Project Table of Contents
- What kind of energy should I harvest?
- City ordinance and neighborhood considerations
- Installing the tower base
- Building and securing the tower
- Building and installing the wind turbine
- Selecting the type of turbine
- Choosing AC or DC
- Prototype, aka “Mark 1”
- Building the “Mark 2” (this article)
- Video of the finished Mark 2 in action
- Preventing “reverse flow”
- Regulating and controlling the charge
- Dump Loads
Building the “Mark 2”
For my second stab I decided to go with “all new stuff,” after all, my turbine would become the first one in my city, and I wanted it to be good looking and function well.
Many of the wind turbine hobbyists are using an Amatek 38 Volt DC motor for their projects. This motor outputs pretty well, and is above the 12 volt’s needed to start charging batteries. I bought one on eBay for about $60 delivered.
This motor doesn’t have a hub with it like my treadmill motor did, so I purchased an aluminum hub and 5.8”arbor on eBay for about $25 delivered. You mount the blades to the hub using nylon lock-nuts, and mount the hub assembly to the arbor with a machine screw (75 cents at Ace Hardware), then slide the arbor over the motor’s shaft and tighten it down using the set screws (included with the arbor).
The Mount and Tail
Next, I upgraded from my tail mount to a custom-built furling mount I bought on EBay ($30 delivered). This tail should pivot a bit easier than my old one, it looks better, and should furl the blades out of the wind should the wind get too strong.
Putting the Whole thing Together
I covered my motor with a section of ABS pipe (I used 3-inch, you should use 4-inch to make it easier). This will keep the rain, sleet, and snow (and subsequently ice) off the motor.
Next, I bent some threaded bar around the motor and through the tail mount’s holes, and secured it with washers and lock-nuts (under $5 at Ace Hardware). I attached the tail at this time.
I had to do some grinding of the top part of my tower (which is a 12-inch length of 1.25-inch thick-walled pipe nipple). The thick-wall made the nipple too thick for the tail’s pivot to fit around. An hour on the grinder and I had a near-perfect fit that pivoted freely (this also got me out of watching most of Mystery Science Theater 3000’s Manos, The Hands of Fate).
I mounted my PVC blades (6 of them) to the hub, and attached the hub to the arbor, then set the whole head assembly atop my prototyping pole.
This design starts up well in low winds, but doesn’t get spinning all that fast, so before mounting it atop my tower I reduced the number of blades to three.
Of course, the wind wasn’t blowing, so it’s just sitting there atop the tower. On Halloween day 2008, the wind finally whipped up enough to set it spinning atop the roof (see next video). I had the wires shorted at this time since I was still working on securing the guy wires, hence why it’s spinning so slowly.
Once I had the guy wires fixed, I still had some noticeable “thunk thunk thunk” vibrations coming from the turbine: my blades weren’t well enough balanced. I again shorted the wires to prevent any damage.
That night the wind whipped up. The torque being put on the blades was so great that it wanted to spin the hub separate from the arbor. Ironically, the blades that I used were still for the rotation of the old treadmill motor, and unscrewed the machine screw holding the hub on the arbor. The entire hub assembly fell to the ground. Nothing was damaged, not even the blades. Rather than refining my blades, I decided to buy a set of blades, again from eBay (about $80 delivered).
These new blades are sharp as a knife and have a perfect airfoil to them. They are just about the same length, but should enable (and withstand) much higher speeds. Speed, after all, is what you’re after: the faster your blades spin, the faster the motor/generator spins, which yields exponentially more power, and power is what we’re after.
I mounted the blades last night (this time with the right rotation to them) and my wife and I raised the tower again. We secured the tower to the house, then guyed it in place.
The Murphy’s Law of Wind Turbines has cropped up again, it says that you won’t have any wind for several days after you raise your turbine. So far every time I’ve raised my turbine that’s been the case.
Right now the motor is “unloaded” (meaning I don’t have any batteries or other load attached, and the wires from the motor aren’t shorted). This means that the turbine will spin freely. As soon as I see that happen I’ll post another video.