EHMotorMakingManual

Electric Hubcap^tm
Motor Making Manual

by Craig Carmichael
Inventor and Developer of the Electric Hubcap Motor and Motor Controller
Started: Sept 22, 2008 - Last Rev: 2010 Feb 9th (Interim version)

Note:
This motor needs speed reduction to the car wheel. Only a very oversize motor would have enough torque if directly connected. A a versatile, efficient, mechanical torque converter is currently being designed. (Other options are planetary gears, chain drive, etc.)

Disclaimer:
This publication is free information about a new invention whose potential hazards are significant but not well known, and the author will accept no liability for anything that happens to anyone as a result of any use made of it. You are on your own. You have been warned!

1. Motor Workings

Electric Hubcap Overview
Electromechanical Basis
Electronic Workings
Electromagnetic Workings
Mechanical Workings
Construction Principles
Battery Power Supply

2. Motor Components Selection

What the Electric Hubcap motor consists of
Creating a set: Center Hub & Axle Assembly + Rotor + Stator
Optics or Hall Effect Magnetic Switches
Theoretical: Larger & Small Motors

3. Making the Stator Coils

Winding the Coils
Nail Strips
Epoxy Casting or Varnishing the Coils
Special Installations

4. Assembling the Stator

Coil Bolt Holes & template
Nyloc Nuts
Wiring up the coils, Leads, Plugs
Optics Circuit Board & Cable

5. Assembling the Magnet Rotor

Mounting the Rotor
Rotors & Axles
Supermagnets
Magnet Bolt Holes (Optional)
Magnet Placement, handling the magnets, magnet placing jig(s)
"Epoxy Steel" epoxy glue
Larger rotors with more magnets (eg: 11", 5-stud)
Optics Interrupter “Can”

6. Mounting the Motor

Brake Drum Housing Attachments
Fitting and vehicle suspension considerations
(up-down travel of wheels with weight, bumps and potholes)
Around-the-wheel Arms
Stator Arms
Nyloc Nuts & things that fall off while driving

Section 1. Motor Workings

Electric Hubcap Overview

   The Electric Hubcap is a 'pancake' shaped three phase, axial flux, supermagnet motor designed for mounting on the wheel of a motor vehicle. A versatile, efficient mechanical torque converter couples it optimally to the wheel. Its unique features combine to make it an ultra-efficient drive system, delivering an estimated 1.5 times or greater thrust to the wheel than a typical electric vehicle drive (operating through the vehicle's transmission) for the same energy input. So little energy goes to waste that it doesn’t need a liquid cooling system. The motor's magnets act as fan blades to cool the coils.

   This is a very simple motor to make at home from commonly available automotive mechanical parts - some of which may perhaps even be found at an auto wrecker for maximum economy. It can be made mostly with home tools. Some tools are needed, such as cheap drill press, an angle grinder for cutting metal, and various other common tools -- but no welder, metal lathe or other major specialty tools. (I just C-clamp the drill press to a work table when I need it - no installing necessary!) (Note: in recent configurations a 'cut down' trailer hub has been used - sorry, that has to be done on a lathe.)

   It is also easier to simply add a motor to the wheel of a car than to rip out the gasoline engine and all the associated parts and fit a bigger motor to the inefficient and inappropriate drive train, and it leaves gasoline operation available "as usual", eliminating worries about running out of battery charge at a bad time or place.

The “Production Prototype” Electric Hubcap motor mounted on the car.
(The original direct-coupled configuration without the torque converter is shown.
The torque of this configuration is insufficient.)

   The magnet rotor (above, yellow and black) is a brake disk rotor with supermagnets. It and a trailer wheel axle are bolted onto the car wheel lug nuts. The axle sticks out to hold the trailer wheel hub (center). The hub holds the motor stator (blue), which is another brake disk rotor with heavy electromagnet coils bolted onto it. The coils face the magnets on the rotor with an ~8mm air gap between. The arms and brackets connect the stator to the axle (to the brake drum backing plate) to prevent it from turning.

   Of course, the Electric Hubcap type of motor can be used anywhere a motor of its characteristics -- high efficiency, a few horsepower, high torque, lowish RPM range -- is needed. (It could for example make a great washing machine motor (eliminating much complex mechanism), a variable speed lathe motor (eliminating V-belts and pulleys), a marine or submarine propeller driving motor, and so on. Larger versions could power ships, locomotives, busses and perhaps even aircraft.)

   This type of motor is run in a six-state power sequence by a solid state electronic control system. At any given time, one phase is driven high (Battery +36 volts), another low (Battery -ground), and the third is idle, with the three drive wires switching continually based on the rotary position of the supermagnets on the wheel. The basic control contains only a small number of commonly available electronic parts, and a dozen high power mosfets (= metallic oxide semiconductor field effect transistors) that drive the motor coils. With no microcontroller to program, this is a straightforward "hobby electronics" construction project.
   A microcontroller version could offer more features.
   A simple Optical Commutator in the motor, or three Hall effect magnetic switches, synchronizes the six-state motor coil timing sequence with the rotation of the supermagnets on the car wheel.
   A potentiometer, for vehicle use connected to the accelerator pedal, determines the amount of thrust the motor provides via a pulse width modulation (PWM) circuit in the controller.
   A safety circuit prevents overdriving the motor and controller, eliminating the potential for burnout under certain conditions.
   Detailed descriptions and schematics are given in the separate manual for making the controller, Manual for Making the Electric Hubcap Motor Controller. Another manual is to be created for making the mechanical torque converter, and installing Electric Hubcap drive systems is to be detailed in yet another manual.

   More completely, the power to the motor is regulated (a) by the choice of battery voltage, (b) the construction, wiring and connection configuration of the motor coils, and (c) by the pulse width modulation (PWM) of the supplied voltage.

   The three phase “Y” motor wiring configuration is used, and the three coils of each phase are wired in parallel in order that the motor runs on a much safer 36-40 volts DC instead of the 108-120 volts that it would use if they were in series. The only disadvantage to low voltage operation is that the current is correspondingly higher, necessitating heavier power wiring. However the wire gauges are still reasonable, and the power wires are quite short. (At 12 volts the wires would have to be awfully fat.) And, the lower voltage rated mosfets have better specs.

   Officially, the motor type is called a “permanent magnet synchronous motor” or PMSM, and you’ll see this acronym again, but driven with a PWM motor controller having magnet position feedback it is the drive signals which are synchronized with the motor rotation rather than the other way around. It is also called a "brushless motor".

Electromechanical Basis

   Mounted on a car wheel or axle, the spinning rotor of the Electric Hubcap (“EH”) motor provides torque pulses to the mechanical torque converter's inertia rotor. This rotor is attached to the vehicle wheel by link pins and a flexible coupling.
   The flexible coupling is for suspension - it allows the motor to tilt up and down as the car wheel moves up and down with roadway bumps.
   A typical proceedure would be to gear down the motor by at least five to one in order to magnify the torque by the gear ratio and operate at a higher RPM in order that the car be able to start on an uphill grade and have acceptable acceleration at low speed. But this makes for very high motor RPMs at highway speeds, eg 6000 or more. This is overspeed for most motors large enough to propel a car, so gear shifting is required, complicating design and operation. It also seems amazingly inefficient: automotive transmissions typically waste 30-40% of the engine's power internally.
   For another example, a car starter motor can propel the car (along with turning the car's engine) in first gear because it is geared down 16:1 or more to the engine flywheel, and a further (eg) 4:1 in the transmission with the car in first gear. Thus its torque is magnified 64 times at the wheel. It would also be turning at a very high RPM before the car is going very fast, eg, on the order of 6400 RPM at 10 Km per hour.
   With the mechanical torque converter, the "gear ratio" is continuously variable, and this is automatic and, with correct design parameters, optimum over the design speed ranges of motor and vehicle wheel. Thus the Electric Hubcap is able to supply very high torque at, eg, 750 RPM to get the car to start rolling, while on the highway with the wheel turning 1000 RPM, the motor is still only turning 1750 RPM to provide the same thrust.
   The PMSM motor itself, with its supermagnets always at full strength, has much more torque at stopped and low speeds than any other electric motor family. (Their magnetic flux is in fact much higher than the flux in the stator electromagnet coils that drive them.)
   The “standard” EH stator has nine cylindrical toroid coils spread around what was the inner disk brake pad braking surface of a car disk brake rotor. These face six supermagnet magnetic poles similarly spread around the outside of the rotor. The coils are 1” tall x 2” round iron core diameter (the “magnetic size”), and a total of about 3” diameter with the copper wire “donut” around the core (the physical size). The magnet poles are formed of two supermagnets each, the twelve magnets each having dimensions 1/2” (thick) x 1” x 2”. (These also act as 'fan blades' to cool the coils.)

   Up to the the point of magnetic saturation of the iron cores, the magnetic flux is proportional to the electric current through the coils, not to voltage or power. In fact, the voltage and power required to push the required heavy current through the resistance of the copper coils and overcome the residual magnetic retention (hysteresis) of the coil iron is waste energy. The lower the voltage needed to push the current through, the less energy is being wasted. We have:

36 volts * up to 120 amps = up to 4320 watts/5.76 HP (being wasted) at the moment we apply full power before the car starts rolling.

