GB2069260A - Electric vehicle propulsion system - Google Patents

Abstract

Each wheel of an electric vehicle is driven by a respective stepping motor 32, 34, 36, 38 supplied by an alternator 16 driven at constant speed by an engine 12. Each motor has a first pair of stator windings (147, 151) supplied from respective alternator phases with rectified AC pulses of variable frequency and phase through SCRs Figure 5 (not shown) controlled by members 76, 86 in response to driving pedal and steering controller 72. When increased power is required members 76, 86 control further SCRs Figure 10 (not shown) to supply a second pair of stator windings (647, 651) on each motor with pulses of DC from a battery 48. When the vehicle speed reaches the alternator speed the SCRs Figure 5 (not shown) are turned off and further SCRs Figure 6 (not shown) are controlled to pass AC through the windings (147, 151) to drive the motors as synchronous motors. During regenerative braking the AC output of the motors is rectified in member 68 to charge the battery 48, the braking force being varied by connecting the motor windings in series or parallel. Members 72, 76, 80, 86, 90 vary the supply frequency of the motors on one side relative to the other to provide steering. In a modification Figures 12 and 13 (not shown), combustion of wood fragments, in the chamber of a pressure vessel mounted on the vehicle rear, is initiated by igniting in the chamber gas from an external source. Air is supplied by compressor. As soon as combustion has become self-sustaining, the supply of gas is terminated. Meanwhile, the pressurized gas emitted from the vessel is discharged through a valve into a turbine which drives the alternator 16. <IMAGE>

Description

SPECIFICATION Electric vehicle propulsion system A constant-speed continuously-running low-powered diesel engine or turbine drives a two-phase alternator, the output from which, for direct drive, flows to the stator pole piece windings of four independently-rotating stepping motors operating synchronously with the alternator. Each stepping motor is connected to a traction wheel of a motor vehicle, thereby propelled art a limited maximum speed sufficiently to overcome normal wind resistance over a level road. In starting, during acceleration, and for propulsion at lower speeds, direct current from a storage battery is caused to pulsate and is added to the current from the alternator to the stepping motors.A control circuit selectively controls the frequency of a variable frequency generator electrically connected to the pulse-responsive electrical power system to vary the frequency of the current supplied to the stepping motors and thus vary the vehicle speed. During idling, the alternating current from the alternator is rectified and recharges the battery. During braking, the consequent driving of the stepping motors causes them to generate alternating current which is rectified and returned to the battery. By varying the frequencies of the current delivered to the right side motors as compared with those delivered to the left side motors and vice versa, in response to the turning of the steering wheel in rounding a curve in the road, a differential action is obtained.

In a modification, combustion of fragmented slow-burning solid fuel, such as wood fragments, in the combustion chamber of a portable combustion receptacle or pressure vessel mounted on the rear of the vehicle, is initiated by igniting in the combustion chamber combustible starting fluid gas, such as propane gas from an external source and ignited by a spark plug. Air is supplied by an air compressor driven by a prime mover such as a turbine or electric motor. As soon as combustion of the solid fuel has become self-sustaining, the supplying of this starting gas is terminated. Meanwhile, the pressurized gas emitted from the burning solid fuel in the combustion receptacle is discharged into the power turbine by way of a throttle valve. The output shaft of the turbine drives a speed-reducing transmission which in turn drives the alternator.

Background of the invention Research on fuel consumption of conventional motor vehicles driven by internal combustion engines has shown that approximately one-half of the fuel consumed by such an engine is expanded and atmospheric pollution increased during starting and idling, especially during urban driving with frequent halts for stoplights and traffic. Fuel has also been wasted in such vehicles through the differential mechanism and through momentum losses by braking, not only in traffic halts but also in downhill running. In view of the increasing scarcity of liquid fuels, there is a likelihood of their being in the near future obtainable, if at all, only at prohibitively high costs.The modified portable electric power plant of my present invention drives the alternator of my principal system from a gas turbine receiving power gas from a portable combustion receptacle or pressure vessel in the combustion chamber of which suitable subdivided slow-burning solid fuel, such as wood, is burned to produce such hot and expanded power gas.

Summary of the invention The invention principally resides in the provision of independent stepping motors individually driving the vehicle's traction wheels, as these motors are operating synchronously with a two-phase engine-driven alternator while receiving alternating current from that alternator driven by a continuously-running constant-speed internal combustion engine of considerably less power and fuel consumption than would be required for all-around propulsion of the vehicle by an internal combustion engine alone but increased, when needed, by direct current supplied from am storage battery and caused to pulsate at the proper frequency. The invention also resides in the provision of means which converts inertial energy otherwise lost in braking or free-wheeling onto alternating current electricity which is rectified and returned to recharge the storage battery.If further resides in electrical means responsive to the turning of the vehicle's steering wheel for reducing the frequencies of the current supplied to the stepping motors on the inside of a road curve from those on the outside thereof, thereby providing an electrical differential.

The modification of the invention resides primarily in the provision of the portable combustion receptacle or pressure vessel wherein combustible slow-burning solid fuel particles, fragments or blocks, preferably of wood, are ignited by being initially supplied with a combustible starting fluid, such as fuel gas ignited by a spark plug or glow plug and subsequently terminated when the combustion of the solid fuel particles becomes self-sustaining. The modification further resides in the provision of the turbine-powered alternator driven by the pressurized hot output gas from the combustion chamber of the combustion receptacle, the electricity thus generated being supplied to the place of utilization, such as the herein disclosed electric vehicle propulsion system.The modification still further resides in the provision of duplex combustion receptacles utilized alternately for enabling continuous operation to be effected by having one such solid-fuel-filled combustion receptacle always held in reserve for use when the other combustion receptacle has exhausted its fuel supply.

In the drawings, Figure lisa block diagram of the stepping-motor-driven vehicle propulsion system supplied with alternating current from a continually-running constant-speed engine-driven alternator aided by pulsating direct current from a storage battery; Figure 2 is a diagrammatic top plan view of the chassis of the vehicle of Figure 1.

Figure 3 is a diagrammatic central vertical section along the line 3--3 through the vehicle of Figure 2; Figure 4 is a vertical cross-section taken along the line 4--4 in Figure 2; Figure 5 is a circuit diagram of the two-phase electrical system involved in the propulsion of the stepping motor of Figure 1; Figure 6 is a logic circuit diagram employed in direct drive or free-wheeling of the vehicle of this invention; Figure 7 is a circuit dig ram of the variable frequency differential action obtained in rounding a curve in the present vehicle.

