My related essay on technology of Owen Magnetic car is here: Technology of Owen Magnetic car with Entz electromagnetic transmission
My related photo essay on the recently closed Wells Auto Museum is here: Tribute to the Wells Auto Museum
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Overview
Introduction
Leno's (upright) Baker Electric
Battery
      Is the battery in the Wells car 48V or 60 V?
Baker Roadster specification
Battery box metal plaque
      Battery box metal plaque decoded
Wells Baker display plaque
      Confusing Wells 1908 Baker plaque
Motor control
Motor configuration
      Standard traction approach
      Does 300% overload rating mean the Baker motor can output 10.5 hp?
      Motor curves
How much hp is needed?
No electronics in 1908
Leno accelerates his Baker
      Current adjusts automatically
Watts and amps, decoding the plaque numbers
Baker volt-amp meter
Jay Leno on Baker Electric history
** Schematic of early Baker Electric
Resistive control of DC series wound motors in trains
Resistor watts and style
      Train resistors
      Assembling a high power resistor bank for a train
      Engineering considerations
Photos of controller components during restoration of a 1911 upright Baker Electric
Baker related links

Detroit Electric cars
Steinmetz, the engineer
Detroit Electric technology
     1914 Detroit Electric controller --- before and after
      Detroit Electric going into reverse
      Battery options

1890s Commercial electric era
     Missing drum controller
1st generation of high power electric cars
      Mercedes Mixte and Porsche Semper Vivus
2nd generation of high power electric cars
     Woods dual power
      Owen Magnetic

Owen Magnetic -- Baker goes high power and high tech in 1916
      Entz double machine
Analysis of the Entz/Owen Magnetic electromagnetic transmission (excerpts)

Overview
        The Baker years of 1900 to 1915 spanned the range when individual electric cars were popular. Because 1,000 lbs of batteries could only deliver 2-3 kw for 2-3 hours, the hp rating of these cars was low (2-4 hp) and their range was limited. Prior to 1900 was the era of commercial electric vehicles: taxis and trucks, many made by Electric Vehicle Company of Hartford Conn, which sold cars under the brand name Columbia. After 1915 there was a short lived period of a few high power, high performance electric drive cars where the battery was replaced by a combustion engine coupled to a dynamo. While this increased the available power by x10 or so, and solved the range problem too, it produced an expensive and heavy car. The most notable of these high power, electric drive cars was the Owen Magnetic, which had a unique electromagnetic transmission designed by Justus Entz. Walter Baker acquired the patent rights to Entz drive train in 1912 and guided the Owen Magnetic into production in 1915 where it survived until 1922.

Introduction
        My first view of an antique electric car was a 1908 Baker Electric at the Wells Auto Museum, Wells ME, the museum now unfortunately closed. As a retired EE engineer who did motor control, I was curious about early electric cars like the Baker electric. I wanted to know more about the power train, the battery, the motor, and how the motor was controlled.

        The Wells Baker electric was a 1908 model that had been owned by a Rockefeller and its seating had been somewhat customized with facing rear seats added. All the Baker models are included in a period book summarizing car models available in 1907 and comparison of its Baker sketches to my Wells photos tells me that that the Wells (Rockefeller) car was probably a customized version of the Baker M chassis Roadster (seen below). Baker had several body styles, most which were very high, totally enclosed and well appointed inside, no steering wheel (steered with a bar), with no obvious battery compartment that were marketed primarily to women. The Roadster was one of only two models that were more conventional in appearance, designed to appeal to a man, with a large 'engine compartment' in front (holds the batteries), a steering wheel, not fully enclosed and performance was featured ('fastest electric on the market').

        Baker Runabout was a slightly smaller version of the Roadster. A Baker add says the Runabout was designed for "professional and business men", and many users don't recharge until they have driven it 100 miles (undoubtedly a claim about as accurate as manuf claims for battery life in tablet computers). So what's a Runabout worth? This auction site reports a 1912 Baker Runabout, which had been modified for street driving with an 18 hp electric motor and modern batteries, sold for 85k in 2012.  1910 Baker Victoria (open 2 seater with steering lever) with an auction est 30k-50k sold in 2009 for 77k. However, a 2007 NYT article about antique electric cars reported much lower auction prices, saying a 1915 Baker Electric (or Detroit Electric or Rausch and Lang) runs 9k to 20k depending on condition (unclear if this is pre or post restoration). These 2007 prices were based on the Gold Book, published by Manheim Auctions, but a google search shows the Gold Book, once the standard, has in recent years been replaced by the 'NADA Appraisal Guides', but I can find no values for any Baker Electrics in a NADA search.

Leno's (upright) Baker Electric
        Turns out that a good source of information about the Baker comes from Jay Leno. His extensive collection of cars includes an enclosed model 1909 Baker Electric which runs, and there are a couple of Youtube videos of him discussing how the car works and showing him driving the car. This 2007 NYT article which discusses Leno's car includes addition details. Leno says his upright Baker Electric will go 110 miles (4-5 hours at 20-25 mph), but note his Baker is powered by 12 modern deep discharge 6V lead-acid batteries (72V). Leno's 1908 car coupled the motor to the differential via an (enclosed) speed reducing chain drive. As Leno demonstrates the driver had four controls: acceleration/speed lever (left hand), steering bar (right hand), and two brakes pedals in the floor (one for each of the rear brakes). The brake description might be wrong. A write up by an auction house on a 1910 Baker says one of the brake pedals worked the rear wheel brakes and the other a brake on the drive shaft. This Ebay site has the best listing of antique car prices I found (no electrics).

        Notice the Leno drives from the back seat. The only indicator of the car's performance, its 'dashboard' if you will, is a single combined volt/amp meter, which the photo shows is tucked under the rear facing fron seat.

Battery
        Leno's car uses modern lead-acid batteries, six deep discharge (electric vehicle) 6 volt batteries in the front compartment and six more in the back. The voltage of a lead-acid battery cell is 2V nom (2.16V open circuit for one deep discharge battery I checked), so a six volt battery is composed of three cells in series. With 12 six volt batteries the voltage available to run the electric motor in Leno's Baker is 12 x 6 = 72V (78V open circuit), which agrees quite nicely with the 80V given on the Well Baker plaque. (I later noticed that Leno in his YouTube video comparing his Baker to modern electric cars he says explicitly that the voltage of his Baker is 78 volts.)

       Leno says his Baker is 'maintenance free' and that the original insulation of the windings have held up well. In other words the motor and controller are (probably) original, and it can be operated quite nicely from the 72-78V that the modern batteries deliver. Slight differences in cell voltage resulting from changes in the technology of lead-acid cells over a century would translate into only small differences in top speed. On the other hand a change in the number of cells could produce a somewhat larger change in top speed proportional to the voltage change. For example Leno is now using 36 cells and if originally the car had used 30 cells (?), which is what the Wells battery compartment contains, then the car's top speed with 36 cells would be increased 20% or about four miles per hour (22 mph => 26 mph).

       I had puzzled over the picture of the Wells Baker battery compartment, so the information from the Leno videos provided a useful baseline. Leno's car is run on (12 x 3) = 36 lead-acid cells in series. Each cell in older lead-acid batteries is identified by cap (used to add the acid-water mixture). A count of the cells in the picture of the batteries 'under the hood' of the Wells car is 30 = (5 x 6) arranged in two containers with 12 cells each and one half sized container with six cells. The interconnects in the upper right initially confused me as it was not a simple series connection, but I think I now see that all 30 cells are connected in series. This would provide 60-65V from modern lead acid batteries. This doesn't square very well with the Wells plaque that says the battery consisted of "4-80 volt 96 amp HR exide cells". I originally took this to mean the battery compartment held four 80V batteries connected in parallel, but this is obviously wrong. I now suspect the electrical information on the Wells plaque was written by someone who had little understanding of electricity. If the 'thin exide' cells of the 'Electric Storage Battery Co' of Philadelphia had an open circuit voltage of 2.66V, which I suppose is possible, then it would provide an open circuit voltage of 80V = (30 x 2.66V), but still it is unlikely as the chemistry of the lead-acid storage battery has changed little since it was invented in 1859.

        When I noticed this problem, I drew out all 30 cells and drew in all the interconnects to figure out just how the cells in this battery are wired up. What I found was this. The top side (lead) jumpers show clearly that the left 12 cell box is wired as a 24V battery. The center 6 cell box is wired as a 12V battery. The right 12 cell box is also wired as a 24V battery, but (for some reason) configured as three 8V strings in series.

Three 8V strings in series
       The regular cell-to-cell shorting bar pattern connecting the cells in series in the right box appears to breakdown in the upper right rear, but notice there is a wire from the right box rear cell on the left that wraps around the back of the right box that looks like it connects to 2nd cell from rear on the farthest right. If this is right, then the right 12 cell box is configured as 24V battery composed of three 8V strings in series. Why?

        This could work. It's logical from a maintenance point of view. It may be cleaner than trying to tap off 8V for headlight power from the motor string, which would invariably lead to cell unbalance that a charger could not fix, and so may be unworkable. However, it does complicate the charger design and interconnect because it must put out two separate voltages 48V and 12V. If you mostly drive during the day, routine overnight charging could be just 48V, recharging the 12V center unit as needed when the headlight start to dim.

        On the one hand it is surprising that the highest power Baker car of 1908 would run on such a low voltage, but on the other hand the trend was for voltages to go higher over the years. The wiring diagram (below) shows the 1902 Baker ran on 36V (curiously no connection for headlamps is shown), so it might be in 1908 the voltage was 48V and a year later in 1909 (Leno's car) it was higher at 60V (or 72V).

        In terms of power and range of the car there's not too much difference between the 48V or 60V. At 48V 80% of the batteries under the hood are powering the motor. If the average power to cruise along at 22 mph is 20% less than I previously estimated, it is still compatible with a 3.5 hp motor and the car's range is the same. Previously I assumed the motor was driven near its continuous rating of 3.5 hp at top cruising speed, but there may very well have been a 20% safety margin.

        An 80/20 split for motor/headlamps also passes a reasonableness test. When the battery capacity of an electric car is discussed, the focus is usually on range, but with how much battery to have for headlamps the issue is time. The battery Ahr is rated at 21A for 6 hr.  48V @ 21A is about 1 kw, so there is enough motive power to drive around slowly for six hours or so, and if this is at night, you need the headlamps to stay on. I have no information on the wattage of the Bakers headlamps, but a reasonable guess might be 100 watts each (200 watts total). The center box 12V battery has 25% of the capacity of the two outer boxes, which means it can put out 250 watts for six hours. This matches up nicely with my guess that about 200 watts might be needed to run the headlamps. An 80/20 split provides enough power for six hours of night time low speed driving with headlamps.

Baker Roadster specification
       I later found a spec for the model M roadster 1907 (below), and it says the car had 32 cells, pretty close to the 30 cells in the battery compartment at Wells. 32 cells would give a battery voltage of  64V to 69V. Baker sold the car with different brands of batteries, so the battery in the Wells Rockefeller car may very well be the original. The wiring is clearly old, the terminal to terminal connections are soldered, 'The Electric Storage Battery Co.' was a major supplier of lead-acid batteries in the early 1900s, and most importantly the electrical information on the metal plates attached to the battery boxes indicates it had the power and energy storage to drive the 3.5 hp motor and achieve the speced range (60 miles). Note also the 3.5 hp motor of this car has a 300% overload rating, which means for a brief time (minutes) it is capable of outputting three times its rated torque and increasing its power output by the square root of 3 (x1.73) to 6 hp. When Old Rhinebeck Aerodrome was restoring their 1911 Baker upright to running condition, they replaced the missing battery with ten six volt batteries (10 x 3 = 30 cells), which would give a battery voltage of 60V to 64V.

Battery box metal plaque
       I was initially unable to make sense of the metal spec sheet mounted directly on each of the larger battery containers, which say "40 cells ... in 4 trays". The wording on the Wells plaque (below) is probably based on this. First of all, where are the four trays?  My photo clearly shows each of the larger containers has only 12 refill caps, which (almost for sure) means 12 cells (or 24V nom). Adding in the six refill caps of the smaller center box gives the battery a total of 30 cells (60V to 64V), this is not unreasonable since it is pretty close to the speced 32 cells of the 2007 Roadster (see above).

Battery box metal plaque decoded
        (update)  Ok, I think I have figured out how to decode the plate. A mounted spec plate like this would be expected to be quite accurate. Electric Storage Battery Co manuals are online, and they show that their storage batteries were designed to be taken apart by the user so the plates and separators could be cleaned. It may very well be that inside each large 12 cells box are to be found 4 smaller boxes each with 3 cells in a row. This is the '4 trays'. Each tray is essentially a 6V battery, so from this perspective the Wells Baker battery is made up of ten 6V batteries, four of the 6V batteries in the large boxes and two in the smaller center box.

        The plate text begins "40 cells type MVG11 plates in 4 trays", but this does not mean 40 cells in the total battery nor 4 batteries (in parallel), which the plaque writer seems to have assumed. What I think it very likely means is that each tray (of 3 cells) is composed of 40 (stacked) plates. The text 'cells type MVG11' is a description of the type of plate used. A typical 2V cell of a lead-acid battery is composed of series of alternating positive and negative plates with the positive plates connected together and the negative plates connected together. The paralleling of many plate pairs inside each 2V cell provides lots of surface area for ion transfer and explains why each cell of a lead-acid battery can supply high current.

        The text continues, "normal service rating 21 amps for 6 hours".  This is 21A x 6 hr = 126 Ahr, which since all the cells of the battery are in series, is also the Ahr rating for the whole battery. Notice this disagrees with the 96 Ahr written on the Well Baker plaque. It would give the 30 cells of the whole battery a nominal power output of 60V x 21A = 1,260 (about 1.26 hp) for six hours, or 3.78 hp for two hours, which matches up well with the (continuous) 3.5 hp rating of the motor. In two hours @ 30 mph (likely top speed of the Roadster) the car could go 60 miles, which is in fact the speced range of the 1907 Roadster (see above).

