turning now to fig1 , 1 a , 2 and 2 a , a brief description concerning the various components of the present invention will now be briefly discussed . as can be seen in fig1 , a material reducing apparatus 2 is diagrammatically shown therein . the material reducing apparatus 2 is arranged to reduce materials such as debris , logs , tree stumps , tree limbs , brush , yard waste , pallets and the like into particles having a desired smaller particle size . according to this embodiment , the material reducing apparatus 2 includes a chassis or frame assembly 4 having a pair of tracks 6 which facilitate travel and maneuverability of the material reducing apparatus 2 to a desired location of a particular work site or onto a transportation trailer . it is conceivable that the chassis or frame assembly 4 may instead include a plurality of rotatable wheels and have a conventional hitch which facilitates connection to a conventional towing unit for towing the material reducing apparatus 2 to a desired site or location . the material reducing apparatus 2 is readily transportable to a site where materials to be reduced have accumulated , the material reducing apparatus 2 has a receiving bin 8 which includes a feed end 10 for receiving deposited materials that are to be reduced by the material reducing apparatus 2 . the receiving bin 8 has a pair of opposed upstanding sidewalls 12 which facilitate containment of the material that is deposited therein . a known feed conveyor 14 , such as a belt - type conveyor , extends along a length of the receiving bin 8 , e . g ., the conveyer 14 has a length of about 18 feet for example , and is provided for conveying the materials to be reduced , which are deposited within the receiving bin 8 , toward a material reducing rotor 16 which is positioned adjacent a discharge end of the receiving bin 8 . during operation , the conveyor 14 conveys the deposited materials along the feed conveyer 14 , in the direction indicated by arrow 15 , toward the upwardly rotating rotor 16 . a top feed roller 18 , ( see fig2 ) which assists with holding down the material being feed to the rotor 16 , is positioned at the discharge end 20 of the feed conveyor 14 immediately adjacent but preceding the rotor 16 . normally , the rotational speed of the feed roller 18 will be automatically controlled , via a main control system 22 , depending upon the load of the engine 24 driving the rotor 16 . the feed roller 18 normally assists with compaction or crushing of the material to be reduced and also assists the feed conveyor 14 with conveying the material to be reduced into the rotational path of the rotor 16 . it is to be appreciated that the materials fed into the rotor 16 are partially reduced when such materials are impacted by the strikers or hammers 26 which are mounted to the peripheral surface of the rotor 16 . to assist with further reduction of the material , at least one anvil ( s ) 28 is strategically positioned along a width of the rotor 16 , but slightly radially spaced therefrom , such that the strikers or hammers 26 , carried by the rotor 16 , will pass closely adjacent to the anvil ( s ) 28 , without contacting the anvil ( s ) 28 , and the material is further sheared / reduced in a conventional manner into smaller particles by such interaction of the strikers or hammers 26 rotating past and slightly underneath the anvil ( s ) 28 . a conventional grate assembly 30 , such as a screen or grate , is located after the anvil ( s ) 28 and this grate assembly 30 only allows material of up to a specified size , i . e ., determined by the size of the holes or openings 32 provided in the grate assembly 30 , to pass through the grate assembly 30 and onto a discharge conveyer 34 . the material that is reduced , by the material reducing apparatus 2 , to or less than the specified size readily passes through openings 32 in the grate assembly 30 and is deposited on the discharge conveyor 34 located vertically under the grate assembly 30 . the grate assembly 30 in combination with the strikers or hammers 26 produce a conventional shearing action of the material which assists with further reduction of the material . the discharge conveyor 34 then conveys the screened material either to a desired container or merely onto a storage pile . separated conventional power or drive sources ( not shown or described in further detail ) provide driving power to both the feed and the discharge conveyors as well other components of the material reducing apparatus 2 . as previously mentioned , the feed conveyor 14 extends along the length of the receiving bin 8 and conveys the material that is deposited into the receiving bin 8 toward the rotor 16 . the feed roller 18 is positioned adjacent to the discharge end of the conveyor 14 and a first end of a pair of arms 36 ( see fig3 a ) support the feed roller 18 while an opposite end of the pair of arms 36 are pivotally supported by the chassis or frame assembly 4 . the pivot point or location of the pair of arms 36 is designated as element 38 and is located generally forward of a vertical plane p which extends through and bisects the rotor 16 into two halves , i . e ., the pivot point 38 is located between the vertical plane p and a rotational axis a of the feed roller 18 . the feed roller 18 is thus simultaneously pivotable toward and away from both the rotor 16 and the discharge end 20 of the feed conveyor 14 . such pivotal movement of the feed roller 18 is generally indicated by double arrow 39 . the pair of arms 36 also support a shroud or hood 40 which encloses a portion of the feed roller 18 and assists with channeling and redirecting all of initially impacted material toward the anvil ( s ) 28 where such material may be further reduced by a shearing action between the strikers or hammers 26 and the anvil ( s ) 28 . a drive mechanism 42 for the feed roller 18 may either by carried by the chassis or frame assembly 4 or is preferably mounted to the arms 36 and provides additional weight for biasing the feed roller 18 downwardly toward the feed conveyer 14 as this generally assists with holding down the material to be reduced as such material is being impacted by the strikers or hammers 26 of the rotor 16 . the exterior surface of the feed roller 18 typically has a plurality of nubs or other protrusions 44 which provide a gripping action that assists with conveying the material as the feed roller 18 normally rotates in its forward feed direction . the weight of the feed roller 18 , the drive mechanism 42 , the arms 36 and the associated components mounted to the arms 36 along with the rotation of the feed roller 18 assist with forcing the material under the feed roller 18 where such material is initially crushed / compacted between the feed roller 18 and the feed conveyor 14 as the material is continuously fed to the rotor 16 . normally the arms 36 of the feed roller 18 are at least hydraulically actuated by a pair of hydraulic feed roller actuators 46 to assist with raising and lowering the feed roller 18 away from and toward the feed conveyer 14 . the pair of hydraulic feed roller actuators 46 respectively couple the chassis or frame assembly 4 to the pair of arms 36 to facilitated pivoting movement of the feed roller 18 about its pivot point 38 . the main control system 22 controls operation of the pair of hydraulic feed roller actuators 46 to allow infinite adjustment of the downward pressure that the feed roller 18 can exert on the material to be reduced . the main control system 22 controls the feed roller 18 so that it rotates at a rate such that its peripheral speed is either the same as or greater than a travel speed or rate of the feed conveyor 14 . when the feed roller 18 rotates at a higher rotational speed , any material that may be piled high in the receiving bin 8 t e . g ., tree , branches , limbs , brush , pallets , etc ., is pushed down and into the entrance of the rotor 16 at a more rapid rate than the conveyor speed 14 . this speed difference tends to relieve any congestion at the entrance as long as the material is rapidly cleared away from the entrance to the rotor 16 which is normally accomplished by the rotor 16 rotating at a speed of between 1 , 000 - 1 , 800 rpms , for example . as is conventional in the art , a periphery of the rotor 16 has a plurality of spaced apart striker or hammer support blocks 48 mounted to the exterior surface of the rotor and each striker or hammer support block 48 supports a replaceable striker or hammer 26 . typically , the striker or hammer support blocks 48 , e . g ., about 24 striker or hammer support blocks , are strategically arranged , e . g ., in an offset helix layout , for maximum grinding efficiency . each striker or hammer support block 48 supports a striker or hammer 26 to the rotor 16 in a conventional manner , via at least one bolt for example , such that the strikers or hammers 26 rotate at a relatively high rate of speed for impact against the material that is being conveyed into the rotor 16 by the feed roller 18 and the feed conveyor 14 . as noted above , a conventional engine 24 drives the rotor 16 in an upward rotational direction , as indicated by arrow 21 . since the rotor 16 is driven at a much higher rotational speed than both the feed roller 18 and the feed conveyer 14 , the strikers or hammers 26 effectively reduce the material by an impact cutting action . the particles thus reduced by the strikers or hammers 26 are propelled and redirected by the shroud or hood 40 toward the anvil ( s ) 28 . the particles then impact against the anvil ( s ) 28 which , in combination with the striker or hammer 26 , further reduce