Figure 8 is a logic circuit diagram for the two-phase alternating current emitted from the alternator and rectified by silicon-controlled rectifiers; Figure 9 shows the regenerative braking circuitry for recovering and rectifying alternating current from the vehicle wheel stepping motors acting as wheel-driven generators; Figure 10 is a block diagram constituting Figure 9 of Fengler British Patent NO. 1,174,289 of June 1967 but receiving power current from a direct current power source in the present vehicle propulsion system, and with its output to additional stator windings designated by different reference numerals.

Figure 11 is a cross-section like Figure 7 of my said prior patent but showing said additional stator windings of my present stepping motors; Figure 12 is diagrammatic side elevation, partly in central vertical section, of a portable solid fuel electric power plant for electrical powered vehicles according to a modification of the invention; and Figure 13 is a diagrammatic top plan view of the power plant shown in Figure 12.

General arrangement The block diagram shown in Figure 1 illustrates the general arrangement of the assembled components of the stepping motor vehicle propulsion system, generally designated 10, according to the invention, the details of which are shown in detailed circuits of Figures 5 to 9 inclusive. The vehicle propulsion system 10 (Figure 1), assumed to be a four-wheel driving system with independent motor driving to the individual vehicle wheels, originates with a power source 12 consisting of a continuously-running constant-speed internal combustion engine such as a Diesel engine or a gas turbine having a drive coupling 14 connecting it to a two-phase 400-cycle approximately 22 kilowatt alternator 16.From the alternator 16 the main alternating current output connection 18 proceeds through a junction 20 and an alternating current output connection 22 with branches 24, 26, 28, and 30 to the right-hand front driving stepping motor 32, the left-hand front driving stepping motor 34, the right-hand rear driving stepping motor 36 and the left-hand rear driving stepping motor 38 respectively. The driving stepping motors 32, 34,36 and 38 are separately designated because the motors on opposite sides of the vehicle receive alternating current of different frequencies at different times to provide an electrical differential action for the vehicle when rounding curves or turning corners in the roadway.In this respect, as described more fully below, the different revolution imparted to the right-hand motors 32 and 36 from those imparted to the left-hand motors 34 and 38 provide a corresponding action to the mechanical differential mechanism of a conventional automobile. It will be seen later that the output connection 22 and branches 24,26,28 and 30 carry alternating current from the alternator 16 in direct drive but also carry pulsating direct current regulated by two pulsating current frequency generators 76 and 86 described below.

From the junction 20 a two-phase full-wave rectifier 42 receives alternating current through the alternating current connection 44 and transmits it through the two-phase full-wave rectifier 42 and connection 47 to a storage battery 48, to charge the latter under the regulation of a battery-charged monitor 50 connected thereto through the connection 52 and connection 54. Braking is accomplished primarily by the motors 32, 34,36 and 38 acting as alternators through their mechanical connections to the vehicle ground wheels and consequently alternating current through the current connections 56, 58, 60,62 is transmitted to the accelarating and decelerating current controller 64 from which it proceeds through the alternating current connection 66, rectifier 68 and direct current connection 70 to the storage battery 48.A bypass connection 46 directly connects the storage battery 48 to the regenerative braking current receiver 64 around the rectifier 68 during acceleration of the vehicle to supply additional pulsating direct current to the stepping motors 32,34, 36and38.

The above-mentioned electrical differential action is controlled through a steering-wheel-connected differential controller 72 which transmits signal frequency differential control regulated by turning the steering wheel through a connection 74, variable frequency generator 76, connection 78 and right-hand side stepping frequency regulator 80 through the connection 82 to the accelerating and decelerating current controller 64 and through the connection 84, left-hand variable frequency generator 86, connection 88, left-hand side stepping frequency regulator 90 and connection 92 to the accelerating and decelerating current controller 64. From the latter signals proceed by way of the connections 56, 58, 60, 62 to the right-hand stepping motors 32 and 36 and left-hand stepping motors 34 and 38 at different frequencies, depending upon the direction and amount of turn as governed by the differential controller 72 operated by the vehicle steering wheel. The term "connection" may consist of a single line or a plurality of lines, as explained in connection with Figures 5 to 9 inclusive.

Power source The power source 12 for driving the alternator 16 through a mechanical connection 14may consist of a conventional internal combustion engine, such as a Diesel engine or gas turbine, either of which is smaller than is ordinarily necessary in a conventional motor vehicle which requires such a power source to propel the vehicle from a standstill through acceleration to a high speed, as well as in idling. The power delivered by the power source 12 needs only to be sufficient to drive the alternator 16 to produce an output therefrom adequate to enable the stepping motors 32, 34, 36 and 38 to overcome the wind resistance and road friction encountered by the vehicle in level road operation.

The advantage of this constant speed of the Diesel or gasoline engine or gas turbine is that it operates at a much higher efficiency than an engine which is required to accelerate and decelerate, as in vehicles propelled directly by conventional internal combustion engines or turbines. Moreover, the emissions produced by such constant-speed engines are very low in contrast to the high emissions produced by variable speed engines. In addition, the constant speed engine gives a much better fuel economy than an engine which is called upon to accelerate and decelerate repeatedly during operation. It is well-known matter of fact, for example, that the efficiencies of internal combustion engines running continuously at constant speed to drive electrical generators in generating plants is nearly twice that of the best internal combustion engines used in the present-day automobile.

The alternator 16 driven by the power source 12 is a two-phase alternator with an output preferably of 120 amperes in each phase operating continuously at a maximum frequency of 450 cycles per second at a voltage of 60 to 84 volts with the two phases 90 degrees apart. This gives enough electrical output to overcome the wind resistance and rolling resistance of the vehicle in direct drive, with the output of alternating current delivered directly to the stepping motors 32,34,36 and 38 direct-connected to each of the individual vehicle wheels. The alternator 16 employed in the vehicle propulsion system 10 of this invention must operate at a sufficiently low speed in revolutions per minute in order to fit the torque curve of a Diesel engine, if so powered.The frequency should be variable between 300 and 450 cycles per second depending upon the revolutions per minute of the power source 12 to which the alternator 16 is coupled. It will be understood, however, that if this required frequency can be more economically or efficiently produced through an alternator 16 having a higher speed in revolutions of its rotor, a small turbine may be used as the power source 12 in place of the Diesel engine.