Battery kwh comparison to modern electric cars
       It's interesting to compare the kwh rating of this Baker battery with a modern electric car battert. The baker kwh rating (ideally) is 7.56 kwh = (21A x 6hr x 60V). The electric car with the largest capacity battery (as I write) is the Tesla model S, which has an 85 kwh battery. A more modest extended ranage electric car like the GM Volt has a 16 kwh battery. So the Baker's 1,000 lb (roughly) lead acid batteries had about 1/10th the kwh rating of the lithium ion battery which fills the floor of the Tesla Model S, or about half the kwh capacity of the more modest Volt battery.

Wells Baker display plaque
       Here's my photo of the plaque on display at the Wells Auto Museum next to its 1908 Baker electric car. The electrical description of the battery on this plaque, specifically the text "4-80 Volt 96 amp HR exide cells", is at best vaguely worded and likely was written by someone who did not understand much about lead-acid batteries and garbled the information on the metal spec plates attached to the two large battery boxes. It is I believe just plain wrong and has mislead other sites with Wells pictures. It certainly disagrees with the information on the metal spec plates mounted on what I think was probably the original battery of the car.

Confusing Wells 1908 Baker plaque
        On a quick read the above Wells plaque appears to say the car's battery was composed of four 80V batteries (supposedly in parallel). Four 80V batteries is absurd. Four 80V batteries would require 4 x 40 cells = 160 cells. Each cell is identified by a refill cap, and the cap count for the total battery is 30. Note even enough cells for one 80V battery let alone four. A lead-acid battery with 30 cells (in series) has a voltage of 60V to 64V, not 80V.  The battery mounted metal spec plate says the cells could output 21A for 6 hr, this is (21A x 6hr) = 126 Ahr, not 96 Ahr. In other words the plaque has the voltage about 33% too high (80V/60V = 1.33) and the current capacity about 33% too low (96Ahr/126Ahr = 1/1.31). The mysterious "4" in the text of "4-80" is a mis-reading of the metal spec plate that (properly interpreted) is saying each of the two large battery boxes is internally is composed of four (removable) "trays", each of which would contain 3 cells (in a row) built from 40 plates.

        One possible explanation for the 80V and lower 96 Ahr is that when the plaque was written the display car might have been missing its battery (lead-acid batteries wear out), or it had a different battery. The battery I saw was clearly old and fits well with the car specs, but that doesn't guarantee that it was the original battery.

Motor control
        The control of the motor in the Baker Electrics, from the perspective of more than a century later(!), is dead simple. The drive train has four components: battery, DC motor, and between them a resistor string whose ohms can be varied by a switch assembly.

        A cleverly engineered set of high current switches, operated by a single rotating lever, changes where in the resistor string the battery is connected and/or how many resistors are shorted out. A lot of resistors switched in means high ohms limiting the current that can flow into the motor resulting in low torque and low speed. In effect this is first 'gear'.  To accelerate the car the resistors of the string are bypassed step-by-step, lowering the ohms thus increasing the current into the motor resulting in more torque and speed. Additional switches in the switch assembly, activated by rotating the lever in the reverse direction, flip the direction of current in one of the motor windings. This flips the orientation of one of the two magnetic fields inside the motor, which reverses the push-pull action between the two magnetic fields causing the motor's torque polarity to reverse. These four components give the car step-wise control of speed (primary) and torque (secondary) in both the forward and reverse directions. And this simple configuration even automatically regenerates some of the car's kinetic energy back to the battery under some conditions, such as when the car's speed is retarded going down a steep downhill.

Motor configuration
       The DC motor is series wound, meaning the stator (field) winding and rotor winding (via brushes) are wired in series. An auction description of a 1910 Baker says its series wound DC motor was manufactured by GE and had four poles. Series conection of the field and rotor windings makes both the motor torque and ohmic heat loss in the motor windings a function of the current squared. This keeps the motor efficient when it's not working hard, say at lower speeds on level ground. Operating at 1/3rd of its rated torque its heat loss is also down to 1/3rd. Of course at lower speeds more external resistors switched in, so there is some heat loss in the resistor string, but when the car is run near its top speed the resistor string is totally bypassed reducing its heat loss to zero.

Standard traction approach
        As I did more reading about the controls in early electric cars, I slowly began to realize its basic control design was (probably) not new. It was the standard traction design of the era: a DC series wound motor with switched variable resistance to vary the speed/torque. This was used in early electric trains and trolleys, which preceded electric cars by a few years. A train with multiple high power motors would typically use contactors (relays) to switch resistances in and out. This made the acceleration somewhat herky-jerky, but in a train or trolley it was acceptable, and at the time there was little that could be done about it. For the electric car the design was scaled down and implemented more simply, reducing complexity making the car more easily drivable. The low power of electric cars (just 3.5 hp motor in the largest Baker) reduced the current which allowed the switching to be done without contactors. A single rotating cylinder, directly moved by the driver, with multiple, high current sliding contacts could do the job, do all the switching of resistance and flipping of torque direction. Baker ads (somewhat pompously) called this cylinder: "continuous torque drum type controller".

Does 300% overload rating mean the Baker motor can output 10.5 hp?
        Does Baker's 300% motor overload rating mean its 3.5 hp motor can (briefly) put out 10.5 hp? In a word, no. It means it can put out 300% of its (continuous) torque rating for a brief period. As explained in next paragraph, in a series connected motor speed must drop as current rises, so at 300% torque overload output power is 6 hp.

        The 1902 Baker wiring diagram (below) shows its motor was series connected, meaning the field winding carries the same current as the armature winding, and this was probably true of all Baker motors as it minimizes the load on the battery at lower torque and is the simplest way to configure the system. In a series connected motor the torque goes as the current squared because the motor torque constant kt rises with current [Torque = kt x current]. This means at x3 torque the current is up by [sqrt{3} = 1.73] and kt and kv (kv is the motor voltage scaling constant, the same parameter at kt in different units) are also up by 1.73. With kv up by 1.73 the speed of the motor must by down by 1.73 to keep the motor EMF equal (nom) to the battery voltage [EMF = kv x speed]. Motor power is [torque x speed], so torque up by 3 and speed down by 1.73 must mean motor power is up by 1.73 [3.5 hp => 6 hp]. This is consistent with the what the battery sees too. The battery has a (nominal) fixed voltage, so when it is outputting x1.73 more DC current is is outputting x1.73 more power.

