DIY Stir Plate

Looks good, but have you checked that you can get a good vortex with 5L? I should also think that a larger stir-bar would help in that regard, but have you checked that what you've built can rotate a larger stir-bar reliably?

Again, looks great...just curious that you can do what you've planned.

 

I get a good vortex in water too, but when you add yeast...especially after they've begun multiplying, I find that I have to turn up the speed a bit to keep a good vortex.

Keep us updated on it, I hope everything works as planned.

 

I don't really know. I bought a stir-plate with a similar design, and it explicitly states that it will not work with the bigger stir-bars, which is why I was curious about yours. I haven't opened it up...so it could be that your fan has a larger diameter...which could make the difference.

 

Looking at your first photo, you should easily be able to spin a 1.5" stir bar and probably 2". This based on the spacing between your two circular magnets glued to the fan blades. My results with a home made stir plate were exactly as JohnSnow posted: 2L of water gave a great vortex, but I limited out at 1.5L of yeast slurry. Those little yeast buggers are no push-overs and don't really like being spun around.

I believe the concern is over the torque of the fan and how that is transmitted to the stir bar ... but I struggled mightily with dynamics ...

Hope the quad goes well and the oxygen you add to it will also do wonders in the yeast starter.

 

I'm in the midst of making my own, what did you use for a speed regulator? and with the fear of hijacking, that looks like a 9 volt fan, will the 5v i have be big enough?

 

you will need to match the potentiometer (aka speed control) with the fan. and you will want to provide the proper voltage, more or less, by using the right voltage regulator (an AC/DC convertor, aka wall wart, think about it...)
there are a lot of websites that can tell you exactly which Radio Shack parts to use. otherwise, got to a RS store, explain what you want to do and hopefully there will be someone there who knows electronics. not very hard to do. some time with Google to match your fan with a pot and voltage regulator is needed if there is no pro help. then you just have to follow a simple wire diagram and solder.

that is a really nice job on the stir plate btw.
Cheers.

 

thank you much

 

Not really sure . . . my feeble knowledge of magnetism makes me think it is vital to keep the N/S orientation intact. Maybe stack the magnets but adding them side-by-side might confuse the stir bar. If anyone has experience . . . please chime in.

I would not even think about brewing a "big, big, quad" without oxygen. Pumping air through a diffusion stone will leave the yeasties gasping. Oxygen in starters also gives them a jump-start.
http://www.wyeastlab.com/hb_oxygenation.cfm

Another big improvement with a stir plate is the time you save with starters. When everything clicks correctly you can have krausen rise and fall in much less than the normal 24 hours. It is common to complete the starter cycle in 12-18 hours . . . speeds up the whole brew process.

 

That look very cool. Can you publish the parts list?

 

The Wyeast link answers your question. You can call an ambulance right before pitching yeast . . . they always have oxygen on board.

 

Grate looking SP, Nice work

 

Thought gasping meant yeast would not get enough oxygen via a diffusion stone.

That is correct. With air only (shaking or stone) your max saturation of oxygen in wort is 8ppm. Wyeast recommends at least 10ppm for most beers. For a big big quad you need higher levels and that is only possible with pure oxygen. Lack of proper oxygenation will lead to inadequate yeast growth and associated problems. You have a first class stir plate and 5L flask . . . don't stop there.