CA1091267A - Undercarriage for adverse terrain vehicle - Google Patents

Abstract

UNDERCARRIAGE FOR ADVERSE TERRAIN VEHICLE

ABSTRACT OF THE DISCLOSURE
A detachable undercarriage for use on adverse terrain vehicles comprises an elongate hollow load-bearing frame having three or four axles rotatably supported thereon. Sprockets are mounted on at least two of the axles, and chains are constrained around the sprockets to drivingly interconnect the axles. The center axle in the three axle embodiment and the center two axles in the four axle embodiment are positioned below a plane extending through the axes of rotation of the outermost two axles to facilitate skid steering of vehicles incorporating the under-carriage. Alternatively, all the axles can be aligned with larger wheels mounted on the center axle in the three axle embodiment or the center two axles in the four axle embodiment to facilitate skid steering. In certain applications of the nonaligned axle embodiments structure is provided for selectively aligning all the axles to increase vehicle stablity. Also included in the undercarriage is a drive assembly having a motor connected to a transmission mounted inboard or outboard of the frame. In one configuration, an endmost axle is chain driven from the trans-mission, with the middle axle being chain driven from the endmost axle. In an alternate configuration, an endmost axle and the middle axle are directly chain driven from the transmission.

Description

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72c BACKGROUND AND SU~ ARY OF THE INVENTION
This invention relates generally to undercarriages for adverse terrain vehicles, ~nd more partic~larly to i~ detachable undercarriage having either three or fo~r tired wheels which may be utilized to support and propel virt~ally any type of mechanism.
Traditionally, adverse terrain vehicles have been track 'type vehicles. ~or example, track type bulldozers, loaders, `cranes, and similar devices have been known for decades. In some instances track type mechanisms of this type have utilized undercarriages to support and propel the mechanism. Such an iundercarriage may comprise a frame for attachment to the mechanism, structure mounted on the frame for guiding a track around a pre-¦,determined course, and a drive motor for actuating the trackaround the course and thereby propelling the mechanism supported ~by the undercarriage.
' More recently, adverse terrain vehicles utilizing tired .
- wheels have been developed. For example, see U.S. Patent Number ; 3,799,362 granted to Applicants herein on March 26, 1974. However there has not heretofore been provided an undercarriage whereby a i-0 tired type vehicular supporting and propelling apparatus adapted ; for adverse terrain usage could be adapted to virtually any type ` of mechanism. It has also been found to be desirable to provide a tired type adverse terrain undercarriage having greater load carrying capacity than has been available heretofore.
The present invention comprises a detachable under-carriage for adverse terrain vehicles which overcomes the foregoing and other problems long since associated with the prior j. .
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art. In acco~dance with the broader aspects of the invention, an undercarriage includes an elonqate hollow frame having a plurality of axle members rotatably supported thereon. Each axle member extends to a wheel support ~.e~ber. Solid or pneumatic tired 'j wheels can be utilized~ Preferably all the wheel s~pport members !are positioned on the same side of the frame. A drive assembly includes a motor and a transmission mounted on the frame with a dual drive sprocket and separate chains connecting the output of the transmission to one of the endmost axle me~bers and to a O middle axle member driven by the transmission to the other endmostI axle. The motor can be of either the hydraulic or electric ¦ I varietyO
Either three of four nonaligned axle members carrying I wheels of equal diameters can be utilized. In the case of three , ~ axle members the center axle member and in the case of four axle members the center tWG axle members rotate about axes situated below a plane extending through the axes of rotation of the endmost two axle members. This facilitates the skid steering of ; a mechanism supported and propelled by the undercarriage, while 0 simultaneously making wheels carried by ali of the axle members .,. .
available for ground contact under adverse terrain conditions. If '':
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desired, structure may be provided for bringing all of the axle members into alignment in order to provide increased stability.
Either three or four aligned axle members carrying wheels of uneq~al diameters can be utilized. The center axle in i the case of three axle members and the center pair of axles in the !
case of four axle members carry wheels relatively laryer than those carried by the endmost axle members. The same result is accomplished, namely the facilitation of skid steering of the mechanism supported and propelled by the undercarriage with the ) 'concurrent availability for ground contact under adverse terrain ; Iconditions of all the wheels.
In accordance with still other aspects of the invention, the frame is a hollow load-bearing structure comprised of structural members around its entire periphery and throughout its -i entire length. This facilitates attachment of a mechanism to the undercarriage at any point along the entire length and around the entire periphery of the frame The positioning of the hydraulic or electric motor relative to the frame can be varied in order to vary the spacing between the axle members. The motor is ) preferably drivingly connected to one of the axle members by means ; of a first drive sprocket connected to the output of the motor, a second drive sprocket connected to one of the axle members, and a drive chain interconnecting the two drive sprockets.
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. ,, - ~ _ , ~ 7 In accordance with one aspect of the invention there is provided an undercarriage assembly for supporting and propel-ling a mechanism, comprising: an elongate hollow load bearing frame adapted for connection to the mechanism; at least three axle members each having a wheel receiving member at one end thereof; at least three wheel members each mounted on and secured to the wheel receiving end of one of the axle members;
means rotatably supporting the axle members at longitudinally spaced points along the frame with each of the axle members extending through the frame and being rotatably supported ill o~pJcit~ cidoc cf tho frame; the middle wheel member extending . below a plane lying tangent to the bottoms of the endmost - wheel members to facilitate skid steering; a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members; drive means comprising motor means and transmission means mounted on the frame between one endmost axle member and the middle axle member;
first drive sprocket means having two sets of teeth thereon . positioned within the frame and mounted for rotation by the drive means; second drive sprocket means positioned within the frame and mounted on the middle axle member; first drive :
chain means constrained around the first drive sprocket means on one set of teeth and the sprocket means on the endmGst axle member adjacent the drive means; second drive chain means constrained around the first drive sprocket means on the other set of teeth and the sprocket means on the middle axle member; and third drive chain means constrained around the second drive sprocket means and the sprocket means on the other endmost axle member; said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly to the output of the drive means for concurrent rotation ,J

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under the action thereof.
In accordance with another aspect of the invention there is provided an undercarriage assembly for supporting and pro-pelling a mechanism, comprising: an elongate hollow load bearing frame adapted for connection to the mechanism; at least three axle members each having a wheel receiving member at one end thereof; at least three wheel members each mounted on and secured to the wheel receiving end of one of the axle members; means rotata~ly supporting the axle members at longi-tudinally spaced points along the frame with each of the axle members extending through the frame and being rotatably sup-ported in opposite sides of the frame; the middle wheel member extending below a plane lying tangent to the bottoms of the endmost wheel members to facilitate skid steering; a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members; drive means mounted on the frame between one endmost axle member and the middle axle member; first drive sprocket means having two sets of teeth thereon positioned within the frame and mounted for rotation , : . . 20 by the drive means; second drive sprocket means positioned within the frame and mounted on the middle axle member; first drive chain means constrained around the first drive sprocket ., ~ .
means on one set of teeth and the sprocket means on the end-most axle member adjacent the drive means; second drive chain :, :
: means constrained around the first drive sprocket means on -the other set of teeth and the sprocket means on the middle :
. axle member; and third drive chain means constrained around ;. the second drive sprocket means and the sprocket means on the other endmost axle member; said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly -to the output of the drive means for concurrent rotation U

