For two years a 3D Printed axal wind turbine has been happily freewheeling on the fence outside Hammerspace. We call it our Whirlygig, and the constant Missouri wind really gets it going. Now it’s time to turn our whirlygig into a source of electrical power!
A Turbine with History
The Whirligig was one of the first projects I 3D Printed with my shiny new MakerBot Z-18, Its segments were designed to take maximum advantage of the printer’s 12 x 12 x 18 inch build volume.
Unfortunately MakerBots 5th Generation product line had a rocky launch. The interchangeable Smart Extruders needed more testing and development and had an exceptionally high failure rate, sometimes after only a few hours of use. Both segments of the Whirligig show evidence of under extrusion and skipping. At the time I was happy these parts came out at all, and used Bondo to strengthen the weak segments.
The Turbine’s Design
The Whirligig is a basic Axial Wind Turbine design. Its printed scoop segments spin on a shaft which is just six foot long piece of gas pipe. A ¾ inch delrin sphere at the top of the turbine acts as head bearing and two large metal bearings between the segments keep them spinning parallel to the shaft. Splined couplers tie the spinning parts together and allow limited flex and movement between the segments.
Each segment is made of three corkscrewing scoops. The wind direction here in Missouri is unpredictable, rapidly changing speed and directing. A corkscrew arrangement guarantees that some part of the turbines scoops are always facing the incoming wind.
Two Years in the Elements
It was interesting to see how it how two years in the elements had affected the Whirligig’s 3D Printed parts. It’s made from a mix of ABS and PLA plastic. ABS for the load bearing parts like brackets, and PLA for the large detailed parts like the scoops, couplers and bearing surfaces.
Before I could pull it apart for closer inspection, I had to cut away the accumulated vines.
Amazingly the PLA parts showed almost no degradation at all. The color hadn’t faded and the plastic was still as strong as the day it was printed.
The ABS parts where another story. Both brackets were badly sun faded and had begun to lose their layer to layer adhesion. I could practically pull them apart in my hands.
The ¾ inch delrin sphere and PLA bearing cup that rest on it were still intact, with only limited evidence of surface wear. The gas pipe cut a deep ring into the base of the sphere, but two years of spinning in the Missouri wind did surprisingly little damage.
The two sealed metal bearing where another story… Water got to them, probably through the gaps in the 3D Printed parts.
Upon inspection I realized the two bearing hadn’t been in contact with the wall of the gas pipe. They had only been acting as bushings, keeping the pipe centered in the spinning turbine. All of the weight of the Whirligig’s spinning parts was being supported by the ¾ inch delrin sphere. Delrin is impressive stuff!
What We're Going To Change
For the Whirligig to generate electrical power we’re going to need to add some kind of generator. There are a few ways to do this.
My first inclination is to build a three phase alternator. An alternator uses magnets spinning over coils of wire to generate power. The advantage to this is there is no direct mechanical connection between the spinning turbine and the generator. The magnets are placed in a ring attached to the turbine blades, and the coils are held stationary attached to the gaspipe. The downside is that I have to build 100% of the system from scratch.
The second option is to use a stepper motor as a generator. It has the advantage of being an off the shelf component, but is mechanically is much more complex to attach to the spinning turbine.
In the next two articles, I’m going experiment with each of these methods of generating power. Ultimately I will chose one to power a display on the Hammerspace Fence.
Until next time!