agitator instead of stir plate

I had issues making my stir plate work when I built it and now that I actually need to use it, its still got issues. Then I had a eureka (maybe). What about an agiator instead. Right now I have the stir plate tilted slightly, some tape creating a ledge to keep the flask in place and am just letting the little magnet scramble about. If the motion does not have to be circular in nature then shouldn't any comotion help the yeasties reproduce faster?
I'm tired of trying to make my stir plate work, so I'm going with this idea now.
Any thoughts???

I would just try getting your stir plate to work as a stir plate. I built one a few weeks ago and it works great. If you post what is wrong with it I'm sure we can help you get it going. They are extremely simple little contraptions.

I would think that a stir plate would be able to do a better job at keeping all the yeasties in suspension better than agitating.

It's better than nothing, however part of the idea of the stir plate and bar is to get the vortex which introduces constant air into the mix causing better "reproduction" in the yeasts early stages which is the goal of the starter process anyway. What is wrong with the plate?

Technically, you don't NEED to have a stirplate to make a starter anyway. You could just say "eff it" and shake the starter up whenever you walked by it to introduce O2. So, I would imagine that the agitation wouldn't be a bad thing. Might now be any better than just shaking, though, Would bug the **** out of me to hear it bouncing around constantly.

"Would bug the **** out of me to hear it bouncing around constantly."
Thats why its now on the porch.
The O2 thing makes sence. But if fish aquariums just require a minute amount of surface movement, mabe this would be enough.
My problem is that I can not get the magnet to stay spinning longer than 20-30 seconds. Last year when I built it I tried everything from lower voltage to changing the space between the fan and surface of the plate. The magnet is from a hard drive and it is centered. I'm just about done trying.

Having the stir bar get thrown can be caused by three things.

1. Your fan is too high of RPMs and you never slowed it down far enough for it to work.
2. Your magnet isn't completely centered.
3. You dont have a strong enough magnet.

I made mine with small disc magnets and with only one on each side it would throw the stir bar. Stacking a second set of magnets on top of the first ones allowed me to turn it up about half way before it would throw the bar. I ended up with four of them stacked up at each end and I havent had any problems with it throwing the bar.

It sounds like you need another magnet on there or switch to a stronger one.

Edit: one more thing, do you have a pot to adjust the speed? I noticed while I was playing around with the different number of magnets that if I started it at full speed it would throw the bar, but if I started it out low and then increased the speed slowly that I was able to get it going faster that way.

What are you putting the starter in? Does it have a smooth, flat bottom?

You could also try a small stir bar if you can find one.

Go figure... I stacked a second magnet on top of the other and am having much better luck now (knock on wood).
Thanks

crane said:

Having the stir bar get thrown can be caused by FOUR things.

1. Your fan is too high of RPMs and you never slowed it down far enough for it to work.
2. Your magnet isn't completely centered.
3. You don't have a strong enough magnet.
4. Your stir bar is too long (or short) most folks seem to like a 1" or 1.5"

Click to expand...

fixed that -

Overall, I agree with crane's #1. I have to start mine very slowly, and it never reaches high-speed...
if your stir bar moves at all, there is probably sufficient magnet-to-stirbar attraction for this to work (although if it's too strong, that causes trouble too). Work on the speed control portion so you can get that fan to turn slowly. Then you'll be on the right path.

sashurlow said:

Go figure... I stacked a second magnet on top of the other and am having much better luck now (knock on wood).
Thanks

Click to expand...

Great. I am glad we could help. As HG mentioned if you don't have a potentiometer for speed control you should add one.