the particles through shear cutting action . the anvil ( s ) 28 is fixedly mounted to a portion of a pivotal clamshell assembly 50 which is pivotal relative to a remainder of the chassis or frame assembly 4 to facilitated maintenance and / or servicing of the internal components . as a result of such arrangement , the anvil ( s ) 28 is fixedly mounted to cooperate with the strikers or hammers 26 , during operation , and shear or reduce the material . the interaction of the strikers or hammers 26 with the anvil ( s ) 28 typically shear the material , that was initially partially reduced by impact with the strikers or hammers 26 , to further reduce the material to a size that will readily pass through the openings in the grate assembly 30 . it is to be appreciated that the openings 32 in the grate assembly 30 can have any desired size so that the material can be reduced to anywhere from a course particle end product to a more uniform very fine end product . the grate assembly 30 generally has a curved profile , which closely conforms to the rotational path of the rotor , and has a plurality of openings therein . a first end of the grate assembly 30 is mounted adjacent the anvil ( s ) 28 and receives the material as such material is reduced by the shearing action . the material that is substantially reduced but still too large to readily pass through the openings 32 in the grate assembly 30 will be forced by the strikers or hammers 26 against the grate ( located in close proximity to the rotor teeth ) to further break up the material typically to a size that will pass through the openings . as will be noted from fig5 a - 5c , the grate assembly 30 generally extends from the anvil ( s ) 28 around the periphery of the rotor to the position adjacent the discharge end 20 of the conveyor 14 . the material passing through the grate assembly 30 , at any point between the anvil ( s ) 28 and the discharge end of the conveyor 14 , is normally deposited on the discharge conveyor 34 for transfer . the grate assembly 30 generally comprises two mating sections 60 , 62 which , when mated together , form the grate assembly 30 which extends from the anvil ( s ) 28 around the periphery of the rotor 16 to the position adjacent the discharge end 20 of the conveyor 14 . the upper section 60 of the grate assembly 30 is normally pivotally connected , at pivot point 64 , to the chassis or frame assembly 4 to allow the upper section 60 of the grate to be pivoted radially away from the rotating strikers or hammers 26 and the rotor 16 in the event that a hard material or metal is in the process of being reduced . the upper section 60 is coupled to a high speed release device 78 which rapidly , e . g ., within less than about 200 milliseconds , moves / pivots the upper section 60 of the screen assembly 30 , about its pivot point 64 , to adequately space the screen or grate 104 of the upper section 60 away from the strikers or hammers 26 of the rotor 16 and prevent any damage from occurring to the internal components of the material reducing apparatus 2 . a further discussion concerning operation of the high speed release device 78 will follow below . the lower section 62 of the grate assembly 30 is supported , in normally a fixed manner , adjacent the strikers or hammers 26 of the rotor 16 . however , a number of shear pins 68 connect the lower section 62 to the chassis or frame assembly 4 so that in the event that the lower section 62 , for some reason , is impacted significantly by a hard material , one or more of the shear pins 68 will shear away , in a conventional manner , and allow the lower section 62 to pivot or fall , due to gravity , away from the rotor 16 . a hook or stop feature 66 is provided so as to prevent the lower section 62 from falling too far away from the rotor 16 and inadvertently causing damage to the lower section 62 . this break away arrangement thus minimizes the amount of damage which may otherwise occur to the internal components of the material reducing apparatus 2 . instead of the release device 78 for the uppergrate assembly 60 , the upper grate assembly 60 may be mounted so as break away when subjected to a significant impact , e . g ., at least one shear pin ( not shown ) may be provided for retaining the upper grate assembly 60 in a normally fixed operational position . in the event that the upper grate assembly 60 is struck by a relatively hard material , then such impact against the upper grate assembly 60 causes the shear pins , which retains the upper grate assembly 60 in a fixed position , to shear or break and minimize damage to the internal components . this safety feature generally minimizes undesired jamming or significant damage to the internal components , such as the rotor 16 , the strikers or hammers 26 , the striker or hammer support blocks 48 and / or the anvil ( s ) 28 during operation . alternatively , instead of having a substantially fixed anvil ( s ) 28 , the anvil ( s ) 28 may be mounted so as break away along with the upper grate assembly 60 when subjected to a significant impact , e . g ., at least one shear pin ( not shown ) may be provided for retaining the anvil ( s ) 28 and the upper grate assembly 60 in a fixed operational position . that is , both the anvil ( s ) 28 and the upper grate assembly 60 are mounted so as to shear one or more pivot pins , when subjected to a significant impact , and pivot about a pivot axis or point 64 . as a result of such arrangement , in the event that the anvil ( s ) 28 and / or the upper grate assembly 60 is struck by a relatively hard material that is not readily shearable by the strikers or hammers 26 and the anvil ( s ) 28 , then such impact against the anvil ( s ) 28 causes the shear pins , which retains the anvil ( s ) 28 and the upper grate assembly 60 in a fixed position , to shear or break and minimize damage to the internal components . this safety feature generally prevents undesired jamming or significant damage to the internal components , such as the rotor 16 , the strikers or hammers 26 , the striker or hammer support blocks 48 and / or the anvil ( s ) 28 during operation . the shaft 70 of the rotor 16 is provided with an accelerometer 76 ( see fig4 ) which is mounted to a bearing housing 72 of the shaft 70 supporting the rotor 16 . the accelerometer 76 detects the impact of the strikers or hammers 26 with any hard material or object , such as metal , e . g ., and the vibrations transmitted to the rotor 16 and the shaft 70 caused by the strikers or the hammers 26 impacting against a hard material . depending upon the sensitivity of the accelerometer 76 , the accelerometer 76 can be adjusted to detect contract of the strikers or hammers 26 with virtually any material having a specific hardness . when the accelerometer 76 detects such contact , the accelerometer 76 generates an output signal which is sent to the main control system 22 for evaluation . in the event that the main control system 22 determines that the strikers or hammers 26 contacted a material having a specific hardness ( see fig5 a ), e . g ., the detected vibration is above a certain level and / or the rotor 16 experiences a specified load , the main control system 22 immediately sends a signal to reverse the rotational direction of the feed roller 18 so that the feed roller 18 immediately rotates in an opposite rotational direction , i . e ., rotates in a direction which withdraws the material from the rotational path of the rotor 16 ( see fig5 b ). the rotational direction of the feed conveyer may also be automatically reversed as shown in fig5 b . in combination with such reversal motion of rotational direction of the feed roller 18 , the control system 22 also slows down the engine 24 which drives the rotor 16 , or may possibly completely stop rotation of the rotor 16 . once this occurs , an operator can then shut down any other operating components and inspect the material reducing apparatus 2 and undertake any necessary corrective action , e . g ., remove any metal or other hard material from the material reducing apparatus 2 before such hard material can cause any damage to the internal components of the material reducing apparatus 2 . in the event that multiple signals are detected by the accelerometer 76 within a short duration of time , the main control system 22 can undertake more drastic corrective action such as ( see fig5 c ), in addition to reversing the rotational direction of the feed roller 18 and reducing the rotational speed of the rotor 161 the control system 22 can also hydraulically actuate and pivot the upper grate assembly 60 radially away from the rotation path of the strikers or hammers 26 . this is accomplished by very quickly actuating the release device ( s ) 78 to move the upper grate assembly 60 radially away from the rotor 16 within a response time of about 200 milliseconds or less and most preferably moving the upper grate assembly 60 radially away from the rotor 16 within a response time of about 20 to 30 milliseconds following generation of the signal by the accelerometer 76 . as can be seen in fig6 , a hydraulic pump 80 operates when the material reducing apparatus 2 is initially started . this pump 80 pumps hydraulic fluid from a sump 82 to a release manifold 84 where the supplied hydraulic fluid is stored in a primary accumulator 86 as potential energy for actuating the release device 78 . when a sufficiently large “ hard ” piece of material , such as metal , contacts a striker ( s ) or hammer ( s ) 26 of the rotor 16 , this vibration generated by such contact travels through the rotor 16 and the shaft 70 to the accelerometer 76 where the vibration is detected and measured . the accelerometer 76 will , in turn , generate a signal indicative of the detected vibration ( s ) and transmit this signal to the control system 22 where the signal is analyzed , in a conventional manner , to determine the potential size and / or type of material which was contacted by the striker ( s ) or the hammer ( s ) 26 or the rotor 16 . if the received signal is determined to be too high , e . g ., above a desired threshold , then the control system 22 determines that the striker ( s ) or the hammer ( s ) 26 contacted a “ large ” piece of hard material or metal m and immediately sends a signal to the release manifold 84 . through internal valving , not shown in detail , the release manifold 84 releases the stored hydraulic fluid stored within the primary accumulator 86 and this energy is rapidly conveyed to an input side 88 of one or more cylinders 90 of the release device 78 which rapidly bias the respective internal piston 92 away from the pivotal upper grate assembly 60 . as the upper grate assembly 60 is respectively connected to the internal pistons 92 via a linkage arm 94 , such movement also causes the upper grate assembly 60 to be carried away from the rotating path of the rotor 16 . the entire release operation , which sufficiently spaces the upper grate assembly 60 radially away from the rotating path of the rotor 16 by at least a few inches or so , occurs within about 170 milliseconds . it is to be appreciated that the upper grate 60 assembly must be adequately spaced from the rotating path of the rotor 16 so as to allow sufficient clearance for the large “ hard ” piece of material m to pass between the upper grate assembly 130 and the rotor 16 , without causing any significant damage to the internal components of the material reducing apparatus 2 , and be ejected onto the discharge conveyor 34 . while the hydraulic fluid is rapidly conveyed to the input side 88 of the release cylinders 90 from the primary accumulator 86 , hydraulic fluid is also rapidly conveyed from an opposite side 96 of the release cylinders 90 , via internal valving not shown in detail , and this hydraulic fluid is collected and stored in a restoring accumulator 98 so that the large rush of hydraulic fluid , from the release cylinders 90 , is adequately controlled . the hydraulic fluid which collects and is stored in the restoring accumulator 98 can be utilized to rapidly return the upper grate assembly 60 to its normal operational position adjacent the rotating path of the rotor 16 or , alternatively , may be subsequently dumped into the sump 82 . to facilitate such rapid actuation of the upper grate assembly 60 , the primary accumulator 86 is typically able to supply of about 30 gallons per second of the hydraulic fluid to the release device 78 . in addition , restoring accumulator 98 is generally able to accommodate removing of about 150 gallons per second of hydraulic fluid from the opposite side of the release cylinders 90 . by transferring such high volumes or hydraulic fluid to and removing hydraulic fluid from the release device 78 , the release device 78 responds very rapidly and is thus able to substantially instantaneously pivot the uppergate assembly 60 about its pivot point 64 to sufficiently space the upper grate assembly 60 away from the strikers or hammers 26 and thereby minimize the possibility of any damage occurring to the internal components as a result of a hard material or metal being reduced within the material reducing apparatus 2 . as can be seen in fig7 - 7b , the upper grate assembly 60 normally has a number of bolts 102 which secure the screen or grate 104 ( e . g ., 1 to 1½ inch thick plate metal which has a plurality of rectangular holes 108 burnt therethrough and bent into a generally curved profile ) to the upper grate assembly 60 . typically eight bolts 102 are utilized to secure the screen or grate 104 to the upper grate assembly 60 and a mating horseshoe shaped protective shrouds 106 are utilized to protect the heads of the bolts 102 as well as prevent rotation thereof while also preventing premature wear of the bolt heads . the upward cutting action of the strikers or hammers 26 induces a flow pattern that is beneficial for discharging the reduced material through the grate assembly 30 . the strikers or hammers 26 , as they impact and then sever the material being fed by the conveyor 14 and the feed roller 18 , is normally propelled upwardly along the shroud or hood 40 and thus essentially will be flowing in an air flow through the grate assembly 30 . since certain changes may be made in the above described failsafe system for a material reducing apparatus or machine , without departing from the spirit and scope of the invention herein involved , it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention .