Australian Stirplates - Need Testers

[pbrosnan]

That's about how much I paid for my stirplate posted from America...

Mind you that was when the AUD was @ 92c to the USD, if it slips back below .80 or .70 it would be a lot more.

Don't want to thread hijack but do you have any more info on that? The one I bought from the US was at least 3 times that. The one on offer here seems very reasonable.

cheers

Patrick.

 

[MeLoveBeer]

Hmm... had problems overnight with my stirplate and starter

Monitored it for about 3 hours before going to bed last night, but woke up this morning with the stir bar off its axis, no whirlpool and then had trouble getting another one going before leaving for work. My suspicion at this stage is that the fan and magnets have moved in the box.

Will have another play this evening and see what I can determine.

 

[megabyte]

My suspicion at this stage is that the fan and magnets have moved in the box.

Darn.. I was afraid this could happen on your unit as well as florian's. I suspect that the fan has come unstuck from inside the lid of the box.
It's stuck on with this stuff: - which is useful because it's just the right thickness to keep the magnets close to the lid of the box without touching. It's meant to be very strong in its intended application, but there isn't much surface for contact on the fan itself, so over time, or with manhandling it seems that it can come unstuck.

This happened to me just recently. I hoped it was a one-off event, but still on the units I finished on Monday night and last night I added a small dot of superglue to the fan before attaching the tape and it seemed to hold the fans on a lot stronger. Florian's and yours were the units I had already constructed and packaged previously so they didn't have the glue addition.

If you know your way around a screwdriver you can fix it by opening the box and reattaching the fan by firmly pressing it back onto the tape on the lid of the box and if possible, I would also recommend adding a dot of superglue to the corners of the fan before you reattach it to make sure it stays there for good. There's a chance that it was dislodged in the post and you may not need any glue at all but it wouldn't hurt.

If you don't feel up to the job, just PM me and I'll be happy to ship it back and fix it at my cost.

Cheers,
Mick.

 

[MeLoveBeer]

No worries Michael, I'll have a crack at it and will let you know how I go.

 

[MeLoveBeer]

Ok, I've just opened it up and the fan has come loose. Maybe its worth screwing the fan into the bottom of the case with 4 long screws and spacers? (to adjust the fan to the correct height) Should only add about 50c to the build cost and would be much more robust.

 

[MeLoveBeer]

Right, so after re-securing the fan, the unit has now run for approx 14 hours without skipping a beat (with a 2 litre starter). At this stage I haven't used superglue or anything to reinforce the bind, just pushed the fan back on to the strips.

My intial comments are as follows:

• Would be nice if the unit had some sort of indication as to where the fan is located so you can easily center the flask on the plate. Its nice and easy when you're testing with clear liquid, however you can't see through a starter where the magnet centers itself
• Perhaps its worth looking at the possibility of centering the fan in the case; this would mean a larger base and increased stability for large starters and would make it heaps easier to center the starters on the unit (see the comment above)
• I think it would be worthwhile securing the fan from the bottom of the case with long screws and spacers to get the right fan height; I'm just not convinced that the tape will hold for the long term (even with superglue)

Got to say that I'm very happy with the unit overall and will continue to supply feeback.

 

[megabyte]

Thanks for the feedback melovebeer. All very good points!

• Would be nice if the unit had some sort of indication as to where the fan is located so you can easily center the flask on the plate. Its nice and easy when you're testing with clear liquid, however you can't see through a starter where the magnet centers itself

That's a good point. The fan is about 2cm off center to make space for the PCB and wiring. It never bothered me since I built them myself and already knew where the fan would be, but it's not right for me to expect you guys to guess it. I found that if you just put a stirbar onto the top of the box and run it for a few minutes (not in a flask), the bar will leave a swirly circle mark on the stirplate which may help a bit. Still, your next point is the ideal solution.

• Perhaps its worth looking at the possibility of centering the fan in the case; this would mean a larger base and increased stability for large starters and would make it heaps easier to center the starters on the unit (see the comment above)

Agreed. This could be solved by either using a larger project box or revising the layout inside the existing box so the fan can be mounted in the center. The larger box sounds like a better option, but aside from the increased parts cost it will also be more expensive to post so we need to keep that in mind. Either way, you're right. Something needs to be changed to get the fan mounted in the center.

• I think it would be worthwhile securing the fan from the bottom of the case with long screws and spacers to get the right fan height; I'm just not convinced that the tape will hold for the long term (even with superglue)

I will look into getting some spacers to mount the fan to the base. This may not be so easy since spacers only come in specific lengths and the distance from the stirbar is critical to performance. If I can find a suitable spacer, it shouldn't affect the parts cost significantly, but it will make the build take a little longer with the extra drilling. I agree that it's a worthwhile improvement though to know the fan is there to stay. Then the unit would be practically indestructable!

Once again, thanks for the feedback. All very good points which I'm happy to take on board.

 

[MeLoveBeer]

Sounds good Michael. If you find a solution to the fan mounting (the spacers etc), any chance I could get details so that I can make the same mod?

 

[daryl5412]

I mounted the fan with long small diameter (say 3mm) countersink bolts when i manufactured my stirplate. Get some extra nuts and washers and lay it out like this

drill through lid of the box and countersink the outside of the lid.

screw-lid-washer-nut --> nut-washer-fan-washer-nut.