Wells 1908 Baker 3.5 hp DC motor
(my photo)

Motor curves
        From 1912 Horseless Age here are some performance curves for an electric motor designed for a vehicle. This motor here is operated at a fixed voltage of 80V. This is a Westinghouse motor and the vehicle is not identified, but this is a somewhat larger motor than the Baker. This is a 4-5 hp (continuous) motor because the lower curve (right hand scale) shows the motor can run 3 hours at [50A x 80V = 4.0 kw] starting from 25C without overheating. Assuming 50A is the continuous rating, then the curves show that like the Baker motor this motor has a 300% torque overload rating to 150A (25 min @ 100A and 8 min @ 150A). Efficiency @ 50A is about 85%, which makes the mechanical output power about 4.6 hp for 4 kw input. From the efficiency, assuming all the losses are resistive, we can say @ 50A the motor dissipates about 600W of heat [12V x 50 A = 600 watts, 12V/50A = 0.24 ohm]. Speed ranges from 1,100 to 1,600 rpm @ 50A (under load).  The lower speed for series field connection of winding and the higher speed for parallel connection.

        A close look at the curves @ 50A shows the hp is about the same for series and parallel field connections; the parallel connection having lower torque and higher speed, which is consistent with lower kt (and lower kv). Not sure I understand this. I worked only with AC motors in my career and don't know a whole lot about DC motors, but I would have thought a parallel connection (at fixed 80V) would nominally double the kt vs a series field connection. Seems backwards.

How much hp is needed?
        The larger Baker cars had 3.5 hp motor, which in overload could output 6 hp. This hp seems very low, but consider, Walter Baker, founder of Baker Electric, built a 3,100 lb electric race car that could do 104 mph. According to this site, the motor in the Baker racer was only 12 hp (yes, the car was streamlined in shape). The motor manufacturer of its series wound DC motor was Elwell-Parker who had begun around 1897 manufacturing high current, medium voltage series DC motors for battery transport. If Baker used an Elwell-Parker motor in his racer, from what I know of engineering there's a good chance that Elwell-Parker motors were used in Baker production cars.

        Turns out my speculation was right. Later doing a search on Elwell-Parker I found that they are still in business, and on their site they say beginning in 1899 they began designing motors (and controllers) for Baker Electric. Another indication of the (probably) close relationship between Baker and Elwell-Parker is both were based in Cleveland. I had assumed Baker had designed the switch controller, but maybe it was Elwell-Parker. The Detroit Electric car reportedly used an Elwell-Parker motor and controller too. In 1909 Detroit Electric bought Elwell-Parker to gain exclusive use of their motor and controller patents, but spun them off in 1920 which is how Elwell-Parker survived.

No electronics in 1908
      While modern motor control focuses on controlling the motor current because it provides direct and rapid control of torque, current control is only possible with electronics (combined with current sensing and current feedback loops). However, in 1908 prior to the days of electronics the only way to vary the speed of the car, assuming the motor is direct coupled to the wheels, would be to vary the voltage applied to the motor. It might seem that building multiple taps into the battery cell string might do the trick, but it is fraught with problems, not the least of which is that the cells of the battery would not be equally loaded. A far better option is to insert a resistor between the battery and motor with means to change the resistance. This allows the motor's current, torque and speed to be varied. It's might not be as efficient, but it's simple, robust and flexible allowing the acceleration profile of each car model to be 'tuned' by adjusting ohms of the resistor string. With this type of control the driver 'shifts' the car by advancing a lever that (in steps) switches out more and more of the series resistance as the car speeds up, until at full speed the resistance is entirely gone, i.e. the battery voltage is directly applied to the motor. The Wells Baker plaque hints that this is the method of control when it notes that (top) speeds are "without using resistance".

Leno accelerates his Baker
       Leno in one of his videos driving his car shows how his Baker is 'shifted' as it speeds up, and he uses the word "rheostat", which typically refers to a power resistor (usually with a slidable contact). The Wells plaque implies that its high performance Baker model (Roadster) might have had a 'transmission' too to give it ten speed ranges (3 to 30 mph 'without resistance'), but I can find no confirming evidence for this. My guess is the lower performance women's model that Leno drives has the motor direct coupled to the wheels (no transmission). As the car accelerates, he is shown 'shifting' three or four times by pushing forward a level ('four quadrants') that he says (gradually) puts more current into the motor. The impression I get is that the lever is probably operating a switch with multiple contracts that in steps shorts out more and more of the series power resistor string until at top speed (22 mph) the resistance in series with motor is totally shorted out (removed from the circuit), so the battery voltage at top speed is directly applied across the motor. Leno appears to accelerate by just moving forward a single level, strong evidence there is no transmission in his 1909 Baker. And importantly this makes his Baker easy to drive, important for a car sold principally to women.

        A Baker ad says this: "The safest control -- The continuous torque drum type controller is absolutely proof against sparking and 'freezing'. The only perfectly safe controller." This is a reference to the forward and reverse torque/speed lever that operates the switches that changes the motor current and switches the polarity of the motor field winding to change the direction of the torque.

Current adjusts automatically
        With a simple series resistor control of a DC motor the motor current automatically adjusts (within limits) based on motor speed. When starting out at zero speed the motor has no back EMF, so the current (and hence torque) is set by the battery voltage divided by the total resistance. Leno makes the point that his Baker has great low speed torque and even fully loaded it can climb any hill. As the car speeds up more and more of the battery voltage drops across the motor back EMF causing the current (and hence torque) to roll off until at top speed most of the battery voltage is applied across the motor EMF.

        This natural variation of the motor's internally generated voltage (EMF) with speed, which all motor have, provides a sort of automatic control of current and torque. If the car encountering a hill needs more torque to climb it, it will slow down and the slower speed of the motor (alone) will reduce its EMF. This automatically provides more voltage across the series resistance, thus increasing the current and torque just when needed so the hill can be climbed. It's an automatic feedback mechanism.

        To go 50 miles @ 22 mph will take 2.27 hours of driving. If the battery is speced at 96 Ahr, then the maximum current it can deliver for this time is 42.3A = (96 Ahr /2.27 hr). Thus the power output from the battery (internally) is (80V x 42.3A) = 3,384 watts, and this is generally consistent with the car having a 3.5 hp motor. Clearly I picked numbers to come out right, still from what I read my guesses are not unreasonable for typical Baker electric (don't know about the higher performance Wells car). So we can ballpark that an 80V (open circuit) battery outputting 40A or so continuously for a little over two hours could take the car about 50 miles or so (level ground @ 3.2 hp) up near its top speed consistent with the stated battery Ahr (96 Ahr) and consistent with the thermal rating of a 3.5 hp motor, which was the largest motor used in Baker electric cars.

        (update) --- Using numbers from the battery box metal spec plate the battery voltage is lower (60V), but with a higher current (63A for 2 hr) that more than compensates providing a higher 60 mile range, consistent with the 1907 Roadster spec and the the motor rating (3.5 hp).

Baker volt-amp meter
        Here's the Baker volt-amp meter from a 1912 runabout, which had a 72V battery. It's operating current can be (roughly) estimated from the range of the amp meter. Assuming it had a 3.5 hp motor (?), the battery current with the motor at its rated power would be approximately 3,500 watts/72V = 49A. I found one piece of Baker literature that talked about their motors being capable of brief overloads to 300% (x 3 torque, 3.5 hp => 6 hp). x1.73 higher power means approx x1.73 higher current from the battery (49A x 1.73 = 85A), which fits nicely into the amp range on the Baker meter below. Note the amps go both positive and negative. Negative current does not mean the car is traveling in reverse. Negative current into the battery means the battery is charging, which can happen for example when the car is being (electrically) braked while going downhill. This meter is the total instrumentation in a Baker Electric car.

Jay Leno on Baker Electric history
        Jay spouts off on the Baker history, saying at one point there were 15,000 of 'this car' (maybe he means his upright Baker model or maybe all electric cars) in NYC where they were also used as taxis. In one of the YouTube videos he explains that in 1909 most cars had gas headlights, 'turning them on' requiring getting out and applying a flame to ignite the acetylene gas. In contrast the Baker headlights were electric (bulb), so no muss no fuss, and the interior of the car sported an electric light too. Before the electric starter (invented 1912) most women couldn't (or didn't) drive because it required cranking the car to start it, and steam cars were messy requiring 30-45 min warm up before you could move. In contrast with an electric car you just got in and turned a key, hence the Baker upright, enclosed models were designed and marketed to appeal to women.  Leno mentions that Henry Ford's wife, Clara, drove an electric car, every two years Henry Ford bought her a new Detroit Electric car.

        I identified Leno's model from the Baker catalogue of 1909 available online from the New York Public library. The Baker upright models were called coupes, and the identifying characteristics of Leno's coupe are that it seats four (see interior, above left) and it has rounded glass windows in the front corners.

Schematic of early Baker Electric
        I was surprised that a Bing image search (for Baker power resistors) turned up the wiring diagram (schematic) of a 1902 Baker Runabout (Runabout was a slightly smaller version of the Roadster). This was an early Baker and used six 6 volt batteries for a battery voltage of 36 volts. For the non EE engineer the voltage is only loosely related to the power a car can deliver. Power is the product of current and voltage, so the same power can be delivered at half voltage with double current. As a practical matter (to keep amps down and wire sizes reasonable), battery voltage needs to rise as power rises. Modern electric cars generally have a 300V battery.

        This diagram confirms my guess that the 'throttle' lever of the car operates a (rotary) switch with multiple contacts that stepwise switches in/out the resistors inserted in series with the motor. The car is put in reverse by a standard switch crossover arrangement (shown above the motor) that reverses the current in one of the winding (field winding) of the series wound DC motor. The text explains that the 'reverse' (torque) modes, activated by moving the throttle lever backwards in steps, functioned also to electrically brake the 1902 car since it had no mechanical brakes (except for a holding brake). Pretty neat! Later Baker electrics did have mechanical stopping brakes.

        The text associated with the 1902 diagram explains that the R1, R2, R3 current limiting power resistors were each a foot long and two inches in dia with a resistance each of about 1 ohm. R2 and R3 are hard wired in parallel to give a resistance of 0.5 ohm. This makes the available series resistances 1.5 ohm, 0.5 ohm and 0 ohm. The switch sequence is NEUTRAL (S2, S3, S4 all open), SLOW (S2 closed, S3 and S4 open, 1.5 ohms), MEDIUM (S2 and S3 closed, S4 open, 0.5 ohm), and FAST (S2, S3, S4 all closed, 0 ohm). The rotary switch was a heavy duty affair since it was handling and switching the full current of the motor. Notice the sequence of switch closing (S2, then S2, S3, then S2, S3, S4) can be implemented by a copper rotor plate that slides across and shorts stator contacts arranged in order S2, S3, S4. Note that this is not the only switch sequence that works.

        The car's 'shifting' works the same if only one switch is closed at a time (S2 slow, S3 medium, and S4 fast). S2 feeds the voltage into the top of the resistance string, S2 into the center of the string, and S4 bypasses the string. This could be implemented by a sliding bar that connects the rotor to stator terminals S2, S3, or S4 in sequence. In fact this seems more straightforward to me, but since the reference that gave the original sequence actually had one of the Baker rotary switches, I presume they looked at it and based their sequence on the switch itself.

        The reason the two switch sequences give the same result is basic circuit theory says it doesn't matter if resistors in the string that are bypassed (not carrying current) are left open at one end or shorted. However, there may be 2nd order characteristics that favor one option over the other. For example, the inductance of the power resistors is likely to cause some sparking when it is switched out, so it may very well be that one switch configuration has less sparking than the other and hence will be more reliable.

        Actually resistive control is one of a trio of of switch/resistor control methods for DC motor. The other two being various series and parallel arrangements of multiple DC motors and the use of resistor switched across the motor field winding to 'weaken' the DC motor's magnetic field by allowing some of the main current to bypass the field winding. Less field winding current means its magnetic field is weaker, and perhaps counter intuitively, this mean a higher train speed. The motor EMF is the proportional to [(field magnetic strength) x speed], so a weaker field magnet means a higher speed is needed to get the same EMF. The result is even with all the main resistors in the series string shorted and the DC voltage is switched drrectly across the motor, the motor speed can be further increased via switching in (one of more) of field bypass resistor. Some of these techniques were used in some electric cars too.

        The use of this type of motor control pre-dating electric car (in USA) has implications for both the theory and engineering of the early electric cars. Its wide use in trains of the time meant that series wound DC motors were well understood: the shape of the torque curve, how they act as generators and how to design them for high efficiency over a wide speed range. Important to the engineering of the cars because it meant that vendors skilled in making rugged high power resistors were in business. True the car's DC motor of a few hp was tiny by train standards. The DC motor even in early 1879 electric locomotive was 2,300 kw, more than x100 times larger than in an electric car. Still a lot of the technology as to how to make the resistors probably existed, so the car manufacturers probably had skill resistor manufacturers they could approach for a custom resistor. Even today much of the high power resistor business is custom business.

        The link below details how relays in trains were used to short the resistors of the series string as the train accelerated. It says that in UK trains the  operator did this manually up until WW1, when a current sensing relay was introduced to partially automate the sequencing. But I think it was done manually far longer in the trains of Boston subways system. I well remember traveling into Boston on its very old subway cars as a child in the late 40s and early 50son. Each time the train accelerated out of stop there were several quite distinctive jerks of the car as the train accelerated. This jerking was, of course, due to the relays under the train switching out its motor series resistors in steps. Each time the resistor string ohms are reduced the current surges until the trains speeds up to increase its back EMF. A current surge is a torque surge, and this is what caused the repeated jerks of the train that the passengers all felt each time it left the station.

         http://www.railway-technical.com/tract-01.shtml#DCMotorControl

        (update) --- A photo I later found of the resistors circa 2011 (see below) shows a set of long skinny bars that serpentine up/down. It is unclear if there are resistor wire elements inside, or whether the bars are solid, the metal alloy chosen for high resistance. A solid bar would be more rugged, but achieving such a high resistance (0.5 to 1 ohm) in this geometry would require a special high resistance metal alloy. A further advantage of a solid resistance bar would be lower inductance than one built with (coiled) wire, and this could be important as it would lead to less sparking when the resistor was opened under load, and Baker ads noted that less sparking (hence less pitting and more reliability) was a feature of their switched controller.