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under the action thereof.
In accordance with still another aspect of the invention there is provided an undercarriage assembly for supporting and propelling a mechanism having drive means, comprising:
an elongate hollow load bearing frame adapted for connection to the mechanism; three axle members each having a wheel receiving member at one end thereof; three wheel members each mounted on and secured to the wheel receiving end of one of the axle members; means rotatably supporting the axle members at longitudinally spaced points along the frame with each of the axle members extending through the frame and being rotat-ably supported in opposite sides of the frame; the middle wheel member extending below a plane lying tangent to the bottoms of the endmost wheel members to facilitate skid steering; a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members; first drive sprocket means having two sets of teeth thereon posi-tioned within the frame between one endmost axle member and the middle axle member and mounted for rotation by the drive means; second drive sprocket means positioned within the frame and mounted on the middle axle member; first drive chain means ~- constrained around the first drive sprocket means on one set of teeth and the sprocket means on the endmost axle member adjacent the drive means; second drive chain means constrained -~
around the first drive sprocket means on the other set of teeth and the sprocket means on the middle axle member; and third drive chain means constrained around the second drive sprocket means and the sprocket means on the other endmost axle member; said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly to the output of the-drive means for concurrent rotation under the action thereof.
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;DESCRIPTION OF ~HE DRAWINGS
A more complete understanding of the invention may be had by referring to the following Detailed Description when taken in conjunction with the accompanying drawings, wherein:
FIGURE 1 is a side view of an undercarriage for an adverse terrain'vehicle incorporating a first embodiment of the invention;
' FIGURE 2 is a top view of the undercarriage shown in I FIGURE 1 in which certain parts have been broken away more clearly 0 i,to illustrate certain features of the invention;
, FIGURE 3a is an enlarged horizontal sectional view of the rear portion of the undercarriage of FIGURE l;
; 1' FIGURE 3b is an enlarged horizontal sectional view of the front portion of the undercarriage of FIGURE 1, and comprising ¦~a continuation of FIGURE 3a;
,, j. FIGURE 4 is a side view of a first modification of the ,~
undercarriage of FIGURE l; `'~
. FIGURE 5 is a side view of a second modification of the s ''undercarriage o~ FIGURE l;
"o ' FIGURE 6 is a side view of the speed shifter assembly ,':. mounted on the hydraulic motor of the undercarriage of FIGURE l; ¦ :
FIGURE 7 is a side view of the undercarria~e for an .','.` ',adverse terrain vehicle incorporating a second embodiment of the ' `r, .invention;
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,5 FIGURE 8 is a top view of the undercarriage shown in ,, .
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FIGU~E 9 is a diagrammatic illustration of a portion . of a hydrostatic drive control apparat~s useful in conjunction with the present invention;
FIGURE 10 is a detail of a wheel height adjustment assembly which may be used in conjunction with the invention;
FIGURE 11 is an illustration of the application of the invention to a front-end loader;
FIGURE 12 is an illustration of the application of the . invention to a front-end loader with a backhoe;
) ' FIGURE 13 is an illustration of the application of the : invention to a mobile drilling rig;
FIGURE 14 is an illustration of the application of the ' invention to a backhoe;
I I FIGURE 15 is a side view of a third modification of j, I
i ' the undercarriage of FIGURE l; , r i FIGURE 16 is a top view of the undercarriage shown in FIGURE 15 in which certain parts have been broken away to illustrate more clearly certain features of the invention;
FIGURE 17 is a side view of an undercarriage for an ) adverse terrain vehicle incorporating a third embodiment of . the invention;
i FIGURE 18 is a side view of an undercarriage for an , adverse terrain vehicle incorporating a fourth embodiment of the invention;
~j ~ FIGURE 19 is an enlarged horizontal sectional view of the carriage of FIGURE 1 having an alternative drive system;
~ . FIGURE 20 is an illustration of the application of I ~ the invention to a power loader; ¦ r i~
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~ 12~;7 ,472C i FIGURE 21 is an illust~ation of the application of _ r the invention to a power loader of heavier duty than that of FIGURE 19;
FIC-URE 22 is an illustration of the applieation of the invention to a power loader havin~ a knuckle boo~ crane;
and FIGURES 23 and 24 are illustrations of the application : -, of the invention to a rotary drilling rig vehicle.
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DETAILED DESCRIPTION -; Referring now to the Drawings, and particularly to -~ PIGURES 1 and 2 there~f, there is shown a detachable underca~riage for an adverse terrain vehicle 10 incorporating the invention.
j Normally, of course, a pair of parallel undercarriages 10 are - employed to support the adverse terrain vehicle. The under carriage 10 consists of an elongate hollow load-bearing frame j,12. Frame 12 is formed entirely of a material such as steel ¦Icharacterized by high strength and rigidity to permit attachment !i f undercarriage 10 to virtually any type of mechanism by connec-¦Itions at selected points along the entire length and around the entire periphery of frame 12. A related feature of this structure is greater load carrying capacity. ~urthermore, frame 12 can ~be of sealed construction so that it can serve as a lubricant , reservoir, if desired, as well as a structural member. Drain r ~plugs 14 and 16 are located at the bottom and outside surfaces, respectively, of frame 12 to facilitate draining or replenishing i,of lubricants therein.
,: The undercarriage 10 is supported by three tired wheels O , 18; the three wheels including a forward wheel 20, a middle wheel i 22, and a rear wheel 24. The wheels 18 are of equal diameter and ., 1~
include tires of either a solid or a pneumatic type. Wheels 18 ¦',rotate about axles 26. Preferably all three wheels 18 are positioned on the same side of frame 12; however, depending on the `5 l~particular adverse terrain vehicle, it may be desirable to locate ¦one wheel 18 on the opposite side of frame 12. Preferably, axles j - ,! 26 extend completely through frame 12 and are rotatably supported ~ within both adjacent vertical surEaces of frame 12.

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i 1091'~7 ~472C ll ; Also included in undercarriage 10 is drive assembly 28.
Drive assebly 28 incorporates a motor 30 which can be of a dual speed variety in that structure is provided within motor 30 for selecting either a high or low speed range of operation. Such selection is effected by manipulation of lever 32. Alternatively, motor 30 can be of the constant speed variety. In addition, motor 30 can be of the electric or the hydraulic types. ~eferring momentarily to FIGURE 6 in conjunction with FIGURES 1 and 2, undercarriage 10 is provided with a fluid operated cylinder 34 having a piston 36 connected to lever 32 by means of iink 38.
jCylinder 34 is adapted for operation from a remote point, such as ~the operator's compartment of an adversé terrain vehicle incor-porating undercarriage 10, to selectively place motor 30 in the ,desired operational range.
I Referring again to FIGURES 1 and 2, motor 30 is con-nected directly to speed reducer 40, which can be a multiple or constant speed type. Speed rèducer 40 is slidably mounted on frame extension 42 by means of bolts 44. Frame extension 42 extends upwardly from the inside rearward top surface of frame 12 0 ,and speed reducer 40 is bolted substantially perpendicular there-to. Speed reducer 40 has output shaft 46 to which drive sprocket "48 is attached by means of setscrew 49, as is best shown in FIGURE
3a. If, for example, motor 30 is of the hydraulic type, motive I,energy is received from the output of remotely located hydraulic 'Ipumps tnot shown) driven by an engine mounted on the adverse terrain vehicle to which undercarriage 10 is attached. The power transmission by means of the pressurized hydraulic fluid from the , ,',, .
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aforementioned pumps, or from a remote power source (not shown) in the case of an electric motor, to motor 30 and hence to drive sprocket 48 through speed reducer 40 comprises the hydrostatic drive system which functions to both propel and steer under-i carriage 10.
Motive power is first applied to drive sprocket 48 which is constrained to second sprocket 50 by means of chain 52. Chain 52, which is constrained around drive sprocket 48 and second sprocket 50, serves to transfer rotative movement to axle 26, upon which first sprocket 50 is mounted. Sprockets 48 and 50 and chain 152 are totally enclosed in a sealed housing 54 which is detachably secured to both frame extension 42 and frame 12. Housing 54 ¦serves not only to protect these parts of the drive system, but more importantly, can constitute a reservoir for lubricant in ~which chain 52 and sprockets 48 and 50 continuously operate.
Accordingly, drain plug 56 is provided at the rearward lower end i~ !i f housing 54.
A tension adjusting means for chain 52 is provided in ~ibolt 58. Bolt 58 is threadably mounted on brace 60 and acts in 0 ¦ compression directly against the collar of speed reducer 40, which ¦ is slidably mounted on frame extension 42. Thus, by either clockwise or co~nterclockwise rotation of bolts 58, tension in ¦chain 52 may be varied.
Motor 30 is in direct operative relationship with the :~ 5 1I forward, middle and rearward wheels, 20, 22, and 24, respectively, I of undercarriage 10. Constituting part of the drive system, axle 26 of rear wheel 24 receives power by means of first sprocket 50 ', .
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~ 9 _ 'lV~Z67 ,472C ll l'which is connected to drive sprocket 48 by means of chain 52.Also attached to axle 26 of rear wheel 24 is sprocket 62.
Sprocket 62 is co~pled by means of chain 64 to sprocket 66, which is connected to the axle 26 of middle wheel 22. Sprocket 68 is i also attached to the axle 26 of the middle wheels 22 of the set, and in turn is coupled by means oE chain 70 to sprocket 72.
~,Sprocket 72 iS secured to the axle 26 Of the forward wheel 20 of the set, whereby motor 30 is operatively connected to all three ,wheels 18 on undercarriage 10. Tension adjustment assemblies 74 are provided for assuring proper tension in chains 64 and 70.
In order to arr2st movement of undercarriage 10, brake assembly 76 is provided. Brake assembly 76 consists of a brake disc 78 and three caliper assemblies 80. Turning momentarily to IFIGUR~ 3b in conjunction with FIGURES 1 and 2, caliper assemblies ,5 180 (only one of which iS shown) are anchored to frame extension 82 ~ ~by means of bolts 84. Consequently, the caliper assemblies 80 ;: ! remain stationary at all times, while the brake disc 7~, which is jlsecured to axle 26 of the middle wheel 22, rotates therewith.
¦'ISpecifically, brake disc 78 rotateS within the slots of the three 0 lcaliper assemblies 80 which house the brake pucks and their i~hydraulic actuating cylinders. To arrest movement of the undercarriage 10, the actuating cylinders cauSe the pUcks to ¦frictionally engage discs 78. By means of chains 64 and 70, this Ibraking force is directly transmitted to the rearward and forward wheels, 24 and 20, respectively. In this manner, the force of one ; !'brake assembly 76 is simultaneously applied to all wheels on the `
undercarriage 10. It will be noted that brake assembly 76 lS

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~472C l ~disposed to the interior of axle spindle 86, to which wheel rim 88 is secured by threaded lugs 90. This location for brake assembly 76 is advantageous in that it affords protection from dirt, rocks, mud, or other debris typically encountered by an adverse terrain vehicle.
Middle wheel 22 protrudes below a plane 92 extending tangent to the bottom surfaces of the wheels 18 comprising the ~forward wheel 20 and the rear wheel 24. This fact embodies a !i significant feature of the present invention. A relatively short - 0 ¦,wheelbase is desirable because it facilitates skid steering of the vehicle. However, this advantage is offset by decreased overall vehicle stability, which is especially troublesome in the case of ,an adverse terrain vehicle with variable loading arrangements. In ¦jcontrast, a longer wheelbase affords maximum vehicle stability but ~does not permit effective skid steering.
r ~I The present invention economically and simply ¦,accomplishes the objectives of both short and long wheelbases by means of a lower middle wheel 22. For example, when operated over a hard, smooth surface, undercarriage 10 will be able to rock . 0 leither forwardly or backwardly, depending upon the location of the l~center of gravity and the loading characteristics of the ;Iparticular adverse terrain vehicle. The vehicle rests on only two wheels at any given moment, while an end wheel remains available ¦Ifor stabilization. Therefore, the wheelbase of the vehicle will ^5 jlcomprise the distance between the middle wheel 22 and one of the ,; I,endmost wheels, either 20 or 24. Consequently, the effort 'required to effect skid steering of the vehicle is substantially ~ 11 ~
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~;472C ', reduced over that which would be re~uired if the wheelbase always 'comprised the distance between the endmost wheels 20 and 24. At the same time, the rocking feature of undercarriage 10 allows instant utilization of the stability inherent in a longer ;5 wheelbase.
Assume now that the vehicle to which undercarriage 10 is ` ,attached is operated over a softer surface, such as sand, mud or - 'loose dirt. All three tired wheels 18 will engage the' adverse jlsurface because they will sink into the adverse surface until 0 Ilvehicle flotation occUrs. Superior traction, stability and jmaneuverability will be achieved since each wheel 18 directly '~icontacts the surface, and all wheels 18'are drivingly inter-jlconnected. Furthermore, total pressure under any individual ' ~ wheel is substantially reduced, which lessens surface rutting as ~ .
;'5 !well as the vehicle's susceptibility to bogging down.
:':' 11 ~i Turning now to FIGURES 3a and 3b, there is shown in ,Idetail the drive system for ùndercarria~e 10. Motor 30 is coupled ; 'to speed reducer 40. Speed reducer 40 is attached to frame ¦ -extension 42 by means of bolts 94 in conjunction with nuts 96. By ~'0 means of slots 98, speed reducer 40 is adapted for slidable movement relative to frame extension 42 when acted upon by tension adjusting bolt 58, which is best shown in FIGURE 1. Attached to the output shaft 46 of the speed reducer 40 is sprocket 48. '' "Setscrew 49 secures sprocket 48 to output shaft 46. Chain 52 in ¦ Iturn connects sprocket 48 to sprocket 50. Sprocket 50 is affixed to axle 26 of rear wheel 24 by means of nut 100. It will be noted that all three axles 26 are rotatably supported by the inner r l - 12 -"
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bearing assemblies 102 and outer bearing assemblies 104. Inner bearing assemblies 102 are supported by cups 106 which are detachably secured to frame 12 by means of bolts 108. In contrast, outer bearing assemblies 104 are permanently affixed . ¦to frame extensions 82 of frame 12.
¦ Sprocket 62 is also attached to axle 26 of rear wheel 24 by means of keyway 110, thus sprocket 62 rotates in unison.with sprocket 50. Sprocket 62 in turn is connected by means of chain .. 64.to sprocket 66, which is secured.to axle 26 of middle wheel 22 by means of a keyway 112. Located substantially adjacent to sprocket 66 and also.attached to axle 26 of middle wheel 22 by means of keyway 112 is sprocket 68. Chain 70 is constrained for rotation around sprockets 68 and 72. Sprocket 72 is affixed to . ~axle 26 of forward wheel 20 by means of keyway 114. Consequently : ~motor 30 is directly connected by a series of sprockets and chains to each wheel 18 of undercarriage 10.
. The tension in chains 64 and 70 is adjusted by means of I forward and rear tension adjustment assemblies 74. Tension -. adjustment assemblies 74 include idler sprocket 116 which engage .l the slack or return sides of either chain 64 or 70. Idler ¦ :
sprocket 116 is rotatably conr.ected to pin 118 by means of journal bearing~l20. The pin 118 which rotatably supports idler sprocket :. 114 is disposed and secured between two vertical adjacent wall . surfaces of slider assembly 122. Slider assembly 122 is constrained for vertical movement by stops 124 and 126. Vertical movement of slider assembly 122 is accomplished by means of - adjustable screws 128. ~ither clockwise or counterclockwise ''' . .