   If we had room temperature superconductors very little waste energy would be used to start the car rolling. Copper, though the second best known conductor of all materials, has resistance, which wastes energy to overcome in supplying the current.
   To further digress into the subject of wires, there’s a reason copper is almost universal for motor use:
Silver is the best conductor. But it is only a few percent better than copper and very expensive. It might increase efficiency from, eg, 90% to 92%, and there may be situations where silver is a better choice, but car motors probably isn’t one of them. Silver wire for the Electric Hubcap would cost perhaps a couple of thousand dollars instead of forty or fifty dollars for copper. (2009 prices)
Aluminum is the third best conductor. It is often used for electrical wiring, and a larger gauge of this cheaper metal can compensate for its somewhat lower conductivity. However, in motor coils there isn’t much room to put copper wire that’s as heavy as is desirable, let alone wires occupying more space. This contributes to motors overheating easily. Aluminum would make for less powerful coils that waste more energy.
Also, aluminum is more prone to becoming brittle and failing with vibration and in sometimes damp environments, the contacts corrode more easily and work loose by expansion and contraction with temperature changes. Bad connections not only make the car run badly, they may blow up motor controllers. So, though tempting for heavy cables, it may be a poor choice of wire for any vehicle use.
Also, work hardened copper (hammered, bent back and forth, squashed,...) is up to 5% less conductive than annealed (soft) copper.
   No alloy listed has as good conductivity as these pure elements.

   There is one more factor governing torque: the large diameter of the Electric Hubcap locates the magnetic forces farther from the axle, providing more leverage from the same magnetic force. In effect, having the magnets and coils at 4-1/2 inches effective radius from the center provides a torque advantage of over two to one versus a similarly magnetized radial flux PMSM with a two inch effective radius.
   Further increasing the diameter without adding more coils and magnets (or increasing their size) will decrease the flux density over parts of the rotation. I don’t pretend I’ve worked out the optimum except by an "eyeball" sense of proportions. Increasing the diameter while adding more magnets and coils (or using bigger ones) to maintain the flux density will of course provide more torque.

   Once the vehicle is moving, the low RPM motor still needs a high torque, but power comes into play. E = 1/2 MV², so power of a given motor is closely related to the square of motor speed, the RPM. Also the power, Watts, = Volts * Amps.
    But as speed increases, a motor starts to act as a generator. If, say, one is supplying 36 volts and the motor is generating 18 volts, the maximum current to the motor drops by half. At the speed where the motor is generating almost 36 volts, it won’t go any faster and has no power to spare. This dictates the maximum RPM (which hopefully is below where the motor will fly apart).

   Another facet of coil operation is that in an inductor, current lags voltage. On measuring the inductance per phase as 0.60mH, it turned out to be only a 3º lag at 1000 RPM, or 100 Km/hour with smaller 13 inch wheels, which is within reasonable limits for efficient operation. Over 2000 RPM or so it might become significant, but that's about the EH's maximum RPM.

Electronic Workings
   Electronics are an important part of any modern car motor design. In the case of the Electric Hubcap, they energize the coils in synchrony with the rotation of the magnets. Without that, a synchronous motor can’t be used as a car drive.
   The control electronics, however, are simple, with a simple optical or Hall switch 'commutator' signals telling the motor controller which coils and polarities to activate based on where the magnets are in their rotation. This feedback system is an integral part the motor.
    The optical part is in the motor itself, with a rotating component and a stationary component. Or, three hall effect solid statte sensor switches are mounted on the stator - the simpler new system.
   For the optical system, A plastic “tuna tin” (ABS pipe end cap) with slotted sides rotates with the magnet rotor. Wherever there’s a north magnet, the sides are solid, and for a south pole, there’s a slot. The stationary section is a circuit board with 3 light emitting diodes (LED’s) and 3 phototransistors, one pair for each phase. These are rotated 40º from each other around the axle, the same as the angle between adjacent coils. The light from each LED to its phototransistor is interrupted by the solid sides of the rotating “tin” and passed through where there’s a slot, much like a computer mouse. (In fact I got the LEDs and phototransistors for the prototypes from old computer mice.) The pairs are arranged around the sides of the can separated by the angle between phase coils on the stator.
With everything lined up, the proper timing for the coil drives is output directly from the phototransistors with no need for interpretation. The three phototransistor outputs can directly feed the motor controller chip to actuate the coil drives, to generate the six-state drive sequence.
   For the Hall effect sensors - the new system - the three sensors are simply mounted on the stator between the coils and near to the passing rotor magnets. There are minor timing inaccuracies with this system (because they don't switch until slightly after the midpoint between two opposite magnets), but it's close enough, easier to make and install, and it's not sensitive to the stray light or dust buildup that might hamper the optical system.

   To run the motor in reverse, the signals are simply digitally inverted (inside the motor controller chip.) If there is no microcontroller, this is done simply with 3 gates of a quad XOR gate chip. Of course, ‘forward’ and ‘reverse’ depend on the sensors and on whether the motor is on the left or right side of the car.

Electromagnetic Workings

   The three motor wires are driven in a six state sequence. Since there are 9 coils and 6 magnet poles, they line up the same every 120º and the sequence repeats itself 3 times per revolution. (This 3:2 ratio of coils to magnets is necessary for proper three-phase PMSM operation.)
Each phase wire is driven for 2/3 of the time, and only two phases are driven at a time. All three are never on at once. Each coil is “on” for two states then “off” for one, and at the midpoint of its “on” state, the other two coils swap over as the magnets rotate. The three states, high, off and low, or 36 volts, undriven and ground, create magnetism north, off and south in the coils. Here is the sequence:

ø A	---------------N--------------			--------------S--------------
ø B	S-----------		--------------N--------------			-------------S
ø C		--------------S--------------			--------------N--------------
	0º	60º (20º)	120º (40º)	180º (60º)	240º (80º)	300º (100º)

When one line is driven to +36 volts while another line is driven to 0 volts, the coils driven to +36 are north at their top ends and south at the bottoms, while the coils driven to 0 volts are the opposite magnetic polarity. Both sets of coils provide the same magnetic strength. (Don’t ask me which, “N” and “S”, is really which!) Two wires (and hence two phases) are driven at a time, one high and the other low. The third phase coils are idle. Each set of coils goes N, N, off, S, S, off, repeatedly. The intervening off state, not going directly from high to low, reduces the inductive spikes made by the coils, reducing the amount of filtering required.

The power is timed so that adjacent coils become north and south as a magnet passes between them, one coil repelling the magnet and the other attracting it to provide turning torque. As the magnets pass directly over a coil, it is turned off. Energized coils here would simply repel or attract the rotor magnets to the stator coils without providing turning force. Note that right in the middle of one set of coils being “north”, the other two sets swap being “south”, and vise versa.

With spread out magnets along the rotor, it is the position of the center of force that is being considered.

At the risk of being repetitive, here is another representation of the six state drive sequence:

State	Phase A coils (0º)	Phase B coils (40º)	Phase C coils (80º)	North Rotor Magnets	South Rotor Magnets
0	36v (N)	0v (S)	-	10º to 30º	70º to 90º
1 <	36v (N)	-	0v (S)	30º to 50º	90º to 110º
2	-	36v (N)	0v (S)	50º to 70º	110º to 10º
3	0v (S)	36v (N)	-	70º to 90º	10º to 30º
4	0v (S)	-	36v (N)	90º to 110º	30º to 50º
5	-	0v (S)	36v (N)	110º to 10º	50º to 70º

   Note that at all times (disregarding the PWM that repeatedly turns all the drives on and off during their "on" times) one phase is driven high and another one phase is driven low, providing continuous north-south magnetic thrust forces at all points of rotation.
   The maximum rotational force is generated when the rotor magnet pole is directly between two energized coils, one attracting it and the other repelling it.
   Since the sequence repeats every 120º, each coil is north for 40º then off for 20º (half the sequence), then south for 40º and off again for 20º (the other 60º half). That 120º also sees the two magnet poles, north and south, 60º each, go by the three coils of phases A, B and C.

   The astute student will notice that with only three photo-optic elements, the six states aren’t entirely decoded for the six inputs to the MOSFET driver. “A” would seemingly be high for 60º and then low for 60º of the 120º cycle with no “off” time, instead of only on for 40º and off for 20º. Where is the translation? For the answer we look to the digital logic and to the way the optics connect to it.

The truth table for an IR2130 MOSFET driver chip is:

Input for HIGH drive
(phases A, B & C are alike) input for LOW drive
(A, B & C are alike) MOSFET Outputs:
High side & Low side

1 (“off”) 1 Both Off

1 0 Low On, High Off

0 (“on”) 1 High On, Low Off

0 0 Both OFF (NOT both on!)

    If both high and low of a phase were on at once, the high and low side MOSFETs would create a short circuit from the 36 volt batteries to ground, and blow the fuses (and maybe burn up first themselves). The chips don’t let that happen, and they also insert a very short delay in any transition directly between high and low drives being on to ensure the same. Other logic chips could provide the same functionality - the IR2130 does it on one chip.
   We utilize these protection circuits to supply the 3 high and 3 low drives (6 inputs) from just the three phototransistor outputs by crossing phases over to the Low drive inputs. The overlap in times gives the “off” states. This is covered in more detail in the motor controller manual.