The minimum current output of the alternator 16 would preferably be 20 kilowatts with each of the two phases thereof producing an output of 120 to 170 amperes. While the desired voltage produced by the alternator 16 is between 60 and 84 volts, under special circumstances 120 volts would be preferable inasmuch as 120 volts is the voltage used by the aircraft industry in aircraft systems.

The output of the alternator 16 provides alternating current to be used in driving each wheel by its individual stepping motor 32,34,36 or 38 independently through a special solid state control circuit described below. Operation of its two-phase alternator at approximately 400 cycles per second is required because the special stepping motor 32, 34, 36 or 38 described below has a stator with only two rotating but separate magnetic fields. One such field attracts the nearby magnet of the rotor, if this magnet is of the opposite polarity, while the second repels that nearby magnet of the rotor if that magnet is of the same polarity.

As will be seen below in connection with the operation of the invention, in the "direct drive" operation of the invention, the stepping motors 32, 34, 36 and 38 are locked into synchronization with the alternator 16, without slippage, hence the alternator 16 must produce a two-phase alternating current to drive this particular type of motor. The vehicle propulsion system 10 (Figure 1) can therefore be considered as propelled by electronically-commutated stepping motors 32,34,36 or 38 which are also capable of operating from an alternating current power supply 16 wherein the frequency and phase of the stator currents are regulated through the variable-frequency generators 76 and 86 and silicon-controlled rectifiers (Figure 5) to maintain the magnetic fields at their maximum torque conditions, independent of rotor speed or current frequency supplied.In this manner, the stepping motors 32,34,36 and 38 of the vehicle can operate over a wide range of speeds while supplied with alternating current from the fixed-frequency two-phase alternator 16 or the stepping frequency regulator 80 or 90.

The storage battery 48 employed in the vehicle propulsion system 10 (Figure 1) needs only to be sufficiently large to assist the output of the alternator 16 driven by the small continuously-running constant-speed engine 12 during starting and acceleration, the direct current from the storage battery 48 being electronically commutated by the variable frequency generators 76 and 86 to deliver direct current pulses at the desired frequencies to the stepping motors 32, 34,36 and 38. While the vehicle is standing still, the engine or turbine 12 does not slow down and idle but continues to run at constant speed so that the rectified output of the alternator 16 is then used to charge the battery 48.It will also be seen below (Figure 9) that a regenerative braking system 64 has been provided which, during braking operations, employs the stepping motors 32, 34, 36 and 38 as generators supplying current which when rectified recharges the battery 48.

Solid-state control system for output of fixed-frequency two-phase alternator In Figure 5 there is shown the solid-state control system, generally designated 600, which supplies full-wave direct current from the two-phase alternator 16 to energize and control the stepping motors 32, 34, 36 and 38 of Figure 1 for bidirectional rotation of the vehicle wheels. Figure 5 thus represents the charge in the full-wave circuit 220 in Figure 26 of my above-mentioned previous patent No. 1,174,289 to adapt it to the reception of the two-phase output from the two-phase alternator 16 herein.Use is made in Figures herein of the same reference numerals from 147 to 382 for corresponding parts as in Figure 26 of my previous patent No. 1,174,289 of June 1967 for the convenience of those skilled in the art, and who are hereby referred thereto in order to avoid apparently needless repetition and duplication of description. Furthermore, since the reference numerals in my said previous patent 1,174,289 end at 568, to avoid any possible confusion the reference numerals used in the remainder of the present specification and drawings start at 600 and remain thereabove.

From Figure 5 is will be seen that the present circuit 600 is generally similar to the circuit 220 of my said prior patent 1,174,289 but divided into different portions because of the two-phase alternating current representing the output of the two-phase alternator 16 rather than the single-phase alternating current input or current supply source in my said prior patent 1,174,289. For a detailed description of the elements of the circuit 600 shown in the present Figure 5, and the generally similar circuit 220 in Figure 26 of my said patent 1,174,289, reference is made to my latter prior specification.

In my improved circuit 600 (Figure 5) a subcircuit makes use of the left-hand upper half, renumbered 602 of my patent circuit 220 for receiving the output 606 of the first phase of the alterntor 16, whereas an additional subcircuit corresponding to the right-hand upper half, renumbered 604, receives the output 608 of the second phase thereof. The entire circuit 600 provides for a separate transmission of electrical energy to the stepping motors 32, 34,36 and 38 by the provision of pulses of direct current to the two stator circuits for each wheel, each circuit creating alternate north and south poles.In particular, the output of the first phase 606 of the alternator 16 is connected to the first group 602 of silicon-controlled rectifiers 276, 278, 280, 282, 376,378,380 and 382, which supply current to the stator windings 147 of the stepping motors 32,34,36 and 38, whereas the second group 604 of silicon-controlled rectifiers 288, 290, 292, 294, 388, 390, 392,394 receives the output of the second phase 608 of the alternator 16 from the connections 604 thereof and supply direct current pulses to the second stator winding 151 of each such stepping motor. The proper timing of these pulses to statorwindings 147 and 151 requires an adjustment of the times the "delay lines" retard the shut-off impulses over the reed switches 306 and 308 to the "NOR" logic modules 272, 274, 284, 286.

As stated above, in order to achieve the desired great savings in petroleum fuel, the power plant 12 of the present invention is undersized and insufficient to enable the vehicle to accelerate at a needed rate, for instance, to enter high speed traffic lanes safely on expressways or to ascend steep grades. It is therefore necessary to boost the output of the stepping motors 32,34,36 and 38 during acceleration and on grades to more than double their output in "direct drive". To accomplish this (Figures 10 and 11) third and fourth windings 647 and 651, in addition to the windings 147 and 151 are provided on alternate stator pole pieces 144 and 146 of stepping motors 32,34,36 and 38.These additional third and fourth windings 647 and 651 are fed pulsating direct current impulses from the storage battery 48 by using, in Figure 10, a slight modification of the wiring diagram shown in Figure 9 of my above-mentioned patent 1,174,289 wherein the block 20 labelled "A.C. Power Source" is replaced by "D.C. Power Source", namely the storage battery 48. To this circuit is added the "commutating capacitors" necessary to temporarily shut off the silicon-controlled rectifiers and their network. In this manner, a square wave output is supplied to the stepping motors 32,34, 36 and 38, aided in starting and accelerating by direct current from the storage battery 48 caused to pulsate at the proper frequency as controlled by the variable frequency generators 76 and 86.For forward motion of the vehicle, the positive half of the square wave is used while the negative half thereof is suppressed. When the vehicle is to travel in a reverse direction, such as in backing, the positive half of the square wave is suppressed and only the negative half is supplied to the line 248.

When the vehicle attains a speed of 44 to 45 miles per hour, the circuitry shifts over to direct drive of the stepping motors 32,34,36 and 38 by the alternator 16, as shown in Figures 6 and 8, which locks each of the statorwindings 147 and 151 directly in synchronism with the alternating current output of the alternator 16.

In Figure 8, the designation 147 designates the first set of pole piece windings of each stepping motor in series, whereas 151 designates the second set of pole piece windings in series. The four additional "NOR" modules 610,612,614,616 when energized through the line 635 (Figure 6) will shut off the silicon-controlled rectifiers 276, 278, 380,382 in the first phase 606, but the remaining silicon-controlled rectifiers 280, 282, 376 and 378 will connect the motors 32,34,36 and 38 directly to the first phase of the alternator 16 when in "direct drive".The remaining four additional "NOR" modules 618,620, 622 and 624 will shut off the silicon-controlled rectifiers 292,294,388 and 390 in the second phase 608, but the remaining silicon-controlled rectifiers 288, 290,392 and 394 will connect the motors 32, 34, 36 and 38 directly to the second phase of the alternator 16 when in "direct drive". Now the stepping motors 32,34,36 and 38 are operating as synchronous motors, but this can only happen when the speed of the vehicle has reached the minimum constant speed of the alternator 16 and the phase of the motors is in step with the alternator.

Otherwise, the reference numerals in the Figures 6 and 8 correspond to those in Figure 26 of my said prior patent 1,174,289.

Logic circuitry for placing all wheels in direct drive or free-wheeling In order to extend the logic circuitry of Figure 5 to cause the logic circuits thereof to enable the placing of all four traction wheels of the vehicle either in a direct-drive condition or in a free-wheeling condition, the logic circuit shown in the lower half of Figure 5 has been modified in Figure 6 by adding six reed switches 626, 628, 630,632, 634 and 636. Four of these additional reed switches, namely the reed switches 626,628, 630 and 632 are normally closed and when not energized let current run from the reed switches 306 and 308 of the "NOR" modules 272,274,284 and 286 which normally remain in the stepping condition.

When, however, the vehicle is in a "direct drive" condition, and when electric power is directed to the four reed switches 626, 628, 630 and 632, they interrupt the four lines so that any current which would otherwise come through the reed switches 306 and 308 is now interrupted. The effect of this occurrence is that the "NOR" modules 272,274,284,286 stay in a conducting condition regardless of which side of the flip-flops 262 and 264 is conducting. Because these "NOR" modules are not interconnected through two additionally normally-open reed switches 634 and 636, all "NOR" modules will conduct without interruption and all stepping motors 32, 34,36 and 38 will become directly connected to the two-phase alternator 16 (Figure 1).

On the other hand, when free-wheeling is desired (Figure 5), the power of the four additional reed switches 626, 628, 630 and 632 connects the two sides of the reed switches 306 and 308 so that wherever output of the flip-flop 262 and 264 happens to be "on", that output is also conducted through to the "NOR" modules, thereby interrupting the conducting condition of all four of the "NOR" modules 272,274,284 and 286. With the circuitry in this condition, the gates of a II all silicon-controlled relays are without current, so that no current can flow through to the stators of the stepping motors 32,34,36 and 38.

Regenerative braking action In the circuit shown in Figure 26 of my above-mentioned prior British patent 1,174,289, two "NOR" modules are in a conducting condition in their stepping arrangement, namely "NOR" modules 272,284,274 and 286, such conducting being in sequence when stepping is occuring in a forward direction but in a reverse order when stepping is occurring in a reverse direction. When a step is completed, however, the power from the flip-flops 262 and 264 is also conducted through the two reed switches 306 and 308 and through the delay lines between these reed switches, the prior activated "NOR" module is shut off through the succeeding impulse, thereby permitting only one "NOR" module to conduct, namely the last "NOR" module which is in a stepping condition.This occurrence produces a holding force in the half circuit of the stator of the motor 32,34,36 or 38, without starting the next step.

Should the next step be slower than the previous sequence of steps, the rotor of the particular stepping motor 32,34,36 or 38 will be subjected to a stronger retardation through the holding force. Should the vehicle go faster than the impulses arriving on line 248 (Figure 5), that holding force will be overcome and the particular motor 32,34,36 or 38 will then act as an alternator as well as a brake. Either of the stators with windings 147 or 151 will now produce a braking force upon the traction wheel of the vehicle. Should this braking force still not be sufficient and the impulses arriving in line 248 (Figure 5) go down to zero speed, then the stator windings 147 and 151 of either front wheel 32 or 34 will be first connected in parallel and then in series, as shown in Figure 9.By this series arrangement the output of the stepping motors is increased and the maximum braking force consequently created.

The stator windings 147, 151 647 and 651 of the rear wheel stepping motors 36 and 38 are connected in parallel, however, because the braking effort at the rear of the vehicle must be less than that occurring at the front of the vehicle. As shown in Figure 9, all of the four groups ofstatorwindings 147 and 151 are connected individually to four adjustable step-up transformers 638,640, 642 and 644 to raise the generated output voltage to be always higher than the voltage of the storage battery 48. This generated and transformed alternating current voltage then passes through four full-wave rectifiers 646, 648, 650 and 652 of the rectifier assembly 68 (Figures 1 and 9).The output of these rectifiers is preferably returned to the storage battery 48 through the connection 70 by of an adjustable rheostat (not shown), thereby controlling the maximum braking force of each motor 32,34,36 or 38. This arrangement not only prevents skidding and the pulling to one side of the street or road but also (Figure 9) results in the addition of four levels of braking force available, not counting the free-wheeling condition. In a truck or tractor-trailer combination vehicle, more motors and controls are thereby available for the possible preventing of "jack-knifing". However, in this latter arrangement, sensors for the slipping and consequent stalling of the traction wheels during braking must be provided.

Electronic differential system In Figures 1 and 7 are shown the arrangement for providing electronically a differential performance of the vehicle wheels on opposite sides of the vehicle corresponding to the action of a mechanical differential mechanism in a conventional motor vehicle. Figure 7 also uses the same reference numerals as Figure 5 and - as Figure 26 in my said patent 1,174,289. In order to perform a turn, such as in rounding a curve in the roadway or turning a corner, the wheels on the opposite sides of the vehicle must necessarily be travelling at slightly different speeds. According to the present invention, this electronic differential is governed by the steering gear 92 of the vehicle. Depending on the rolling status of the tires and the angle of the steering arm to the right orto the left, the variable frequency generator 76 or86 forthe right-hand or left-hand side respectively causes the frequency of the square wave signal being fed into the line 248 (Figure 5) to be slowed down if on the inside of the curve or corner while at the same time the wheels on the outer side of the curves are turning more rapidly as governed by the higher frequency of their respective stepping motors.

When the vehicle is travelling in a straight-forward direction, however, the frequencies from the variable frequency generators 76 and 86 are of course equal.

Chassis suspension for stepping motors of the vehicle The preferred front and rear suspensions 654 and 656 of the stepping motors 32,34,36 and 38 in a typical vehicle chassis 657 are shown diagrammatically in Figures 2,3 and 4. The suspension 654 or 656 consists of two spot-welded front and rear suspension arm assemblies 658 and 660 which are hinged at the front and rear at 662 and 664 on the center line 655 of the vehicle. The pivot axis 662 or 664 of this hinge is preferably higher in front than in the rear, so that if and when the wheels hit an obstruction or pothole, they can move somewhat backward on the upstroke thereof. Such action softens the impact, because the center line drops below the centers of the wheels and consequently prevents scuffing and uneven wear on the tires.The stepping motors 32, 34, 36 and 38 for the traction wheels 666,668 670 and 672 respectively (Figure 2) are fastened to the extension arm assemblies 658 or 660 and pivot around the same pivot axis 662 or 664 on the center line 655 of the vehicle 657. The distance at the top between the housings of the two adjacent motors 32 and 34 or 36 and 38 is so dimensioned that the axle will encounter the chassis frame (not shown) ahead of the housing, thereby taking up the play allowed. In the downward stroke, however, the axles are limited in their travel by shock absorbers (not shown). A heavy duty compression spring 674 (Figure 4) connected between upstanding arms 676 and 678 on the housings of the motors 32 and 34 or 36 and 38 eliminates the need for front and rear sway bars because the compression spring 674 acts in the same manner.The pivot axes 662 and 664 of the hinges 663 and 665 are eccentric and thereby allow adjustment for the toe-in of the front and rear axles of the front and rear suspensions 654 and 656 respectively.

Depending on the chosen torque output of the motors, the center line of the motor can lie higher than the center line of the wheels and the spur gear on each wheel would achieve a mechanical advantage. The motors 32 and 34 for the front axle are fastened to the suspension arm assembly 654 but would each have a conventional constant velocity universal joint 675 so as to permit the kingpin to have the required inclination for camber and caster.

By being anchored at the top of the apron, the kingpin would swing practically vertically and not in a circular arc like the rear wheel. Each such hinge 663 or 665 (Figures 2 and 4) is anchored at front and rear to the chassis frame and all of the wheels swing around the correspondingly low hinge axis 662 or 664 on a swinging arm assembly 658 or 660 that is much longer than those in present production practice. As a result of the above-mentioned construction, the ride of the vehicle 657 is improved and any side sway is eliminated.

Summarizing the present invention, the block diagrams of Figure 1 and Figures 2,3 and 4 show an electrical train 10 for independently driving each wheel 666,668,670 and 672 of the vehicle 657 and for braking each such wheel separately. Direct drive supplies alternating current from the alternator 16 either directly to the stepping motors 32, 34, 36 and 38 or through the two-phase full-wave rectifier 46 to the storage battery 48. The charge monitor 50 shuts off the internal combustion engine 12 when the battery 48 is fully charged or when it begins to develop gassing, which indicates that the battery 48 is almost fully charged and would be damaged if overcharged.

Operation To start the vehicle from a standstill, the operator by means of the accelerator pedal (not shown) orders the differential controller 72 (Figure 7) to start sending positive stepping signals or pulses from the right-hand or left-hand variable frequency generators 76 and 86 through the stepping controls 80 and 90, thereby energizing these controls so as to send electric current to the stators of all four motors 32, 34,36 and 38. This differential controller 72 is connected to the conventional steering control arm (not shown) of the front wheels of the vehicle by means of a position sensor (not shown) which indicates if a differential speed should exist between the right-hand and left-hand set of wheels.

The speed of outgoing stepping signals or pulses is controlled through a conventional accelerator pedal which, when depressed, sends a lower or higher voltage to the variable frequency generators 76 and 86.

When the vehicle has reached the speed of approximately 45 miles per hour, the "direct drive control" (Figures 5,6 and 8) connects all motors 32,34,36 and 38 to the two-phase alternator 16 so that all these motors run at the same speed as the alternator 16 in a synchronous relationship. In this "direct drive" condition of operation, no current is drawn from the battery 48, hence the vehicle upon long trips is independent of the size of the battery. When the position of the accelerator pedal signals a slowing down of speed to the stepping motors 32,34,36 and 38, the revolving magnetic field in each stator thereof also slows down, with the result that the rotor thereof also attempts to slow down, consequently slowing down the vehicle 657.Should the position of the accelerator pedal indicate zero speed, namely a halt of the vehicle, and thereby lock the magnetic fields of the stators of the stepping motors 32, 34, 36 and 38, the permanent magnets in the rotor of each of said motors will generate an alternating current in each stator. This alternating current is rectified in the regenerative braking rectifier 64, 68 as described above, and returned to the storage battery 48 to recharge the latter.

Conventional hydraulic four-wheel disc brakes are preferably retained in this vehicle 657 to serve as additional safety brakes. Furthermore, in a tractor trailer combination, if a stepping motor of the type herein described is provided for each wheel of the tractor and for all wheels of the trailer, it is possible to drive such a tractor-trailer combination in the same manner as an electric interurban train where each axle group has its own electric motor, and a single controller controls all motors. Finally, as there is unused space beneath such a trailer chassis, a large storage battery can be conveniently installed in that space. As a consequence, a smaller tractor is thereby able to haul a larger load and, at the same time, a similar saving of petroleum fuel is achieved by charging the battery from an electric public utility energy outlet at each terminal station.

Figures 12 and 13 show a portable solid fuel electric power plant, generally designated 710, consisting generally of a duplex combustion unit 712 adapted to contain and burn the combustible solid fuel F, such as wood blocks or fragments, and to deliver the hot power gas thereon to a power turbine 714 which drives, through a reduction gear set 716, an alternator 718 which produces the electric current desired. Compressed air for aiding and accelerating the combustion of the solid fuel F is provided by a power-driven air compressor, generally designated 720, connected to the combustion unit 712. Combustible starting fluid, such as propane, for initiating combustion of the solid fuel F is supplied by a combustible gas supply unit 722, also connected to the combustion unit 712.

The duplex combustion unit 712 consists of two identical single combustion units 724 and 726, only one of which is placed in operation at a given time, the other such unit being filled with solid fuel F and held in reserve until combustion has used up substantially all of the solid fuel F in the other single combustion unit, whereupon the second combustion unit is placed in operation and the first combustion unit is filled with solid fuel F at the next opportunity. Each combustion unit 724 or 726 consists of a vertically-elongated combustion receptacle or combustion pressure vessel 728 of heat-resistant material, such as steel, with cylindrical lower and upper walls 730 and 732 of different diameters joined to one another by a frusto-conical intermediate wall 734 and enclosing a combustion chamber 735.A circular grate 736 is mounted between the walls 730 and 732 at their junction, the lower wall 730 thus providing an ash receiver 738 closed by a bottom wall 740. The lower wall 730 is flanged at its lower end for the attachment of the bottom wall 740. To simplify the showing the combustion receptacle 728 is shown as a single-walled whereas in actual practice it would be lined with a suitable refractory material such as fire clay for heat resistance and also surrounded by fire-resistant insulating material (not shown) for insulation.

The upper end of the upper wall 732 is flanged for the reception of a top plate or cover plate 742. Like the walls 734 and 732, the top wall 742 is also preferably double-walled and preferably lined with refractory material, such as fire clay for heat resistance and insulation. The top wall 742 is centrally apertured for the reception of a pressure relief valve 744. The bottom wall 740 is clamped to the lower wall 730 by any suitable clamping means and is preferably hinged or otherwise pivoted or slidably mounted by conventional means, to enable the ashes to be dumped from the ash receiver 738 into a suitable ash pit at the location of the fuel replentishment station. The solid fuel F is preferably wood fragments which are ordinarily waste products of saw mills or other lumber producing or working establishments, saw dust being a common example of such subdivided or particulate wood.Such subdivided or fragmented wood contains a great amount of latent energy which is released slowly rather than explosively during combustion in a stead flow of hot power gas.

Combustion is initiated by combustible starting fluid, such as propane, contained in a tank 746 and supplied through a conduit 748 and a conventional control and check valve 750 and thence by two conduits 752 (Figure 13) to duplex burners 754 below each of which is a spark plug 756 connected by a conventional conductor cable (not shown) to a conventional source of high tension electricity (not shown) or a platinum wire glow plug similar to ones used in gas appliances.

Also connected to the control and check valve 750 is the outlet or discharge duct 758 of the fructo-conical casing 760 of the compressor 762 at the lower end of the power-driven air compressor 720. The upper end of the casing 762 is joined to the intake duct 764 thereof and receives air through an intake filter 766 by way of an air throttle valve 768. Mounted on the upper end of the air compressor casing 760 and air intake duct 764 is the air compressor drive motor 770 which may consist, for example, of an electric motor or turbine.

Encircling the lower end of the intermediate wall 734 of each combustion unit 724 or 726 is a power gas discharge conduit or manifold 772, each of which opens into a outlet conduit 774 which in turn discharge the power gas into a joint discharge conduit 776 containing a power gas throttle valve 778. The joint discharge conduit 776 is connected to the intake portion 780 at one end of the conventional power gas turbine 714. The power gas, after passing through the power turbine 714 and imparting rotation to its successive rotors and between its intervening stators (not shown) emerges at its exhaust portion 782 at the opposite ends of the turbine 714. This action imparts rotation to the shaft 784 extending between the power turbine 714 and the reduction gear set 716.This gear set 716 may consist, for example, of that gearset disclosed and claimed in my United States Patent No. 4,155,276 issued May 1979 for High-Ratio Speed Reduction Transmission.

The output shaft 786 of the reduction gear box 716 extends therefrom to the two-phased alternator 718 which generates 400-cycle alternating current in response to the rotation of the shaft 786. The alternating current generated as a result of this action is delivered from output terminals 788 and 790 through suitable conductor cables to the place of utilization such as, for example, to the distribution circuit of the principal form of my present invention described above with reference to Figures 1 to 11 inclusive herein.

The operation of the portable solid fuel electric power plant of the modification of the present invention shown in Figures 12 and 13 of the drawings hereof is believed to be self-evident from the foregoing description of its construction and arrangement. In one of its intended uses, the cmponents of this power plant are mounted on the vehicle to be propelled, with the duplex combustion unit 712 mounted on the rearward and thereof where the surplus heat will be dissipated most efficiently. Each of the combustion receptacles 728 is filled with solid fuel F, preferably a mainly cellulose material in the form of subdivided wood fragments, wood blocks or wood sawdust.The tank 746 of the combustible starting gas supply unit 722 is filled with the combustible starting gas such as propane or other suitable combustion-initiating substance, and the electric driving motor 770 of the air compressor 720, having been connected to the vehicle storage batteries is set in operation or, in the alternative, the turbine substituted for it is placed in operation. in either event, compressed air is discharged by the air compressor 60 through the outlet duct 758 and control and check valve 750 to the conduit 752 of the combustion unit 724 or 726 to be initially used, with the other combustion unit 726 or 724 temporarily shut off and held in reserve.The spark plug 756 is then energized to ignite the starting gas flowing through the particular conduit 752 which is intended to be used at the moment, causing the burner 754 thereof to emit flames from the thus-ignited starting gas. These flames, in turn ignite the solid fuel F which, when sufficiently ignited to be self-sustaining in combustion, no longer require the supplying of the starting gas from the tank 746, whereupon the supply thereof to the conduit 748 is terminated.

