the magnets spaced further apart but actually found it ran better like this. They are sat on top of half a cotton reel so are fairly far away from the fan and don't slow it down.

It wasn't the stir bar that was coming loose, rather the cotton real came unstuck from the fan hub.

For anyone considering making one it really was very easy. I found some wiring diagrams online which included some fairly complicated additions and after buying all the bits realised I didn't have a clue, so just wired the potentiometer in line and put the other bits in a cupboard.

 

[serum]

I did similar, tried a complicated circuit which didn't work and then just wired it up with a switch and used a power adapter with switchable voltage. Works a treat.

I've got round magnets rather than the long ones. I found having them close together meant the motor wouldn't spin as fast for some reason.

 

[Simonh82]

Thanks guys, on my last trip to Geterbrewed I actually bought a flask with the intention of building/ buying one.

If you are looking for conical flasks check out www.betterequipped.co.uk. They are the only place I've found 5L flasks for something I would consider a reasonable price. The search on their site is a bit rubbish so search for 5000ml rather than 5L.

Their smaller flasks are really reasonable but you do have to pay postage unless you order loads.