Abstract:
The disclosure is directed to a transmission, and more particularly to a semi-Continually Variable Transmission (sCVT), a semi-Continuous, Variable Displacement Motor, a semi-Continuously Reciprocating Multiplex Pump (sCVDP) and an infinitely variable transmission (IVT).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/759,025, filed Jan. 31, 2013, the disclosures of the foregoing applications is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to transmission, and more particularly to Semi-Continuous Variable Transmission (sCVT), and infinitely variable transmission (IVT). 
         [0003]    Although CVTs and IVTs were typically used in the automotive field, their torque capabilities and reliability have been limited in the past. Conventional transmissions allow for the selection of discrete gear ratios, thus limiting the engine to providing maximum power or efficiency for limited ranges of output speed. 
         [0004]    There are several classifications of CVTs; hydrostatic, friction and traction. Friction CVT is one of the most common forms of CVTs in use. These CVTs are based on friction between two or more rotating components to transmit power between a motor and a wheel axle, the radius for the point of contact can be varied, this typically archived with a variable-diameter pulley (VDP). Friction/traction CVT has proven problematic to certain applications due to large size (weight), high cost of components, material fatigue resulting in performance lost and other issues. 
         [0005]    Alternatively, Toroid Traction-Drive transmissions use the high shear strength of viscous fluids to transmit torque between an input torus and an output torus. In properly designed traction drives, power is transferred from the driving roller to the driven roller through the shearing of the fluid film between the toroids (conical portions) and the rollers. Toroid Traction-Drive transmissions has proven problematic to certain applications due to transient elastohydrodynamic lubrication problems, size (weight), overheating of pads, loss of friction and other issues. 
         [0006]    Likewise, Hydrostatic (HST) CVT is typically based on hydraulic pump coupled to a hydraulic motor, where, by varying the displacement per revolution of pump and motor, the transmission ratio will define the torque and speed typically controlled by external means. HST though, has proven problematic to certain applications due to low efficiency of transmission, limited speed range and narrow shift range. Low speed high efficiency, high speed low efficiency. 
         [0007]    CVTs/IVTs are currently being developed in conjunction with hybrid electric vehicles. As CVT/IVT development continues, costs may be further reduced and performance will improve, which in turn makes further development and application of CVT/IVT technology desirable. 
       SUMMARY 
       [0008]    Disclosed, in various embodiments, is a hydromechanical, continuously variable and/or infinitely variable transmission. Specifically, disclosed are transmission wherein the number of pistons involved in generating the movement varies depending on the torque demands of the system. 
         [0009]    In an embodiment provided herein is a hydromechanical, semi continuously variable transmission (sCVT), which can include Semi Continuous Variable Displacement Motor (sCVDM), semi Continuous Multiplex Reciprocating Pump (sCMRP) or (sCVDM) with regular hydraulic pump or (sCMRP) with regular hydraulic Motor (IVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a plurality of bores disposed radially at the distal axial end, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of valve housing each having a proximal axial end and a distal axial end disposed axially above the plurality of bores defined in the transmission housing, the valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of pistons, each slidably coupled within the bore defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal radial surface of the cylindrical transmission housing, configured to engage a drive shaft; a plurality of valves, each disposed within the valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having an elliptical head having a longitudinal axis and a transverse axis perpendicular to the longitudinal axis disposed at the proximal end of the drive shaft, wherein the distal end extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft head; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of actuators, each operably coupled to the valve; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of pistons at a predetermined location along the periphery of the cylindrical transmission housing, the location of the actuators configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0010]    In another embodiment, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a cylindrical space, configured to receive a plurality of axially oriented pistons, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of spool valve housing each having a proximal axial end and a distal axial end disposed radially, the spool valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of axially oriented pistons, each slidably coupled within the cylindrical space defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal axial surface of the cylindrical transmission housing, configured to engage a drive shaft head; a plurality of spool valves, each disposed within the spool valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having a drive shaft head defining a cylinder, the cylinder having an internal surface and external surface and being closed in the distal end, with the proximal end defining a sinusoidal surface configured to engage the distal end of the piston, and wherein the distal end of the shaft extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end of the drive shaft is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of servo motors, each operably coupled to the cylindrical transmission housing; means for converting each servo motor&#39;s rotational motion to reciprocating linear motion, the conversion means operably coupling each spool valve to each servo motor; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of actuators at a predetermined location along the periphery of the cylindrical transmission housing, the location of the pistons configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0011]    In yet another embodiment, provided herein is a vehicle comprising: an engine; a hydraulic pump coupled to the engine, wherein the hydraulic pump is a hydromechanical, Semi Continuously Variable Transmission (sCVT). 
         [0012]    In yet another embodiment, provided herein is a method of modulating the transmission ratio between a motor&#39;s drive shaft and a wheels or gear operably coupled to the motor, the method comprising the steps of: coupling the motor drive shaft to a hydraulic pump; coupling the hydraulic pump to a hydromechanical, Semi Continuously Variable Transmission (sCVT); coupling the hydromechanical, Semi Continuously Variable Transmission (sCVT), to a gear or a wheel, whereby the hydromechanical, Semi Continuously Variable Transmission (sCVT), is configured to rotate a drive shaft coupled to the gear or wheel using hydraulic fluid pumped by the hydraulic pump to actuate a plurality of pistons disposed radially or axially around the drive shaft head; and, by adding or reducing the number of working pistons per revolution of the hydromechanical, sCVT&#39;s drive shaft head, continuously varying the flow of the hydraulic fluid by discrete variable displacement per revolution, thereby changing the volume of displacement per revolution and modulating the ratio between a motor&#39;s drive shaft and the wheel or gear operably coupled to the motor. A. 
         [0013]    These and other features of the hydromechanical CVT will become apparent from the following detailed description when read in conjunction with the drawings, which are exemplary, not limiting, and wherein like elements are numbered alike in several figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0014]    For a better understanding of the hydromechanical CVT, with regard to the embodiments thereof, reference is made to the accompanying drawings, in which like numerals designate corresponding elements or sections throughout and in which: 
           [0015]      FIG. 1  shows and exploded view of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0016]      FIG. 2  illustrates an isometric rear view of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0017]      FIG. 3  illustrates an isometric front view of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0018]      FIG. 4  illustrates a front view of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0019]      FIG. 5  illustrates view of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0020]      FIGS. 6A-6D  illustrate in  FIG. 6A  illustrates a cross section embodiment of the radial piston orientation of the hydromechanical continuous variable transmission along Y-Z plane, while  FIG. 6B , is a magnified illustration section C in  FIG. 6A , and  FIG. 6C  is an illustration of a rotating valve shown in  FIG. 6B , and  FIG. 6D  is alternative linear spool valve to that of  FIG. 6B ; 
           [0021]      FIG. 7  illustrates a cross section of an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission taken along section B-B of  FIG. 5 ; 
           [0022]      FIGS. 8A-8D  illustrate various embodiments of pistons with an elliptical axial cross section with  FIG. 8A  showing a piston type A and  FIG. 8B  showing an embodiment of piston type B used in the radial piston orientation of the hydromechanical sCVT, axial arrangement pistons are shown in  FIGS. 8C and 8D . 
           [0023]      FIGS. 9A and 9B  show an alternative configuration of the elliptical drive shaft head with front view ( FIG. 9A ) and isometric view ( FIG. 9B ), illustrating the change in curvature at the vertices of the ellipse; 
           [0024]      FIG. 10  illustrates an embodiment of a square head of a transmission drive shaft; 
           [0025]      FIG. 11  illustrates spatial and temporal orientation of the pistons in an embodiment of the radial piston orientation of the hydromechanical continuous variable transmission during one operation cycle; 
           [0026]      FIG. 12  shows and exploded view of an embodiment of the axial piston orientation of the hydromechanical continuous variable transmission; 
           [0027]      FIGS. 13A and 13B  show detail D ( FIG. 13A ) and detail E ( FIG. 13B ) illustrated in  FIG. 12 ; 
           [0028]      FIGS. 14A and 14B  show an isometric front view ( FIG. 14A ) of an embodiment of the axial piston orientation without the piston housing, and an isometric rear view ( FIG. 14B ) of an embodiment of the axial piston orientation without the piston housing; 
           [0029]      FIGS. 15A and 15B  show a rear view ( FIG. 15A ) of the axial piston orientation of the hydromechanical continuous variable transmission defining cross section F-F, with cross section F-F illustrated in  FIG. 15B ; 
           [0030]      FIGS. 16A and 16B  show detail H ( FIG. 16A ) and detail G ( FIG. 16B ) defined in  FIG. 15B ; 
           [0031]      FIGS. 17A and 17B  illustrate the isometric view ( FIG. 17A ) and top view ( FIG. 17B ) of the drive shaft and drive shaft head used with the axial piston orientation of the hydromechanical continuous variable transmission; 
           [0032]      FIGS. 18A and 18B  show an exploded view of a configuration of servo motor ( FIG. 18A ) and detail K ( FIG. 18B ) defined in  FIG. 18A . 
           [0033]      FIG. 19 , illustrates a schematic of an operation cycle of the radial piston orientation of the hydromechanical continuous variable transmission; 
           [0034]      FIG. 20  illustrates an embodiment of a vehicle comprising the hydromechanical continuous variable transmission; and 
           [0035]      FIG. 21  is a schematic view of the components in an embodiment of a vehicle comprising the hydromechanical continuous variable transmission. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    Provided herein are embodiments of Semi-Continuous Variable Transmission (sCVT), which can include, or be interchangeable with Semi Continuous Variable Displacement Motor (sCVDM), semi Continuous Multiplex Reciprocating Pump (sCMRP) or (sCVDM) with regular hydraulic pump or (sCMRP) with regular hydraulic Motor (IVT). The sCVT described herein is characterized in that the number of operating pistons in contact with the drive shaft head varies depending on the demand of the system, in terms of torque applied to the drive shaft in the case of a motor, or the product of the desired flow-rate and viscosity of the fluid pumped in the case of a pump. 
         [0037]    Operation of hydrostatic transmission is based on converting mechanical rotational motion into fluid flow by powering a hydrostatic pump, and back to mechanical rotational motion by using hydrostatic motor. In hydraulic systems pressure generated, can represent torque and flow rate can represent speed. In hydrostatic (pump or motor or both). Increasing pump displacement (in other words, flow rate) will increase the hydrostatic motor&#39;s speed and decrease the torque; while reduction of pump displacement (e.g., flow rate) will decrease the hydrostatic motor&#39;s speed and increase torque applied to the hydrostatic motor&#39;s drive shaft. 
         [0038]    In the disclosed technology, fluid flow is continuously varied by discrete variable displacement per revolution. The displacement volume per revolution of the hydromechanical sCVT motor/pump can be divided into a number discrete volumes, (displacement per revolution volume divided to the number of cylinders, each part of volume is a cylinder), with all cylinders being located either radially at the base body around an elliptical drive shaft head, or axially along a cylindrical drive shaft head having a lip defining a sinusoidal surface, and control, monitor and operate by transmission CPU (central processing unit, electronic or mechanical), each cylinder has a piston and by adding or reducing the number of working pistons in an operation cycle, based on the torque demand in the case of a motor and the product of viscosity and flow rate in the case of a pump, the displacement per revolution can be varied and transmission ratio between the motor and the wheels can be set accordingly. 
         [0039]    In the hydromechanical sCVT assemblies described herein fluid flow rate is continuously varied by discrete variable displacement per revolution of the hydrostatic motor&#39;s drive shaft head. Accordingly, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a plurality of bores disposed radially at the distal axial end, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of valve housing each having a proximal axial end and a distal axial end disposed axially above the plurality of bores defined in the transmission housing, the valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of pistons, each slidably coupled within the bore defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal radial surface of the cylindrical transmission housing, configured to engage a drive shaft; a plurality of valves, each disposed within the valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having an elliptical head having a longitudinal axis and a transverse axis perpendicular to the longitudinal axis disposed at the proximal end of the drive shaft, wherein the distal end extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft head; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of actuators, each operably coupled to the valve; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of pistons at a predetermined location along the periphery of the cylindrical transmission housing, the location of the actuators configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0040]    Alternatively, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a cylindrical space, configured to receive a plurality of axially oriented pistons, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of spool valve housing each having a proximal axial end and a distal axial end disposed radially, the spool valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of axially oriented pistons, each slidably coupled within the cylindrical space defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal axial surface of the cylindrical transmission housing, configured to engage a drive shaft head; a plurality of spool valves, each disposed within the spool valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having a drive shaft head defining a cylinder, the cylinder having an internal surface and external surface and being closed in the distal end, with the proximal end defining a sinusoidal surface configured to engage the distal end of the piston, and wherein the distal end of the shaft extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end of the drive shaft is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of servo motors, each operably coupled to the cylindrical transmission housing; means for converting each servo motor&#39;s rotational motion to reciprocating linear motion, the conversion means operably coupling each spool valve to each servo motor; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of actuators at a predetermined location along the periphery of the cylindrical transmission housing, the location of the pistons configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0041]    A person skilled in the art would recognize that the hydromechanical sCVTs described herein can be used as reciprocating pumps as well as a motor and therefore, the embodiments of the hydromechanical, Semi Continuously Variable Transmission (sCVT), assemblies disclosed are used interchangeably with semi Continuous Variable Displacement Motor (sCVDM), semi Continuous Multiplex Reciprocating Pump (sCMRP). 