This way the fan can be moved up or down to suit the magnets. It also gives you a reference from the outside where the centre of the fan is.

:icon_cheers:

 

[megabyte]

Sounds good Michael. If you find a solution to the fan mounting (the spacers etc), any chance I could get details so that I can make the same mod?

Of course! I'm still not sure about what spacers will work. I'll do some measuring tonight and see if they are readuly available. I'm still not certain this will work though since even if it's a couple of mm too short you'll be throwing the stirbar at lower speeds.

Now throwing the stirbar, that's a topic I'll have to discuss more in this thread when I get a chance..

 

[megabyte]

Hi Guys, just a few updates...

Firstly I'd like to thank everyone again for all their interest and willingness to help out testing the stirplates. We've had a few teething problems with the fan mounting and I'll be very interested to hear if anyone else has the same troubles.

A couple of stirplates haven't shipped yet as I'm still waiting on their payments. I'll send another PM to these guys this afternoon.

Recently I mentioned I would discuss the topic of throwing the stirbar. This occurrs at high speeds when the stirbar succumbs to the forces of friction and chaos and the magnetic pull from the magnets in the stirplate isn't strong enough to hold it in place. At high speeds the stirbar can come "unstuck" at which point it will stop stirring and just bounce around in your wort (this is where stirbars get their nickname - "fleas"). There is no automatic recovery from this scenario. Once it's bouncing around it won't start stirring again until you manually reset it. To do this you have to stop the stirplate, reposition the stirbar so it's held back in place by the magnets, then gradually ramp up the speed again. This can take a bit of a knack if you've already pitched your yeast and can't see the stirbar inside your flask.

As you can imagine, if you're asleep or away from your stirplate when the stirbar is thrown, you might come back hours later to find that it hasn't been stirring the whole time. Not. happy. jan.

Anyhow, the trick to reliable stirring is to choose a safe, moderate speed.

If you stir too slow, you risk the motor staling if for some reason it encounters more friction.
If you stir too fast, you risk throwing the stirbar and it has also been suggested that this may stress the yeast. There is a very wide envelope of speeds that are acceptable and reliable and I usually just aim for a medium speed where there is about an inch of vortex in the surface of the wort.

After choosing a speed, it pays to make sure you're safe by moving your flask around and even lifting it a few milimeters from the plate while it's running. If it is still stirring after this test it's very unlikely that it will stop working while it's unattended.

So why build stirplates that can spin so fast?
The speed of the stirplate is relative to both the characteristics of the fan motor and the voltage it is run at. By changing one of the resistors in the regulator circuit it would be possible to limit the maximum voltage supplied to the fan, restricting its speed to make it harder to throw the stirbar. However there may be some cases where a bit of extra power is required, especially if larger stirbars are used. Knowing the information above, I'm confident that any user can select an appropriate speed for highly reliable stirring.

There is also another reason why the stirplate speed is left unrestricted and I'm open to speculation about this one. I found that when using a smaller flask, it is possible to stir it so fast that the vortex in the surface of the wort can reach all the way down to the stirbar at the bottom of the flask, churning air into the wort. I found this useful as a sanitary way of aerating the wort before pitching yeast.

So it goes like this:
1. Add water and malt extract to your flask.
2. Bring it to a boil in the microwave to sanitise.
3. Cool it to desired temperature in an ice bath.
4. Drop in sanitised stirbar and aerate with stirplate at high speed.
5. Slow down the stirplate to a safe speed then pitch yeast.

I've used this method a few times for reactivating yeast cultures, however it may be overkill.

Keep the feedback coming guys,
Cheers,
Mick.

 

[bjay]

Just got mine in post ,,, will have a mess around tomoz

bjay

 

[QSR]

No reply from sent PM ??

 

[megabyte]

No reply from sent PM ??

Sorry QSR, I have no record of any PMs from you. :huh:

Have I missed something?

 

[QSR]

Yes Michael........just checked my sent messages..........this is twice now in about a month that I have sent PM's to people and they have disappeared into cyber space ( sorry, not your fault ).....dont know where the messages have got to.
I was wanting to order one of these stir plates from you.........but I suspect you probably do not have any left by now though do you?
If you have please PM me ( if it works ) with your account details so I can pay you please.

 

[megabyte]

Ahh I see. Darn.

Sorry you missed out, all stirplates are accounted for now. There were lots of takers and not enough to go around but that could be a good thing if I can't address some issues.

I have more parts on order though so there will no doubt be more available at a later date, just gotta fine tune the design a bit first.

Stay tuned,
Mick.

 

[MeLoveBeer]

Bit of an update Michael... the stir plate didn't skip a beat once I resecured the fan (ran it constant). Pitched a healthy 2L starter into a pilsner about 3hrs ago and already seeing plenty of activity.

 

[megabyte]

That's great news.
It's good to hear some positive results.
Let me know if the fan comes unstuck again.

-Mick.

 

[The Scientist]

I love the idea of being able to turn the speed up to oxygenate the wort before pitching. Now thats an impressive vortex, even my blender will be jelous

 

[bjay]

I have mine spinning with just water as i dont need a starter just yet,Maybe get one going next week
seems pretty quite and the speed control is good,I will leave it running for a while to see how it goes
What would be good would be a timer of some sort ,So it only comes on every hr
The stir bar is not to hard to get located once you have done it a few times

bjay