Hard Disk Generator...
Part # 5 (Feb 11th 06)...
After several suggestions and a few general issues about
"Part#4" addressed via the otherpower.com
forum, I was armed with enough enthusiasm to wind several more test coils...
The main difference this time was the shape and size of the
coil center. Toward the end of the last post I was headed in the wrong direction
with the larger core, but rather, long thin cores would improve the output.
Shown are 150 & 200 turns of single strand, 75 & 100
turns of 2 strand and 3 strand.
The 3 Strand coils were a significant improvement on their
"oversized" core counterparts from 2 weeks ago.
|
|
Vac
1/4" air Core Coils
|
RPM
|
75t-3s
|
100t-3s
|
280
|
0.82
|
1.1
|
400
|
1.26
|
1.65
|
450
|
1.46
|
1.97
|
Given the above I was calculating a cut-in speed around 300
RPM with 12 coils wired in series and even planning to incorporate some form of
active switching that would dynamically switch half the coils over to parallel
boosting the charging current at about 500 RPM to double the cut-in...
Those days were swell... thinking about how I was going to use
all that power... How I'd automate as many steps as possible given that I'd
likely have 3, maybe four of these units flying once the ground thaws and more
towers could be installed.
The first step was to introduce as many new variables as
possible that could make tracking progress harder.
The image to the right is the first step in that direction...
I call it a "Sub-Stator".
The thin slots machined into the larger ring are positioned to
accurately place the coils equi-distant relative to the magnets spinning above
and below.
The cores were filled with a mixture of resin & high
density Black-sand.
The sand was sifted through a total of 5 times to remove as
much inert matter as possible.
The idea here being that if coreless coils performed as above,
"Cored" coils would work even better!
The idea of making the cores long and thin would minimize the
"Cogging Effect" on the rotors.
The sub-stator was to be 1/4" thick on it's base, so I
opted to re-enforce it with a single layer of woven fiber glass.
Unpredictable Variable #3 - If the test coils were tested with
a 5/32" gap (via the plastic strip), I'm unsure why I would ever have opted
to introduce 3/32nds more material, actually even more as the completed stator
can't be dragging on the rotors.
The base of the sub-stator was cast with an addition of
"John Deere" green alkyd urethane paint.
I have no regrets over this variable as it gave me a chance to
determine if laminating or layering resins is possible...
The ability to now colour parts is also something that
certainly will be useful in the future.
And indeed, Resin can be layered or laminated with good
results.
The sub-stator came out exactly as I'd hoped.
The coils were another story though... For what ever reason I
had convinced my self that I could wind the coils right onto the sub-stator...
No.
So the coils were hand wound and placed as best as possible.
Because the coils were less than perfect due to the winding,
it was obvious that 100 turns of 3 strands was out of the question, so I opted
for 75 turns.
The coils were wired 6 in series, leads hung free and the
other 6 in series with their leads hung free of the Stator.
With the sub-stator complete, it was centered and cast with
resin into the full stator mold.
Given that the coils were adding considerably to the over-all
height of the stator I aggressively clamped a top board onto the assembly in an
attempt to bring things back into trim.
After an hour of curing, the stator mold is opened to reveal
the assembly below.
Since I was on a resin experimenting kick, I opted to use a
"Construction Yellow" this time. As well I added approx 20% by volume
Talc to the resin.
In spite of my now over zealous modification to the
basic resin mixture I was quite happy with the mechanical strength of the
finished product even if the colour was slightly off from what I was aiming for.
I think that the above underscores the confidence that I had
in this incarnation of the stator, after all what could go wrong, I had the data
from the test coil...
Given that I have certainly made a commitment to this new
hobby of learning about power generation, I took the time to make a couple of
test bridge rectifier fixtures.
The 4 leads are wired to alligator clips for quick connections
and disconnecting for testing various stator assemblies.
Once assembled into the test jig and mounted onto the drill
press I pause to admire my handy work.
It sure looks slick...
Perhaps I shouldn't even test it, just assemble the frame,
make some blades and fly it as is...
Well, Fuck! after putting it through it's paces twice, and
double checking the simple electrical connections I was completely deflated.
The Cut-in speed was closer to 600 RPM than 300, and the
current was a meager 300ma at 700RPM into a flat battery that I'd run-down
specifically for this test.
As much as I wanted to revert to that child-like state where
anger is expressed with the hurling of objects and stamping of feet, I
restrained myself to about 10 or 15 minutes of profanity that erupted like one
that has taken to speaking in tongues.
Then it started to settle in where I'd gone so wrong, when
once this project held such promise. The Sub-Stator added some thickness, the
sloppy coils added some more, the way the coils were wired under the sub-stator
added even more. The overall height of the completed stator assembly required
that I cut a spacer to hold the rotors apart a full inch, actually 1.06" to
be exact, as I had to machine it off on the lathe.
The previous tests were performed with a 0.6" spacer so I
guess almost doubling the gap between the rotors would translate into half the
power or less.
Beyond the cost of materials and the time required to learn
such a simple lesson so completely I have few regrets. If nothing else the
experimenting with the resin was worthwhile.
So in conclusion, The next revision will NOT have a
sub-stator, but will aim for as close to an overall thickness of 0.5"
Max to return the rotors to their previous separation. The AWG#24 wire will be
shelved and a suitable replacement investigated.
I thought I'd end this segment on a more positive note and
include some pics of how I cleaned up my desk...
I cut the floor mount rack in half and bolted the upper
portion under the stairs with 1" by 1/8" steel straps into the Oak
risers of the stair case.
I like the way it looks like it's floating in mid air.
The bottom half of the rack is what I was after...
Looking at it now I can hardly believe that all that gear was
once on the desk itself.
The stereo, video and Digital FX units all interface into the
PC and are pumped out via the Peavey Speakers.