        Let's assume traction power for a train car was x100 higher than for an electric car (300 kw vs 3 kw). If the resistor control bank dropped (max) say half the supply voltage, then (VI = P) numbers for the train would be [300V (1/2 x 600V supply voltage) x 500A (motors) = 150 kw (heat dissipation)]  vs for a car  [30V (1/2 x 60V battery voltage) x 50A (motor) = 1.5 kw (heat dissipation)]. Surprisingly these numbers show the resistance (V/I = R) of the train's bank could (potentially) be the same as that needed for a car [300V/500A (train) = 30V/50A (car) = 600 mohm].  Resistors are pliable things easily hooked up in various parallel and series configurations to vary the resistance.

Assembling a high power resistor bank for a train
       General engineering principles tell us it is not desirable to try and make the very high power train resistor bank out of just a few resistors. For train's numbers of 150 kw (heat dissipation) and 500A (current) it is far better to assemble its resistor bank from a large array of smaller, lower power  resistors. There are three reasons for this. One, you want the resistor bank spread out so it can dissipate its heat effectively (into the air); two, wiring is simplified if the current is spread out by using a parallel array of resistors; and three, for mounting under the floor of a subway or trolley car a wide, thin form factor is preferred. (This latter constraint does not apply for resistor banks used in electric locomotives.)

        For example a train resistor bank [300V x 500A = 150 kw; 300V/500A = 600 mohm] might potentially have been assembled from 100 resistive units each with 1/100 the total power rating [30V x 50A = 1.5 kw; 30V/50A = 600 mohm] arranged x10 wide (parallel) to handle the current [50A => 500A; 600 mohm => 60 mohm] and stacked x10 in series to handle the voltage [30V => 300V; 60 mohm => 600 mohm]. The point of this little exercise is to show that the resistors needed by the electric car people in the 1900s were perhaps not so different, and potentially even the same, from what was already being manufactured for controlling DC motors in the early generation of electric trains and trolleys.

Photos of controller components during restoration of a 1911 upright Baker Electric
        The 1907 Baker electrics were speced at 6 forward speeds and 3 reverse speeds. This means the speed control lever needed 9 (detent) positions + neutral. The control configuration (very likely) being the same as in 1902 schematic (above) except that five resistors (min) were needed in the resistor string and the battery voltage had been increased.  Restorers at the Old Rhinebeck Aerodrome working on their 1911 upright Baker have photographed its controller switch assembly and resistor assembly. The rotating controller switch assembly has ten sliding contacts on 10 gapped ring segments plus a detent mechanism for the 6 forward and 3 reverse settings. It switches in and out seven power resistors, which can be seen adjacent to the motor, and also switches the polarity of the motor stator (field) winding to reverse the motor's direction. The switch assembly is sealed in a box to keep out dirt and contamination. The resistors, being rugged and needing to dissipate heat, are left exposed.

Baker related links
        https://www.youtube.com/watch?v=OhnjMdzGusc  --- My Classic Car show (full 30 min) includes visit to Leno's garage to see his Baker electric
        https://www.youtube.com/watch?v=CRwEXaHTwsY --- Leno compares his Baker electric to a modern electric car (6 min)
        http://www.sunrise-ev.com/controllers.htm --- Schematic of 1902 Baker electric with an explanation of the controls
        https://bakerelectric.wordpress.com/2012/12 --- Photos of switch and resistor assembly in 1911 Baker being restored
        http://www.electric-cars-are-for-girls.com/baker-electric-car.html --- Photos of a 1912 Baker restoration
        Video includes a 1911 Maxwell gasoline engine crank start
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Detroit Electric cars
        A competitor of Baker was Detroit Electric. Detroit Electric was owned by Charles P. Steinmetz. I remember by my uncle, who was an engineer at GE, speaking of a great engineer at GE named Steinmetz, but I no idea what Steinmetz had done. There is a Wikipedia page on Steinmetz. Born 1865 that would have made him age 35 in 1900 when electric cars were just getting going in the USA. Baker Electric was started in 1899. Steinmetz died in 1923, age 58 when my uncle was only 4 years old, so my uncle only knew of Steinmetz by his reputation inside GE. His Wikipedia page says after the company Steinmetz worked for was bought by GE in 1893 "he quickly became known as the engineering wizard in GE's engineering community".

Steinmetz, the engineer
        Turns out that all EE engineers owe Steinmetz a great debt. In engineering school we are taught the best way to analyze AC circuits is to use complex variables and transfer functions. It's an easy, but rigorous method to get answers without the need to write and solve long and tedious equations. Steinmetz (age 28) proposed this method of AC analysis in a ground breaking paper of 1893, "Complex Quantities and Their Use in Electrical Engineering". AC sinewave signals, say as seen on an oscilloscope, can be described by two parameters: height (magnitude) and phase (how many degrees is the sinewave shifted from some reference angle). Any (continuous) AC signal can be considered the sum of two signals: in-phase (0 degree) signal and a quadrature (90 degree) signal. Complex mathematics is a perfect fit for describing this. The real mathematical term describes the 0 degree signal and the quadrature 'j' term, which mathematicians call the imaginary term, provides a convenient representation of  the signal component that is 90 degrees out of phase with the 'real' term.

        Steinmetz worked as a young man on large power transformers. A major heat loss term in such transformers comes from the hysteresis properties of the steel, ant this was another area of EE engineering where Steinmetz made major contributions. Hysteresis can also be important in motor design. I read Steinmetz designed an improved motor for his Detroit Electric cars, and given his expertise on hysteresis, my guess is that he worked to minimize this loss term in his improved  motor. Steinmetz also worked on induction motors, as did I. He had over 200 patents some of which were improvements to the induction motor. A 1976 paper on the history of induction motors points out that a 100 ph induction motor (circa 1976) fit into the same frame size as a 7.5 hp induction motor of 1897, demonstrating huge improvements in magnetic design and materials.

Detroit Electric technology
        Detroit Electric started making electric cars in 1907, a few years after Baker. In 1912 Detroit ads say they have the largest factory in USA for the manufacturer of electric cars, and they claim to be largest manufacturer of 'electrical pleasure vehicles'. Curious turn of phrase, probably selected to exclude electric trucks, which Baker began manufacturing in 1907 and maybe Baker taxis too. The Detroit Electric Wikipedia page says that during their peak years (1910s) they manufactured 1,000 to 2,000 cars a year with total production during their years in operation of 13,000 cars.

        Baker during its heyday, 1900s, is often described as the largest manufacturer in USA of electric cars. The Baker Wikipedia page says in 1906, before Detroit Electric began manufacturing electric cars, Baker production was 800 cars a year. A 1910 Baker ad claims they are the "oldest and largest manufacturer of electric motor cars in the world". ('Oldest' claim is somewhat dubious given that electric cars began popping up in Europe in the late 1800's about 15 years before Baker began operation.) In 1913 Baker was overtaken in sales by Detroit Electric (says the Baker Wiki page).

