First I would like to thank all of you here who have taken the time to design, test, build, and prove workable the smaller turbines. The information gathered here is a wonderful tool. After three days of reading, I think I am almost ready to start building, although I have a couple questions, as well as a request.
Due to my location, I doubt I could get away with putting up a 16 footer. I am limited to a "30 foot maximum height" according to the city's regulations. Therefore, I think if I make a small genny (5 foot rotor dia) and put it on a 20 foot pole (keeping the entire structure safely below the 30 foot limit) I should be able to run a good homebrew RE right across the street from a shopping center - which is a huge open space providing me with a fairly unobstructed breeze. After seeing the pitiful output from my solar panel investment (not knocking the no-moving-parts, no noise, almost zero maintenance, very expensive electricity generation device) now that the grey days of winter are moving in, I see this as the most cost-effective option for boosting my capacity (unless I can figure out the 5hp 15 degree differential stirling generator.)
(yes that was a joke)
Here's my thoughts on the design of the generator:
2500lb trailer spindle & 5 bolt hub (already in hand)
Single magnet disc (not sure yet if it will be a brake disc or a custom turned steel)
Still debating stationary laminate, or spinning disc laminate on backside of stator.
Trying to come up with a way to use .095 PCB for the stator, - not copper etched, but my thought is that if I can figure a way to locate the windings on the PCB & leave them open (aside from a thick coating of high temp black BBQ paint) there will be much less heat retained. Also, if I can keep the windings flat & thin enough to run a VERY tight gap, I should see decent output from this small mill.
Magnets already in hand - 12pcs 1.25 X .5 X .125 NEO's. I know the general rule here is to use the largest mags that can be fit. My hope is that I can make do with these, & I think at 5' I would have a hard time turning larger mags effectively.
One thing I am not completely clear on is the furling methods used. I understand the offset from vertical center creates the yawing force, but as for the hinged tail... If the tail is made rigid, would the surface area of the tail vs. the surface area of the rotor determine yawing? My thought is that a hinged tail would be a possible point of failure. Where this will be located, a hinge freezing & causing a self-destruct is not an option. Freezing is a definite consideration. High wind gusts are also not uncommon. Thinking of building this today I was listening to 60mph gusts howling past the house. If the tail must be hinged, can someone point me to a thorough explanation (drawings always make things clear) of how the hinged tail is setup & what makes it operate. There hasn't been much information I have run across explaining this.
Also, a thought on delta vs. star wiring... & an offer to try to help out with making small mills more efficient for all. If a very small line is added to the windings (5-10 turns, one coil?onephase?all?) to be used as a reference line - Could an automatic star/delta switch circuit be made to use that voltage as a reference for switching between the two configurations without any human intervention? I would be willing to add the line in on my stator if anyone with the knowledge would be willing to help with designing a control circuit to manage the switching. A proofreading afterthought - an addition to this control circuit to shunt the lines at a peak rpm. I don't know if this would fry the stator under this condition, but as long as the windings could manage it, this would be a nice failsafe for slowing things down when all else didn't. As I see it, after all the refinements that have been made by people on this forum, that seems to be one of the largest gains yet to be made.
Any comments or suggestions on this brain dump are welcome.
Thanks to all.
John K.
