Long time reader, first time post. I've taken a lot of ideas from these forums, so I figured share a few of my own.
This winter we've been trying to cut back on heating, so the temperature dips considerably at our house at night. When I wake in the morning, it's usually well into the 50's. As you all undoubtedly know, this is bad for yeast growth on slants and in starters, so I was desperately looking for a cheap incubator. This led me to start looking at thermoelectric coolers like the ones that Coleman puts out, but I figured that I would have to build a controller to keep it within a couple degrees.
I had been looking around for a couple days, when I accidentally came across a product that Think Geek makes available on their website. Looking at the pictures I roughly figured out the height by the diameter and height of the cans. I was certain I could fit a one liter flask on my home made stir plate in there without any problems, but I didn't know if I could use a two liter flask.
Turns out that I was off by about an inch for the 2L flask, so all I needed was a lower profile stir plate and I was golden! So, for Christmas I had asked my SWMBO for Northern Brewer's low-profile stir plate
, but she thought it would be better to get me a chest freezer to convert into a keezer. I agree... God, I love her.
I however still needed a lower-profile stir plate than the one that I built, so I started looking around for parts. Since I was upgrading, I figured I'd change the design a bit to meet certain criteria.
One of my biggest complaints about my previous plate was the way that computer fans are mounted in most stir plate designs; one usually has to pad the top to prevent the flasks from resting on the screw heads. I also noticed that fan motors tend to not have as much torque to turn at their full speed, meaning that I couldn't get a really good twister going on a 2L flask.
I picked up a couple of cheap ($2) motors from All Electronics
, but I had to guess on their strength. I was lucky that they worked out well. Later, while in a kitchen shop I noticed a 2" deep, 6" aluminum cake pan which, when turned over, makes a perfect platform for a stir plate. Put those together with some custom bracketry made from 3/4" aluminum angle, a flywheel from a plastic gear and some magnets, a potentiometer, and a power jack and I've got a stir plate that cost less than $20, is half the height of my original, and is much
And while I was at it, I tapped the 12V line coming from the fridge itself. Now I can have my two liter flask churning away in my incubator without having to force the door closed on a second power line.
Right now I'm working on the Mk II version of the stir plate, which will feature a 3D printed flywheel that will be more balanced than the plastic gear that I'm using now. And while I'm at it I may have the bracketry printed as well.
More pictures can be found at the following links:BTW, I'm aware that some people have been having problems with instability when using an aluminum surface between the magnets and the stir bar. I've seen none of this once I discovered the proper spacing of the magnets (~1-1/8" for a 1" stir bar) and got them to within 1/16" of the surface.