Meanwhile, the hot combustion power gas emitted by the burning solid fuel F is discharged through the power gas discharge conduit 772 and thence through the outlet conduit 774 into the joint discharge conduit 776 past the power gas throttle valve 778 into the intake portion 780 of the power gas turbine. This action by the thrust of the hot combustion power gas between the blades or vanes of the successive rotors and the stators imparts rotation at high speed to the shaft 784 connecting the power gas turbine 714 to the reduction gear set 716. The latter reduces the speed of rotation to that required to operate the alternator 718, which thereupon delivers 400-cycle alternating current to its output terminals 788 and 790 for further transmission to the place of utilization mentioned above.

More particularly, in the propulsion of an electric vehicle, the operation is as follows. When the driver gets into the car, he turns the ignition key, whereupon the valve 750 opens to let propane gas flow from the tank 746 into the combustion chamber 735. This is now ignited by a spark plug and burns the wood chips. After the wood chips have well caught fire, a heat sensitive switch (not shown) shuts off the gas and the spark plug. This also happens if the gas fails to ignite. After reaching a pressure above atmospheric pressure the throttle 768 opens to the compressor drive turbine 770, or optionally the electric motor 770 starts the compressor 762, which now blows enough air into the combustion receptacle 728 to admit sufficient oxygen in order to continue the burning process of the wood.Even if this starting procedure introduces a time lag of 10 to 15 minutes, the driver meanwhile can start the car and propel it temporarily with battery power, hence will not be required to wait.

As soon as the pressure through the threefold expanding hot air has reached the required level, and the opening of the main or power throttle 778 allows the full power output of the power turbine 714, the alternator 718 is cut in and thereupon regenerates its 300-400 cycle two-phase alternating current to help accelerate the car two full speed, as explained above in connection with the principal form of this invention. As soon as full speed is reached, the battery current for temporary propulsion is shut off. The alternator 718 and the four stepping motors 32, 34, 36 and 38 are so sized that they can overcome the rolling and wind resistance of the car. As also explained above, when the vehicle is decelerating, the energy of deceleration will be recuperated and will flow into the battery.When the vehicle is stopping or waiting at a traffic light, the full output of the alternator 718 will quickly recharge the vehicle propulsion battery so that the battery power thereof can be subsequently used for accelerating the vehicle.

The air compressor 762 and its turbine or motor 770 are completely detached from the power turbine 714.

Their duty is solely to maintain a certain predetermined pressure in the combustion chamber 735 and in the adjacent combustion receptacle or pressure vessel 728, for example 80 to 100 p.s.i. When this pressure is reached, a pressure switch (not shown) closes the valve 768 in the air intake 766 of the compressor, as well as the throttle or switch 768 for the compressor or motor 770 respectively so that at this time no air is pumped into the combustion chamber 735. When the pressure in the combustion chamber 735 has decreased to the permissible minimum p.s.i., the throttle or switch 768 at the compressor turbine or motor 770 opens again, as well as at the throttle at the air intake of the air compressor.Air is thereupon pumped into the combustion chamber 735, thus adding oxygen thereto, and through the concurrent burning of the wood particles, pieces or blocks, the pressure is again raised to the designed 80 p.s.i. For example, let it be assumed that while driving at 50 m.p.h. the compressor unit 720 pumps air into the combustion chamber 735 for about five seconds, and then closes for about 15 seconds. Under these circumstances, the fuel wood F in the combustion chamber 735 remains hot but does not burn.

Even the water content of wood is not a drawback to this power plant because such water is evaporated at 100 p.s.i. to produce steam, which assists the hot power gas in turning the rotor of the power turbine 714.

Moreover, the quality of the wood used as the fuel F is not important. All kinds of wood can be used, even branches, tree stumps, dead wood, in fact any burnable part of the tree, soft and hard wood. For convenience of handling, the wood fuel may be cut into small blocks of about four inches square. Such wood may also be bagged, like charcoal for backyard grilles.

When the retail price of scrap wood is converted into British thermal units and compared with the retail price of gasoline, the cost of such wood fuel Turns out to be equivalent to about 20 cents a gallon.

Furthermore, there is no sales tax nor highway tax added, as with gasoline, so that the cost of such wood fuel is still much less than the dollar a gallon we are now paying for gasoline fuel. As a consequence, wood is not only an alternate and renewable fuel but it is also economical and much safer to handle than flammable and explosive gasoline.

Conventional gas turbines require a certain time to build up adequate pressure, and this is detrimental to stop-and-go traffic. As explained above in connection with the principal form of the invention, battery power is used to overcome this problem.

The wood chips or blocks used to heat the compressed air and to produce the power gas in each combustion chamber 728 can be the waste of the timber industry which, at the present time, is completely lost. The U.S. logging industry estimates this waste at 120 million dry tons annually. This waste could produce the equivalent energy in the present power plant of 400,000 barrels of oil daily.

It is ordinarily assumed that a pound of dynamite possesses more energy than a pound of wood, whereas the reverse is actually the case. A pound of dynamite holds only half the energy of a pound of wood. All that dynamite does is release its energy in a split second, whereas slow-burning wood takes a much longer time to do so. Moreover, 2.5 pounds of wood contains exactly the same amount of energy as one pound of gasoline.

The fuel F may also consist of the processed cellulose waste material known as "Biomass" fuel which includes not only wood scraps and sawdust but also sugar cane, bamboo, chaparrall, corncobs and eucalyptus preferably made into highly-compressed fuel briquettes. One such continuous-extrusion machine for preparing fuel briquettes from such waste materials is described in an article in the journal Industrial Research Development of page 37 of the December 1978 issue entitled "Machine Cuts Biomass Fuel Cost". This machine is said to convert wood waste and "every known kind of biomass residue" into such briquettes which burn with very little ash and which make use of waste material which is otherwise almost always thrown away, as by being buried or burned.

Claims (22)

1. An engine-driven-alternator individual-wheel motorized electric propulsion system for a four-wheel motor vehicle provided with a steering mechanism, said system comprising an engine-driven two-phase alternator having a two-phase alternator output, a plurality of electric stepping motors adapted to be drivingly connected one to each vehicle wheel and having motor inputs, each stepping motor having a rotor and also having a stator with a multiplicity of pole pieces arranged in first and second sets disposed in alternate sequence with the pole pieces of each set having alternate opposite windings imparting alternate opposite polarities to the stator pole pieces of each set upon energization thereof, each stator pole piece having a first winding adapted to be energized by pulses of rectified alternating current and a second winding thereon adapted to be energized by pulses of direct current, a storage battery, a pulse-responsive electric power system including a plurality of gate-controlled rectifiers having power current input means and also having power current output means, a stepping motor control circuit interposed between and connecting said alternator output to said motor inputs and including switching means connected to the gates of said gate-controlled rectifiers and responsive to the reception of positive or negative pulses for selectively energizing said first and second windings of said stator pole pieces separately and simultaneous ly and thereby effecting step-by-step rotation of said rotors, variable frequency generating means electrically connected to said pulse-responsive electric power system including said plurality of gate-controlled rectifiers, and a frequency control circuit for selectively controlling the frequency output of said variable frequency means.

2. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein said variable frequency generating means includes a right-turn variable frequency generator and a left-turn variable frequency generator connected in frequency-regulating relationship to the right side and left side stepping motors respectively, and wherein there is provided a variable frequency generator control device connected to the vehicle steering mechanism and responsive to the operation thereof to effect differential variation of the frequency of electric current supplied to and proportioned between said right side and left side stepping motors.

3. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein engine control means is provided regulating the speed of said engine and alternator to rotate at a substantially constant speed and constant alternating current frequency output respectively.

4. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 3, wherein the vehicle is provided with an operator-actuated vehicle speed regulator, wherein the -output of said alternator, after changing its frequency through switching, is connected to said first windings of said motor stators, and wherein said switching means connects alternator-synchronized pulsating direct current from said storage battery to said second stator windings in response to a power demand from the jattainment of a predetermined vehicle speed or acceleration.

5. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein said gate-controlled rectifiers include a first set of full-wave first-phase rectifiers connected to receive the first phase output of said two-phase alternator and also include a set of full-wave second phase rectifiers connected to receive the second phase output of said two-phase alternator.

6. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein means is provided for dividing the alternating current output of the variable frequency generators into positive and negative polarity half waves, and wherein means is provided for suppressing the half waves of one polarity corresponding to forward motor driving operation whereby to effect selective backing of the vehicle.

7. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein there is provided a second set of full wave rectififers with one such second set rectifier having an input connected electrically to each stepping motor to receive alternating current therefrom during vehicle speed braking retardation with said stepping motors driven as alternators by their respective vehicle wheels, and with said second set rectifier having an output connected to said storage battery in recharging relationship therewith, and wherein said braking retardation means is provided for diverting the output of said engine-driven alternator to said gate control rectifiers and thence to said storage battery.

8. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein there is provided a storage battery charging monitor electrically connected in engine speed regulating relationship between the engine and said storage battery for reducing the speed of said engine and consequently reducing the corresponding output of said alternator in response to the indication by said monitor of said storage battery having attained a fully-charged condition.

9. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein said engine is an internal combustion engine running with almost constant speed.

10. An engine-driven-alternator individual-wheel-motorized electric propulsion system, according to claim 1, wherein said engine is an expansive fluid turbine running with almost constant speed.

11. A portable slow-burning solid-fuel power plant, comprising combustion receptacle means having a combustion chamber therein adapted to burn and convert pieces of slow-burning solid fuel into a pressurized gas, said combustion receptacle means having an air inlet and a power gas outlet, a power-gas-operated turbine having a power gas inlet portion and an exhaust gas outlet portion and a rotary power output member, conduit means for conveying power gas from said outlet of said combustion receptacle means to said inlet portion of said turbine, an alternator having a rotary power input member and electric current output terminals adapted to deliver therefrom the electric current generated by said alternator in response to its drive by said power-gas-operated turbine, a speed reducer operatively connecting said rotary power output member of said turbine to said rotary power input member of said alternator, means for selectively supplying a combustible starting fluid to said combustion receptacle means, means associated with said combustion receptacle means for igniting said combustible starting fluid, and means for supplying air inder pressure to said combustion receptacle air inlet.

12. A portable slow-burning solid-fuel power plant, according to claim 11, wherein said starting fluid is a combustible gas.

13. A portable slow-burning solid-fuel power plant, according to claim 11, wherein said air supplying means is a power-driven air compressor.

14. A portable slow-burning solid-fuel power plant, according to claim 11, wherein said combustion receptacle means includes two combustion receptacles for alternate operation, wherein said air-supplying means also includes separate independent air supply conduits extending from said said compressor to said combustion receptacle, wherein said conduit means includes separate independent power gas conduits extending from said power gas outlets of said combustion receptacles, and wherein means is provided for selectively supplying compressed air to one of said combustion receptacles while shutting off the supply of compressed air to the other combustion receptacle.

15. A portable slow-burning solid-fuel power plant, according to claim 14, wherein said means for selectively supplying a starting fluid includes means for selectively feeding and starting fluid to one of said combustion receptacles while cutting off the supply of said starting fluid to the other of said combustion receptacles.

16. A portable slow-burning solid-fuel power plant, according to claim 14, wherein said selectivelysupplying means for compressed air includes a valve device communicating alternately and selectively with one of said air supplying conduits while cutting off communication with the other of said air-supplying conduits.

17. A portable slow-burning solid-fuel power plant, according to claim 11 wherein said combustion receptacle means includes a vertically-elongated pressure vessel with a pressure relief valve in the upper portion thereof and with a grate structure in the lower portion thereof and with an ash receiver below said grate structure.

18. A portable slow-burning solid-fuel power plant, according to claim 17, wherein a starting fluid burner is disposed in said pressure vessel above said grate structure, wherein a starting fluid container is disposed remote from said burner, and wherein conduit means is provided for conveying said starting fluid from said container to said burner.

19. A portable slow-burning solid-fuel power plant, according to claim 18, wherein said igniting means includes an electrically-energized igniting plug such as a spark plug or a platinum wire glow plug disposed adjacent said burner and adapted to be connected to a suitable source of electricity.

20. A portable slow-burning solid-fuel power plant, according to claim 17, wherein said ash receiver has a closure member movably mounted on said pressure vessel at the bottom thereof and selectively movable between closed ash-retaining and open ash-ejecting positions.

21. An engine-driven-alternator individual-wheel-motorized electric propulsion system substantially as hereinbefore described with reference to the accompanying drawings.

22. A portable slow-burning solid-fuel power plant substantially as hereinbefore described with reference to the accompanying drawings.