         [0042]    The displacement per revolution of the hydromechanical sCVT described herein can be controlled using the volume defined by the bores defining a displacement part. Each part is comprised of a cylinder defined by the bore, where the number of cylinders can depend on volume of displacement required per revolution and sCVT performance in terms of torque vs. motor speed. The cylinders can be located around (radial) or along (axial) the drive shaft, for example, an elliptical wheel disposed as the head of the drive shaft in the radial configuration transmission case, and can be controlled, monitored and operated by, for example, a transmission CPU (central processing unit, which can be either electronic and/or mechanical), each cylinder can comprise a piston; wherein; by adding or reducing the number of working pistons in an operation cycle, the displacement per revolution will change and transmission ratio between the motor and wheels or gears can be set accordingly. 
         [0043]    The transmission ratio between engine (in other words, a jet engine, a hydraulic motor, an electric motor, internal combustion engine and/or hybrid or a combination comprising at least one of the foregoing) and the wheels or gears coupled thereto can be continuously changed by discretely varying the number of working pistons in an operation cycle whereby the desired ratio can be set at any given moment. For example; in circumstances where the highest transmission ratio is required (high speed, low torque), the hydromechanical sCVT can use the minimum number of pistons to set the desire ratio of the transmission&#39;s drive shaft head (e.g., a cylindrical drive shaft head defining a sinusoidal lip). 
         [0044]    In an embodiment, one operation cycle is considered to be 360° (degrees) rotation of sCVDM&#39;s or sCMRP&#39;s drive shaft head, and each piston can contribute to the rotation of the transmission&#39;s drive shaft head (e.g., an elliptical drive shaft head, or cylindrical drive shaft head defining a sinusoidal lip) causing the shaft to rotate a given number of degrees. To calculate the minimum pistons required to complete a revolution, 360° can be divided by the degrees of rotation imparted by a single piston stroke. The minimum number of pistons, operating sequentially (in other words, one after the other), will rotate the sCVDM&#39;s or sCMRP&#39;s drive shaft one cycle and so on. 
         [0045]    In circumstances where the lowest ratio is needed (e.g., upon start of motion from a standing position), the sCVT&#39;s CPU, according to a predetermined programming plan, will cause all the pistons in the working zones to operate, to achieve maximum torque. The sCVT&#39;s CPU can be configured operate the pistons in a sequential manner with smallest possible intervals, the value of intervals in degrees can be calculate by dividing 360 degrees by the number of pistons in the hydromechanical sCVT. 
         [0046]    In an embodiment, in the sCVT&#39;s operation, the transmission ratio can shift from highest ratio to lowest ratio or any desire ratio in between at the same time as continuously variable ratio (in other words; to set the desire ratio there is no need to traverse all the way from lowest to the highest ratio, but rather, the desired ratio is achieved in a single operation). 
         [0047]    The hydromechanical sCVT can have several sub-assemblies. for example:
   Hydraulic power supply sub-assembly, which can comprise a pump (e.g. sCMRP), and all hydraulic pipes and connections. The pump can be mounted on, for example, the engine body or the chassis and be operably coupled to the engine&#39;s drive shaft, either directly or through various transfer gears (e.g., spur gear, beveled gears, planetary gears and the like). The hydraulic pump can be a positive displacement pump, a diaphragm pump or other, similarly effective high-pressure pumps.   Bypass sub-assembly, which can comprise a subassembly divert valve operated by the sCVT&#39;s CPU for example, when the vehicle comprising the hydromechanical sCVT is stopped on a flat road and the engine is kept idle.   Hydraulic accumulator sub-assembly, which can comprise pressure tanks, hydraulic actuators (e.g., bladder, diaphragm bladder, piston (either spring or gas controlled) and/or metal bellows) and pipes, which can accumulate the vehicle&#39;s acceleration energy when the vehicle comprising the hydromechanical sCVT moves downhill or when the vehicle&#39;s operator operates the vehicle&#39;s braking system, whereby the subassembly returns this energy back to the hydromechanical sCVT. Hydraulic pressure fluctuations can also result from pump ripple, opening/closing of valves, actuators bottoming out and so on. The selection and design characteristics of accumulators can vary between the applications. For example, the hydraulic accumulator tank can comprise a housing (e.g., cylindrical tank) with a septum separating the hydraulic fluid side and the compressible gas side (for example, dry nitrogen because of its low thermal expansion properties). The accumulator can have a predetermined gas pressure and the hydraulic system can often be used to manipulate the pressure of the oil used in the accumulator depending upon a specific application. Rapid increases and decreases of hydraulic power demands (occurring for example, during acceleration resulting from lane shift when bypassing another vehicle, or upon braking) can shock the hydraulic pump, lines and valves. Open-center systems using, for example positive-displacement pump (in other words, systems that constantly provide hydraulic flow while the engine is running) must return to sump (e.g., a reservoir) when there is no hydraulic need. This can be done, for example, by use of a relief valve or a ‘dump’-valve on the pressure side of the system.   Spool Valve as Hydraulic distributor, which can supply the hydraulic flow according to the operation cycle, to the working cylinders in the sCVT module. The hydraulic distributor can be used for distributing the flow of the hydraulic fluid supplied from the pump to a receiver, such as the hydromechanical sCVT, during, for example, starting, stopping, or reversing of the hydraulic sCVT. The hydraulic distributors can be of the cock, slide-valve, or valve type and may have direct (e.g., manual/mechanical) or remote (e.g., hydraulic, pneumatic, electric) controls.   Elliptical/square or cylindrical drive shaft head defining a sinusoidal lip supervisor, which can be used to monitor the precise position of the elliptical/square/sinusoidal lip drive shaft head during the operation cycle. The supervisor used can be, for example, a mechanical supervisor comprised of a mechanical cam shaft coupled to the drive shaft head, or an electrical supervisor comprised of an electronic Encoder connected to the drive shaft head. The encoder can rotate with the drive shaft head, detects the rotation condition of the drive shaft head and then can provide the hydromechanical sCVT&#39;s CPU with a signal that indicates the rotation condition, in other words, a pulse signal for acquiring a count value (encoder count) corresponding to the amount of movement (rotation amount) of the drive shaft head. Upon acquiring the signal from the encoder, the hydromechanical sCVT&#39;s CPU can control the number of cylinders/pistons and their engagement location around the drive shaft head, ensuring the vehicle operates along the ideal operating line (in other words, on the line optimizing engine torque as a function of vehicle velocity), thus minimizing fuel consumption.   Tire grip valve sub-assembly, which can be coupled to the hydraulic line of each of wheel and which can monitor the hydraulic pressure according the load balance on each wheel shaft. The tire grip valve can control the hydraulic pressure in the line from fully open until the line is closed.   Oil reservoir and filtration container sub-assembly, which can be adapted to receive the hydraulic oil after operation, filter, cool and prepare the oil for next operation.   Control box and operation system sub-assembly, comprising a CPU (central processing unit), and other electrical circuits and electronic components configured to receive data from all sensors (e.g., fluid pressure, encoder count and position, velocity, load/wheel etc.), process the information and operate the hydromechanical sCVT module in accordance with road conditions and programming software.   Sensors. The sCVT system can include several sensors to receive data from vehicle system. The sensors can be, for example, pressure gauge in several locations along hydraulic system described. Likewise, sensors for Engine/Wheel RPM, encoder- position of the elliptical/square drive shaft head, RPM of the hydromechanical sCVT&#39;s or sCVDP&#39;s shaft, position of gas pedal and acceleration. Other sensors used in the systems and methods provided, can be a torque load sensor coupled to each wheel&#39;s shaft (positive or negative depending on the direction of rotation), position of drive gear handle, position of steering drive system or a combination of the foregoing sensors.   The hydromechanical sCVT module, referring to a hydraulic motor or pump with discrete displacement per revolution, capable of providing a variable transmission ratio at any hydraulic pressure supplied by a pump coupled to the engine of the vehicle. module can operate sCVDM or sCMRP.   
 
         [0058]    In an embodiment, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a plurality of bores disposed radially at the distal axial end, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of valve housing each having a proximal axial end and a distal axial end disposed axially above the plurality of bores defined in the transmission housing, the valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of pistons, each slidably coupled within the bore defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal radial surface of the cylindrical transmission housing, configured to engage a drive shaft; a plurality of valves, each disposed within the valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having an elliptical head having a longitudinal axis and a transverse axis perpendicular to the longitudinal axis disposed at the proximal end of the drive shaft, wherein the distal end extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft head; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of actuators, each operably coupled to the valve; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of pistons at a predetermined location along the periphery of the cylindrical transmission housing, the location of the actuators configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0059]    Alternatively, and in another embodiment, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a cylindrical space, configured to receive a plurality of axially oriented pistons, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of spool valve housing each having a proximal axial end and a distal axial end disposed radially, the spool valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of axially oriented pistons, each slidably coupled within the cylindrical space defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal axial surface of the cylindrical transmission housing, configured to engage a drive shaft head; a plurality of spool valves, each disposed within the spool valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having a drive shaft head defining a cylinder, the cylinder having an internal surface and external surface and being closed in the distal end, with the proximal end defining a sinusoidal surface configured to engage the distal end of the piston, and wherein the distal end of the shaft extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end of the drive shaft is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of servo motors, each operably coupled to the cylindrical transmission housing; means for converting each servo motor&#39;s rotational motion to reciprocating linear motion, the conversion means operably coupling each spool valve to each servo motor; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of actuators at a predetermined location along the periphery of the cylindrical transmission housing, the location of the pistons configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors. 
         [0060]    Also, provided herein is a method of modulating the ratio between a motor&#39;s drive shaft and the wheel or gear operably coupled to the motor, the method comprising the steps of: coupling the motor drive shaft to a hydraulic pump; couple the hydraulic pump to a hydromechanical, sCVT (semi-continuous variable transmission) module by hydraulic pipes; coupling the hydromechanical sCVT to a gear or a wheel, whereby the hydromechanical sCVT module is configured to rotate a drive shaft coupled to the gear or wheel using hydraulic fluid pumped by the hydraulic pump to actuate a plurality of pistons disposed radially around the drive shaft head; and, by adding or reducing the number of working pistons per revolution of the hydromechanical, sCVT module&#39;s drive shaft head, continuously varying the flow of the hydraulic fluid by discrete variable displacement per revolution, thereby changing the volume of displacement per revolution and modulating the ratio between a motor&#39;s drive shaft revolutions per minute and the revolutions per minute of a wheel or gear operably coupled to the motor. 
         [0061]    A more complete understanding of the components, processes, and devices disclosed herein can be obtained by reference to the accompanying drawings. These figures (also referred to herein as “FIG.”) are merely schematic representations based on convenience and the ease of demonstrating the presently disclosed devices, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments. Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function. 
         [0062]    Turning now to  FIG. 1  showing an exploded view of an embodiment of the radial piston orientation of the hydromechanical sCVDM or sCMRP module  100  described.  FIG. 1  shows transmission housing base disc  110 , comprising an inlet port  117  for a hydraulic fluid; a cylindrical transmission housing  101  having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing  101  defining a plurality of bores  102   i  disposed radially on transmission housing  101 . Bores  102   i  can be arranged in an array rather than in a single radial row, whereby the array comprises a plurality of rows arranged radially around housing  101 ; and wherein each row can either be axially aligned or offset with respect to other rows of bores  102 . 
         [0063]    Plurality of valve housings  105   j  each j th  housing having a proximal axial end and a distal axial end can be disposed axially with respect to the valve housing  105  above and aligned with the plurality of bores  102   i  defined in the transmission housing  101 . Each j th  valve housing  105   j  can be configured to have an inlet port  114  and an outlet port  113  maintained in fluid communication with a hydraulic pump (not shown, See e.g.,  FIG. 12 ) and operably coupled to actuator cylinder member  602   r , which extends through apertures  116   m  defined in transmission housing base disc  110 . A plurality of pistons  300   p  (showing only 3 of 28), each p th  piston slidably coupled within i th  bore  102   i  defined in the periphery of the cylindrical transmission housing  101 , wherein the proximal end of piston  300   p  extends into the internal radial surface of cylindrical transmission housing  101 , configured to engage drive shaft  500  with drive shaft head  501 . 
         [0064]    A plurality of valves  200   q , (showing one spool valve embodiment) each q th  valve being slidably disposed within j th  valve housing  105 , each q th  valve  200   q  can be operably coupled to the n th  actuator cylinder member  602   n  and be configured to regulate fluid communication between the distal end of the p th  piston  300   p  and the hydraulic fluid by exposing or blocking the inlet port  114  and the outlet port  113  of the hydraulic fluid. Also shown in  FIG. 1 , is means  620  for converting each n th  servo motor&#39;s  601   n  rotational motion to reciprocating linear motion. Means  620  comprising cylindrical cap  623  having pin  625  disposed axially at the closed distal end, and configured to engage spool valve  200   q . 
         [0065]    Drive shaft  500 , having a distal end and a proximal end, can have an elliptical or square head  501  disposed at the proximal end of drive shaft  500 , wherein the distal end extends beyond transmission housing cover disc  111  and can be operably coupled to a wheel or a gear (not shown see e.g.,  FIG. 20 ) and the proximal end is operably coupled to encoder  400 . 
         [0066]    Encoder  400  can be centrally coupled to the transmission housing base disc  110  and coupled to the elliptical or square (see e.g.,  FIG. 11 ) drive shaft head  501 . 
         [0067]    Transmission housing cover disc  111 , can be coupled to the distal end of the cylindrical transmission housing  101 . In addition, a plurality of actuators cylinder member  602   n , each n th  actuator can be operably coupled to each q th  valve of valve  200   q . 
         [0068]      FIG. 1  also shows mounting brackets  118 , oil outlet ports  119  in transmission housing cover disc  111 , seal  109 , disposed between the proximal end of transmission housing  101  and transmission housing base disc  110 , with bearing  112  that can be used for operably coupling drive shaft head  501  to encoder  400 . 
         [0069]    Turning now to  FIGS. 2-5 , showing a rear ( FIG. 2 ) and front ( FIG. 3 ) view of assembled embodiment of the radial piston orientation of hydromechanical sCVDM or sCMRP module  100 , showing transmission housing base disc  110  and transmission housing cover disc  111 , with electric plug  610  (and  610 ′). As shown, actuator valves sub-assembly  600  ( FIG. 2 ) can comprise valve (e.g., rotating valves or spool valves) actuators  601   n , radially disposed and operably coupled to valve housing  105   j , with actuator  400  visible ( FIG. 2 ) and hydraulic fluid inlet port  117  being in fluid communication with each inlet port  114  of the j th  valve housing  105   j  (not shown, see e.g.,  FIG. 1 ). Likewise  FIG. 3  shows the distal end of drive shaft  500  protruding beyond transmission housing cover disc  111 , which define hydraulic fluid outlet ports  119 . sCVDM or sCMRP module  100  can be mounted onto, for example a wheel shock absorber sub-assembly using mounting brackets  118 . The location of mounting brackets  118 , as well as their number, shape, size and other parameters can be altered to ensure proper attachment of sCVDM or sCMRP module  100  to a gear or a wheel. 
         [0070]    Turning now to  FIG. 6 , showing in  FIG. 6A  in a greater detail, a cross section of a front view of the hydromechanical sCVT  100 , along Y-Z plane, wherein valve actuators (e.g., servo motors)  601   n , radially disposed and operably coupled to valve housing  105   j , each j th  housing having a proximal axial end and a distal axial end can be disposed axially with respect to the valve housing  105  with rotating valves  200   q  being operably coupled within housing  105   j  configured to spin above piston  301  exposing or blocking inlet port  114  or outlet port  113  (not shown, see e.g.,  FIG. 1 ) synchronously with the motion of the p th  piston (e.g.,  301 ). As shown, plurality of pistons  300   p , each p th  piston (e.g.,  301 ) being slidably coupled within i th  bore  102   i  (not shown, see e.g.,  FIG. 1 ) defined in the periphery of the cylindrical transmission housing  101  (not shown, see e.g.,  FIG. 1 ), wherein the proximal end of piston  301   p  extends into the internal radial surface of cylindrical transmission housing  101 , configured to engage drive shaft  500  with drive shaft head  501 .  FIG. 6A  also shows encoder  400  centrally coupled to the transmission housing base disc  110  with seal  109 , encoder  400  operably coupled to the elliptical or square drive shaft head  501 . Also shown in  FIG. 6A  is biasing means  320  disposed between upper boss  325  and lower boss  326 , configured to bias piston  301  away from drive shaft head  501 , when the piston is not engaged by actuator  601   n  via encoder  400 . 
         [0071]    As illustrated in  FIG. 6B , valve actuators  601   n  (e.g., servo motor, see e.g.,  FIG. 19A ) are located on each head of piston  300   p  housing and can comprise a rotating valve cylinder  200   q , (see e.g.,  FIG. 6C ), q th  rotating valve operate by electric relay actuator or electric motor actuator cylinder member  602   n , this rotating valve assembly control the inlet port  114  and outlet ports  113  of valve housing  105   j . As illustrated, rotating valve  200  comprises proximal end  201  configured to mate with the distal tip of actuator cylinder member  602   n , and distal end  202  configured to rotate within housing  105   j , with surface curves  203  and  204  defining the gates configured to block or open inlet port  114  and outlet port  113  the valve actuators assembly  600  can operate in three modes: (1) inlet port  114  opened and outlet port  113  closed, (2) inlet port  114  closed and outlet port  113  opened, (3) inlet  114  and outlet  113  ports are closed, whereby, in the third mode (3) valve  200   q  can be located between two other modes, when valve assembly transitions from any mode to any other, the transition passes through the third mode.  FIG. 6B  also illustrates valve head  201  of rotating valve  200 , with seal distal end  202 . Hydraulic pressure outlet tube  106  is coupled to each outlet port  113 , while hydraulic fluid inlet tube  107  is coupled to inlet port  114 . Electronic actuator valve connecting point  201  abuts actuator cylinder member  602   n , coupled to transmission housing cover disc  111 . O-ring  205  can be disposed on rotating valve  200 , to provide a proper seal between valve actuator  200  and housing  105 . 
         [0072]      FIG. 6C  illustrates an embodiment of a rotating valve  200 , that can be used in sCVDM or sCMRP module  100  provided herein, showing tip  201  configured to engage actuator cylinder member  602   n . Rotary valve  200  can consist of a rotating spool  200  which via curved surfaces  203  and  204  align with inlet port  114  or outlet port  113  in the valve housing  105   j  to give the required operation. In an embodiment, creating the corresponding two (or more) bores allows operation of the valve with minimal hydraulic losses. O-ring  205 , ( FIG. 6B ) seals the inlet from outlet port, thus, when closed, there are less hydraulic losses (leaks). 
         [0073]    An alternative linear spool valve is illustrated in  FIG. 6D , where spool valve(s)  200   q  are located on each head of piston  300   p  housing  105   j  and can comprised a valve cylinder  200   q , (see e.g.,  FIG. 1 ) and double pistons connected by hollow bar, the pistons operate by electric relay actuator or electric motor actuator cylinder member  602 , this valve assembly control the inlet port  114  and outlet ports  113  of cylinder, the valve  200  can operate in three modes: (1) inlet port  114  opened and outlet port  113  closed, (2) inlet port  114  closed and outlet port  113  opened, (3) inlet  114  and outlet  113  ports are closed, whereby, in the third mode (3) valve  200  pistons can be located between two other modes, when valve assembly transitions from any mode to any other, the transition passes through the third mode. The valve actuators assembly  600  can act as electric hydraulic distributor.  FIG. 6D  also illustrates piston head  201  of spool valve  200  and air passages  210 , disposed within hollow valve actuator  200 . Hydraulic pressure outlet tube  106  is coupled to each outlet port  113 , while hydraulic fluid inlet tube  107  is coupled to inlet port  114 . Electronic (or servo motor) actuator cylinder member  602  valve connecting point  201  abuts actuator cylinder member  602   n , coupled to transmission housing cover disc  111 . O-ing  205  can be disposed on piston distal end  202  of valve actuator  200 , to provide a proper seal between valve actuator  200  and housing  105 . 
         [0074]    Turning now to  FIG. 7 , showing in a greater detail, cross section B-B of  FIG. 5 , a side view of sCVDM or sCMRP module  100 , with the radial piston orientation wherein pistons  300   p  are radially disposed around elliptical (see e.g.,  FIG. 9A ) or square (see e.g.,  FIG. 11 ) drive shaft head  501 . In the shown embodiment, two types of pistons  300   p  are shown, “regular” type having an elliptical cross section that by arranging the pistons with the narrow aspect radially can enable increasing the number of pistons per diameter of sCVDM or sCMRP module  100 . Piston type A  301  and Piston type B  302  are further illustrated in  FIGS. 8A and 8B . Pistons  300   p  slidably move in a reciprocating manner (referring to a movement where the piston repeats its position) within bore  102   i . Also shown in  FIG. 7 , are electric plugs  610  used to couple sCVDM or sCMRP module  100  to the vehicle&#39;s CPU. Two types of pistons are shown in  FIG. 7 , Piston type B  302  with a roller bearing to reduce friction with drive shaft head  501 , and piston type A  301 , without. As shown piston  302  type B is at 3 o&#39;clock and another, at 12 o&#39;clock. Pistons  301  type A are shown at 6, 9, and 11 o&#39;clock. Turning now to the position of the pistons in the operation cycle as illustrated for example in  FIG. 7 ; piston  302  at 12 o&#39;clock as shown is in discharge position (see e.g.,  FIG. 11 ) based on the spin direction of elliptical drive shaft head  501 . Piston  301  type A at 12 o&#39;clock shown with biasing means  320  is at a hold position, held away from drive shaft head  501  with biasing means  320  and does not participate in turning drive shaft head  501 . Piston  302  type B at 3 o&#39;clock and piston  301  type A at 9 o&#39;clock, are in a transient zone (see e.g.,  503 ,  FIGS. 9A ,  9 B) of the major axis of elliptical drive shaft head  501 . Based on the control system (CPU), these pistons completed the discharge operation and are now available to further participate in the operation cycle, or remain in a hold position. Had these pistons been in hold position, this would have been the point (in other words, at the point where, for example, piston head  305  (see e.g.,  FIG. 8B ) of piston  302  type B is slidably, frictionally coupled to drive shaft head  501 ) the CPU could have ordered these pistons to initiate their participation in the operation cycle. Similarly, piston  301  type A at 6 o&#39;clock is likewise at the transient zone (see e.g.,  504 ,  FIGS. 9A ,  9 B) of the minor axis of elliptical drive shaft head  501 , at which point the piston transforms from a working position to a discharge position. 
         [0075]    Turning now to  FIG. 8 , showing piston  301  in  FIG. 8A , having a proximal end configured to provide the surface for the hydraulic fluid work in pressing the piston toward the elliptical or square drive shaft head. Distal end of piston  301  terminates in a solid surface, configured to slidably engage elliptical or square drive shaft head  501  outer surface  502  (see e.g.  FIG. 9A ) thus rotating drive shaft  500 . Alternatively in an embodiment or in addition in another embodiment, as shown in  FIG. 8B , piston type B,  302  can comprise in its distal end roller bearing  305  configured to span the width of elliptical or square drive shaft head  501  and reduce the friction between piston  302  and elliptical drive shaft head  501 .  FIG. 8C  shows an embodiment of piston  304  used with the axial configuration of sCVDM or sCMRP module  100 , having contact head  306  configured to slidably couple to cylindrical drive shaft head  501  having a sinusoidal lip  502  (see e.g.,  FIG. 13A ).  FIG. 8D , shows an embodiment of axial piston  303 , having a distal end with bracket  310  and frusto-conical roller bearing  311 , whereby the angle defined by frusto-conical roller bearing  311  is configured to assure the wider base of frusto conical roller bearing  311  and the narrower end of the frusto-conical roller bearing  311  rotate at the same speed thus preventing unnecessary friction and heat. Bracket  310  extends longer at the internal wall of cylindrical drive shaft head  501 , wherein ball bearing  315  is embedded in the internal arm of bracket  310 . The pistons can take any shape so long as they provide hydraulic fluidity during operation. 
         [0076]    Frusto conical roller bearing  311  defines a slope that can be calculated whereby the angle is determined by equating the ratio between the external diameter OD (see e.g.,  FIG. 17B ) of cylindrical drive shaft head  501  having a sinusoidal lip  502  having width l (see e.g.,  FIG. 17A ), and the wider base of frusto conical roller bearing  311  and the ratio between the external diameter ID (see e.g.,  FIG. 17B ) of cylindrical drive shaft head  501  having a sinusoidal lip  502  having width l (see e.g.,  FIG. 17A ), and the narrower base of frusto conical roller bearing  311 . To obtain the surface angle, either the diameter of the wider base, or the diameter of the narrower base of frusto conical roller bearing  311  will have to be fixed, and can be done based on technical considerations known to those skilled in the art. 
         [0077]    Turning now to  FIGS. 9-10 . As shown in  FIG. 9 , the major and minor axis at the vertices are shorter and longer respectively (in other words, the major axis at the vertices is shorter and the minor axis at the vertices is longer), and along arcs A  503  and B  504 , define a circular arc, rather than parabolic arc  502 , with arc  503  length defined by the equation: 
         [0000]    
       
         
           
             
               
                 
                   A 
                   = 
                   
                     
                       
                         n 
                         A 
                         ∘ 
                       
                       360 
                     
                      
                     2 
                      
                     π 
                      
                     
                         
                     
                      
                     
                       r 
                       A 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein:
       A is the length of arc  503  at the major axis vertices;   n A ° is the central angle in degrees; and   r A  is the radius of the major axis at the vertices
 
and arc  504  length defined by the equation:
       
 
         [0000]    
       
         
           
             
               
                 
                   B 
                   = 
                   
                     
                       
                         n 
                         B 
                         ∘ 
                       
                       360 
                     
                      
                     2 
                      
                     π 
                      
                     
                         
                     
                      
                     
                       r 
                       B 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein:
       B is the length of arc  504  at the minor axis vertices;   n B ° is the central angle in degrees; and   r B  is the radius of the major axis at the vertices
 
and where arcs  502  are defined by the ellipsoid function where the angle is 90 degrees. For each major and minor semiaxis, n A,B ° can be between about 2° and about 20°.
       
 
         [0084]    As illustrated in  FIG. 9A  it isn&#39;t a continuous ellipse shape, wherein the vertices of the ellipse can be radial in shape and not in parabolic shape as described, e.g., in  FIG. 7 , the radial vertices surfaces can be designed for adjusting transition zones, and the arc length is adapted to alter the functionality of the transition mode, and could be different from one category to another (in other words, earth movers, ATV, pumps, sedans and the like), this can allow the designer greater flexibility to design the transitions modes, and synchronize the spool or rotating valve with elliptical drive shaft head  501  revolutions. 
         [0085]      FIG. 10  shows square drive shaft head  510 , turned by pistons, for example pistons shown in  FIG. 8A , wherein head  510  is operably coupled to drive shaft  500  turning in cylindrical transmission housing  101 . 
         [0086]    Turning now to  FIGS. 11 , and  19 , illustrating in  FIG. 11 , sCVT with 28 pistons and operation zone respectively for each piston, while  FIG. 19  illustrates a schematic of sCVT in circumstances with the highest ratio and operational sequence of 6 pistons in the operation cycle of an embodiment of the radial piston orientation of the sCVDM or sCMRP module  100 , comprising 28 pistons  300   p , as shown in  FIG. 11 , located within bores  102   i  configured to engage elliptical drive shaft head  501  in a given position, the operation cycle divided to operation zones, working zones, and discharge zones which located sequentially, and 8 transient zones disposed between each of the working and discharge zones. For example, as shown in  FIG. 19 , operation cycle of elliptical wheel  501  by six (6) pistons  300   p , each working zone describe by arc, the inner arcs are the first part of working zones the outer arcs are the last part of working zones, the elliptical drive shaft head  501  at given position, and piston No.  21  is the first working piston, the piston forces the elliptical wheel to rotate about 77.15 degrees. After about 60 degrees of elliptical wheel rotation piston No.  12  is actuated an starts working engaging elliptical drive shaft head  501 , causing it to rotate, with pistons No.&#39;s  21 , and  12 , working together along about 17.15 degrees. At the end of the 17.15 degrees piston No.  21  finishes working and piston No.  12  continues rotating elliptical drive shaft head  501 . Once elliptical drive shaft head  501  has rotated 120 degrees piston No.  3  start working, again with an overlaps of 17.15 degrees with piston No.  12 , with the next working piston No.  22  starts engaging elliptical drive shaft head  501 , followed after the next 60 degrees by piston No.  13  with piston No.  4  being that last work to accomplish one operation cycle of elliptical drive shaft head  501 . 
         [0087]    Turning now to  FIGS. 12-15 , illustrating in  FIG. 12 , an exploded view of an embodiment of the axial piston orientation of the hydromechanical, semi continuously variable transmission (sCVT)  1300 , comprising: transmission housing base disc  110 , comprising an inlet port  117  (not shown, see e.g.,  FIG. 15A ) for a hydraulic fluid with cylindrical piston housing  1302  having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, cylindrical piston housing  1302  defining a cylindrical space, configured to receive a plurality of axially oriented pistons  300   p , wherein the proximal axial end of the p th  piston  303  or  304  (see e.g.,  FIGS. 8C ,  8 D,  15 B) is operably coupled to transmission housing base disc  110 . Plurality of spool valve housing  105   j  (not shown, see e.g.,  FIG. 15B ), each having a proximal axial end and a distal axial end disposed radially, the spool valve housing having inlet port  117  and radial outlet port  113  being in fluid communication with a hydraulic pump and operably coupled to actuator  601   n  with plurality of axially oriented pistons  300   p , each slidably coupled within the cylindrical space defined between the walls of cylindrical piston housing  1302  having internal wall  1303  (not shown, see e.g.,  FIG. 15B ), and each piston (e.g.,  304 ) having a proximal end and a distal end, wherein the proximal end extends into cylindrical piston housing  1302  having internal wall  1303 , configured to engage drive shaft head  501 . Also shown are plurality of spool valves  200   q , each disposed within the spool valve housing  105   1  valve  200   q  operably coupled to actuator  601   n  and configured to regulate fluid communication between the distal end of piston  303  and the hydraulic fluid by exposing or blocking inlet radial port  114  and radial outlet port  113  of the hydraulic fluid. Drive shaft  500  illustrated having a distal end and a proximal end, drive shaft  500  having a drive shaft head  501  defining a cylinder, the cylinder having an internal surface and external surface and being closed at the distal end, with the proximal end defining a sinusoidal surface (or lip)  502  configured to engage the distal end of piston  303  or  304 , and wherein the distal end of drive shaft  500  extends beyond transmission housing cover disc  1301  and the proximal end of drive shaft  500  is operably coupled to encoder  400 . Encoder  400  is centrally coupled to transmission housing base disc  110  and coupled to the drive shaft  500 . Transmission housing cover disc  1301 , is coupled to the distal end of cylindrical transmission housing  1311 . As shown in  FIG. 12 , plurality of actuators, or servo motors  601   n , each operably coupled to the cylindrical transmission housing  1311 . As illustrated in  FIGS. 12 and 13A  means for converting each n th  servo motor&#39;s  601   n  rotational motion to reciprocating linear motion  620 , the conversion means operably coupling each q th  spool valve  200   q  to each n th  servo motor (or actuator)  601   n    
         [0088]    Turning now to  FIG.13 , illustrating in  FIG. 13A , detail D from  FIG. 12 , showing means  620  for converting each n th  servo motor&#39;s  601   n  rotational motion to reciprocating linear motion. Means  620  comprising cylindrical cap  623  having pin  625  disposed axially at the closed distal end, and configured to engage spool valve  200  (not shown, see e.g.,  FIG. 12 ) and an open proximal end configured to receive dowel  605  operably coupled to servo motor  601  drive shaft and having sinusoidal groove  606  etched therein, wherein groove  606  is configured to detent member  622  can be coupled to cap  623  with bearing disc  621 , and transmission housing&#39;s external wall  1302  (see e.g.,  FIG. 15B ). Rotation of dowel  605  with servo motor  601 , bearing disc  621  slidably rotates within groove  606 . Movement of bearing disc within sinusoidal groove  606  can cause cylindrical cap  623  to reciprocally move axially. To ensure cylindrical cap  623  does not rotate with dowel  605 , a double channel is etched into transmission housing&#39;s external wall  1302 , operably coupled to bearing disc  621 , for example, with an additional bearing (not shown). 
         [0089]      FIG. 13B  illustrates a magnified portion of detail B in  FIG. 12 , showing an embodiment of axial piston  303 , having a distal end with bracket  310  and frusto-conical roller bearing  311 , whereby the angle defined by frusto-conical roller bearing  311  is configured to assure the wider base of frusto conical roller bearing  311  and the narrower end of the frusto-conical roller bearing  311  rotate at the same speed thus preventing unnecessary friction and heat. Bracket  310  extends longer at the internal wall of cylindrical drive shaft head  501 . 
         [0090]    Turning now to  FIG. 14 , illustrating in  FIG. 14A  front isometric view of axial configuration of the axial piston orientation of the hydromechanical, semi continuously variable transmission (sCVT)  1300  (see e.g.,  FIG. 12 ), without cylindrical piston housing  1302 , and with drive shaft  500 , extending through transmission housing cover disc  1301  at the distal end, while proximal end is operably coupled to encoder  400 . As shown, cylindrical drive shaft head  501  defines a sinusoidal surface (or lip,  502  not shown, see e.g.,  FIG. 14B ) configured to be rotated by pistons  300   p , for example, friction piston  304 , being in fluid communication with spool valve  200   q , with actuators, or servo motors  601   n , operably coupled to cylindrical transmission housing  1311 , comprising outlet port  119 . As shown actuators  601   n , can be a servo motor, having lead  650 , motor portion  640 , motor gear assembly  645  and servo motor encoder  648 . 
         [0091]    Turning now to  FIG. 14B , showing a rear isometric view with only a couple of pistons and without cylindrical piston housing  1302 , for illustration purposes only. As shown, drive shaft  500 , extending through transmission housing cover disc  1301  at the distal end, while proximal end is operably coupled to bearing  112 . As shown, cylindrical drive shaft head  501  defines a sinusoidal surface (or lip) configured to be rotated by pistons  300   p , for example, friction piston  304 , or roller piston  303  operably coupled to cylindrical transmission housing  1311 , comprising outlet port  119 . Also shown is roller piston  303  having a distal end comprising bracket  310  with and frusto-conical roller bearing  311 , whereby the angle defined by frusto-conical roller bearing  311  is configured to assure the wider base of frusto conical roller bearing  311  and the narrower end of the frusto-conical roller bearing  311  rotate at the same speed thus preventing unnecessary friction and heat. Bracket  310  extends longer at the internal wall of cylindrical drive shaft head  501 . 
         [0092]    Turning now to  FIG. 15 , illustrating a rear view of the axial piston orientation of the hydromechanical, semi continuously variable transmission (sCVT)  1300  (see e.g.,  FIG. 12 ), with actuators (or servo motors)  601   n , oriented axially around transmission housing base disc  110 , defining hydraulic fluid inlet port  117 , with actuator lead  650  and encoder  648  visible, as well as hydraulic fluid outlet port  119 .  FIG. 15A  also defines cross section B-B, illustrated in detail in  FIG. 15B . 
         [0093]    As shown in  FIG. 15B  illustrating cross section F-F in  FIG. 15A  of the axial piston orientation of the hydromechanical, semi continuously variable transmission (sCVT)  1300 , comprising: transmission housing base disc  110  transmission housing is  1302 ,  110  is rear part with inlet  117  and radial fluid inlet port 114  (see e.g. FIG.- 12 ) and holes connection between inlet  117  and radial inlet port  114 , comprising inlet port  117  coupled to torus inlet manifold  114  for a hydraulic fluid with cylindrical piston housing  1302  having a proximal axial end and a distal axial end, and internal radial surface and external radial surface, cylindrical piston housing  1302  defining a cylindrical space, with internal wall  1303 , configured to receive plurality of axially oriented pistons  300   p , (see e.g.,  FIG. 12 ) wherein the proximal axial end of the p th  roller piston  303  or friction piston  304  is operably coupled to transmission housing base disc  110  of transmission housing comprised of a cylinder having external wall  1302  and internal wall  1303 . Plurality of spool valve housing  105   j , each having a proximal axial end and a distal axial end disposed radially, with outlet port  113  operably coupled to actuator  601   n  having lead  650  with the plurality of axially oriented pistons  300   p , each p th  piston slidably coupled within the cylindrical space defined between the walls of cylindrical piston housing  1302  having internal wall  1303 , and each piston (e.g., friction piston  304 ) having a proximal end and a distal end, wherein the proximal end extends into cylindrical piston housing  1302  having internal wall  1303 , configured to engage drive shaft head  501 . Also shown are plurality of spool valves  200   q , each disposed within the spool valve housing  105   j  valve  200  operably coupled to actuator  601   n  and configured to regulate fluid communication between the distal end of, e.g., roller piston  303  and the hydraulic fluid by exposing or blocking inlet port  117  coupled to torus inlet manifold  114  and outlet port  113  of the hydraulic fluid. Drive shaft  500  illustrated having a distal end and a proximal end, drive shaft  500  having a drive shaft head  501  defining a cylinder, the cylinder having an internal surface and external surface and being closed at the distal end, with the proximal end defining a sinusoidal surface (or lip)  502  (not shown see e.g.,  FIG. 14B ) configured to engage the distal end of roller piston  303  or friction piston  304 , and wherein the distal end of drive shaft  500  extends beyond transmission housing cover disc  1301  and the proximal end of drive shaft  500  is operably coupled to encoder  400 . Encoder  400  is centrally coupled to transmission housing base disc  110  and coupled to the drive shaft  500 . Transmission housing cover disc  1301 , is coupled to the distal end of cylindrical transmission housing  1311 . 
         [0094]    As shown, plurality of actuators, or servo motors  601   n , each operably coupled to the cylindrical transmission housing  1311  with means for converting each n th  servo motor&#39;s  601   n  rotational motion to reciprocating linear motion  620 , the conversion means operably coupling each q th  spool valve  200   q  to each n th  servo motor (or actuator)  601   n . Also shown in  FIG. 15B  is biasing means  320 , configured to bias roller piston  303  away from cylindrical drive shaft head  501 , when the piston is not engaged by actuator  601   n  via encoder  400 . In addition, as shown in detail E, roller piston  303  further comprises a distal end comprising bracket  310  with and frusto-conical roller bearing  311 , and wherein ball bearing  315  is sandwiched between internal arm of bracket  310  and internal wall of cylindrical drive shaft head  501 . 
         [0095]    Details of  FIG. 15B  is further magnified in  FIG. 16 , where  FIG. 16A  illustrates detail D in  FIG. 15B , showing actuator cylinder member  602   n , means for converting each n th  servo motor&#39;s  601   n  rotational motion to reciprocating linear motion  620 , the conversion means operably coupling each q th  spool valve  200   q  to each n th  servo motor (or actuator)  601   n . As shown; means  620  comprising cylindrical cap  623  having pin  625  disposed axially at the closed distal end, and configured to engage spool valve  200   q  and an open proximal end configured to receive dowel  605  operably coupled to actuator (or servo motor)  601   n  drive shaft and having sinusoidal groove  606  (not shown, see e.g.,  FIG. 13A ) etched therein, wherein groove  606  is configured to receive bearing disc  621  rotatably coupled to detent member  622  (not shown, see e.g.,  FIG. 13A ), wherein disc  621  traverses the wall of cylindrical cap  623  along axial plane  633 . A second assembly of detent  621  and rotatably coupled disc  622  is disposed at 180°, likewise configured to slidably engage groove  606  etched in dowel  605 . Also shown in  FIG. 16A , is biasing means  320 , configured to bias roller piston  303  away from cylindrical drive shaft head  501 , when the piston is not engaged by actuator  601   n  via encoder  400 . Further shown in  FIG. 16A , are inlet port  117  coupled to torus inlet manifold  114 , outlet port  113 , and valve housing  105   j . 
         [0096]    Turning now to  FIG. 16B , showing detail E in  FIG. 15B , where roller piston  303  further comprises a distal end comprising bracket  310  with and frusto-conical roller bearing  311  is operably coupled to bracket  310  arms with roller bearing shaft  312 , and wherein ball bearing  315  is sandwiched between internal arm of bracket  310  and internal wall of cylindrical drive shaft head  501  and is configured to both roll and turn while piston  303  is rolling and in contact with sinusoidal surface (or lip)  502 , of cylindrical drive shaft head  501 . Also shown in  FIG. 16B , is biasing means  320 , configured to bias roller piston  303  away from cylindrical drive shaft head  501 , when the piston is not engaged. 
         [0097]    Turning now to  FIG. 17 , showing an isometric view ( FIG. 17A ) and top view ( FIG. 17B ) of an alternate embodiment of drive shaft  500 , having a distal end and a proximal end, drive shaft  500  having a drive shaft head  501  defining a cylinder, the cylinder having an internal surface and external surface and being closed at the distal end, with the proximal end defining a sinusoidal surface (or lip)  502  configured to engage the distal end of roller piston  303  or friction piston  304  (not shown, see e.g.  FIG. 14B ). As shown sinusoidal lip  502  is not continuous and at the minima and maxima points, the curvature changes, and can be radial in shape and not in parabolic shape. The radial minima and maxima of the wave surfaces can be designed for adjusting transition zones, and the length can be adapted to alter the functionality of the transition mode, and could be different from one category (in other words, earth movers, ATV, pumps, sedans and the like), to another, this can allow the designer greater flexibility to design the transitions modes, and synchronize spool valve  200   q  with elliptical drive shaft head  501  revolutions. 
         [0098]      FIG. 18 , illustrates in  FIG. 18A  the coupling between an actuator, or for example a servo motor  601   n , having lead  650 , motor portion  640 , motor gear assembly  645  and servo motor encoder  648 , and means  620  comprising as shown in  FIG. 18B , cylindrical cap  623  having pin  625  disposed axially at the closed distal end, and configured to engage spool valve  200  (not shown, see e.g.,  FIG. 15B ) and an open proximal end configured to receive dowel  605  operably coupled to servo motor  601  drive shaft and having sinusoidal groove  606  etched therein, wherein groove  606  is configured to receive disc  621  rotatably coupled to detent member  622 , wherein disc  621  traverses the wall of cylindrical cap  623 . A second assembly of detent  621  and rotatably coupled disc  622  is disposed at 180°, likewise configured to slidably engage groove  606  etched in dowel  605 . 
         [0099]    Turning now to  FIG. 20 , illustrating an embodiment of a vehicle comprising the hydromechanical continuous variable transmission (sCVDM or sCMRP module)  100  described herein located at each wheel hub. 
         [0100]      FIG. 21 , is a schematic view of the components in an embodiment of a vehicle comprising the radial orientation hydromechanical continuous variable transmission  100  described herein which schematically illustrates the electronic and mechanical Hydromechanical sCVT system. The system can comprise an efficient pump (e.g., the axially oriented piston sCVDP  1300  described herein) operably coupled to the engine shaft, and bypass subassembly, sensors, control box CPU, accumulator system, friction control valve, and reservoir container to filtered and cool the hydraulic oil, and electronic Hydromechanical sCVT shaft optionally coupled to each wheel shaft. 
         [0101]    All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. “Combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, the terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to denote one element from another. The terms “a”, “an” and “the” herein do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the film(s) includes one or more films). Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. 
         [0102]    In an embodiment, the term “coupled”, including its various forms such as “operably coupling”, “operably coupled”, “coupling” or “couplable”, refers to and comprises any direct or indirect, structural coupling, connection or attachment, or adaptation or capability for such a direct or indirect structural or operational coupling, connection or attachment, including integrally formed components and components which are coupled via or through another component or by the forming process. Indirect coupling may involve coupling through an intermediary member or adhesive, or abutting and otherwise resting against, whether frictionally or by separate means without any physical connection. In another embodiment, the term “coupled”, including its various forms such as “operably coupling”, “operably coupled”, “coupling” or “couplable”, refers to and comprises circumstances whereby two or more components in communicate with each other. “Communicate” (and its derivatives e.g., a first component “communicates with” or “is in communication with” a second component) and grammatical variations thereof are used to indicate a structural, functional, mechanical, electrical, optical, or fluidic relationship, or any combination thereof, between two or more components or elements. As such, the fact that one component is said to communicate with a second component is not intended to exclude the possibility that additional components can be present between, and/or operatively associated or engaged with, the first and second components. 
         [0103]    In addition, the term “slidably coupled” is used in its broadest sense to refer to elements which are coupled in a way that permits one element to slide or translate within, or with respect to another element. 
         [0104]    The term “plurality”, as used herein, is defined as two or as more than two. The term “another”, as used herein, is defined as at least a second or more. The terms “including” and/or “having”, as used herein, are defined as comprising (i.e., open language). 
         [0105]    The term “engage” and various forms thereof, when used with reference to the elliptical drive shaft head, refers to one or a plurality of coupled components, at least one of which is configured for releasably engage elliptical drive shaft head. Thus, this term encompasses both single part engaging elements and multi-part-assemblies. 
         [0106]    The term “boss” generally refers to protuberance on a part designed to add strength, facilitate alignment or motion, provide fastening, provide, etc. Exemplary boss elements include shapes such as a tab, detent, flange, pole, post, etc. 
         [0107]    The term “biasing means” refers to any device that provides a biasing force. Representative biasing elements include but are not limited to springs (e.g., elastomeric or metal springs, torsion springs, coil springs, leaf springs, tension springs, compression springs, extension springs, spiral springs, volute springs, flat springs, and the like), detents (e.g., spring-loaded detent balls, cones, wedges, cylinders, and the like), pneumatic devices, hydraulic devices, magnets, and the like, and combinations thereof. Likewise, “biasing means” as used herein refers to one or more members that applies an urging force between two elements. 
         [0108]    Accordingly, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: a transmission housing base disc, comprising an inlet port for a hydraulic fluid; a cylindrical transmission housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, the transmission housing defining a plurality of bores disposed radially at the distal axial end, wherein the proximal axial end is operably coupled to the transmission housing base disc; a plurality of valve housing each having a proximal axial end and a distal axial end disposed axially above the plurality of bores defined in the transmission housing, the valve housing having an inlet port and an outlet port and being in fluid communication with a hydraulic pump and operably coupled to an actuator; a plurality of pistons, each slidably coupled within the bore defined in the periphery of the cylindrical transmission housing having a proximal end and a distal end, wherein the proximal end extends into the internal radial surface of the cylindrical transmission housing, configured to engage a drive shaft; a plurality of valves, each disposed within the valve housing, the valve operably coupled to an actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and the outlet port of the hydraulic fluid; a drive shaft, having a distal end and a proximal end, the drive shaft having an elliptical head having a longitudinal axis and a transverse axis perpendicular to the longitudinal axis disposed at the proximal end of the drive shaft, wherein the distal end extends beyond a transmission housing cover disc and is operably coupled to a wheel or a gear and the proximal end is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the elliptical drive shaft head; a transmission housing cover disc, coupled to the distal end of the cylindrical transmission housing; a plurality of actuators, each operably coupled to the valve; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of pistons at a predetermined location along the periphery of the cylindrical transmission housing, the location of the actuators configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors, wherein, (i), the plurality of bores, comprise between 8 and 56 bores, (ii) the elliptical drive shaft head further comprises a radial layer, (iii) having cylindrical bearings axially disposed between the radial layer and the elliptical drive shaft head, operably coupled to the elliptical drive shaft head, configured to rotate around the drive shaft independently of the elliptical drive shaft head, (iv), the piston proximal end is operably coupled to a bearing configured to engage the periphery of the elliptical drive shaft head, (v) the bores defined by the radial surface of the cylindrical transmission housing are disposed radially at the distal axial end in an array comprising at least two rows of bores, (vi) wherein the drive shaft is configured to engage all rows pistons in a single head, (vii) wherein the drive shaft is configured to engage each row of pistons in a single head, (viii) the input to the control module is received from a wheel or gear torque sensor, the drive shaft torque sensor, the encoder, a motor revolution per minute sensor, a gear or wheel revolution per minute sensor, hydraulic fluid pressure sensor, or a combination comprising the foregoing, (ix) wherein the drive shaft head defines at least two diametrically opposed working zones; at least two diametrically opposed discharge zones; and at least two diametrically opposed transition zones, (x) wherein, at a fixed or increasing hydraulic fluid pressure, the higher the load on the wheel or gear, the larger is the number of pistons engaged by the control module in the working zone, and (xi) wherein, at a fixed or decreasing load on the wheel or gear, the higher the hydraulic pressure, the smaller is the number of pistons engaged by the control module in the working zone, wherein (xii) at the vertices of the ellipse defined by the elliptical head, the major and minor semiaxis are different and define a circular arc between center angle of about 2° and about 20°, with radii that are shorter and longer respectively than the major and minor semiaxis at the remaining ellipse curvature, wherein (xiii) the valve is a rotating valve and (xiv) the actuator is a servo motor configured to rotate the rotating valve, wherein (xv) the valve is a spool valve, and the actuator is a servo motor, further comprising means for converting rotational motion to reciprocating linear motion, wherein the means for converting rotational motion to reciprocating linear motion are operably coupled to the spool valve, and wherein (xvi) the unengaged pistons are biased away from the elliptical drive shaft head. 
         [0109]    In another embodiment provided herein is a vehicle comprising: an engine; a hydraulic pump coupled to the engine; and a hydromechanical sCVT assembly, the hydromechanical sCVT in fluid communication with the hydraulic pump, wherein the hydromechanical sCVT is operably coupled to two wheels on opposite sides of the vehicle, wherein (xvi) the vehicle further comprises optionally, an additional hydromechanical sCVT of claim  1 , the hydromechanical sCVT in fluid communication with the hydraulic pump coupled to each additional wheel of the vehicle; a high pressure accumulator; a low-pressure accumulator; and a reservoir container, all in fluid communication with the hydraulic pump, (xvii) and a hydraulic line having a proximal end coupled to the hydraulic pump and a distal end operably coupled to a proportional valve, wherein the proportional valve is operably coupled between at least a pair of the hydromechanical sCVT described herein,. 
         [0110]    In yet another embodiment, provided is a method of modulating the ratio between a motor&#39;s drive shaft and wheel or gear operably coupled to the motor, the method comprising the steps of: coupling the motor drive shaft to a hydraulic pump; coupling the hydraulic pump to a hydromechanical, semi-continuous variable transmission (sCVT); coupling the hydromechanical, semi-continuous variable transmission to a gear or a wheel, whereby the hydromechanical, semi-continuous variable transmission is configured to rotate a drive shaft coupled to the gear or wheel using hydraulic fluid pumped by the hydraulic pump to actuate a plurality of pistons disposed radially around the drive shaft head; and, by adding or reducing the number of working pistons per revolution of the hydromechanical, semi-continuous variable transmission&#39;s drive shaft head, continuously varying the flow of the hydraulic fluid by discrete variable displacement per revolution, thereby changing the volume of displacement per revolution and modulating the ratio between a motor&#39;s drive shaft revolutions per minute and the revolutions per minute of a wheel or gear operably coupled to the motor, whereby (xviii) the number of working pistons in an operation cycle per revolution of the hydromechanical, semi-continuous variable transmission&#39;s drive shaft head will set the transmission ratio at any given gear or wheel moment coupled thereto, (xix) the number of working pistons in an operation cycle per revolution of the drive shaft head in the hydromechanical, semi-continuous variable transmission, is configured to operate the motor along the optimum fuel efficiency curve (IOL) of the motor torque as a function of the motor drive shaft RPM, (xx) the plurality of pistons are disposed radially around the drive shaft head of the hydromechanical, semi-continuous variable transmission in one or more rows, and (xxi) the drive shaft head of the hydromechanical, semi-continuous variable transmission is elliptical. 
         [0111]    In yet another embodiment, provided herein is a hydromechanical, semi continuously variable transmission (sCVT), comprising: transmission housing base disc, defining an inlet port for a hydraulic fluid; a cylindrical piston housing having a proximal axial end and a distal axial end, and an internal radial surface and external radial surface, wherein the cylindrical piston housing defining a cylindrical space, configured to receive a plurality of axially oriented pistons, wherein the proximal axial end of the piston is operably coupled to transmission the housing base disc; a plurality of spool valve housing, each having a proximal axial end and a distal axial end disposed radially, the spool valve housing having inlet port and outlet port and being in fluid communication with a hydraulic pump and operably coupled to actuator; a plurality of axially oriented pistons, each slidably coupled within the cylindrical space defined between the walls of cylindrical piston housing having an internal wall, and each piston having a proximal end and a distal end, wherein the proximal end extends into cylindrical piston housing having internal wall, configured to engage a drive shaft head; a plurality of spool valves, each disposed within the spool valve housing and operably coupled to actuator and configured to regulate fluid communication between the distal end of the piston and the hydraulic fluid by exposing or blocking the inlet port and outlet port of the hydraulic fluid; a drive shaft having a distal end and a proximal end, the drive shaft having a drive shaft head defining a cylinder, the cylinder having an internal surface and external surface and being closed at the distal end, with the proximal end defining a sinusoidal surface configured to engage the distal end of the piston, and wherein the distal end of the drive shaft extends beyond the transmission housing cover disc and the proximal end of the drive shaft is operably coupled to an encoder; an encoder centrally coupled to the transmission housing base disc and coupled to the drive shaft; a transmission housing cover disc coupled to the distal end of cylindrical transmission housing; a plurality of actuators, or servo motors each operably coupled to the cylindrical transmission housing; means for converting rotational motion to reciprocating linear motion, the conversion means operably coupling each spool valve to each servo motor; and a control module, configured to receive input from a plurality of sensors and engage a predetermined number of actuators at a predetermined location along the periphery of the cylindrical transmission housing, the location of the pistons configured to impart continuous radial motion to the drive shaft head, wherein the number of piston engaged depends on the input received from the plurality of sensors, wherein (xxii) the plurality of pistons, comprise between 5 and 168 pistons, (xxiii) the piston proximal end comprises a bracket operably coupled to a roller bearing configured to engage the sinusoidal surface defined by the proximal end of the drive shaft head, (xxiv) the roller bearing is frusto conical, and wherein (xxv) the bracket further comprises a ball bearing, captured within the bracket and configured to both roll and turn upon contact with the internal surface defined by the cylindrical shaft head. 
         [0112]    While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended, are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.