I have been meaning to post these pics for a few weeks now. My aim is to build an alternator that comes as close as I can get to matching my 7.5m diameter helicopter blades (obtaind for free). Given my limited resources ($$$) I doubt I can get to the 10kW @ 200RPM that I need (the magnets I should use are too expensive for me), but I want to get as close as practical so that I don't have to chop too much off the length of the blades to compensate. I have managed to source (for free!) a truck axle and suitably sized rims to enable me to build a dual rotor radial flux alt. I have been collecting microwave magnets and currently have approx 100. I also have 80 odd 3/4" diameter x 3/8" thick neos whick fit nicely in the hole in the centre of the microwave magnets. My plan is to double up the micro mags and put 24 rows of 3 on the drum, with the same number opposite on the inside of the larger rim. This will give me a total of 144 doubled up microwave mags (288 mags in total) so I'm going to have to dismantle a few more microwaves yet... I'll order more neos to suit (cost me US$1.40 each including freight to NZ and are the only thing I have paid for so far). The axle/drum weighs weighs over 150Kg (~350lb). The rims weigh another 60Kg (130lb). The blades themselves only weigh 10Kg (22lb) each. The brake mechanism is operational and will be retained for emergency operation.
This is the axle showing two of the three rows of mags I plan to fit. There is a ridge on the drum that needs to be machined down to fit the third row. The larger rim is mounted over the drum with the smaller rim to be used to fix the blades mounted out the front:
The drum with magnets from the front:
The drum from the rear showing the brake mechanism:
The rims mounted on the axle:
A view from the back showing the location of the magnets:
This is only a mock-up so the magnets are not precisely placed. I plan to make some 'seats' for the magnets to improve the coupling to the drum/rim and to close up the air gap. Depending on finances I may only fit neos to the topmost microwave magnets and fill the centre of the lower ones with iron.
The stator will be 3 phase overlapped coils cast in resin forming a cylinder that will be mounted off the axle in between the magnets. At this stage I plan to have the blades fixed (no pitch control - unless I can come up with a way to accomplish this within the resources I have available...) I don't plan to have a tail but hope to use a wiper motor to turn the unit via a wormdrive (using an flywheel from a car). Given the power I hope to make, I think that 48V is the only sensible option to limit the current to reasonable levels.
I am really out on a limb here with reagrds to how much power I am going to make. I have no way to gauge even if I'm going to get anywhere near my target. Worst case is that I end up with a really heavy 15 foot odd turbine...
Comments welcome!