       A 1914 Detroit Electric used 14 six volt batteries (84V), which could be reconfigured in series or parallel. A parallel configuration of a group of batteries lowers the battery voltage. This is an advantage when the car is driven slowly as it reduces heat loss in the series resistor, hence improving the range of the car. Here's a picture of the (switch) controller of a 1914 Detroit Electric from a restoration by Union College. Note with its multiple sliding contacts it is quite similar to the earlier Baker controller (above).

        Detroit ads say their cars in 1917 had five forward speeds, and one speed reverse. The speed range of these models was 6 to 25 mph. Note 1917 (during WWI) is quite late in the electric car era, Baker had merged another Cleveland electric car builder, Rauch and Lang, in 1916. Like the Baker the motor speed in the Detroit was controlled by moving forward a single (horizontal lever) that operated the multiple switch controller (shown below). Detroit ads point out that they added a twist to the control level: a backward pull of the lever applied mechanical brakes "without even touching the foot pedals" .

1914 Detroit Electric controller --- before and after
        Here's a good look at another Detroit Electric 1914 multi-switch controller, and it shows what a tear down and metal cleaning can accomplish. This is from a Detroit Electric restoration described on the Detroit Electric web site. The shorting bars are screwed into a wooden cylinder, which is rotated by the driver to control the speed of the car. It had originally been painted black, but it was sanded and varnished (turning it a deep red color) during the clean up to clearly show that it is wood.

Detroit Electric going into reverse
        Below is a screen capture from a Detroit Electric video. In the photo the driver is putting the car into reverse using the lever in his left hand (right hand is the steering tiller). You can hear heavy clanking as the car goes into reverse. It sure looks and sounds like the Detroit has a mechanical reverse and getting into reverse doesn't look easy. Why a mechanical reverse, especially since it was easy to get the electric motor to go backwards, just some extra switches to reverse the field current?  Leno says that to reverse his Baker he just needs to pull his speed/torque lever backwards. This is because the Baker controller reversed the motor torque electrically. (When you see something odd like this, sometimes patents are involved. The Baker preceded the Detroit by several years, so maybe they had patented their reversing controller.)

Battery options
       Detroit ads indicate that their electric car in the 1910s could be supplied with any of four different batteries: Edison, Ironclad, Detroit and Exide. The Edison battery was not lead-acid. It was a rechargeable nickel-iron battery that was an upgrade, very expensive ($600) considering that a whole car (Model T) could be bought for that price. The nickel-iron battery is sort of early version of the modern rechargable NiMH battery. It was robust with a high energy density, but expensive since it used a lot of nickel. The Germans used nickel-iron batteries in the V1 and V2 rockets to power their navigation systems. The Wells Baker Electric had an Exide battery, but in later years the Baker could be supplied with the Edison iron-nickel battery too.

        In this video a Detroit Electric owner at an antique car show is describing his car saying it cost him 2,300 dollars for a set of 14 golf cart batteries (84V) that weigh 1,000 lbs. This brings home why electric cars of the time were so much more expensive than gasoline powered cars, it was the cost of the batteries! A Detroit 1917 ad shows their three models (all enclosed) ranging in price from 1,775 to 2,395 were all powered by a 42 cell battery (84V nom).

1890s Commercial electric era
        The years of Baker Electric (1900 to 1915) were the heyday of individual electric cars, but electric vehicles were around earlier. These years (1890s) could be characterized as the commercial electric era. Most of the electric vehicles were taxis, delivery trucks and some buses. There were reportedly thousands of  electric taxis in NYC in 1900. The major manufacturer (in USA) of electric vehicles at this time was the Electric Vehicle Company with a manufacturing plant in Hartford Conn. And guess who worked at Electric Vehicle Company, none other than Justus B. Entz, who years later will sell his patent right for his controller including a magnetic transmission to Walter Baker, who will bring it to market as the Owen Magnetic.

            According to this reference the NYC electric taxis evolved from the Electric Road Wagon designed by  Electric Carriage and Wagon Company of Philadelphia, this company later being bought up and becoming part of the Electric Vehicle Company. Their taxi had two 1/2 hp electric motors, 44 cell battery and range of 30 miles.

        The Electric Vehicle Company built and sold electric cars for individuals too, which they sold under the brand name Columbia. According to Wikipedia the Columbia Electric Runabout (below) was the best selling electric car in 1900 and in 1903 the first electric car to reach 1,000 sold. According to Wikipedia, "Between the motor and the chain drive was a transmission with three forward and two reverse speeds." (another spec says three forward and one reverse speed).  Pictures and specs of the Columbia Runabout here: 14 mph (downhill), twenty cells (40V), GE motor 40V, 30A (1.2 kw, 1.6 hp),  40 mile range.

No drum controller?
       If the transmission really was located 'between the motor and the chain drive' as Wikipedia says, then it was mechanical, perhaps some sort of chain shifting between gears. This means early electric cars were missing a feature that made the Baker Electric (and other later electrics) easy to drive, the single lever drum type controller that controlled the torque/speed of the motor by switching in various size resistors. Also these early electric cars were relative low power (1.6 hp) and low speed (14 mph).

        I searched out other views of the Columbia Runabout to get a better look at the driver controls. The side views (above) provides a good view of the steering bar, chain drive, volt-meter, brake pedal, but how is the car shifted? On the right image look behind the front tire. There's a curved bar with what appears to be a handle at the end, and there is an identical handle on the other side of the car. My guess is this is the shifting lever, that the driver has to reach (way!) down and grab that handle to shift the car. If this is right, it shows that the new technology Baker brought to the market was the speed control via their drum speed controller. This made the car much easier to drive than the Columbia Runabout and critically easy enough so women could drive it.
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1st generation of high power electric cars
        In the 1900s a couple of European manufacturers offered for sale a high power electric car. This was achieved by replacing the battery as the main power source with a combustion engine powering a dynamo (generator). Since some battery remained, these are often today called hybrid cars, but their distinguishing characteristics was high power, size and performance. The largest electric motor available in a Baker electric was a dinky 3.5 hp, far, far less than the hp available from combustion engines of the time. The engine/dynamo combos replacing the battery were rated 25 hp, 45 hp, and I think Mercedes even had a 75 hp option. Because these engines were only making electricity their RPM was uncorrelated with the car's speed, so they could run at a fixed speed improving gas mileage.

        In the heyday of electric cars Mercedes and Porsche each offered for sale an electric car with the power coming not from a large battery but from an engine/dynamo combo. Since some battery remained, the car was a hybrid of sorts. A combustion engine/dynamo combo could be designed to provide far more power than a battery pack, x10 or even x20 more power, so these manufacturers took advantage of the high power and designed a high end electric car. These expensive, high power (hybrid) electric cars did not sell well and were only offered for sale for a few years.

Mercedes Mixte and Porsche Semper Vivus
       In researching early electrics I came upon an article about an electric-hybrid car in development from Mercedes. Mercedes was going to show at a 1907 auto show a new car called the 'Mercedes Mixte'. In lieu of batteries this car powers its four electric motors, one attached to each wheel, with a dynamo built into a high power gasoline engine rated at 45 hp. Compare 45 hp to the 3.5 hp available from the battery pack of the largest Baker electrics. The controller on this car appears to be similar to other electric cars with the torque controlled by progressively switching in more or less resistance. However, the substitution of a dynamo (generator) for batteries probably involved one loss. With a battery there is natural dynamic braking of an electric going downhill, the driving motor works as a generator reversing the battery current flow pumping energy into it. While this might possibly have worked in an early electric hybrid, I think it is unlikely. This car was put into (limited) production for a while.

        Porsche in 1900 developed something similarcalled the Semper Vivus. This prototype for a very early electric hybrid car retained a fairly large battery recharged by two tiny (2.6 kw) combustion engines. With battery power and DC generators on the combustion engines there was no need for cranking at start, the generators were worked as starter motors for the engines. When it went into (limited) production a year or two later, most of the battery was gone (leaving just enough battery to start the engine) with a much larger 25 hp engine/generator now providing the power to run the electric motors in the wheels. It was a very expensive car and only 65 were sold through 1905.

        Nice photos of the Semper Vivus prototype exist online, but it is not a restoration, it is a built from scratch replica of the early car done by Porsche a few years ago that took them three years. It's clear this is a large car. Guess where its two electric motors are?

2nd generation of high power electric cars
Woods Dual Power
      In USA the Woods company manufactured a combusion/electric car called the 'Woods Dual Power'. This car had a combustion engine mechanically coupled to the wheels in the normal manner, but with an electric motor wrapped around the drive shaft. Because it contained a clutch that could disconnect the engine, drive power could be shifted by the driver between electric and combustion. There is a detailed description of it here. The author of the article on the Wood Dual Power claims the car is also known as the Owen Magnetic (wrong!), and that this name is better known because Leno has one in his collection. A check of the Wikipedia page  'Owen Magnetic' confirms that the Owen Magnetic and the Woods Dual Power were completely different cars manufactured by different companies.

Owen Magnetic
       Leno owns one of the dozen or so surviving Owen Magnetics, and he describes his 1916 Owen Magnetic as having no mechanical connection of the combustion engine to the wheels (correct). Electric motors provide all the torque to the wheels in this car. It is a USA version of the much earlier European high power electrics with a dynamo powered by a large powerful combustion engine, but the Owen Magnetic had a unique twist. It's dynamo and electric motor formed a double machine that functioned also as an electromagnetic transmission allowing the driver to easily shift gears. The dynamo/electric motor were combined into a single housing that bolted to the combustion engine.

        As I researched this car, curiously the story doubled back to the Baker Electric. Walter Baker held some of the key patents used in the Owen Magnetic. While the first Owen Magnetics of 1915 were manufactured in Manhattan (factory on 5th Ave!) in 1916 production was moved to Cleveland and for a couple of years the newly merged Baker and Rauch and Lang electric car company also made the Owen Magnetic!

Owen Magnetic -- Baker goes high power and high tech in 1916
        The Owen Magnetic car, which began production in 1915 under license from Walter Baker, was a high power electric car where the battery was replaced by a combustion engine/generator, but it was most notable for having an electromagnetic transmission. The only car ever to include such a transmission. A manual shift transmission that made driving easy because it shifted without clutching or gear synchronizing.

        Baker Electric car technology seems to have changed little over the 15 years or so of Baker Electric's existence so it came as a huge shock when deep into writing this essay on Baker technology I stumbled onto a high tech, high power electric car that Baker manufactured for a two or three years beginning in 1916. This car was the Owen Magnetic (cool name). In 1912 Walter Baker had bought up the patents on an electromagnetic transmission from its inventor, Justin B. Entz, and he licensed Raymond and Ralph Owen of New York to design the high power Owen Magnetic car with Entz's electromagnetic transmission. Entz's electromagnetic transmission was a tricky double machine that, like the Prius transmission of 1997, featured a power splitter and two parallel power/torque paths. The prototype Own Magnetic car was shown in an auto show in 2014 and began limited production (250 cars) in NYT in 2015. Baker soon absorbed R. M. Owen and moved production of the Owen Magnetic to the newly merged Baker & Rauch and Lang factory in Cleveland.

        The picture below shows the Own Magnetic was a large, impressive and expensive car. Many references note that Enrico Caruso owned one, and now Leno has one too. The gear shift lever was inside the steering wheel. There was no clutch.

        On a quick look it appeared that the Owen Magnetic was similar to the earlier Mercedes and Porsche high power electrics where a high hp gasoline engine/dynamo (generator) replaced the battery, but a deeper look shows the Owen Magnetic was much more high tech. It employed a very tricky, very advanced, double machine that was the work of master motor designer, Justus B. Entz, former chief electrician of the Edison Machine Works, who had worked on the concept for nearly twenty years.

Entz double machine
        A straight forward replacement of the battery in an electric car would employ a generator driven by a combusion engine. The voltage (fixed or variable) from the engine/dynamo would be only electrically coupled to an electric motor that would power the car. In other words there are two separate rotating shafts, that of the motor/dynamo and of the electric motor, with only an elctrical connection between them.

        But the Owen Magnetic was from a control perspective a very different machine. Its generator (armature) and electric motor (armature) were mounted on the same shaft, so they always turned at the same speed, and critically the coupling between the generator and motor was both mechanical (torque) and electrical. From a control perspective this a highly complex, double machine, and nothing I have seen online explains how it really works. To understand it the patents of Entz would need to be dug out and studied. And as the diagram (below) shows mechanically this integrated double machine 'transmission' of the Owen Magnetic was quite complex.

        Below are few excerpts from that essay just to give a little flavor of the detail of the analysis: Circuit model, gearing equation and mathematical analysis of the Entz/Owen Magnetic electromagnetic transmission plus the configuration of the two machines in all the gears from the key Entz patent.

         It is critical if the Entz is be a real transmission that the load on the engine not vary as the transmission is shifted through it gears. For gears where max speed is lowered by '(1/n)', the (total) torque applied to the drive shaft must increase by 'n' to keep power out of the transmission constant [P = T x speed].
 

Deeper dynamo field weakening
        1st gear in table above is for (my assumed) 2:1 split in the field current of the dynamo (meaning 1/2 of the current flows in the field winding). The pattern of the 1st gear results in table 1 make it relatively easy to extend it for deeper levels of dynamo field weakening (3:1 and 4:1 splits), which widen the range of the transmission driving 1st gear torque higher and corresponding max shaft speed lower. A study of these two tables reveals a lot about how field weakening works in Entz's double machine. And it provides good insights on how the transmission really works, meaning how it is able to increase the torque at lower gear ratios.
 

        From Entz key patent (#1,207,732) for the Owen Magnetic, 'Motor Vehicle Control' filed 1915, showing the double machine wiring in seven forward gears: