Patent Publication Number: US-7222618-B2

Title: Concrete cutting saw

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/644,120, filed Jan. 14, 2005. 

   BACKGROUND 
   Concrete cutting saws, often referred to in the industry as slab saws, are used for cutting concrete and bituminous structures such as roadways and airport runways. As an example, when large slabs of concrete are poured, the surface of the slab is cut to divide the slab into smaller sections to relieve stresses and to allow for some degree of expansion and contraction which may otherwise undesirably crack the slab. Slab saws are also used to cut the edges of a portion of a slab that is to be removed. Additionally, such saws may be used inside of a building to perform similar functions on concrete floors. 
   Slab saws include a frame or housing typically mounted on wheels. Subject to the practicalities of saw size, a large, high horsepower reciprocating piston engine such as a Wisconsin 65HP engine has typically been used in concrete saws due to their relatively high torque for a given horsepower rating. Automobile engines such as a V6 engine have also been used to power large slab saws, but the resulting size of this saw has limited its utility and acceptance. However, reciprocating engines have a very steep torque curve in that the torque produced by the engine typically falls substantially as RPM decreases or increases around a relatively narrow ideal range. The saw includes a large diameter diamond tipped masonry cutting saw blade. When the saw is started, the operator positions the saw along a guide line, such as a chalk line, and lowers the saw blade into the concrete. As the saw blade cuts through the concrete the slab saw advances guided by the operator following the chalk line. A lubricant such as water is fed to the saw blade to lubricate, remove material, contain dust and cool the blade. 
   Current slab saws typically use a belt and pulley system to drive the saw blade. A drive pulley is placed directly on the crankshaft or fly wheel of the motor. Power is transferred to the blade through a series of subsequent belts and pulleys. It is preferable to rotate the saw blade at a particular number of revolutions per minute (RPM) while retaining as much horsepower (HP) and torque as possible. The desired RPM for a given saw blade is primarily a function of its diameter. Smaller diameter blades are spun faster than larger diameter blades. A rule of thumb is to achieve 10,000 inches of blade rotation per foot of cut. Thus a small diameter blade spins faster (at a higher RPM) to achieve the 10,000 inches of blade rotation per foot of cut at the same linear cutting pace than does a larger diameter blade. 
   Current slab saws require changing the RPM of the motor, and thereby the horsepower and torque output of the motor, in order to change the RPM of the saw blade. With the RPM change, the reciprocating engines of current art suffer from sometimes dramatic drops in torque output. The alternative is to change the size of the various pulleys in the drive system which is cumbersome and time and labor intensive, and while this can sometimes be accomplished, the necessary sheave sizes can require the reciprocating engine saw to be even larger and more cumbersome. The manipulation of the motor RPM can cause the motor to be operated outside of its operating specifications thus shortening its life and utility. As an example, the industrial version of a V6 motor has a maximum RPM of approximately 5,000 RPM and is recommended to be operated at approximately 2,750 RPM. With a typical one-to-one pulley set up, such a motor can run a saw blade having a recommended operating speed of 2,750 RPM at its recommended RPM. However, use of a smaller diameter blade requiring a higher blade RPM could require increasing the RPM&#39;s of the motor to its limit. On the other hand, the use of a larger diameter saw blade would require lowering the RPM of the motor such that the motor will not function well enough to deliver constant horsepower and torque to the saw blade. Consequently, with current slab saws either the motor or the saw blade are often used outside of its recommended range of RPM in order to accommodate the use of different diameter saw blades with the motors currently in use. The steep torque curve of reciprocating engines allows for only limited sheave changes. Versions of the V6 saw, where some changing of the sheaves or drive belts has been incorporated to manipulate RPM, rendered it to be even larger and further reduced the circumstances for which it is of suitable size. 
   Slab saws can be categorized in a fairly straightforward manner: small, large, and specialty. The utility of a small saw is generally not constrained by its size but rather its power in general commercial use. It is used where access or space limits do not allow a larger saw, for example egress via a 30 inch wide door. A slab saw using an 18HP Honda engine would be an example of this category. Large saws conversely generate substantially higher power, but are constrained by their size in many instances. A saw using a 78HP Deutz diesel would be an example of this category. However, these saws generally do not fit through even 36 inch wide doors. Specialty saws are generally so large or of unique configuration such that their application is generally to a narrow range of functions, such as a deep cut saw for cutting runways at airports for example. It is uncommon for any of the above saws to be configured to use a blade smaller than an 18 inch diameter and larger than a 54 inch diameter with the vast majority of blade use between these two extremes. 
   Slab saws also tend to veer away from the line of cut during operation as a result of the rotation of the saw blade acting as a drive wheel. Consequently, operation of the slab saw requires the operator to apply significant controlling pressure to the slab saw in order to properly steer the slab saw. A sufficient amount of steering force may be required to be applied to the slab saw by the operator resulting in strain and fatigue of the operator. The amount of steering force required is a direct function of the horsepower and torque of the saw. 
   SUMMARY 
   A relatively small footprint, high torque saw for cutting a surface with a rotatable blade. The saw includes a frame base and a rotary motor attached to the frame base. The rotary motor includes one or more rotatable tri-lobular rotors. The rotary motor includes an output shaft adapted to rotate about a first rotational axis. A power transmission system operatively couples the output shaft of the rotary motor to a blade mounting member. The blade mounting member is adapted to rotate about a second rotational axis and is adapted to receive the blade. The power transmission system operatively couples the output shaft of the rotary motor with the blade mounting member such that rotation of the output shaft of the rotary motor causes rotation of the blade mounting member and the blade. The power transmission system reduces the high RPM of the rotary motor and increases the torque at the blade mounting member. The saw includes a steering assembly pivotally coupled to the base frame. The steering assembly includes one or more first wheels that are rotatably attached to a wheel mount. The one or more first wheels are rotatable with respect to the wheel mount about a generally horizontal third rotational axis. The wheel mount is pivotally attached to the frame base such that the wheel mount and the one or more first wheels are selectively pivotal with respect to the frame base about a pivot axis that is generally vertical and perpendicular to the third rotational axis. An actuator selectively pivots the wheel mount and the one or more first wheels about the pivot axis with respect to the base frame to steer the movement of the saw. The saw may also include a lift mechanism including one or more second wheels, a lever pivotally attached to the frame base and to the one or more second wheels, and an actuator attached to the lever. The actuator is adapted to selectively pivot the lever and the one or more second wheels about a horizontal axis with respect to the frame base such that the position of the blade mounting member and blade with respect to the surface to be cut is selectively adjustable. The operating RPM of the rotary motor can be selectively adjusted to rotate a range of blade sizes at a desired RPM. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a side elevational view of the concrete cutting saw as set forth in the present disclosure. 
       FIG. 2  is a top plan view of the concrete cutting saw. 
       FIG. 3  is a bottom view of the concrete cutting saw. 
       FIG. 4  is a rear view of the steering assembly of the concrete cutting saw. 
       FIG. 5  is a partial exploded view of the steering assembly of the concrete cutting saw. 
       FIG. 6  is an illustration of the torque curve of the rotary motor employed. 
       FIG. 7  is a front view of the blade drive assembly of the concrete cutting saw. 
       FIG. 8  is a side view of the lift mechanism of the concrete cutting saw. 
       FIG. 9  is a front elevational view of an alternative shear pin arrangement. 
       FIG. 10  is a side elevational view of the alternative shear pin arrangement of  FIG. 9 . 
   