   To visualize the workings, let us simplify by considering a rotor with only two magnet poles 180º apart, and a stator with three coils 120º apart. The six states then occur over one rotation, 360º, with 60º per state.
   The timing is then that the top coil “A” is off until a magnet pole is 30º past it. Then it turns on with the same polarity as that magnet for the next 120º (to 150º, states 0 and 1 of the table), repelling it.
It then turns off while the other magnet goes by it from -30 to +30º and the first magnet goes from 150 to 210º at the opposite side (state 2).
    Then, with the second magnet 30º past the top coil, it goes “on” with the opposite polarity for the second half cycle (states 3 and 4 from 210º to 330º, with state 5 again being “off” from -30 to +30º).
While the first magnet moves away from the top coil from 30º to 150º, the opposite pole is approaching the top coil and is attracted, going from -150º to -30º from our coil. Most of the repulsion of the first magnet is in the first 60º from 30º to 90º, then that magnet becomes rather distant from the coil. Most of the attraction of the second magnet is in the second 60º as it approaches our coil.
    The other two coils do exactly the same thing, but 120º and 240º out of phase to the top one, between them providing continuous strong thrust at all points of rotation.

   In the first 60º of the 120º swing (30º to 90º), phase “B” has been on, the magnet going -90 to -30 degrees from it, attracting the magnet “A” has been repelling. Thus the magnet is being strongly pushed by the coil just behind it and strongly pulled by the one just in front. The opposite magnet is also being weakly rotated by the same two coils, which are more distant as it is crossing over the third, “off”, coil.
   In the second 60º of the swing (90º to 150º), phase “B” goes off as the magnet goes by it and “C” comes on. Now “C” is pushing and “A” is pulling the opposite magnet immediately between them with the same strong forces, while the first magnet is weakly propelled as it passes by “B”.

   The 9 coils, 6 magnet poles machine, works exactly the same, but the six-state cycle repeats itself three times over 360 degrees, ie every 120 degrees. All the angles are 1/3 and three identical sets of coils are pushing three sets of magnets. So the timing is that the coil is off while a magnet pole passes over it from -10º to 10º past it, a 20º span (state 5). Then it turns on with the same polarity as the magnet for the next 40º (states 0 & 1). This repeats with opposite polarities for the other magnet in the second half of the cycle (states 2 (off) and 3 & 4).

Mechanical Workings

   The car wheel’s regular lug nuts are removed and replaced with long ones that stick out well past the lug bolts, to extend them as threaded sockets. I’m using around 30 mm long nuts. They’re from an auto wrecker (lying around everywhere) and I cut or ground the decorative outer end caps off.
The magnet rotor is bolted onto the wheel via these sockets. From the center an axle protrudes. A trailer wheel rotor sits on this turning axle on regular trailer wheel bearings. The stator is bolted onto this and is thus centered on the wheel and rotor. Thus, the usually stationary axle turns with the car wheel, while the usually turning trailer wheel rotor is stationary. These automotive parts are almost ideal for the purpose - with even the holes in the right places - and avoid a lot of custom machined parts. (Finally I’ve found there’s almost no getting around drilling some lug bolt holes somewhere and I prefer shorter car axle/hub/bearing units.)
   There are probably many types of suitable car wheel hubs & axle assemblies as well as the trailer hub & axle I used, with various spacers, rotors and hole drillings selected to suit. One I have from a Firebird could certainly be used (probably with an entirely flat magnet rotor), and I saw a picture of one that looked almost ideal in a Canadian Tire flyer, though at the store they couldn’t show me one or tell me what model of car it was from. Most of these would be more compact than the trailer hub and axle. A drawback is that being pre-assembled, it will be harder to mount a slotted ring for the optical assembly - it will either have to fit over one end or be placed in two pieces. (Of course, it’s little problem, if required, to cut an ABS piece in half and glue it back together around the axle.)
If I do a second motor myself, I will certainly try using a car axle. The first working prototype used the hub part of a rather hacked one. (Perhaps they’ll get tried in the workshops.)

   Two rectangular steel tube “brackets”, upper and lower, bend around from behind the wheel just afront and behind the tire. They attach to the brake drum backing plate behind the wheel. Two arms, upper and lower, extend left and right from the stator to attach to the brackets. This somewhat springy mounting takes the torque and prevents the stator from spinning instead of the rotor and wheel. (If you are wondering about the strength of the brake drum backing plate for this purpose, recall that the brake shoes attach here and it takes all the force of squealing the brakes!)

Construction Principles

   The motor is mounted on the wheel, which is unsprung, and although it is somewhat sprung by the flexible coupling and mountings, it is subject to levels of vibration not felt inside the car. Furthermore, if a roofrack comes loose, it is likely to be noticed and retightened, whereas the motor is down at the wheel and behind a cover. Many of the parts inside can’t be seen even if the cover is removed, and the whole motor has to be removed to retighten them. Even the brake drum has to be disassembled if the innermost stator bracket bolts come loose.
   And there is more possibility to cause harm if something comes off the motor, wheel or brake assembly, or even comes loose, by losing power while driving, by having a loose part jam the wheel or cause a flat tire, or by dropping a chunk of metal on the road in front of the next car.
   It is therefore critical to have a robust design, to install all the parts very securely, and to have scheduled inspections, frequently in the beginning stages. Fragile parts must be carefully situated and protected.
More on all this later.

Battery Power Supply
   The electric Hubcap runs on 36 volts of batteries capable of supplying up to 100 amps continuous, situated where convenient in the vehicle. Generally it is desirable to locate them close to the motor controller(s) so the heavy leads are short, minimizing voltage drop and cost.
   As I write this, generally the only practical, economical batteries for electric cars are lead-acid. These are rarely an environmental problem as they are normally recycled. With sodium sulfate added to the electrolyte, they can last for 10-20 years.
    They are, however, heavy and bulky. The Electric Hubcap hybrid helps out by needing many fewer of them. Three large "size 27" "deep cycle" 12 volt batteries (50 pounds, $100 each) will run the car. Six of them (two parallel banks of three - 300 pounds), or six 6 volt “golf cart” batteries will do it with some driving range and longer life.

   I will not here enter into speculation of what range is practical or the complex subject of lead-acid battery quirks. On any batteries, the Electric Hubcap will go farther than any other car drive. And because the car becomes a “hybrid” instead of an “electric car”, whenever the batteries are considered “low”, the driver will simply switch to gasoline driving until it is convenient to recharge them, or use “charge while driving” (on gas), with the advanced controller and switch back when they’re recharged.

2. Motor Components Selection
The structural components of the Electric Hubcap motor are:

* Axle & Hub (“spindle”)
* Stator
* Rotor
* Housing/Case
* Mounting Brackets

Normally, the axle, hub and bearings, which I’ll call the “spindle” herein, are what a rotor rotates on. With the EH, the rotor rotates on the car wheel and the spindle holds the non-rotating stator centered on the rotor. The spindle is made from a commonly available trailer hub, axle and bearings, or from a similar assembly made for an independent axle car wheel. These may be found at trailer supplies stores, automotive supplies stores, or auto wreckers.

With most motors, the rotor is inside and the stator is outside - radial flux. With the EH, the rotor and the stator are two disks of similar and unusually large diameter, eg 9 to 11 inches, and the electromagnetic elements face each other like two dinner plates (or whatever) - axial flux.
I was using "10.5 inches nominal" as the diameter when I was hoping to drive the wheel directly, but with the torque converter I think a somewhat smaller diameter and higher RPM is preferable. That reduces the weight somewhat, and perhaps with larger car wheels, it might clear curbs for easier parallel parking. The disks may be brake disk rotors (new or used) or flat steel plate discs. I recommend a plate thickness of about 3/8" (10mm) to provide mechanical strength and to carry the magnetic fields.

Magnet Rotor - N black, S - yellow. 11” diameter disk brake rotor with no fins, shallow hub rise. (Buick Gran Sport rear wheel rotor?) Magnets to 10.5” , leaving 1/4” outside lip.
A “skip tooth” configuration was employed, for sharp transitions between N and S. 18 magnets would be really too many - the rotor is brutally magnetic.
The 100mm, 4 lug bolt holes pattern had to be drilled (before adding the magnets!) to fit the wheel and hubs used.

The stator has 9 coils, three sets of three, spaced 40º apart. The coils for a given phase are 120º apart from each other - the same spacing as the magnet pairs. Each coil is a disk about 1” thick and almost 3” in diameter, and has holes through it for two 1/4” diameter mounting bolts. The magnetic core is a 50mm diameter circle. With the 10.5 inch rotors, the nine coils just fit on the backing plate/disk with little space between them. (Coil details are described fully later.)

For a smaller diameter rotor, the coil cores will have to be reduced from 50mm to a lesser figure, or a bit can be "cut off", flattening two points on the sides to make it slightly pie shaped. The pie pieces will fit in a smaller circle while retaining a maximum of core material, but are a bit more complex, and of course will have - very slightly - higher copper losses. Aim to have an inch (25mm) between coil cores at all points to allow sufficient space for the windings.

Stator with clamped on coils. 10.25” rotor ( Honda, 4 lug holes/100mm pattern, finned), with the copper wire of the coils overhanging outside for 10.5” core outsides to match magnets on rotor. (Well, actually this is the 10.25” O.D. sized prototype. The coils are too close together, and would be better at 10.5”, and the connection wiring didn’t quite fit in the center area (it’s around the outside instead), so I changed the spec to 10.5”. The magnets on the rotor for this actually are at 10.5”.)
The Honda rotor center hub is big enough that the trailer hub fits into it. (In fact, you’d think they were made to match, though it’s only co-incidence.)
The temporary inner bolts are turned against the hub, to back the stator away from the magnet rotor until it can be pulled away by mere human strength.

The housing or case protects the motor from dirt, mud and rocks. I used a 3-1/2” inch length of turquoise colored 12” I.D. PVC plastic culvert pipe (from which part the name “Turquoise Energy” originally sprang).

A nice cover can be placed over the end of the motor. Mine is a stainless steel “wok lid” of the right diameter. (Alternate choice was a mixing bowl.) With a car axle, a much shallower dish should fit.

The upper and lower rear mounting arms reach from the brake drum housing behind the wheel (which takes the torque of screeching brakes) around the front and back of the wheel. They connect to the arms attached to the stator and prevent the stator from rotating. 1/2” x 1” rectangular steel tubing does nicely for the rear arms, giving the rotor assembly a bit of spring. 1/4” x 3/4” flat steel could perhaps work well for the front arms. I used the 1/2” x 1” tube and connected front and rear with 1/8” x 3/4” angled (bent) joining pieces, “strapping”, threaded for 1/4” bolts.

Most of the motor fabrication consists of drilling holes and bolting ready made parts together. Other items are making the coils (unless purchased), glueing the magnets to the magnet rotor and spray painting the metal parts. (eg, rust paint the rotors.) The optics parts and the coils can certainly be made, but are more time consuming. If you choose to buy them, making the motor is an easy project -- much easier than installing the overall system in the car to complete the hybridization.

Creating a set:
Center Hub & Axle Assembly + Rotor + Stator
The center hub assembly mounts the whole motor onto the center of the car wheel. It consists of a standard small trailer wheel axle and hub with trailer wheel bearings. The axle turns with the magnet rotor and car wheel while the hub, attaching the stator, remains stationary. The 6 inch long, 1-1/16 inch diameter (untapered) axle size is suitable. (A shorter axle such as various car hub/axle assemblies would protrude less. All will be a custom fit.) The trailer hubs/axles can be purchased with a mounting base conveniently having four mounting holes that fit a car wheel having four lug bolts. (4 -100mm.)
The magnet rotor and the axle base attach by means of long coupler nuts and extension bolts on the car wheel lug bolts.

Left: Long nuts on wheel. (from auto wrecker; with decorative endcaps cut or ground off.) These provide about 3/8” to 1/2” of free thread on the outer ends. Be sure to get nuts whose threads run the full length - some only go a short distance.
Right: Magnet rotor and trailer axle, showing use of extension on socket wrench to keep hands and tools away from the magnets while doing up the bolts.
(I haven’t had anything crushed doing up bolts (so far) but I’ve had my fingers cut by lug wrenches that grab hold suddenly, dragging my hands across the magnets.)
Also of note, I had originally planned to put 18 magnets on the rotor, hence the uneven spacings - which are probably an advantage anyway. Souths are right next to norths with the gap being in the middle of each pole. (12 magnets is already brutally magnetic and 18 didn’t seem to add any notable thrust to the first working prototype anyway.)

Instead of the trailer axle and hub, there are any number of car axle/hub assemblies (which I’ll call “spindles” herein), made mostly for cars with front wheel drive and-or independent rear wheel suspension. On some, the hub/bearings and axle components are separate, on others they are a single combined unit. I used a combined Firebird spindle for the wave power. There are many different sizes and designs, and one must find rotors that can end up being a good fit for the spindle chosen. One GM combined spindle that is perhaps worthy of note is one with a triangular inner end (3 bolts) that happens to mount the rotors about 44mm apart, Canadian Tire # 013-0500-0. This is a good width for using two entirely flat rotors cut from, say, 5/16” steel plate. This would make the thinnest possible motor, 60mm or 2-3/8” disregarding protruding nuts and bolts.
It is frustrating shopping for these automotive items as the stores know nothing about them and keep them in boxes out of reach at the back, indexed only by the model of car they were originally for. A Canadian Tire flyer showed one that looked very promising, but when I went there they couldn’t tell me which one it was to show it to me!
Taking tools, tape measure and measuring calipers to an auto wrecker may give better results - that’s how I got the Firebird unit - and you might also find rotors to fit the spindle you pick. You want to end up with about 44mm (1-3/4”) spacing between the inside faces of the two rotors. If it’s somewhat narrower, washers can be added to move the rotors apart. If it’s a bit wider washers under the coils can ‘expand’ the coil widths, but if it’s more than a couple of typical 1/4” washer thicknesses extra it’s probably not a good match. Don’t forget to take larger “torx” bits - they’re common for holding the spindles onto the car! (I’d be glad to hear of spindles & rotors that seem to make good sets, to post to the web for all.)
Onto the center of the axle base, a plastic “tuna tin” with slotted vertical sides is affixed to alternately interrupt and pass the light between three LEDs and their associated phototransistors as the wheel turns. It’s just an ABS plumbing pipe cap that needs some cutting and fitting. With a unitary spindle assembly, you may need to cut it in half or thirds and glue it together again around the axle. However, the angles need to be pretty close for good motor operation.

Firebird hub/axle assembly, shown with 12” x 1/4” flat rotor (a bit big but could work or be turned down - 3/8” thick would be better) and Honda (?) rotor. The spacing is too close - not enough room for coils (1”), magnets (1/2”) and air gap (1/4”) (= 1-3/4” = 44mm) - so some spacers would be required, eg to move the flat rotor down. Also required would be a number of custom holes for bolts. For a small 5-stud car wheel, perhaps the hub/axle should be reversed as the other end already has the right holes for that wheel (with its own stud bolts hammered out - they’re usually a press fit) and would bolt right on.

Best Rotors?

But amidst the wide array of possibilities, one might well wonder "What are the best options?" I wouldn't call any of the available disk brake rotors or other hardware for motors "ideal" for Electric Hubcap motor systems, but there are some "good enoughs" here and there. Of the things now available "off the shelf", here are my current favorites (December 18 2009).

I noted just one un-finned disk brake rotor where the center hub was only about 1/2 inch tall, a 1993 Chevy Lumina rear wheel brake disk: all the rest either have taller center hubs or are heavier, thicker "double" plates with fins between.
Not only does that make the Lumina the thinnest, but since the hub is hardly taller than the magnets, the magnets can be mounted on the hub side, making the thickness of the magnet rotor just one inch instead of 1.75 inches or more on other types.
These have 5 stud holes of medium radius. I suspect small trailer axles with this pattern will be hard to find (haven't looked yet). A four hole or smaller five hole stud pattern may have to be drilled in the rotor. (Accurate drilling is a plus, especially for the spinning magnet rotor.)

These rotors are just over 10 inches in diameter. But the 2 inch long magnets hang out over the rim 1/4 inch because the flat area outside the center hub is only 1.75 inches wide. So we'll pretend they're 10.5 inch rotors, which is what the coils are sized for anyway. The coil cores also will need to stick out 1/4 inch, so the coil wires will stick outwards up to 3/4 inch from the rotor rim.
That leaves coils and magnets a bit exposed and unprotected with the cover off, but the cooling should be good, and these rotors are light, about 7-1/2 pounds.
For the stator, there's another advantage over many other single plate rotors: at 1/2 inch thick, the plates are thick enough for good solid threaded holes to hold bolts for the mounting straps/brackets, without having the bolts protrude through to the coils. Many others are about 7/16" or 3/8".

* Rotors (magnet rotor and stator):
...I've just found out there's a "Raybestos" catalog with all rotors indexed by diameter, with useful info about each one and a picture of each one. The ones I asked about were out of production, but I plan to delve deeper into it this month (Feb 2010). It looks like better ones exist than those I've found - thick, unfinned ones ones with four bolt holes for the trailer axle flange and fairly low hubs.

1993 Chevy Lumina (Z-34 car, not van), rear wheel rotor.
"Gren" brand replacement has these numbers on the box (Don't ask me who makes them up!):
C16-9575-2, 682301/5567 "Replaces BD61851, 52-61851", Canadian Tire # 016-9575-2.

Another pretty good rotor is the "Pontiac Gran Sport" rear wheel rotor disk. This rotor is shown above - it seems to be used in a number of GM cars, but I haven't sourced out part numbers. This 11 inch rotor would have more metal around the coils, but still it would probably have coil wires sticking out unprotected a bit. It's a solid rotor (no fins), 11" in diameter with a hub about like the Lumina's except 3/4" tall - still quite short but taller than 1/2" magnets.

More ideally, I envision disks specially cut from plate steel by CNC waterjet cutting. Both rotors would be 3/8" thick. The center holes would be sized to securely weld in a short piece of pipe, and the pipe would be machined at both ends to fit bearing races for a 1 inch diameter axle. Thus there would be no more "hubs" and "lug bolts". The magnet rotor would be 10.75" in diameter, leaving a slight lip around the magnets. The stator disk would be about 11.5", protruding out far enough to protect the coil wires during handling, and with the strap/bracket mounting holes near the outer edge, positioned so protruding bolts will miss the coils. Ventillation holes would be strategically drilled through the plates as seemed appropriate, with the magnets acting as fins to provide the air moving power.
Of course, this vision has not been put to the test.

* Axle/bearings/Hubs
Presuming this installation is for a car and includes a mechanical torque converter, my current thinking is a light trailer axle of the one inch diameter size, six inch length. This would need four bearings and two hubs per usual for such an installation, and doubtless the hubs would have to be machined shorter to fit both on one axle. Of course, it will be helpful if the hubs have the matching 5 bolt pattern to the rotors.

A disk brake rotor of special mention that I noticed at the wreckers is a 1993 Chevy Lumina (Car, not van, "Z34") rear wheel rotor. It’s just over 10” diameter and the large diameter center dome is just 1/2 inch tall. (5 bolts, medium size pattern.) That means it could perhaps have 1/2 inch thick magnets on the hub side, without needing any extra thickness over what a flat rotor would occupy. It could also be used to create a stator with minimal protrusion.
Much later, I decided that this rotor would probably be the optimal magnet rotor, and I spent what turned out to be a whole day hunting them down. (perhaps because I didn't know the year, or else the first two stores just didn't have the right ones -- I ended up back at the wreckers to find it was a 1993.)

I found several things worth noting:

* The Gren "OE" replacement for this is among the cheapest of rotor disks. (yay!)
* The flat space between the large diameter center hub and the outside is only 1-3/4 inches, so 2" long magnets will stick out 1/4" and the effective diameter is 10.5".
* The hub on the "OE" replacement I bought is 9/16" tall, so it sticks out just past the 1/2" thick magnets. Since the coil to supermagnet gap is at least 1/4", this should be fine.
* The metal of the single disk (no fins) is 1/2" thick. About 3/8" is enough, so it weighs perhaps 1-1/2 pds. more than it needs to. It weighs about 7-1/2 pds, lighter than most.

For the "matching" stator disk, one could use a second lumina disk, or the 11" disk mentioned above.
Magnet Position Sensing: Optics or Hall Effect Magnetic Sensors
In order to supply the correct power signals to the coils at the right times in the sequence of magnet rotation, the rotor position must be made known to the motor controller.
The original means I created for doing this is a slotted cylinder wall that turns with the rotor. This alternately interrupts and opens the light path between three LEDs and their three partner phototransistors.
A second technique that I used later was to use three "Hall Effect" solid state magnetic switches, mounted on the stator between coils. These switch state with the polarity of the magnets going by. (I used Allegro Microsystems A1213LUA-T) These look like a small plastic transistor. Another package looks like a small IC chip. They are simpler to mount and not subject to problems with ambient light if the cover is off the motor.

First we'll detail the optical system (historical precedence?), then the magnetic switches.

There are three slots and three “walls” the same length between them, 60º, which rotate with the magnet poles: solid at the north magnets and slots for south (or vise versa), changing where the magnet poles switch. Each pair occupies 120º, the angle occupied on the stator by one set of three coils, phases A, B & C. The three optical LED - phototransistor pairs are set 40º apart, the angle between the individual coils. (According to my theories, they should line up directly with the centers of three consecutive coils, but this isn’t giving good results and has been keeping the motor off the road this last week. I’m writing up and putting this manual on-line anyway, fully knowing this section will want revision in a few days.) There will be found one angle where the motor runs fastest and draws the least current, as found by a clamp-on “ampprobe” meter on one of the three drive lines (and perhaps a tachometer). If you’re not familiar with these interesting meters, they work by magnetism with no actual electrical connection. Again, magnetism is proportional to current flow. Just “clamp” the probe around the wire. There are AC (common) and DC (less common) meters or meter ranges. A DC meter lets you read the total current in the main battery wire. The AC current in each phase of the motor, if it’s turning, should read 2/3 of the total supply current. At the right angle, each state in the six-state drive sequence is timed perfectly by the transitions of the phototransistor outputs. (As I write, I’m about to install a “ligature”, a clamp that can be turned, to mount the optics on so their position can be adjusted. That’s what I used to good effect on the original prototype.)

Accuracy of the slots and optic component angles is important for best operation, and I’m beginning to think three curved plates forming the “solids” mounted out at the inner edge of the north magnets, with an expanded optics mounting to suit may be better than the small “tuna tin” arrangement, but have not yet come up with an arrangement.

That's the optical system. Now we'll describe the magnetic switch system.

Although theoretically less precise than the optical system, the three switches are simpler to mount and not subject to problems with ambient light if the cover is off the motor.
The first cause of reduced precision is magnetic hysteresis: they don't switch until a requisite strength in the opposite magnetic polarity has been reached, rather than switching at the zero point. This was a particular problem when using a magnet rotor with six 2" x 2" magnets. At the outer rim there were wide gaps between magnets, and instead of switching near the mid point, they waited until the next magnet was almost there. I had to re-mount the sensors on the inside side. There was little room there and I had to "miniaturize" the posts and circuit boards. I discovered that using steel mounting posts instead of aluminum helped, doubtless concentrating the magnetic field just under the sensors.
The hysteresis would be less problem with 12 evenly spaced 2" x1" magnets, and still less problem with the "skip tooth" magnet arrangement shown herein.
The second theoretical cause of reduced precision is interference from the magnetic fields of the stator coils. However, I placed the sensors between coils rather than on coil centers, and I made no attempt to measure the effects.
Theory aside, it seemed to work well, so I was happy.
Special Installations
Double motor:
For fitting two motors onto one shaft to get more power in one place, the trailer hub bolts are long enough to hold two stators facing opposite directions. One magnet rotor is mounted to the axle base location as usual, while the other must be fitted with a center hub of 1-1/16” diameter to fit on the other end of the axle, and a keyed slot or other non-slip alignment device must be used. An 8” or 10” long trailer axle would be used to gain the extra shaft length, with some sort of cotter pin and washer or shaft collar arrangement to hold the bearings and hub (made for 6” axle) in place.
If a splined center vehicle axle for front wheel drive is used as the motor axle, the motor could possibly fit right onto a splined front wheel drive shaft in place the transmission/differential box, for an all-electric vehicle with a hidden motor(s).

Concentric Motors:
The general use for these would be for counterrotating propellors for boats or submarines. A solid axle must pass through a hollow one. As with the double motor the two stators could be mounted back-to-back. The shafts would no doubt requires some extra shaft machining with outer and inner shaft bearings (trailer wheel bearings are available).
Larger and Smaller Motors:
The 10.5 inch rotor diameter that I’ve used holds nine 2” core diameter coils and six 2” across magnet poles, for an average magnet and coil radius of about 4.25 inches.

Scaling up the design could be accomplished by either increasing the size of each component - stator, rotor, coils and magnets (or doubling up magnets), or by using more of them.
14 inch rotors would give 6 inches radius with four sets of phase elements (12 coils and 8 magnet poles) instead of three (9 coils and 6 magnet poles). This would provide a torque ratio of 4/3 * 6”/4.25”, or 188% of the torque, would draw 133% as much current to start rolling, and would use four electromagnetic cycles per one wheel revolution. It might well need triple mosfet drivers instead of double - a bigger motor controller, and of course #6 wire instead of #8. With the coils in parallel, it would still be 36 volts. It would probably be suitable for some heavier vehicle than is typical (You would have to find such big rotors, and they would have to fit on the car wheel without extending beyond the rims.)
I’m assuming that Turquoise Energy will be supplying the “standard” size coils, making them, and two magnets per pole, a “simpler” choice.
Nine larger coils - whose cores, wire gauge and number of turns and characteristics would have to be figured out anew, and six somewhat larger magnet poles (18 magnets?), would cover more of the larger rotor’s total surface area and provide more force, optimal for the larger size.

Each coil as described herein occupies about 3.3 linear inches, about an inch in from the outer diameter. A 8.5” rotor has 20.4 linear inches, = 6/3.4, for a six coil stator (and hence 4 magnet rotor) -- if all the components can be fit in. Again these will still be 36 volt motors, but of course the 6 coil version will have somewhere in the vicinity of half the power, 1/4 the torque, and twice the RPM of the 12 coil one, and will draw half the current from the batteries. With the coils in series, the motors could be nominally 72, 108 and 144 volts respectively for 6, 9 and 12 coils and would draw 1/2, 1/3 and 1/4 as much current, respectively. Voltages above 36 volts are recommended only in dry locations, ie, indoors, and will require driver MOSFET transistors with higher voltage ratings. As always, wiring between the controller and the motor should be as short as possible.
Beyond 14”, a lot of rotor area will be “going to waste” with relatively “tiny” elements around the rim and a lot of blank center, and so the coil and magnet sizes will definitely benefit from an increase.
Going smaller, it will get hard to fit the shaft, hub and optics without decreasing the size of the coil and magnet elements.
In fact, the production prototype was based on 10.25” instead of 10.5”, and I had to turn down the trailer hub outer diameter a bit to get it past the insides of the coils freely, make some of the coils a bit smaller to fit them all on, and connect the coils around the outside instead of the inside (where the lead lengths would be shorter). Indeed, 10.75” or 11” would probably be an easier fitting choice if the rotors are available.

Section 3. Making the Stator Coils

Nine coils are required per motor. The easiest way to get the coils is to buy them. Naturally, Turquoise Energy Limited plans to make them for sale. It’s not difficult to wind good coils, but it is somewhat time consuming. It may be worthwhile to wind your own if you’re on a budget, or if you wish to make your motor before our coils are in production.
The materials required for each coil are:

about 275 grams/9.5 oz/12.5m of #14 magnet wire (pref. 150ºc+ insulation)
about 310g/12.5 oz of 1.0” nail gun finishing nails strips
two 1/4” x 2” or longer bolts with 1”+ smooth sides before threads
(hex heads)
Motor Varnish or Casting Epoxy that will withstand high temperatures (150ºc+)
Hi temperature flat black enamel paint for heat transfer to the air (stove paint?).
Small cable ties

Also required is a coil winder jig (see picture) and a jig/plate to put the cores in on.

Winding the Coils

A coil winder on an axle with a two inch/50mm diameter spool, 7/8” wide, and a handle to turn it is fast, easy and does a neat job. (Available at workshop.) Minimally, a cylinder of that size with side walls can wind coils for one motor by hand if care is taken to wind them neatly. If they’re not neatly wound, they might not fit on the stator without touching each other, which could cause a short circuit.
Other options: A car spindle from an auto wrecker might work... even the one you buy for the motor shaft... if you figure out some way to mount it and attach the spool. Or, you could make the spool roughly as shown and mount its center rod in a chuck on a wood lathe or a drill press - whatever it takes to be able to turn it smoothly while feeding the wire in continually.

Coil winding jig. The bearing spindle (left) can be had at a motor shop. The drill chuck with the same threads was a separate purchase. The spool is a piece of plastic (turned on a wood lathe with indents for the big washers) on a 3/8” threaded rod. A nut holds the inner end while the threaded handle holds the outer. Turning backwards winds the handle off, and the outer washers are removed to release the coil of wire. Later, the rear washer was faced by a ‘washer’ of metal cut to fit on the spool, which is pulled to push the coil off the winder from behind - that works better.

The coils shouldn’t stick out above or below the nails, so the 7/8” width is chosen for 1” nails.
Leaving about 40cm of lead wire, wind 70 turns of #14 magnet wire onto the spool. Don’t lose count. If all is well, the end should be just about back to the same side as the beginning. #15 wire is too light for the motor currents. #13 wire won’t fit unless the stator diameter is increased. (If you have trouble getting #14 wire, you can try two strands of #17, soldered together at each end. That gives the same cross section of wire. However, I make no guarantee that the coil won’t be too fat in diameter.)
Give the outer lead 1/2 turn wrap around the inner one so it doesn’t unravel and cut it to length, then wrap the coil with a strip of packaging tape or “magic transparent” tape to help hold it together while you take it off the spool.
Slip a small nylon cable tie on so that the leads are held from unwrapping by it. Remove the tape and put on two more, evenly spaced around to hold the rectangular profile of the coil.
Wind all nine coils the same way. (Ie, don’t reverse directions, start from the opposite side, or whatever.)

Finishing Nail Strip Coil Cores

If solid iron cores were used, the magnets spinning past would generate electricity into the iron. It would be one big short circuit, causing heat, drag and very poor efficiency. Today’s standard practice is to make the entire stator out of die-cut sheet iron pieces, varnished to insulate them from each other and laminated together. You can see these laminates in motors and transformers everywhere.
One might liken this to damming a stream with multiple dams, one after another. They stop the stream from flowing. Putting the laminates the wrong way is like putting dams parallel to the stream: the water will run between them and keep flowing.
The die cut laminate technique isn’t very practical at home, and it’s not even the best way to do it. For us, wanting the strips all one inch tall, strips of one inch insulated nail gun finishing nails solve the problem. They can be spray painted or varnished for insulation and broken apart to any desired length.

The iron alloy used in motor coils needs certain specific characteristics. One is that they shouldn’t magnetize. Take a magnet (eg, one of the supermagnets) and rub it along the nails in one direction. If the nails become magnetized and will attract to other steel objects, they’re not good. Try a different brand. The ones I’ve tried so far have been good: they don’t magnetize. perhaps they’re specifically made that way for some obscure but fortuitous reason. (Easier to handle?)
Another good characteristic is if the nails don’t conduct electricity very well along the strip. This should reduce any remaining stray eddy currents a bit. Some brands are better than others. The main thing, though, is to insulate between the rows.
(BTW: Don’t try sanding or grinding the heads and points off the nails: the filings get in and increase the electrical conductivity between nails within the strip. Breaking the strips apart or bending them too far reduces connectivity but weakens the strip. Generally it’s best just to leave them alone.)

Paint (at least) one side of the nail strips with polyurethane insulating spray paint. This insulates the rows electrically from each other. I found this paint at an electric motor repair shop. (or perhaps auto engine enamel would be fine?) Allow it to dry.

I’ll be making a “jig” with a stainless steel plate. (I’m hoping motor varnish won’t stick to it.) It’ll have two holes 1.625” apart, threaded for 1/4” N.C. bolts.
Two (stainless steel) bolts will be threaded through until the smooth part of the shaft, 2 or 3 inches long, meets the plate. The protruding threaded ends will be cut off so it sits flat on the work table.
The coil of wire is placed, centered, around the bolts. The leads should be directly between the two bolts, not near one of them.

A coil core sans coil, approximately as it should sit on the stator, with the bolts fore and aft and the strips parallel to the rotation. The copper coil wire will stick out beyond and inside the (~2”) mounting face.
Then start filling in the coil center with rows of nails, heads alternately up and down, and the insulation paint separating each row electrically.
The rows go left to right, in line with the bolts (NOT inside to outside of the stator diameter - that’s the direction eddy currents will flow).
Fill the core space, but stop without the core putting pressure on the copper wire, which might rub through the thin insulation on the wire and cause a short circuit.

This isn’t really a precision operation. Efficiency isn’t affected by a bit less iron, though maximum magnetism is. If the core is 90% full of nails, spending a lot of time filling tiny gaps and perfecting every detail can’t help much more. The motor controllers are set up to accommodate a bit of slack. (You will save a bit of epoxy, and-or the coil may be a bit physically stronger - again presumably minor points.)
With the bolts almost at the wire at both ends, it’s probably best not to fill in the few nails that would fit on the outside of the bolts - they’re too likely to break loose, which might cause problems. (This was found out during prototyping.)
Avoid nails sticking out beyond the others top or bottom.

Left: a coil as wound. (A bit thin as it’s #15 wire, oops!)
Right: A finished prototype coil cast in epoxy. (A second coat of epoxy on top wouldn’t hurt - much of it ran down and pooled at the bottom before it hardened.)
br> Epoxy Casting or Varnishing the Coils

Motor coils are subject to being vibrated back and forth not only by mechanical motion but by magnetic forces. They must be immobilized or the thin insulation will soon be worn off somewhere and they’ll burn out. Traditionally they are dipped in motor varnish and baked in an oven for some hours at 240ºC/475ºF. With these coils, multiple dippings and bakings are advisable.
They need to be baked for about 40 minutes. If they’re not done, all the nails will fall out when you try to pick it up and it’ll be a gooey mess. The baking should be done OUTDOORS, eg, in a toaster-oven. The fumes are powerful and noxious. I’m sure the stench would last a long time in a house. (Try a second-hand shop for a toaster oven - plug it in and make sure it works.)

Casting them in high temperature epoxy is another technique, which I used on the prototype. Good epoxy is probably easier to come by in small quantity than motor varnish, which is doubtless bought in five or forty-five gallon pails by typical motor repair shops.
With some home-brew wind power generators the entire stator with the coils is cast as a solid donut of polyester resin. This would quickly overheat in this application.

Finally, daub on some thick, flat black, high temperature enamel such as might be used for wood stoves or solar panels. Flat black radiates and transfers heat to the air best.

Section 4. Assembling the Stator

Coil Bolt Holes & Template

The nine coils are attached at 40º angle intervals around the rotor. The bolt holes are all in-line about 0.9 inches in from the outer edge, so at 9.6” diameter. Select one lug bolt hole as “north” and center one coil on it. The bolts are 1/4” diameter, so drill 1/4” holes. If the coils don’t attach easily, drill one hole of each coil a little bigger, eg, 9/32” or 5/16”. The distance between holes is the same as that used for the bolt spacing in the coils, 1.625”.
Use 2” long bolts. If they fit, put flat washers under each coil. If there is still room, put lock washers on the 18 bolts. Take a coil and bolt it on with two bolts, leads facing the center. Do the other 8. Do the bolts up tightly, but not so as to crush the cores, which are only glued together with motor varnish. (Torque spec: 20 foot pounds??)
A picture of the “production prototype” stator with the coils clamped on is shown on page 17 (“Stator with clamped on coils.”) I am not satisfied with the clamps. They have few threads and might strip, are metal and will pick up eddy currents, and they magnetize.
These metal clamps are the second attempt. First, regular nuts were embedded into the coil cores. They proved inadequate in varnished coils -- one pair pulled right through and the coil jumped up against the magnets. (They might be okay for epoxy cast coils.)
I’d like to try “hacked” (IIRC the name right) “collar nuts”, holding down (eg) flat nylon clamp strips. I might use #10 - 24 bolts and collar nuts instead of 1/4”, at least on the prototype. The #10 collar nuts shanks will fit in the 1/4” coil holes. To use 1/4” bolts and collar nuts on future units, the coil holes would be increased to 5/16”.
Only the wide gap between rotor magnets and stator coils (1/4”?), gives the clearance and leeway to permit clamps on top of the coils, and bolts that stick through just a bit!
TE plans to make and sell solid stator hole templates, and to put PDF ones on line. And a good coil clamping system... once one is figured out!

Wiring up the coils
It is preferable to face the leads inwards and do the wiring in the center if your hub leaves enough room. This both keeps lead lengths shorter and leaves more empty space for cooling airflow around the outside.
The coils of each phase are wired in parallel and the phases are “Y” connected, therefore one side of all nine coils is connected together. On the other side, the three coils of each phase, 120º apart from each other, are connected together and to a heavy lead (#6 if it fits, else #8) that will connect to the cable from the motor controller.

There are a number of ways to bare the end of the wire for connection. The insulation can simply be sanded off, but that’s usually pretty tedious. One popular wind plant maker prefers to burn it off the ends of the coil wires with a propane torch and then clean them off with sandpaper. That works well. I prefer to scrape it off with a small sharp knife (eg: pen knife, paring knife, not exacto knife), and clean it up with sandpaper. (Somewhat more tedious, but I’ve never burned myself yet!)

Make a ring of about #10 wire to attach the “center point” coils ends to. This should be soldered to all the wire ends going clockwise into the coils (or the opposite, as long as they’re all the same). I strip some insulation off the end, then I cut the insulation the spacing for of each coil and slide it down until there are nine bare spots the right distance apart. Wrap with electrical tape - the awkward shape leaves few options but tape unless you can manage to slip some sleeving on to cover each join.
A piece of small diameter soft copper pipe (eg 3/16” I.D., used for oil or propane tank connections) is about right to stuff in three coil wires in one side and the heavy lead (#8) in the other. These are then crimped and insulated. (pieces of large diameter insulation or sleeving, electrical tape. Forget heat shrink as the wires may get quite warm - heat shrink isn’t generally used in motors.)

Crimping the leads: The three coils on one side, the lead on the other, using a piece of copper propane pipe as a large crimp connector. (Two wires are the #14 coil leads; the third is a #10 wire - the coil’s lead was too short.) A piece of sleeving is then slipped over the bare copper

On the ends of the heavy leads, use Anderson Power Products 75 amp Power Pole connectors. These are the only physically compact suitable plugs I’ve found. You can buy single connector units and stack three, or get a three position plug and socket.
The plugs and sockets of the single units are identical - you just turn one over and they mate. There are different colored plastic bodies to identify the three phase wires.
I found the Power Pole connectors at an electronics store, not at any electrical supply.
Marette connectors (“wire nuts”) can of course be used, but leave the possibility of bare wire ends shorting and perhaps blowing the motor controller during installation or later maintenance.

Optics Circuit Board & Cable
The optics board is a somewhat custom mounting job. It needs to be able to shift around the axle until the correct timing angle is found, preferably while the motor is running. (I thought I had that angle worked out, but the timing is obviously not close enough to “right” on the production prototype as I write this preliminary manual. Perhaps some other “correct” angle will be found, the same in all EH motors, then stationary mounting can be considered.)

Optics board wired on PWB: 3 pairs of LEDs/Phototransistors around the axle at 40º spacings. The five connections are made via the five wire trailer plug: 1-Ground, 2-LED current supply, 3, 4, 5, - FotoA, B, C phototransistor outputs. The three LEDs are in series and their supply resistor is on the motor controller board.

The board as shown above is on the original fixed mounting, but the timing is not optimum. A silver “ligature” clamp around the hub for a rotatable optics board mounting (just made, from a flattened piece of #6 nickel-brass wire/rod) is also visible. I then silver soldered a long, flat handle and #4 mounting nuts to it. I put machine screws into the nuts and added electronics supply standoffs to get the right height. I drilled new mounting holes in the board and clamped it onto the top ends of the bolts with nuts.
If the hub is a continuous taper and no metal lathe is available (I confess to turning this indent on a lathe), holes for about three machine screws, to be screwed in above the clamp to prevent it from sliding towards the rotor, can be drilled and threaded.

The board mounted on the ring. A thin temporary handle that I hope won’t hit the magnets sticks out beyond the rim to where it can be adjusted while the motor is running for best performance.
Naturally, the complete, wired optics board with mountings, and the slotted cylinder it works with, is a component Turquoise Energy hopes to offer to builders.

Section 5. Assembling the Magnet Rotor

Shallow Hub Magnet Rotor. 11" rotor ("Gran Torino") with supermagnets at 10.5", leaving 1/4” outer lip. Black is north, yellow south. An ABS slotted optics interrupter cylinder is mounted on the axle plate.
Also note: 5 hole hub was drilled to fit 4 lug car; “skip tooth” magnet pattern; and that the (trailer) axle is screwed to the rotor for magnet safety.

Supermagnets

The neodymium, iron and boron supermagnets (Nd:Fe:B or NIB magnets) are very powerful. It is easy to get nonchalant, but one or two magnets can do serious injury. Never get your finger between two of them! A rotor with a dozen could be deadly. If two magnets get stuck together, there is a special jig to get them apart safely. One of the reasons I chose the 1/2” x 1” x 2” magnet size for hand-made motors is that I would want a machine to handle supermagnets any bigger than that. Also they’re the most common and cheapest large size to buy... perhaps for the same reason.

When the rotor is assembled, put on gloves and place a couple of layers of thin (flexible) sheet steel over the magnets as a safety measure, and put it in a box with some styrofoam over it as well.

Two 1” thick foam safety cutouts. The pieces of sheet metal magnetically clamp it to the magnets. The second one has a large center cutout to permit bolting it to the car wheel without removing it. Once one bolt is well started, the guard may be removed if desired, but less bolts and socket drives end up stuck to the magnets if it’s left on.

That this seemingly innocuous rotor is a very dangerous piece of equipment can hardly be overstressed. The magnet rotor may be thought of as something of the nature of a loaded rat trap (or maybe a leg-hold trap for larger animals!): Working with it is a case when simply moving slowly and deliberately won’t protect you from sudden and perhaps very serious violence from a single misstep.

Holes in the Rotor
< All holes in the rotor should be drilled to fit and checked for fit before putting the magnets on the rotor:
* Lug bolt holes, if the ones on the rotor aren’t right for the car wheel.
* Holes to hold the axle to the rotor.
* Any holes required in the rotor for mounting the slotted “optical commutator” ring.
* Hole for the magnet bolts if using screw-on magnets.

For safety, it is recommended that the motor axle be bolted (or welded?) to the magnet rotor separately from the lug bolts used to hold them on the car wheel, and then kept on the rotor. The presence of the protruding axle will reduce (not eliminate) the chance of having all the magnets clamp flat onto a large flat magnetic object with potentially deadly force.
A specific place the protruding trailer axle won’t help is one attempts to install the stator with the center hub missing. DON’T GO THERE! (Always remember to hold the stator only by its arms when putting it on, then you’ll only have a mechanical disaster instead of a crippling or deadly one.)

Magnet Bolt Holes
Supermagnets can be ordered as simple glue-ons or with two holes for flat head screws to also bolt them onto the rotor. The ones I got with bolt holes would fit #10 machine screws, but I used #8, and I needed the bit of play that allowed for inexact hole positions.
I drilled and tapped the rotor for that size. Again, a template would have been helpful and I expect TE will be making them.
In principle I prefer the bolt-ons, but I did the car motor rotors just with “epoxy steel” glue. It’s after 10 or 20 years that the glue is likely to give way, as I found out on a used electric lawn mower.

Magnet Placement, handling the magnets, magnet placing jig

Up to six magnets can be placed without too much danger, but as more are added between, things get very scary without a safety and placement guide. Here is the latest magnet placement template, top and bottom views:

Magnet placement template, top and underside views. (The pacific dogwood (oiled) was just too beautiful to put ugly screws into from the top!)
It’s set up for the 10.5” diameter rotor size with 18 magnet positions. But I actually only put on 12 magnets, skipping the middle one of each polarity. The template fits over the magnets already on the rotor (if they are correctly placed), while helping to guide the current magnet into place in spite of very strong forces trying to flip it and pull or push it aside, and protecting the worker from getting his fingers crushed between two magnets.
The black mark at the entrance to the slot is some of the “epoxy steel” glue. As you can imagine, it’s impossible at some point in the insertion to keep the magnet from snapping down onto the rotor.
(*Somewhere*, I had pictures of actually putting the magnets on the rotor with this jig. Now I can’t find them!)

"Epoxy Steel" epoxy glue
This is great glue for the magnets! I got it at Rona hardware.

Optics Interrupter "Can" (Optical sensor system)

This little rotor tidbit is the base of the control system. Its slots and solids spinning by three LED/phototransistor pairs indicate the magnet positions to dictate the phasings of the motor controller’s drive signals.
In the prototype shown, a 2” ABS plumbing pipe end cap had most of its end removed to fit around the axle, and the “south magnet” slots were cut out with a hacksaw. It was then bolted onto the axle plate with machine screws.
Operation of the optics system is described in the theory chapter.

The slotted ABS “tuna tin” on the rotor and the optics board on the stator.
When I mounted the board on the new adjustable ring, I sanded the end, the “solids”, a little shorter so they wouldn’t hit the mounting nuts or the wires on the slightly raised board. One little piece was glued back on (methylene chloride or plumber’s ABS solvent cement) where a slot was cut a bit too wide. Adjustments are simple with ABS!

The “slotted tuna tin” shape is preferred over a flat slotted rotor because the stator and rotor can be pulled apart freely without the phototransistors hitting anything, and because only a flat circuit board with normally mounted parts is required.

Section 6. Mounting the Motor

UNUSUAL CAUTIONS: Read carefully before proceeding

DO NOT attempt to fit the stator and rotor together until the rotor is fastened securely to the car wheel. Always keep the safety guard on the magnet rotor: do NOT leave the magnets exposed! Keep the magnet rotor well away from all magnetic metal. DO NOT attempt to fit them together without the arms securely attached to the stator. Be sure the hub is properly in place to receive the stator. The magnetic forces are very powerful (don’t forget they move the whole car) and can easily and very suddenly CRUSH your fingers, which you will be unable to extricate.
One part will suddenly jump into the air to meet the other if they get too close together, and woe on any human body parts in between! (This also applies generally to any magnetic metal and the magnet rotor.)
The magnets themselves can also shatter if they suddenly pull onto something solid (especially two of them coming together), sending off high velocity shrapnel.
When the rotor is mounted on the car and the stator is to be fitted onto it, put in the hold-off bolts to keep the stator back at least 2/3 inch from the rotor, more preferably a full inch.
HOLD THE STATOR BY THE MIDDLE OF ITS MOUNTING ARMS, one on each of the arms for balance, where, when the magnets yank the stator in, your hands won’t contact anything. Keep yourself clear of the center hole, where the axle and-or lug bolts will push through.

Brake Drum Housing Attachments
The mounting arms attach to the back of the brake drum housing behind the wheel. At its center, the stator is firmly attached to the wheel by its axle, but the arms are needed to prevent the stator from turning. They absorb the rotational torque of the motor’s thrust and braking. The brake drum housing is strong enough to handle this force. Consider: the brake cylinder mounts on it and it must be able to absorb the torque of screeching tires.
There are two pairs of arms, upper and lower. The trickiest and most “customized” part of the whole installation is securely mounting and placing these arms so they are out of the way of all moving parts as the suspension rides up and down from the top of its travel to the bottom.

Upper Bracket installation.
The protruding arms of the bracket were later cut shorter, reducing the leverage of the twisting force. The stator arms were bent to meet these shorter ones.
First, the tire wall generally sticks inwards past the housing, so I bolted two thick steel plates to the brake drum housing to extend it beyond the tires. Alternatively, the stand-off blocks could be welded to the rectangular tubing, or the tubing could be bent to fit. (I had to cut the rear block and do some bending of the lower arm anyway, to get it past the shock absorber.)
For mounting, the brakes must be disassembled and holes drilled through the housing Care must be taken to ensure the heads of the bolts are clear of the brake shoes and mechanism, and don’t interfere with operation of the brakes in any way.
(In fact, the front mounting block here pushed on the parking brake cable and the right side parking brake didn’t work well, if at all.)

1” x 2” tubing wouldn’t have fit in. I wanted 0.5” x 1.5” tubing, but local stores only had the 0.5” x 1”. I used that. It probably flexes a bit more than is desirable.
To bend the elbows, first I bashed in the flat center section with a hammer along the area to be bent, from both sides. Then I C-clamped them to something roundish. I can’t remember what it was, except that it had a straight section and I used two big C-clamps, clamping the short arm end, which left the longer center portion to push on.
I did it out at my “anvil”: a flat solid rock sticking out of the ground in the garden, with a 24 oz hammer. It was tough going with nothing to really hold that short end, and I’m sure a very big vice would have been most handy, or a really skukum work table that would have held those C-clamps solid while I pounded.

Fitting and vehicle suspension considerations
(up-down travel of wheels with weight, bumps and potholes)

The bracket should be tested to make sure it doesn’t hit the car at any point in the travel of the suspension.
Jacking up the car on the body near the wheel will cause the wheel to drop down relative to the car until the suspension “tops out”. But that usually moves the bracket into more open space. It’s the other direction where things usually get tight.
To push the car down one must add weight, and perhaps “jump” up and down on the bumper. It should be ascertained that even when the suspension “bottoms out” the brackets don’t hit anything.

Around-the-wheel Arms
Once the arms have been attached, they must be fine-adjusted - again bent - to meet up with the stator arms for easy attachment. The best way to do this is with a piece of rectangular steel that fits inside the tubing, eg a 1/2” x 3/4” x 3’ long steel rod. Stick it in the end and move it around until the arm ends where you want it.

Stator Arms & Strapping

Bolt the arms onto the stator before attempting to mount the stator to the magnetic rotor. The stator’s arms must end near the brackets coming around the wheels. They are then attached together with pieces of steel, “strapping”. I used 1/8” x 3/4” steel bar for this, threaded for 1/4” bolts.

End of stator arm (much hacked prototype) with steel “strap” to connect it to the wheel bracket.
Installing the Rotor Jack up the wheel and remove the lug nuts. Then bring the magnet rotor. Approach the car with extreme caution. The rotor will not seem much attracted to the steel wheel as long as the magnets face outwards. But if the magnets face the car or the wheel in proximity to it, and if the axle isn’t attached or it goes though a gap, they can clamp onto it, and the force will be such as to damage the magnets, crush fingers, and require major effort with a crowbar and wedges to remove.
Nyloc Nuts & things that fall off while driving

Just a final safety reminder that the motor should be solid. “Nyloc” nuts can be valuable for keeping bolts from falling out even if they come loose. So can lock washers and “loc-tite”.
Check everything carefully before enclosing it, and before taking the car on the road. Listen for anything unusual as you start to drive and for the first while.
Check again after 1, 5, 25, 100 and 500 Km.
The one-piece coil casting on my first prototype fell partway off after some tens of kilometers, when some of the bolts came loose. (The design was quite different from later versions.) Amazingly, it did it in a parking lot. I stopped at once and removed it. No harm was done. Potentially, it could have been on a busy highway with nowhere to pull over. It would probably have broken right off and been a serious hazard for cars behind!

Electric Hubcap Specs.

approximate nominal electrical & power specs
Volts: 36 (battery voltage)
Amps: 110 - 120
Watts: 4050
HP: 5
Cooling: moving air & convection; exposed coil surfaces

Overall diameter (with 12” I.D. “culvert pipe” PVC plastic cover): 12.5”
Rotor & Stator nominal Outer Diameter: 10.5”
Overall Motor Length: Varies by spindle & rotors chosen.
Practical minimum length: 8 + 13 + 8 + 25 + 8 mm = 62mm or 2-1/2” (Magnet rotor thickness + magnet width + air gap + coil width + stator “rotor” plate thickness) -- excluding protruding nuts and bolts

Coil Size: 1” thick circular disc, 2.8” diameter
Coil Wires: 70 turns of #14 AWG magnet wire wound on 2” diameter cylindrical former, about .95” across.
Coil Cores: Strips of 1” long nail gun finishing nails, painted on one side and broken to length to create laminated cylinder, 1” tall x 2” diameter. Two voids are left for 1/4” diameter mounting bolts.
Coil Iron: The nails should not become magnetized when rubbed with a supermagnet. (ie, they should not be able to pick up other metal objects.)
Inductance: I measured 0.60 mH on a single coil, and 0.60 mH across any two phases of the assembled motor stator. (Neither figure is a misprint.)
“Glue”: Finished coils are cast in high temperature epoxy or varnished with motor varnish and baked.

Stator: nine coils around rim facing magnet rotor magnets, spaced 40º apart. three phases, each with three coils 120º apart wired in parallel. Motor is wired in “Y” configuration, so one side of each coil (eg the CCW lead in) goes to the center point while the other ends (eg the CW ends) tie to the three supply wires, #8 or #6 AWG.

Gap, stator coils to rotor magnets: 5/16” (8mm) nominal. (There is an optimum somewhere around here... a gap that is too small makes excessive vibration and WORSE motor performance instead of better.)

Rotor Magnets: twelve - 2” x 1” x 0.5” Nd-Fe-B (“NIB”) or other supermagnets, nominal strength 35 - 45. They should be magnetized through the thickness; ie, the large (2” x 1”) faces should be the poles. (Other sizes to make a similar magnetic field would also work fine.)

Electric Hubcap is a trademark of Turquoise Energy Limited.

Input for HIGH drive (phases A, B & C are alike)	input for LOW drive (A, B & C are alike)	MOSFET Outputs: High side & Low side
1 (“off”)	1	Both Off
1	0	Low On, High Off
0 (“on”)	1	High On, Low Off
0	0	Both OFF (NOT both on!)