Copyright 2009 Craig Carmichael - June 3rd 2009
May in Brief
Detailed newsletter articles are posted on the Turquoise Energy
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Electric Hubcaptm Car Drive
Project, Longwinded Detailed Report
* Torque Converter first test, spins car wheel May 20th. Movie.
* Torque Converter Induction Rotor design: An axial flux adaptation of NEMA "Type D"?
* EH Power (oops): consumes max 5400 W (7.2 HP)... Not 3600 W (4.8 HP).
* Copper Loss Calculations: inefficiencies at high currents. Better at lower drives.
* How Much Electric Power is Required?: a 4 HP, 50 Km/Hr, converted car.
* Reconfigured motor free-spins: lower current draw when not turning car wheel.
* Optical Commutator and simplified motor controller with MC33033 chip.
* Micro-Ferrite Ceramic Motor Coil Cores with Niobium?
Turquoise Battery Project,
Longwinded Detailed Report
* Nickel - Iron battery experimentA Great Electric Generator?
* Some Battery Design Principles
It looks like the common lawn mower motor is the fabulous cheapo DC
generator everybody wants but can't find for windplants, micro-hydro,
Bipolar Division of Labour?
Inevitably, having entered the Electric Hubcap in the New Ventures BC
competition, I spent considerable time doing up a business plan.
I don't know what the judges will think of it, but it has some unusual
aspects - such as "open technology" and welcoming competition - that
fly in the face of expected "standard business strategies" and should
make for interesting reading!
Work on the reconfigured motor and torque converter
proceeded at a leisurely pace. By the middle of the month, the motor
spun on the car (I have no other mount for it) without the torque
converter ready. Without having to turn the car wheel, it accelerated
much more quickly and the current draw was much lower.
I finished the first trial torque converter on the 19th,
but I only
had four weaker supermagnets available, which I stuck on with double
sided carpet tape. It transfers torque with slip, allowing the motor to
run faster than the wheel, but the actual torque at the wheel isn't
higher: it's a "torque resistor" instead of a "torque transformer". I cut some radial slots in the induced rotor
that made it into a better rotor - a "non-linear torque resistor" with
a torque curve more like an induction motor rotor (a la NEMA "Type D").
But like the fluid torque converter, it needs a third
element: a non-spinning fulcrum that converts the magnetic torque from
the motor into electricity, and then the electricity back into "geared
down" magnetic motion at the output rotor. This should work - and is
probably potentially quite efficient (ie, better than a gear; certainly
better than a fluid torque converter) - and I'm now figuring out the
hazily glimpsed details of actual operation.
I made a nickel iron battery and, while one wouldn't call it a success as such, in making a chemistry that's known to work and
analyzing the results, I've clarified some important battery design
details in my mind that should make quite a difference on the next
May also finally saw the end of the long continued unpleasant weather, considerably assisting doing work outdoors.
HubcapTM Vehicle Drive Motor
Magnetic Torque Converter: Torque Leverage Without Gears
The magnets were ordered near the beginning of May, but there were some
delays owing to travels of the person I ordered them from. They finally arrived on the 29th. However, I
stuck four "lesser" supermagnets on the rotor with double sided carpet
tape and mounted everything on the car to try it out, on May 20th.
It worked quite nicely, the rotor quickly spinning up and the wheel
soon catching up. I figured if it went too fast the magnets would pull
loose and maybe cause troubles, so I didn't work it very hard. A couple of them shifted a little anyway.
In an induction motor, the AC
voltages in the coils make a rotating magnetic field. In the torque converter, the
rotating supermagnets make a rotating magnetic field. Their effect on
the rotor they turn is the same, except the supermagnet fields are very
strong and use no electricity per se.
If you put a tin can or an aluminum cylinder into an induction motor
as a rotor, it will spin. But it won't have very good characteristics.
Likewise with the flat aluminum plate - it's just a "slip plate" that transfers torque linearly with slip.
An axial flux equivalent of an induction motor rotor, something along the lines of a NEMA "Type D" rotor, will directionize the induced current and retain high rotary torque from speed zero until the slip is small.
But the whole configuration just dissipates the energy of the slipping as heat and there's no more torque than the motor has regardless of slip.
A third element is needed. In the
fluid torque converter, there's an impeller that throws the fluid out
from the center to the sides, a turbine that redirects the fluid
sideways, producing rotary force that varies with the amount of speed
slip, and a stator that catches that the back-spraying fluid and redirects it again to "nullify" the unwanted "equal and opposite reaction" force.
Just as the stator won't turn backwards, the
magnetic one needs a stationary component for the high torque at the
output to push against without pushing directly on the lower torque
input. And just as the stator has to redirect the
fluid flow, this
component must transfer the force by using the generated electricity to
create a second magnetic field, that turns the output rotor at lower
speed and higher torque.
on what info I managed to find about different induction motor designs,
I cut radial slits in the aluminum
plate across the path swept by the magnets, a slightly
skewed slit every 10 degrees (27-28th). Perhaps 72 slits/72 conductor
channels would be better, but it does seem to have better torque until
levels of slip are small even with the 36. On the other hand, on the
29th the magnets finally
arrived and so the test had far better coupling flux available, making
Torque converter's slotted induction rotor.
Before I went to glue them on, I realized that with 12
magnets and 36 slots, they would repeatedly all line up at once and
probably cause considerable vibration. I should have cut 37 slots
instead of 36. The next most obvious thing to do would be to use 11
magnets instead of 12, but that would entail two like poles next to
each other and non symmetry, so I put on just 10.
Gluing the 10 high-grade (42
MGoe?) magnets on the back of the motor rotor. The first 5 are easy -
they're well separated. The next five between them could get tricky,
though the spacing was much easier than with 18 or even 12 magnets, and
I simply C-clamped block of wood beside the first magnets to ensure the
new one didn't get sucked over to the magnet on one side or the other.
completed motor/torque converter rotor, torque converter side. (Needs
repainting!) Counting both sides: 22 high-grade supermagnets.
Inductance by Magnets
The reason metal plates are held up as they pass
magnets is because the magnets generate electricity into them as they
move by. The electrons running around inside the metal generate an
equal magnetic counter field that opposes the motion. In an induction
motor rotor, the electrons are directed along certain paths to magnify
The magnitude of the difference of the "braking" effect in different metals took me by surprise. It would seem the effect is directly proportional to the conductivity of the metal:
Aluminum resisted motion strongly, but nickel-brass just
seemed to slip over the magnets almost effortlessly. This was where I
noticed the difference. Then I tried similar pieces of aluminum and
copper. I took no measurements, but the copper indeed seemed to resist
motion a little more strongly than the aluminum. I suppose the fabled room
temperature superconductors would push through the field very
sluggishly. (Where are those, anyway? It seemed so promising: multiple new substances
that superconducted at higher and higher temperatures, getting up from
near absolute zero towards "Antarctic winter" temperatures 20 years ago.
Then the research seemed to stop. Key researcher retire? Funding
canceled? Ran out of ideas?)
Considering the price and weight of copper, I'll use
aluminum for the torque converter. In typical induction motors, the magnetism is
transferred by iron laminates on the rotor and much less copper or
aluminum is needed. I'm guessing this configuration is actually better with just
the aluminum plate and no iron.
EH Motor Power
W = V *
A. Given 36 volts, the watts being consumed by the motor depends on
the amps flowing. Early on, I measured the battery current as 30 A
while one phase was 20 A. This was in accord with theory: each phase is
only driven 2/3 of the time.
My multimeter only reads up to 30 A and my AC clamp-on
ammeter can only measure the AC phase current, not the DC battery
current. With 100 amps, using the DC meter would ruin it, so I only
used the clamp-on on one phase. Somewhere along the line, I got
confused and stopped multiplying by 1.5. I came up with 36V * 100A =
3600 watts or 4.82 horsepower.
But a measured 100 amps means 150 amps total draw, so the correct
calculation is 36 V * 150 A = 5400 W or
7.23 HP. That seems much more satisfactory... but copper
loss calculations show that the efficiency at high powers will be lower than
expected, and the actual top horsepower output will still be about 5-6.
As an aside on the same subject, the motor needed some
reconfiguring for the torque converter: hubs machined, optical system
remade for a larger diameter "can", and the mounting arms changed to
fit as the stator now sits farther out from the wheel. For the first
time, however, I could have the motor spin without having it spin the
car wheel, as it is no longer directly connected to it and the torque
converter isn't installed yet.
Just spinning its own rotor, it reads around 10 amps
(meaning - ahem! - 15 amps from the batteries), whereas while spinning
the car wheel IIRC it read around 40 (= 60) or more. That's probably a fair
indication of how much friction is involved simply in turning all the
bearings and seals, churning up the oil in the differential and turning
the differential gears, with turning the wheel, axle and rear
driveshaft. (Also, I should try ditching those metal coil clamps and make nylon ones. It would probably drop a few more amps.)
As an aside to the aside, I don't know the RPMs involved.
I'm pretty sure it was going faster without the wheel. (1500-2000 RPM?)
I didn't put it
on full power without knowing the RPM - it started humming, making me
nervous! I really want a new version of the motor controller that will
let me measure RPM! Now that I've improved the circuit, somebody has
given me a link to a "3 phase brushless motor controller" chip that
should do the job with
less parts, ON Semiconductor's MC33033. I ordered a few Saturday night
and they arrived Tuesday, the first business day. I guess queen Victoria's birthday wasn't
a holiday in the US.
Motor Efficiency: Copper Losses
I've said the EH
should have lower copper losses. However, here are some actual calculations. (Ugh, math!) Resistance of the #14 gauge coil wire
is .008282 ohms/meter (roughly!), and there's about 12 meters of wire in each
As long as the motor is turning - and with the torque converter, it's never "stuck" - the waveform is AC. When the battery is supplying the maximum of 150 amps DC (very nominally!),
each phase reads 100 amps AC. As the phases have three coils in
parallel, one sees each coil as a having an AC waveform of 33 amps RMS.
.008282 * 12 = .099 ohms
.099 * 33 sqrd. = 108 W (in each coil)
108 * 9 = 970 W
That's waste heat. I don't think
we're in "needs liquid cooling" territory yet, but certainly it's
getting up there. Air had certainly better be flowing past the coils.
Also with 150 amps flowing, the total power consumption is
36 V * 150 A = 5400 W (= consuming 7.2 HP)
(5400-970) / 5400
= 4430 / 5400
= 82% efficiency. (5400 = 7.2 HP; 4430 W = only 5.9 HP out; loss: 1.3 HP!)
And that's only considering copper losses. (Could we please have those mystical room temperature superconductors?)
Somehow that isn't
the "90+%" I've been speaking of!
Well, let's try it at 50% load, which will presumably be more common than "floored".
16.5 A squared * .099 ohms = 272 * .099 = 27 W
27 W * 9 coils = 243 W (1/4 as much waste heat)
75 A * 36 V = 2700 W (Total input power - 1/2 as much)
(2700-243) / 2700 = 91%. (2700 W = 3.6 HP in; 2457 W = 3.3 HP out, loss: .325 HP)
1/2 the power but only 1/4 as much loss, and over 90% efficiency: that's more like it!
At such high currents, even the main power leads from the
batteries to the controller and from there to the motor have losses.
For example, at 100 amps, the wires from the controller to the motor
(and back - over 7' in all) lose about 1/2 volt, which (W = V * A) is
Here's a table based on 90 max
amps phase reading or 135 DC battery amps, which is probably closer than my
rounded off "150 amps" (again, considering only copper losses):
|% of FULL
(Cu losses only)
With copper loss energy being proportional to the square of the current,
evidently serious copper losses are occasioned by high currents, but the
losses shrink towards insignificance as the current is reduced. All motors will suffer similarly in varying degree.
There are of course
other causes of inefficiency which will lower the figures somewhat:
iron losses; bearing friction; air friction. The torque converter also
has significant losses, but (we may anticipate) less than an automotive transmission. The
friction losses of the car tires, wheels, differential gears and drive
shafts overshadows all this, adding a lot to the required power.
Cruising down a street, a car drive
will tend to be lightly loaded
rather than nearly "floored" a lot of the time, and hence in the better
efficiency range. Exceptions are going up hills, highway speeds, and
stop and go traffic lights every block. Long uphill grades (city or
highway) are likely to occasion the greatest heating of the motors.
After doing all the above, in the last torque converter
test the maximum readings I saw with the motor running steady (working
hard to drive the stopped torque converter) were between the first two
table entries, about 75 amps (25 amps per coil), or 112 DC amps from
the battery. The 90 or 100 amp readings were probably with the rotor
stopped or just starting to turn.
Coil Wire Size
Obviously the efficiency at high currents is related to the size of
wire used. That's limited by what actually fits on the coil.
Somewhere I found a "rule of thumb" guide for the size of
wire to use for "X" amps flowing in a coil, and it indicated that the
#14 size I chose was about right for 30 amps max. It used some number, 4XXX
and AWG in some formula, and said it was conservative. I've tried to
find it again without success.
Looking again, I see other guides, but they're
frustratingly scarce. Partly the problem is finding good search terms
to narrow down the search:
* 500 circular mills per ampere.
* 10 A/mm^2. ("However,
the maximum current density is really determined by how well the design
can get the heat produced via resistive losses out.")
For the first guide rule, I get 8.1 amps. For the second, #14 wire is
1.63mm diameter or 1.3 square mm, or 13 amps. The previous guide said, as best I can recall, about 30.
So the guide rules are not only hard to find, they're wildly
inconsistent with each other. Of course, the
motor would be more efficient at high currents if so much copper as
these latter two ask for could actually fit on the coils! Radial flux
motors do fare better in this regard, having more electromagnet iron
and so more space for the copper. On the other hand, this increases their iron losses, and they weigh more.
I also ran across an ARRL handbook figure for runs of #14
wire: 32 amps in open air and 17 in a cable, which shows the importance
of being able to dissipate the heat. That's why the Electric Hubcap
coils are open to the air on all sides and the rotor magnets will fan
them as it spins. It is reassuring that with the torque converter the
motor will now always be spinning when it's powered.
The lighter weight is a contribution to letting the EH
mount on a car wheel. Nevertheless an objection that may be raised to
its use is the extra unsprung weight - It certainly doesn't improve the
handling. I'm considering whether there may be some way to allow the
outer and heavier part of the motor be able to spring up and down to
some extent. The axle would have to pivot where it connects to the
wheel, which would require some sort of "U-joint" or "CV joint" mechanism.
The idea may or may not be practical. Almost inevitably
the motor would stick out a little farther from the wheel. As minimums
now, 2.5" for the motor, about 2" for the torque converter (as
currently visualized), and maybe 1.5" so the flexing unit doesn't hit
the wheel when going over speed bumps: 6" even with specially made
So... how much power does it actually
take to drive a car? I've recently had converse with someone who
converted an old car. He took out the gas engine (evidently), and put a in 4 HP DC electric motor to drive it via the regular transmission. He said GVW is 900 Kg (2000 pounds).
He said he expected to stay in first gear and be able to
go up to 20 Km/Hr through his cow pastures. What he actually found was
that it could spin the front wheels in first gear (presumably on dirt)
and attain 45 Km/Hr in third on his rough dirt trails. He figured it
would easily do 50 on level pavement.
Now, that motor was operating through the lossy vehicle transmission,
typically 30% loss. (Also it was with some crappy old
batteries. Encouraged by the performance, he's ordered some new
batteries to see what it can do with those!)
If the Electric Hubcap on the wheel actually performs 50%
better as expected, then 5.4 HP * 1.5 ~= 8.1 HP means it would have twice the effective driving
power of the 4 HP car that could probably do over 50 Km/Hr on level
pavement. Of course, vehicles with gas engines would be heavier than his 2000 pound converted car.
From all this, one might estimate that one Electric
Hubcap, with the torque converter for "get-go" and climbing hills,
should provide at least enough drive for practical city driving. This
is in accord with previous optimistic estimates.
Optical Commutator & Simplified Motor Controller
unable to find anything like my "optical commutator" on the web, and
seeing a couple of seemingly bizarre and complex PMSM control
on the web, I had thought that I had probably invented the idea. It did
seem puzzling as it seemed so simple. However, people often miss the
simple and obvious and instead some needlessly complex work is
labouriously hacked out, so I just shrugged.
However, someone has pointed me
to a motor
controller IC chip that has inputs which could be taken straight from
the optical commutator. (MC33033 from "ON Semiconductor".) True the
suggested circuit showed three hall
effect sensors rather than optics, but the essential principle was there, and the text mentions "slotted
optics", implying the chip would expect an optics circuit much like
mine as an input. It even has two options for the sensor angles, the
other of which, using narrower angles, could shrink my "optical
commutator" circuit board.
From the datasheets it looks like this chip tries to do pretty much what the four chips in my controller design do, and with far fewer passive components. Its cycle-by-cycle current limiting eliminates the need for my low speed protection circuit.
However its output drivers are only good for lower power motors
(and 24 volts or less). It looked like
the 28 pin IR2130 mosfet driver chip would still be needed, along with
an inverter chip, just to drive the mosfets. But I had missed seeing a
whole series of 8 pin "half bridge" MOS driver ICs, eg AUIRS2003S and
IRS2183, all with the same pinouts. Three of these small chips driven
by the MC33033 should make the whole motor controller other than the power circuits.
Here it was me that missed a simpler solution (did I say I was
immune?), and it was my motor controller design that was needlessly
complex! I had started in to design a circuit
board with the previous circuit; luckily I didn't get very far as the
whole circuit will now be changed and considerably simplified.
I was wondering how I was going to find a resistor small
enough in value and with enough watts rating to implement the current
limiting sensor for over 100 amps. However, having now looked up the
resistances of copper wire, it would appear that simply about 6 inches
of #12 wire linking to the mosfet ground pins should do the trick!
Micro-Ferrite Coil Cores?
The nail strip cores are great, but is there anything that
would be easier to manufacture? I can just see a factory full of people
placing nail strips in coils - substantial labour! Ferrite cores would be simpler, but the flux density is too low for a motor.
An interesting element is niobium. Evidently it's strongly
paramagnetic and it has the greatest magnetic penetration depth of any
element. It might be an interesting idea to try microcrystalline
ferrite cores mixed with with niobium or niobium oxide powders. This
might give the necessary high flux in a ceramic or porcelain core that
can simply be pressed into a mold and baked in a pottery kiln. ..or
perhaps a pressed powder core. As paramagnetic material has no magnetic
hysteresis, it might be possible to make high flux cores with the "iron
losses" reduced to insignificance, increasing the efficiency of the
Then, the core would be used as the spool to wind the coil
wire directly onto, saving considerable manipulation steps (labour). Since the
ceramic is an electrical insulator, there'd be no need to worry the
wire might short to it.
In addition, if it's not struggling to attain enough flux,
cooling air channels or grooves might be built into the core form to
cool the inner side of the coil wire. If the flux density is
sufficient, it might even be possible to shape the cores with smaller diameter in the middle (viz: ")|||(" ) so a larger
wire size can be fit in the space, reducing copper losses.
(Hmm, no niobium compounds in the pottery catalog - rats!)
As the months wear
on, I've been better comprehending various principles of battery making
wasn't aware of or only dimly understood when I started. This month I
made a vented nickel-iron/alkaline cell just to try one with known
chemistry parameters. While it performed little better
than my other batteries (and in fact not as well as my lanthanum-nickel
cell quite a while back), I figured out a few more things and feel I
probably now have a better grip on it. I'm expecting good improvements
in current capacity and storage capacity on the next try.
So I'm writing a little treatise covering the main points in
sufficient detail to probably enable others to try their own designs, which I'll publish when I'm more certain I have all the
details really pegged. (or which will be disseminated widely as is by my
confidants if I'm unable to continue.)
Bottom: loading Fe electrode with 1" x 1" x 1/4" squares of compacted powder.
Center: Rolling up electrode in polyamide non-woven cloth.
Top: Electrodes with leads through test tube stopper, ready to put into ABC pipe "case".
A Great Electric Generator?
People keep looking for generators to do cheap or sample
green energy projects, in particular windplants. The same idea keeps
coming out: "How about a car alternator?" But car alternators make
crappy generators for such purposes. First, they need quite a high RPM
before they'll put out much. Second, they use around 36 watts
internally, to keep the field coils magnetized. Thus, they can often
consume more power than they produce.
I was fixing my $30 used lawnmower one day (for abut
time), and I thought "Gosh! this is a permanent magnet, DC motor!" Why
wouldn't it make a great generator? Why I didn't see it
in 2005 when I bought and first had to repair the mower (a magnet
had come unglued and broken up - I glued all (most of) the pieces back
in!), and why nobody else seemed to see it, I don't understand.
On a wind power discussion group, one who (I believe) was an
experienced wind plant builder thought that it might make a great 12
volt windplant with a propeller of about 4 feet diameter directly on
the rotor. A smaller blade would give higher RPM and voltage, but less
power. For more power, it would probably need gearing up from a
larger and slower prop. Of course, they could do up to 120 VDC and 1440
W as rated on the mowers.
An interesting footnote to all this is that if I had
thought of using a lawnmower motor as a generator in 2006, I'd probably
have used one for the wave power "proof of concept" demo unit
instead of making an axial flux generator. That would have saved time
and worked better than the generator I then made (which had heavy
magnetic cogging), and I'd probably have done a successful wave power test that year or (more likely) in 2007.
And, I would never have ventured into the axial flux
generators that led me to eventually design and develop the Electric HubcapTM motor! What small things a whole course of events can hinge on!
Bipolar Division of Labour?
In our increasing complex social, economic and technological society,
it is obvious that expecting everyone to be able to do everything is a
non-starter. While cultivating a broad range of interests and skills is
admirable and overspecialization is dangerous, we all must depend on
each other to fulfill many and varied specialized roles for the
maintenance and evolution of higher civilization.
If someone is good at welding, do we seek to make him into
a lawyer or a rancher? No, unless there's a serious glut of welders
around, we pay him to weld.
I can't help wonder why, then, inventors are expected to
work for free and pay their own expenses to do the things that
everybody generally wants to see done, and as soon as they have some one working
product, they are expected either:
(a) to publish it as a patent and
then somehow, again entirely out of their own resources (and often up
against groups of companies with very deep pockets), to force everyone
who uses their idea to unwillingly pay them money - it's a joke!
(b) to seek
support for the product and prove what a great businessman they are,
that their product and their company are both worth investing in. And then, if by some miracle
the investment is forthcoming to launch the enterprise, to actually be
that great businessman and head of a new commercial empire.
If I'm one of the less than 1% of inventors who
successfully make such a transition, albeit the invention has been the
path, I finally start to get paid: not as an inventor or for the
invention or the years of R & D, but as a businessman for running a
Is this not the equivalent of telling the welder to spend
"X" years, whatever it takes (which hasn't been estimated beforehand),
on a welding project, and then to become a salesman as soon as that
project is complete, and to weld no more? If he successfully becomes a
salesman he can promote his cause in order to finally be "paid big" for
There are lots of competent welders. Good inventors are
rare. Why try to force them into a different field for which they are
I am probably one of Canada's top inventors and product
developers. As a businessman I've been mediocre, and as a promoter of
my new products, usually a failure. I don't think fast "on my feet" and I
forget to mention important points I mean to make. In competitive
dealings with others, I'm often slow to realize when I'm making a mistake or
being taken advantage of. I often don't put up a good fight when challenged, so I might
not make a very astute industrialist.
It would seem I have to make this transition in order to
eat, but is it really in society's best interests to insist that I be
the one to promote my own product by personally developing the business? Assuming the Electric HubcapTM
cars and complete hybridizing kits can be wholesaled for $2000, a
potential market of 60% of 250 million gas/diesel cars in North
America is around $300 billion.
Assuming the batteries prove to be the most practical
alternative and can be
wholesaled for (eg) $1500, that's a further $225 billion. While knowing
there are plenty of complicating factors, at face value
- if the batteries are practical and would be successfully developed by
me and not by anyone else (and no one else currently appears to be
working on promising simpler chemistries except Ni-Zn/alkaline, and
those claiming they've been doing that successfully are mostly doing
"AA" cells and don't answer e-mails) - $225 billion is the potential lost revenue for having me be the one to run the Electric HubcapTM making business instead of continuing my battery research.
Furthermore, if I fail at the business where a super,
experienced businessman might have succeeded, that's another $300
billion in lost potential.
Then there's my ocean wave powered floating generators,
which could potentially save the Peace River valley from the Site C