   DETAILED DESCRIPTION 
   While the present disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, embodiments with the understanding that the present description is to be considered an exemplification of the principals of the disclosure and is not intended to be exhaustive or to limit the disclosure to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. 
   A saw  20  is illustrated in  FIGS. 1 through 10 . The saw  20  is of a type often referred to as a concrete cutting saw or a slab saw. However, the saw  20  is adapted for use in cutting various types of materials in addition to concrete structures, including but not limited to asphalt and bituminous structures. The saw  20  includes a housing having a frame base  22  that may be formed from a plate of steel that is approximately three-quarter inch thick. The frame base  22  may have a footprint size, such as approximately thirty-one inches wide or less, that will allow the saw to wheel through a 36 inch wide door (The blade mounting member  60  extends outwardly beyond each side of the frame base  22  approximately 2.5 inches). The overall width of the saw  20  is approximately 36 inches wide or less. The saw  20  includes a generally vertical front panel  24 , rear panel  26  and a pair of side panels  28 . The panels  24 ,  26  and  28  may be made from steel. A handle  30  is attached to and extends outwardly from the rear panel  26 . 
   The saw  20  also includes an adjustable motor mount  34  including a mounting frame  36  that is slidably coupled to the frame base  22  for selective sliding movement with respect to the frame base  22  along a central longitudinal axis  38  of the saw  20 . The mounting frame  36  includes a generally horizontal mounting member  40  such as a plate. While the adjustable motor mount  34  is selectively slideable with respect to the frame base  22  to enable easy access to the motor, the motor mount  34  may be selectively locked in place with respect to the frame base  22  with fasteners or the like. A motor  46 , such as an internal combustion engine is attached to the mounting member  40  of the motor mount  34 . The motor  46  is preferably a rotary motor or engine having one or more rotatable tri-lobular rotors, as opposed to linearly reciprocating pistons as commonly found in V6 and V8 engines. A rotary motor is preferred over a reciprocating engine as it provides a much more constant torque output over its range of operating RPM, and particularly at the lower end of its RPM range than does a reciprocating engine and generates significantly less vibration. However, a rotary motor typically generates lower torque for a given horsepower rating than reciprocating engines. The motor  46  includes a rotatable output shaft  48  and a rotatable accessory shaft  49 . The rotary motor has a maximum RPM of the output shaft of approximately 9,000 RPM. The motor  46  provides approximately 170 peak HP (+/−10HP) and up to approximately 130 foot-pounds (ft-lbs) of torque during operation over a recommended operating range of approximately 1700 RPM to approximately 9000 RPM. The saw  20  is designed to operate the motor  46  between 2000 RPM and 5600 RPM of the output shaft  48  (useable RPM) to properly rotate commonly used blade sizes. The motor incorporates an RPM governor to insure operation within this range. While the motor may operate at RPM as high as 9000, other typical components of a slab saw such as bearings and belts do not hold up at these high speeds. The output shaft  48  is adapted to rotate about a central linear rotational axis  51  that is generally perpendicular to the longitudinal axis  38 . 
   The motor  46  may alternatively provide approximately 85 peak HP (+/−5HP) and up to 65 ft-lbs of torque, such that the 85 HP rotary motor is smaller in physical size than the 170 HP motor, and such that the overall width of the saw  20  may be further reduced to approximately 30 inches wide or less, with a frame base  22  having a width of approximately twenty-five inches wide or less, to allow entry through a 30 inch wide door. Neither saw will require sheave, belt or pulley changeovers to maintain operations within blade and engine specifications. 
   The saw  20  includes a radiator  52  that is located adjacent a fan  50  and that is coupled in fluid communication with the motor  46 . The saw  20  also includes an electrical system including a battery  54  in electrical communication with the motor  46 . The electrical system includes an alternator that is adapted to be driven by the motor  46  and that is in electrical communication with the battery  54 . 
   The saw  20  also includes a power transmission system  58  and a saw blade mounting member  60 . The saw blade mounting member  60  may comprise an elongated shaft. The saw blade mounting member  60  is rotatably mounted to the frame base  22  by one or more bearing members  62 . The blade mounting member  60  is rotatable about its central longitudinal horizontal axis  64  with respect to the frame base  22 . The rotational axis  64  is substantially perpendicular to the longitudinal axis  38  of the saw  20  and parallel to the rotational axis  51 . A generally circular and disc-shaped saw blade is adapted to be removably attached to the blade mounting member  60  for conjoint rotation therewith about the axis  64 . The saw blade is adapted to cut concrete, asphalt, bituminous concrete and other structures. 
   The power transmission system as shown in  FIG. 7 , includes a fixed pulley  201  mounted to the output shaft  48  of the motor  46  for conjoint rotation with the shaft  48  about the axis  51 . The output shaft fixed pulley  201  is rotationally connected by a parallel series of endless belts  53  to a larger diameter pulley  202  which is mounted to a rotatable shaft  29 . The larger diameter pulley  202  may be a flywheel weighing approximately 50 pounds or more. The possible flywheel effect and the movement transfer from the smaller diameter fixed pulley  201  to the larger diameter fixed pulley  202  which reduces the RPM of the blade mounting member  60  relative to that of the output shaft  48  between 2-to-1 and 3-to-1, further increases the effective torque of the 170HP motor to approximately 350 ft-lbs at the blade, and the effective torque of the 85HP motor to approximately 130 ft-lbs at the blade. 
   The shaft  29  is rotationally mounted to the mounting frame  36  and is adapted to rotate about a horizontal central longitudinal axis  32  that is substantially parallel to the axes  51  and  64 . The rotatable shaft  29  is connected to the rotatable blade mounting member  60  by a single serpentine belt  235  running between a sheave  87  attached to the rotatable shaft  29  and a sheave  80  attached to the rotatable blade mounting member  60 . 
   As shown in  FIG. 7 , the sheave  80  is coupled to the rotatable blade mounting member  60  for conjoint rotation by a shear pin  86 . The shear pin  86  is adapted to shear and break if an excessive amount of torque is supplied to the sheave  80  by the rotatable blade mounting member  60  such as, for example, in the event that the saw blade becomes jammed in the surface being cut. The rotatable blade mounting member  60  will rotate freely with respect to the sheave  80 , and the sheave  80  will rotate freely with respect to the blade mounting member  60 , when the shear pin  86  breaks. The sheaves and belts described herein may alternatively comprise sprockets and chains. 
     FIGS. 9 and 10  illustrate an alternative shear pin arrangement that may be utilized. In this arrangement, multiple shear pins  505  extend through the cutting blade  525  and an interior collar  503  and exterior collar  502 . The interior collar  503 , exterior collar  502 , and blade  525  are held against a fixed shaft collar  504  by a bolt  501  counter-bored into the blade mounting member  60 . The exterior collar  502  is conjoined to the blade mounting member  60  by a key  500  to cause the blade  525  to rotate with the blade mounting member  60 . Should the blade  525  become pinched or encounter other excessive forces, the shear pins  505  will shear and allow the blade  525  to rotate freely relative to the exterior collar  502  and blade mounting member  60  protecting the drive train and motor  46  from damage. 
   The saw  20  also includes one or more front wheels  90  rotatably coupled to a shaft  92  having a central horizontal axis  94 . The shaft  92  and wheels  90  are coupled to the frame base  22  by a lift mechanism  100 . The lift mechanism  100  includes one or more generally L-shaped levers  102 . Each lever  102  includes a first arm  104  and a second arm  106 . The levers  102  are attached at the inner ends of the arms  104  and  106  to a rotatable shaft  108  having a central axis  110 . The shaft  108  is rotationally coupled to the frame base  22  by one or more bearings  112 . The axis  110  is substantially horizontal and parallel to the axis  94  of the shaft  92  and the axis  64  of the blade mounting member  60 . 
   The lift mechanism  100  also includes one or more actuators  114 . Each actuator  114  may comprise a hydraulic cylinder having a housing and an extendable and retractable ram. Each actuator  114  includes a first end  116  pivotally attached to the frame base  22  adjacent the blade mounting member  60  and a second end  118  pivotally attached to the outer end of the second arm  106  of the lever  102 . The ends  116  and  118  of the actuator  114  are selectively extendable and retractable with respect to one another along a linear axis. The actuator  114  is coupled in fluid communication with a power supply device  120 , such as an electrically operated hydraulic pump. The hydraulic pump supplies and withdraws hydraulic fluid from the hydraulic cylinder to thereby selectively extend or retract the ram with respect to the housing of the hydraulic cylinder and thereby shorten or lengthen the distance between the ends  116  and  118  of the actuator  114 . The power supply device  120  may be electrically connected to the alternator that is driven by the motor  46  and may also be electrically connected to the battery  54 . 
   When the first and second ends  116  and  118  of the actuator  114  are retracted with respect to one another, the actuator  114  pivots the levers  102  and thereby the front wheels  90  about the horizontal axis  110  of the shaft  108  in a counter-clockwise direction as viewed in  FIG. 1 , thereby vertically lifting or raising the blade mounting member  60  with respect to the surface of the structure that is to be cut. The blade mounting member  60  may be raised above the surface a sufficient distance such that the peripheral edge of the saw blade is spaced completely above the surface to be cut. When the first and second ends  116  and  118  of the actuator  114  are extended with respect to one another, the actuator  114  pivots the levers  102  and front wheels  90  about the horizontal axis  110  in a clockwise direction as shown in  FIG. 1 , wherein the blade mounting member  60  is lowered with respect to the surface of the structure to be cut. The actuator  114  is adapted to position the blade mounting member  60  at a desired height above the surface to be cut such that the saw blade will provide a saw cut with a desired depth. 
   The saw  20  also includes a steering assembly  130 . The steering assembly  130  includes a wheel mount  132  having a generally horizontal plate  134  and pair of mounting members  136  that extend downwardly from respective ends of the plate member  134 . The wheel mount  132  is pivotally attached to the frame base  22  by a pivot member  138 , such as a bolt, which is attached to the frame base  22  and that extends through a central aperture in the horizontal plate member  134 . The wheel mount  132  is pivotally coupled to the pivot member  138  by a fastener  140  such as a bolt and nut. The steering assembly  130  is thereby adapted to pivot with respect to the frame base  22  about a generally vertical axis  142  extending through the pivot member  138 . The pivot axis  142  is generally perpendicular to the longitudinal axis  38 , and the axes  64 ,  94  and  112 . A hydraulic drive unit  148  is attached to each mounting member  136  of the wheel mount  132 . Each hydraulic drive unit  148  includes a rotatable drive shaft  150 . A rear wheel  152  is removably attached to each drive shaft  150  for conjoint rotation therewith. The drive shafts  150  and rear wheels  152  are rotatable about a horizontal linear rotational axis  154  that is generally perpendicular to the pivot axis  142 . 
   An actuator  160  is coupled between the horizontal plate member  134  of the steering assembly  130  and the frame base  22 . The actuator  160  includes a first end and a second end that are selectively extendable and retractable with respect to one another. The actuator  160  may be a hydraulic cylinder having a housing and an extendable and retractable ram. The first end of the actuator  160  is pivotally coupled to the frame base  22  and the second end is pivotally coupled to the horizontal plate  134  of the wheel mount  132 . The first and second ends of the actuator  160  are selectively extendable and retractable along a generally linear axis that is offset from the pivot axis  142 . The actuator  160  is coupled in fluid communication with the power supply device  120  such that the power supply device  120  selectively extends and retracts the ends of the actuator  160  as desired. When the ends of the actuator  160  are retracted from a neutral position wherein the axis  154  is parallel to the axis  94 , the wheel mount  132  and rear wheels  152  pivot about the pivot axis  142  in a counter-clockwise direction as shown in  FIG. 3  such that the saw  20  will turn toward the left when the saw  20  is moved forward. When the ends of the actuator  160  are extended from the neutral position wherein the rotational axis  154  is parallel to the axis  94 , the wheel mount  132  and rear wheels  152  will pivot in a clockwise direction about the pivot axis  142  such that the saw  20  will turn toward the right when the saw  20  is moved forward. 
   The power supply device  120  is coupled in fluid communication with the hydraulic drive units  148 . The power supply device  120  may be operatively coupled to and driven by the accessory shaft  49  of the motor  46  or may be electrically powered. The power supply device  120  provides pressurized hydraulic fluid to the hydraulic drive units  148  to thereby rotate the drive shafts  150  and rear wheels  152  in either a counter-clockwise direction about the axis  154  as shown in  FIG. 1  to provide forward motion to the saw  20 , or in a clock-wise direction about the axis  154  as shown in  FIG. 1  to provide rearward motion of the saw  20 , as desired. 
   The saw  20  includes a dash plate  170  on which one or more controls are mounted. A motor throttle control  176  is attached to the dash plate  170  and is operatively coupled to the motor  46 . A drive speed control  180  is attached to the dash plate  170  and is operatively coupled to the power supply device  120  and thereby to the hydraulic drive units  148 . The drive speed control  180  is selectively moveable by the operator between a neutral position wherein the rear wheels  152  are not rotated by the hydraulic drive units  148 , a forward position wherein the hydraulic drive units  148  rotate the rear wheels  152  in a forward rotational direction, and a reverse position wherein the hydraulic drive units  148  rotate the rear wheels  152  in a rearward rotational direction. The drive speed control  180  is adapted to selectively vary the speed of rotation of the rear wheels  152  and thereby control the speed at which the saw  20  moves with respect to the surface to be cut. The drive speed control  180  may have a variable speed setting. The rotational speed of the saw blade is controlled as a direct function of the motor throttle control  176 . The motor throttle control  176  enables an operator to manually select the RPM at which the motor  46  operates and thereby the RPM at which the saw blade operates. The saw  20  may include a tachometer and other operating gauges and instruments operatively coupled to the motor  46  for displaying the RPM and other conditions at which the motor  46  is operating. 
   A saw blade lift control  182  is operatively connected to the power supply device  120 . The saw blade lift control  182  enables an operator to selectively raise or lower the blade mounting member  60  to a desired position with respect to the surface to be cut through operation of the actuator  114  of the lift mechanism  100 . A steering control  184  is operatively coupled to the power supply device  120  and thereby to the actuator  160 . The steering control  184  enables an operator to selectively pivot the steering assembly  130  and thereby steer the saw  20 . 
   The saw  20  also includes a fuel tank in fluid communication with the motor  46 . A fuel gauge  188  is operatively connected to the fuel tank and provides an indication of the amount of fuel remaining in the fuel tank. The rotary engine  46  may be operated using gasoline, or it may be operated on propane and other fuels as desired. The ability to run the rotary motor  46  on propane enables the saw  20  to be used in close indoor locations. 
   In use, an operator starts the motor  46  and adjusts the saw motor throttle control  176  such that the motor  46  is operating at a desired RPM wherein the saw blade attached to the blade mounting member  60  is rotating at its recommended RPM. The saw blade and the saw  20  are aligned with the cutting path by aligning the cutting guide  196  onto the cutting path guide line. The operator then operates the saw blade lift control  182  to lower the rotating saw blade down into the concrete to a desired cutting depth. The operator then places the drive speed control  180  in the forward position, whereupon the hydraulic drive units  148  rotate the rear wheels  152  to provide forward movement to the saw  20  as the saw blade continues to cut the concrete. The operator can control left and right movement of the saw  20  during cutting by operation of the steering control  184  which controls the actuator  160  and the pivotal movement of the rear wheels  152  about the pivot axis  142 . Control of left or right movement can be utilized to steer the saw along a curvilinear path as well as to counter pulling forces that would otherwise move the saw off an intended straight cut. 
   The hydraulic steering control assembly  130  enables an operator to efficiently operate the saw  20 , although the saw  20  requires more timely and accurate control of its steering due to the faster operation and higher forces provided by the rotary motor  46  and power transmission system. In addition, as concrete saws tend to veer to the right during operation due to the rotation of the saw blade, the hydraulic powered steering assembly  130  of the saw  20  compensates for the increased power provided by the rotary motor  46  and power transmission system as the hydraulic steering assembly  130  does not require the operator to exert constant appreciable force on the saw  20  in order to control its direction or speed of movement. The strength and size of the operator is therefore less of a factor in operation of the saw  20 . In addition, the saw  20  can be operated by a single operator for a longer period of time as operation of the saw  20  does not fatigue the operator to the same degree as current art. 
   Different diameter saw blades can be used with the saw  20  depending upon the cutting conditions, such as the depth of cut that is required. When a first saw blade having a first diameter is to be replaced with a second saw blade having a larger or smaller second diameter, the RPM of the motor  46  can be adjusted to rotate the second saw blade at its recommended RPM while still supplying relatively constant amounts of torque. While the RPM of the motor  46  may be adjusted upwardly or downwardly to compensate for different diameter saw blades, the horsepower and torque output of the rotary motor  46  over this range of RPM remains substantially constant compared with the horsepower and torque output drop that results from changing the RPM of a reciprocating motor away from its narrow ideal range. The use of reciprocating motors in concrete saws is compromised by their relatively narrow recommended RPM range and steep torque curve outside that range. This limits the ability of the saw to operate a range of blade sizes without exceeding the specifications of the engine, the blade, or both, or requires operation using less than optimal torque. Review of current art will show that some saw manufacturers offer several variations of a saw model (e.g. 65 hp) with each variation set up for use with a single different blade size and recommended operation at a single RPM setting unique to that blade size. The flat torque curve and high RPM range of the rotary motor  46  combined with the RPM reducing power transmission system eliminates operation under such conditions or limitations. Consequently the rotary motor  46  of the saw  20  can always supply adequate power while being operated within its specified RPM range of operation, while different diameter saw blades may be used with the saw  20  that are also operated at their recommended RPM. The motor  46  and saw blades are always operated within their RPM specifications. No changing of pulleys or other components is required in order to maintain the motor and saw blades rotating at their specified RPM. The durability, efficiency and reliability of the motor and saw blade are thereby enhanced. 
   The rotary motor  46  provides sufficient horsepower in a small physical size such that the overall size of the saw  20  is substantially reduced from prior concrete saws. Even the 170 peak HP saw  20  has a width between the outside surfaces of the side panels  28  that is sufficiently narrow to fit through a typical 36 inch wide door comparable to reciprocal powered saws of substantially lower power. The saw  20  with a rotary motor therefore can be used in places where a prior concrete saw could not be used due to its size. It allows the use of high torque for faster cutting without requiring as large and cumbersome of a platform as existing art. 
   The torque levels of the saw  20  are well in excess of current art in comparable footprint size and HP ratings. This can be illustrated by comparing the ratio of torque at the blade to the size of the saw between current art and the rotary powered saw. Size of the saw can be proxied by the minimum width through which the saw can pass, which equates to the maximum overall width of the saw. The table below assumes a typical 1-to-1 pulley setup on the reciprocating engines due to their limited RPM range in which their torque peaks (which also limits the variety of blade sizes that can be run within specifications.) This comparison, while showing results favoring the rotary motor saws, is arguably understated as the data presented exhibits peak torque generation of the reciprocating engines which can decrease dramatically as RPM changes. The torque of the rotary powered saws will remain virtually constant throughout its operating range of 2000 RPM to 5600 RPM at the motor output shaft  48  as shown in  FIG. 6 . A larger ratio of torque to minimum clearance ostensibly means a more powerful saw for a given footprint. The saw  20 , with the 85HP rotary motor  46 , has a torque to overall width ratio of 4.0 to 1.0 or greater, and preferably at least approximately 4.33 to 1.0. The saw  20 , with the 170HP rotary motor  46 , has a torque to overall width ratio of 7.0 to 1.0 or greater, and preferably at least approximately 9.72 to 1.0. 
   
     
       
         
             
             
             
             
           
             
                 
             
             
                 
                 
               Peak 
                 
             
             
               Engine Employed 
               Min. Clearance 
               Torque 
               Ratio 
             
             
                 
             
           
          
             
               V6 reciprocating 120 hp 
               36″ 
               240 ft-lbs 
               6.67 
             
             
               Deutz diesel 78 hp recip. 
               43″ 
               177 ft-lbs 
               4.11 
             
             
               Wisconsin 65 hp recip. 
               36″ 
               135 ft-lbs 
               3.75 
             
             
               Honda twin 18 hp recip. 
               26″ 
                32 ft-lbs 
               1.23 
             
             
               Rotary 85 hp 
               30″ 
               130 ft-lbs 
               4.33 
             
             
               Rotary 170 hp 
               36″ 
               350 ft-lbs 
               9.72 
             
             
                 
             
          
         
       
     
   
   The use of a rotary motor  46  requires improved balancing of the components of the saw  20  to distribute weight in a favorable manner. The saw  20  requires sufficient weight over the saw blade to maintain the saw blade in the concrete during cutting and to assist in preventing the blade from walking out of the cut. This is accomplished by positioning of the motor  46  and other components relative to the saw blade, and by increasing the weight of the panels  24 ,  26  and  28  of the saw housing. The panels  24 ,  26  and  28  may be formed from steel having a thickness of at least approximately one-half inch to approximately three-quarter inch. These heavy duty steel panels also add strength to the housing and durability to the saw  20  improving its reliability and operating life. The saw  20  will operate with substantially reduced vibration as opposed to prior slab saws. 
   The saw blades may be diamond tipped and are consequently a very expensive consumable component of the cutting process. The amount of torque driving the rotation of the blade determines the ability of the blade to bite through the material it is cutting. The saw  20  and its rotary motor  46  and power transmission system provide vastly increased torque to the saw blade while maintaining the required RPM of the saw blade. The saw blade thereby has more cutting action or bite per rotation than provided by prior slab saws. This increase in efficiency of operation of the saw blade results in faster cutting action without requiring an increase in RPM and is believed to increase the life of the saw blade and increase the amount of cutting for a given time frame. 
   While embodiments have been illustrated and described in the drawings and foregoing description, such illustrations and descriptions are considered to be exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. The applicant has provided descriptions and figures which are intended as an illustration of certain embodiments of the disclosure, and are not intended to be construed as containing or implying limitation of the disclosure to those embodiments. There is a plurality of advantages of the present disclosure arising from various features set forth in the description. It will be noted that alternative embodiments of the disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the disclosure and associated methods that incorporate one or more of the features of the disclosure and fall within the spirit and scope of the present disclosure.