jl lO~iZt;7 ~72C ', ¦!mo'vement of adjustable screws 128 serves to ~isplace slider ¦assembly 122 vertically, whereby idler sprocket 116 engages idler ¦¦chains 64 or 70 so as to change the tension therein. For example, ilif idler sprocket 116 o~ forward tension adjustment assembly 74 :. jwere manipulated in a vertical direction, it would engage chain ¦70 so as to cause a small but significant increase in the . leffectiYe t~avel distance thereof. ThiS in turn wou~d c~yse chain.
'''~ 170 to-.experience an increase in tensionj because it is o~'sub~ -... ¦s.tantially fixed.length.. .- .... . ......... .... ~- .; -.. .-.-.. ~._-.
. . Protective covers 130 are pr~vided to protect the inward . ends of axles 26 of forward wheel 20 and middle wheel 22'. Covers .~'. 130 are secured to bearing cup 106 by means of screws 132.
.' . Conse~uently, all inward ends of axles 26 on undercarriage 10 are .' . shielded from rocks, dirt, mud, or other hazards to be found in ' .
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ithe terrain over which the adverse terrain vehicle is likel~ to . I operate. : . : - . . .' ' . '~
;' .~ The foregoing description'was directed to the preferred .' . construction of undercarriage 10 wherein each wheel 18 is inter.- .
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connected by a series of sprockets and chains. However, it will . be understood that undercarriage 10 can be operated with other' ; transmission means, such as gears or other means; 'and such that ~ motor ~O;is drivingly connected to less than all of tbe wheels ;~ 18. For example, motor 30 can be drivingly connected to rear .. wheel 24 and middle wheel 22 only, thereby eliminating the need .~ ,for sprockets 68 and 72, chain 70, and forward tension adjustment . ;$, . assembly 74 all of which serve to interconnect forward wheel 20 . .. and middle wheel 22.
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Referring no~ to ~IGURES 4 and 5, there are shown tw~
modifications of the three wheel undercarriage for an adverse ¦
terrain vehicle 10. Referring particularly to FIGURE 4, there is shown an alternative position for the hydrostatic drive assembl~
28. The position illustrated in ~IGUR~ 4 is higher and more rearward than that depicted in FIGURES 1 and 2, but still disposed substantially between rear wheel 24 and middle ~7heel 22. The wheel spacing in FIGURE 4 is relatively closer than that shown in , FIGURES 1 and 2. FIGURE 5 illustrates another alternative posi-¦,tion for hydrostatic drive assembly 28 which permits reduced wheel ~¦spacing of undercarriage 10 over that shown in FIGURE 4. In this 'Imodification, drive assembly 28 is mounted on rear frame extension ¦l134~ The cl~ser wheel placement permitted by the modifications ¦,appearing in FIGURES 4 and 5 facilitates skid steering of under-i !jcarriage 10 because the effort required is substantially reduced r over that which would be re~uired if the wheel base were longer.
Accordingly, not only are thè power requirements for steering the vehicle lowered, but overall vehicle response is improved. More-over, the feature of being able to vary the wheel spacing and/or the hydrostatic drive housing location considerably enhances the adaptability of undercarriage 10 to virtually any type of adverse ',terrain vehicle.
' Referring now to ~IGURES 15 and 16, there is shown ~,another modification of the three wheel undercarria~e for an i ,adverse terrain vehicle 10. At least two significant features attend this modification. ~irst, instead of supporting hydro-`~ static drive assembly 28 with a frame extension attached to the " ' .' . . '' , .
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~i 1 10912~7 ,top surface of frame 12, drive asse~bly 28 is slidably mounted directly on the rear portion of fra~e 12. Frame 12 in F~GURES 15 ~, and 16 includes an integral raised re~r portion which serves to house and protect sprockets ~8 and 50, and drive chain 52.
Besides eliminating the need for a separate housing to protect these parts of the drive system, placement of drive assembly 28 on ;the side of frame 12 opposite wheels 18 makes it less vulnerable ,~ "to flying rocks, dirt, mud and objects likely to be picked up by ~,the wheels of the vehicle. In addition, this location for drive lassembly 28 allows a lower profile which further enhances t adaptability of undercarriage 10 to various types of adverse ' " ¦iterrain vehicles. Bolt 58 is threadably mounted on brace 60 which ,' t,is now attached directly to the rear top and side poetions of ¦Iframe 12. Bolt 58 acts in tension directly on the collar of speed , , ~',,, ,reducer 40 to serve as a tension adjusting means for chain 52.
1,`~, i,The absence of brake assembly',76 secured to middle wheel 22 comprises the second eature of the modification illustrated in I "
FIGURES 15 and 16. Instead, brake assembly 133 is p~sitioned ¦
~' directly between motor 30 and speed reducer 40. Brake 133 may be 'of the AUSCO brand fail-safe type produced by Auto Specialties ~" jManufacturing Co. of St. Joseph, Michigan. It has been found that ," ,'placement of brake 133 in drive assembly 28 requires lower braking effort which results in increased brake efficiency. If desired, ,~ ,'access plates (not shown) can be located in the upper surface of ,frame 12 above the axles for wheels 18. In all other respects "undercarriage 10 with the modification shown in ~IGURES 15 and 16 "operates as was described above.
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~iic 'j ¦1 ~ Referring now to FIGURES 7 and B, there is shown an lundercarriage for an adverse terrain vehicle 136 incorporating la second embodiment of the invention~ The undercarriage 136 - Iincorporates numerous component parts which are'subst'antially !.
¦identical in construction and operation to the component parts' '' of undercarriage 10 illustrated in FIGURES 1 and 2. such identical component parts ~re designated in FIGURES 7 and 8 with ... . the same~reference numeral util'i'zed' in t'he'descrip't'i'on o'~ '"'" "' !
. .. ~nderc~rriage lO,-but are differentia~ed the~e~rom by means o - --. a prime ~') designation. ' - ' "' "'' ''''-' ""-'¦'''-~he primary dif~erentiation between undercarriage 10 and .'~ undercarriage 136 is the fact of a four tired wheel embodiment, .. wherein wheel 138 is the fourth wheel. The extra whe~l 138 is in . . fact another middle wheel. The middle wheels 22' and 138 extend ; below plane 92' which is tan~ent to the bottom surfaces of wheels ' 20' 'and 24'. All wheels 18' are'of equal'diameter 'and includes ' tires of either a solid or a pneumatic type. However the addition of lower middle wheeI 138 requires the'addition of two ' ~more sprockets, 140 and 144, and another chain 142, and may . necessitate an additional brake assembly 76'.
¦ . In many respects similar'to the three wheel configura- ;
tion, t~e. transmission of power in the.four wheel configuration . shown' in FIGURES 7 and 8 proceeds as follows. The hydrostatic . Idrive assembly 28' is mounted on the rearmost upper surface of . jundercarriage 136 and includes motor 30'. Motor 30' is connected - ~
'.' directly to speed reducer 40'. Attached to the output shaft 46'' ~-~ ¦of speed reducer 40' is sprocket 48'. Chain 52' is constrained ....,~ !
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for rotation about sprockets 48' and 50'. Sprocket 50' in turn is secured to the axle 26' of rear wheel 2~'. Also attached to the axle 26' of rear wheel 241 is sprocket 62'. Connected by chain 64', sprocket 66' is constrained to rotate in unison with sprocket¦
62'. Sprocket 66' is mounted on axle 26' of middle wheel 22', as is sprocket 68'. Chain 142 in turn connects sprocket 140, which ';is affixed to axle 26' on second middle wheel 138, and sprocket 68'. Sprocket 144, which is also attached to axle 26' of second ~'middle wheel 138, is connected by means of chain 70' to sprocket 72' which is mounted on axle 26' of forward wheel 20'. Thus, it ., ¦lis apparent that motor 30' is in direct mechanical communication ~with all four wheels of undercarriage 136 by virtue of the afore-. ',mentioned arrangement of sprockets and chains. It ~ill be under-,, Istood that undercarriage 136 can be operated where motor 30' is ,drivingly connected to fewer than all four wheels. Note also'that ,hydrostatic drive guard 146 is provided at a rearward lower ,~ ',position on undercarriage 136 adjacent to drive assembly 28' so as to protect it from the hazards of operation over adverse terrain~
In all other respects, the four wheel embodiment illustrated in ,l .FIGURES 7 and 8 operates substantially the same as the three wheel~
'embodiment shown in FIGURES 1 and 2. .
' 1, In certain applications, it may be desirable to adjust the height of an end wheel of undercarriage 10, or one or both end wheels of undercarriage 136. Referrin~ now to ~IGURE 10, there is shown a wheel height adjustment assembly 148. Adjustment assembly , ~,148 comprises a subframe 150 which is pivotally attached to frame ~, l,12 at pin 152. The outside vertical walls of subframe 150 are i . !
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jjin'terposed between the inside vertical walls of frame 12 so as to llallow connection at, and pivotal movement about, pin 152. A
¦~hydraulic cylinder 154 is attached at one end to a frame 156 mounted on frame 12, and at the other end to a frame 158 mounted on subframe 150. A boot 160 oE highly resilient, flexible material is secu,~ely a'ttached to seal the gap existing between - frame 12 and subframe 150... When actuated, cylinder 154 causes' .. subframe 150 to pivot downwardly about pin 152 so as to bring into . ... 'arignment t'he axes of rotation of wheels I8. Turning momentarily ''' : ;stO-FIGURES 1 a,nd 2 in conjunction with ~IGURE 10, it will be seen .' ¦that provision has been made for the incorporation of one wheel . Iheight adjustment assembly 148 in the three wheei embodiment showr ¦therein, at the loc'ation indicated by arrow 148a. Wheel height . jad-iustment assembly 148 is positioned between forward wheel 20 and mlddle wheel 22. Upon actuation of hydraulic cylinder 154, subframe 150 will pivot downwardly.about pin 152 so as to'bring ~ . ,jthe axes of rotation of wheels 20, 22 and 24 into alignment.
;'' In contrast to the three wheel embodiment of under- !
.. carriage lQ, two wheel height adjustment assemblies 148, indicated ,-. jby arrows 147 and 149, can be incorporated in the four wheel . iembodiment of undercarriage 136. Having reference momentarily to . ~FIGUREg;7~.and 8 in conjunction with FIGURE 10, it will be seen ' , .- ¦that forward wheel height adjustment assembly 148 is located i between forward wheel 20' and middle wheel 138, while rear wheel height adjustment assembly 148 is positioned-between rear wheel .
'~J i~ and middle wheel 22'. ~pon actuation of hydraulic cylinder '.
i ¦l54 of forward wheel height adjustment assembly 148, subframe 150 ,',',, ¦!, ' I
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will pivot downwardly to bring into alignment the axes of rotation of the forward three wheels of undercarriage 136. Similarly, the axes of rotation of the rearward three wheels of undercarriage 136 ¦Will become aligned upon the urging of cylinder 154 of rear wheel ¦¦heigh~ adjustment assembly 148. The simultanëous actuation of cylinders 154 in both assemblies Will cause the axes of rotation o~ all four wheels 18 ' to come into alignment.
The incorporation of wheei height adjustment assemblieis ;
148''affords'a significant advantage in both the three and four wheel lowered center wheel embodiments of the invention. Primar-ily it Will effect better weight distribution and hence impart greater vehicle stability. In particular, during operation of the adverse terrain vehicle over a hard surface, the operator may selectively lower the end wheel or wheels should the skid steering advantages of a short wheelbase no longer be desired. For example, it might be desirable to stabilize a mobile drill rig incorporating the invention after the vehicle had been maneuvered into place. The capability of selectiveiy nullifying the rocking feature of the present invention is particularly useful to ', vehicles whose center of gravity shifts during varioUs operation~l ~modes. It Will be understood that soft surface operation of a ~vehiclè`;'incorporating the invention is the same with or without -the wheel height adjustment feature. All wheels will Contact the ¦soft surface, thus improving the vehicle's traction and flotation ~characteristics.

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With reference to FIGURE 17, there is sho~n an undercarriage for an ad~erse terrain vehicle 210 incorporating ~
third embodiment of the invention. The undercarriage 210 includes¦
numerous component parts which are substantiall~ identical in construction and operation to the component parts of undercarriage ;10 illustrated in FIGURES 1 and 2. Such identical component parts~
~are designated in FIGURE 17 with the same reference numeral utilized in the description of undercarriage 10, but are differentiated therefrom by m~ans of a double prime ('') designation.
¦~ The primary distinction bet~een undercarriage 210 and undercarriage 10 is the fact of a three tired wheel embodiment ¦~wherein the diameters of the wheels 18'' are not identical. More Iparticularly, middle wheel 22'' is of relatively larger diameter ,~than are the endmost wheels 20'' and 24''. ~dditionally, each ¦
wheel 18'' rotates about an axle lying on a common line of icenters, which is denoted by line 212. Thus, larger middle ~heel ¦
22'' still protrudes below the plane 92'' extending tangent to the 3bottom surfaces of forward wheel 20'' and rear wheel 24'', but for completely different reasons than its counterpart in under-!. carriage 10. -,~ ~he~fact of an aligned larger center wheel comprises a jlsignificant feature of this embodiment. The objectives of both a I! short and a long wheel base is accomplished by means of larger ¦middle wheel 22'' r For example, when operated over a hard, smooth ~,surface, undercarriage 210 will be able to rock either forwardly or bac~wardly, depending upon the location of the center of : ''. .
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gravity and the loading characteristics oE the particula~ adverse terrain vehicle. The vehicle rests on only two wheels at any given moment, while the other wheel remains available for stabilization. Consequently, the wheel base of the vehicle when operated over a hard, slnooth surface is the distance between wheel 22'' and one of the endmost wheels, either 20'' or 24" . The effort required to effect skid steering of the vehicle is sub-I stantially reduced with a shorter wheel base, while the rocking t feature of undercarriage 210 allows recourse to the stability ¦jinherent with a longer wheel base. It wil be noted that if ~ i middle wheel 22 " includes a pneumatic tire, the part;al deflation Ithereof will serve to neutralize the rocking feature and brin~ al]
i !three wheels 18'' into contact with the hard, smooth surface to improve vehicle traction and stability. Conversely, greater ,inflation of middle wheel 22'' will serve to augment the rocking ¦Ifeature, if desired. Of course, duri~g operation of undercarria~e ¦,210 over a softer surface, all three tired wheels 18l' engage the~adverse surface because they will sink into the surface until vehicle flotation occurs. Moreover, alignment of the axles of wheels 18'' improves the vehicle performance over both hard and ~,soft surfaces by reducing porpoising and other control problems ~¦associated with multiple nonaligned drive wheels. The power ., . I
¦Itransmission and other aspects of the aligned three wheel embodi-ment ilustrated in ~IGURE 17 are substantially identical to that jof the nonaligned three wheel embodiment shown in FIGURES 1 and 2, j~and the modification thereof, which were discussed hereinbefore `'' -1' .
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: construction and operation to the component parts of un~ercarriage ~ 136 illustrated in FIGURES 7 and 8. Such identical component r 1~ iparts are designated in ~IGURE 18 with the same reference numeral ;iutilized in the description of undercarriage 136, but are differ-,entiated therefrom by means of a triple prime (-l-) designation ¦' The primary distinction between undercarriage 230 and .
~undercarriage 136 is the fact of a four tired wheel e~bodiment i,wherein the diameters of the wheels 18 " ' are not identical. ~ore : li'particularly, middle wheels 22''' and 232 are of relatively larger .
~diameter than are the endmost wheels 20''' and 24'''. ~ddition-,ally, each wheel 18''' rotates about an axle lying on a common . iiline of centers, ~7hich is denoted by line 234. Thus, larger : I.middle wheels 22 " ' and 232 protrude below the plane 92''' ~extending tangent to the bottom surfaces of forward wheel 20 " ' .and rear wheel 24''', but for completely different reasons than .-. !
... their counterparts in undercarriage 136.
The fact of aligned larger center wheels comprises a .
.significant feature of this embodiment. The objectives of both a short and a long wheel base is accomplished by means of larger .
. '.middle wheels 22''' and 232. ~or example, ~lhen operated over a . : :.
.~ !hard, smooth surface, undercarriage 230 will be able to rock s ¦either forwardly or backwardly, depending upon the location of .the center of gravity and the loading characteristics of the ~;

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;Moreover, alignment of the axles of wheels 18''' improves the vehicle performance over both hard and soft surfaces by reducing porpoising and other control problems associated with multiple nonaligned drive wheels. The power transmission and other aspects of the aligned three wheel embodiment illustrated in FIGURE 18 is ' ,'substantially identical to that of the nonaligned four wheel 'embodiment depicted in ~IGUR~S 7 and 8, and the modifications thereof, which were discussed previously.
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. Referring now to FIGURE 9, there is shown a T-handle 162 which can be mounted in the cockpit of the adverse terrain vehicle to which the invention is attached. T-handle 162 perEorms the ~ .
function of controlling the flow of energy from a remote source tnot shown) to the motor(s) o~ the hydrostatic drive system. The T-handle 162 is supported for pivotal movement about horizontal -~ and vertical axes 164 and 166, respectivel~. The handle 162 .includes a pair of handle grips 168 and a lower portion 170 ,, ~extending parallel to handle grips 168. Thus, manipulation of : ¦the handle grips 168 relative to axles 164 and 166 results in a directly corresponding motion in lower handle portion 170.

¦' The lower handle portion 170 of the T-handle 162 is ~ ¦,coupled to a pair of levers 172 by means of a pair of.links 174.
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"The levers 172 serve to control the energy flowrate to the motors.

~In this way, the T-handle 162 is operable to provide complets ".
~:: .. control over the direction, speed, and steering of the vehicle incorporating the invention. ~lanipulation of the T-handle 162 ;solely about the horizontal axis 164 causes movement of both the .. ~ levers 172 in the same dlrectlon by the same amounts. By this ~,~!^, means, the motors are actuated in synchronism for propulsion of ~:

. the vehicle either forwardly or rearwardly along a straight line.
. ,Similarly, manipulation of T-handle 162 solely about the vertical ': ~laxis 166 causes e~ual and opposite flow of motive energy to the ,motors whereby the vehicle pivots about its center, but does not ~.
move either forward or rearward. Of course, any combination of .manipulations about axes 164 and 166 is possible to effect . !: ~
. .,complete control of the adverse terrain vehicle. A pair of .. , " I ' ~

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sprin~s 176 are provided ~or returning the levers 172 to their center or nil position wherein the remote power source (not shown) provides no output to the motors.
In eeference now to ~IGURES 11-1~, there are shown several vehicles to ~hich either the lowered center wheel(s) or larger center wheel(s) embodiments of the undercarriage of the present invention can be adapted. Although each vehicle has a .different operational and loading profile, the present invention is equaly compatible with all. It will be understood that wheel ,height adjustment assemblies 147 and 149, or 148 can be adapted to each vehicle utilizing lowered center wheels to impart additional stability, if desired.
i FIGURE 11 illustrates application of the undercarriage 10 to a front-end loader 188. The heaviest component of the ,machine, the engine 180, is located to the rear of the vehicle. r In the unloaded condition, with the bucket 182 retracted and empty, the center o~ gravity is located rearward near the engine 180 so that the vehicle rests on its rear and middle pairs of wheels.
'After loading and upon extension of the unloaded bucket 182, the icenter of gravity shifts forward, which causeS the vehicle to rock forward to rest upon its forward and middle pairs of wheels.
~ Shown in FIGURE 12, born by undercarriage lOr is a front-end loader 188 equipped with a backhoe 184. The engine 186 ¦is mounted forward. The center of gravity will be located forward ,near the engine 186 when the empty front-end loader 188 is lretracted, and the empty backhoe 190 is tucked in. The vehicle ,in the unloaded configuration will thus be supported by its for-iward and middle sets of wheels. If the front-end loader 188 alone .

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t ~IGURE 13 depicts undercarriage 136 as applied to a 0 j¦mobile drilling rig 192. During transportation, the drilling mast - !¦ 194 lies substantially parallel to the vehicle. The weight o~ the ~mast 194 when added to that of the forwardly located engine 196 ,causes the vehicle to rest upon its for~ard and middle pairs of ,~wheels. Upon raising mast 194 into drilling position, the center ! Of gravity shifts rearward to reposition the vehicle on the rear-!l ward and middle sets of wheels.
j Another backhoe 198 is shown in ~IGU~E 14 supported on ,,undercarriage 136. Owing to the rearward engine 200 location, thel vehicle rests on its rearward and middle pairs of wheels when the ¦ .
~0 bucket 202 is tucked in and empty. During manipulation of the I bucket 202, the vehicle rocks forward to be supported b~ the ~forward and middle pairs of wheels.
. While each of the example applications of the invention ,appearing in FIGURES 11-14 was discussed above as though the ~j ~,vehicle were operating over hard, smooth terrain, it will be under-',stood that while operating over softer terrain, all wheels would contact the surface, achieving better flotation and traction.
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Turning n~w to I~IG~E 19, there is sho~n in detail a modifie~ ~rive system for undercarriage lO. Whereas the drive system 28 shown in ~IGU~E 2 and ~urther shown in detail in ~IGURES 3a and 3b has a speed reducer ~0 attached to a frame extension 42 such that motor 30 is located outboard of frame 12, the modified drive system of FIGURE 19 is arranged such that a motor and speed redùcer 40' are disposed inboard of frame 12.
;- Speed reducer 40' is mounted on frarr~e extension 42' which extends !
upwardly from the inside rearward top surface of frame 12.
o j Speed reducer 40' has an output shaft 46 ' to which a drive sprocket 48' having two sets of teeth 48a' and 48b' is ~; 1 attached by means ~f bolts 49a' and 49b'. Chain 52' connects sprocket 48a' to sprocket 62' attached to axle 26' of rear wheel 1 24. Accordingly, sprocket 62' rotates in unison with sprocket 1 4~a'.
' It will be noted that axle 26' of rear wheel 24 is ¦ rotatably supported by an inner bearing assembly 102' and an ' outer bearing asse~bly 104'. A protective cover 130' is pro-vided to protect the inward end of axle 26' of rear wheel 24.
0 Cover 130' is secured to bearing holder 103' by screws 132'.
Accordingly, the inward end of axle 26' is shielded in the drive system arrangement of FIG~RE l9.
j A chain 64' connects sprocket 48b' to sprocket 68a' ¦ and provides a driving connection between speed reducer 40' 'i ! and axle 26' of middle wheel 22. Located substantially ` adjacent to sprocket 68' and also connected to 2xle 26' o~f~
middle wheel 22 is sprocket 66'. A chain 70' is constrained .'.'. ~. I .
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¦j In accordance with the drive system of FIGURE 19, ¦laxles 26' of the rear wheel 24 and the middle wheel 22 are i ljeach drive~ directly from the speed reducerO Such an arrange^
¦~ment reduces the amount of chain required by the arrangement lo~ FIGURES 3a and 3b.
¦ Although the tension adjustment assemblies shown in I ¦ ~IGURES 3a and 3b have not been shown in FIGURE 19, it is to be ; lunderstood that such mechanisms could be utilized with the drive , :
¦system oE FIGURE 19. Also, although the brake mechanism shown ~ .
¦in FIGURE 3b for axle 26 of middle wheel 22 is not shown in , .
¦FIGURE 19 it is to be further understood that such brake ¦mechanism could be utilized with the drive system shown in !l FIGURE 19. ¦
¦ In reference now to FIGURES 20-24, there is shown . ' : several additional vehicles to which the undercarriage of the present invention can be adapted. I .
IGURE 20 illustrates the application of the under-carriage 10 to a hydraulic power loader 211, The power loader vehicle utilizes a three wheeled version of undercarriage 10.
.. Power Ioader 211 comprises an hydraulically actuated, articulated .~ ¦arm 2i3 havin~ hydraulically actuated claws 214 mounted on the , ¦end thereof. The undercarriage of power loader 211 is further provided with hydraulic stabilizers 216 at the front and rear . ¦¦ends. ' ` ! Shown in FIGURE 21 is a hydraulic power loader 220 ¦ support d on a Eour wheeled version oE undercarriage 136. The .,, 1~ . .. .1 "
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¦' configuration of power loader 220 is substantially identical to loader 211 of FIGURE 20, except the undercar~iage has been ¦replaced by the more heavy duty undercarriage. Hydraulic loader 220 also comprises a hydraulically operated, articulated arm 222 Ihaving a-set of hydraulically actuated scrap grabbers 224 mounted . 'on the end thereof.
. ........... ............Another power loader 231 is shown in ~IGURE 22 sup~orted lon undercarriage 10. Power loader 231 is provided with a knuckle .... boo.m crane 233 comprising an articulated.arm.with a hydraulically O l¦operated hand 235 on the end. As shown, loader 231 incorporates I stabilizers 236 at the front and rear.
. FIGURES 23 and 24 show undercarriage 10 as applied to a mobile rotary drilling vehicle 240. During transportation, . ¦ the drilling.mast 242 is carried in a down position, wherein .i Ithe mast is substantially parallel to the road surface 244 over which the vehicle travels.
¦ -As shown in PIGURE 24, thé drilling mast 242 when . Iraised into the vertical drilling position is disposed at one !end of vehicle 240. The rotary drilling head 246 is raised ~ ~and lowered by a chain 248. Rotation of drilling head 246 is .
¦¦through the application of controlled hydraulic pressure in : I¦lines 249. Vehicle 240 is stabilized in the drilling position by stabilizers 250.mounted at the front and .rear of the vehicle.
. 1l Thus, it is apparent that there has been provided, . .jin accordance with the invention, an ~ndercarriage for an adverse terrain vehicle that fully satisfies the objects, aims and advantages set forth~above. While the invention has been described in conjunction with specific embodiments thereof, `~
~ , 11 . -i ~' ~' "b, ~o~3~z~;7 it is evident that many alternatives, modifications, and . ~i ' variations will be apparent to those s~illed in the art in : vie~ of the foregoing description. Accordin~ly, it is intended to e~brace all such alternatives, modifications, and variations ; as fall ~:ithin the spirit and scope of the invention.

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Claims (24)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An undercarriage assembly for supporting and propelling a mechanism, comprising:
an elongate hollow load bearing frame adapted for connection to the mechanism;
at least three axle members each having a wheel receiving member at one end thereof;
at least three wheel members each mounted on and secured to the wheel receiving end of one of the axle members;
means rotatably supporting the axle members at longitudinally spaced points along the frame with each of the axle members extending through the frame and being rotatably supported by said frame;
the middle wheel member extending below a plane lying tangent to the bottoms of the endmost wheel members to facilitate skid steering;
a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members;
drive means comprising motor means and transmission means mounted on the frame between one endmost axle member and the middle axle member;
first drive sprocket means having two sets of teeth thereon positioned within the frame and mounted for rotation by the drive means;
second drive sprocket means positioned within the frame and mounted on the middle axle member;
first drive chain means constrained around the first drive sprocket means on one set of teeth and the sprocket means on the endmost axle member adjacent the drive means;
second drive chain means constrained around the first drive sprocket means on the other set of teeth and the sprocket means on the middle axle member; and third drive chain means constrained around the second drive sprocket means and the sprocket means on the other endmost axle member;
said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly to the output of the drive means for concurrent rotation under the action thereof.

2. The undercarriage assembly according to claim 1 wherein the middle axle member is rotatable about an axis positioned substantially below a plane extending through the rotational axes of the two endmost axle members.

3. The undercarriage assembly according to claim 1 wherein the elongate hollow frame is rectangular in cross section and is comprised of structural members around its entire periphery and along its entire length so as to facilitate the attachment of the mechanism at any point thereon.

4. The undercarriage assembly according to claim 1 further including a fourth axle member, and wherein the center two axle members are mounted for rotation about axes lying in a plane positioned substantially below a plane extending through the rotational axes of the endmost two axle members.

5. The undercarriage assembly according to claim 1 wherein the means rotatably supporting the axle member comprises bearing means mounted on opposite sides of the frame and rotatably supporting the axle member with the axle member extending through the frame.

6. The undercarriage assembly according to claim 1 wherein each of the axle members extends through one of the sprocket means.

7. The undercarriage assembly according to claim 1 further including means for selectively varying the positioning of one of the axle members and thereby positioning all of the axle members for rotation in the same plane and thereby stabilizing the positioning of the mechanism.

8. The undercarriage assembly according to claim 1 wherein the transmission means comprises:
third drive sprocket means mounted for rotation by the motor means;
fourth drive sprocket means mounted on one of the axle members; and fourth drive chain means constrained around said third and fourth drive sprocket means for effecting rotation of one of the axle members under the action of the motor means.

9. The undercarriage assembly according to claim 1 further including brake means mounted on at least one of the axle members for selective actuation to arrest rotation of said axle member and thereby arresting rotation of interconnected axle member.

10. The undercarriage assembly according to claim 1 further including brake means mounted on the transmission means for selective actuation to arrest rotation of the axle members.

11. An undercarriage assembly for supporting and propelling a mechanism, comprising:
an elongate hollow load bearing frame adapted for connection to the mechanism;
at least three axle members each having a wheel receiving member at one end thereof;
at least three wheel members each mounted on and secured to the wheel receiving end of one of the axle members;
means rotatably supporting the axle members at longitudinally spaced points along the frame with each of the axle members extending through the frame and being rotatably supported in opposite sides of the frame;
the middle wheel member extending below a plane lying tangent to the bottoms of the endmost wheel members to facilitate skid steering;
a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members;
drive means mounted on the frame between one endmost axle member and the middle axle member;
first drive sprocket means having two sets of teeth thereon positioned within the frame and mounted for rotation by the drive means;
second drive sprocket means positioned within the frame and mounted on the middle axle member;
first drive chain means constrained around the first drive sprocket means on one set of teeth and the sprocket means on the endmost axle member adjacent the drive means;
second drive chain means constrained around the first drive sprocket means on the other set of teeth and the sprocket means on the middle axle member; and third drive chain means constrained around the second drive sprocket means and the sprocket means on the other endmost axle member;
said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly to the output of the drive means for concurrent rotation under the action thereof.

12. The undercarriage assembly according to claim 11, wherein the middle axle member is rotatable about an axis positioned substantially below a plane extending through the rotational axes of the two endmost axle members.

13. The undercarriage assembly according to claim 11, wherein the elongate hollow frame is rectangular in cross section and is comprised of structural members around its entire periphery and along its entire length so as to facilitate the attachment of the mechanism at any point thereon.

14. The undercarriage assembly according to claim 11, further including a fourth axle member, and wherein the center two axle members are mounted for rotation about axes lying in a plane positioned substantially below a plane extending through the rotational axes of the endmost two axle members.

15. The undercarriage assembly according to claim 11, wherein the means rotatably supporting each axle member comprises bearing means mounted on opposite sides of the frame and rotatably supporting the axle member with the axle member extending through the frame.

16. The undercarriage assembly according to claim 11, wherein each of the axle members extends through one of the sprocket means.

17. The undercarriage assembly according to claim 11, further including means for selectively varying the positioning of one of the axle members and thereby positioning all of the axle members for rotation in the same plane and thereby stabilizing the positioning of the mechanism.

18. An undercarriage assembly for supporting and propelling a mechanism having drive means, comprising:
an elongate hollow load bearing frame adapted for connection to the mechanism;
three axle members each having a wheel receiving member at one end thereof;
three wheel members each mounted on and secured to the wheel receiving end of one of the axle members;
means rotatably supporting the axle members at longitudinally spaced points along the frame with each of the axle members extending through the frame and being rotatably supported in opposite sides of the frame;
the middle wheel member extending below a plane lying tangent to the bottoms of the endmost wheel members to facilitate skid steering;
a plurality of sprocket means each positioned within the frame and each mounted on one of the axle members;
first drive sprocket means having two sets of teeth thereon positioned within the frame between one endmost axle member and the middle axle member and mounted for rotation by the drive means;
second drive sprocket means positioned within the frame and mounted on the middle axle member;
first drive chain means constrained around the first drive sprocket means on one set of teeth and the sprocket means on the endmost axle member adjacent the drive means;
second drive chain means constrained around the first drive sprocket means on the other set of teeth and the sprocket means on the middle axle member; and third drive chain means constrained around the second drive sprocket means and the sprocket means on the other endmost axle member;
said first and second drive chain means drivingly connecting both the endmost axle member adjacent the drive means and the middle axle member directly to the output of the drive means for concurrent rotation under the action thereof.

19. The undercarriage assembly according to claim 18, wherein the middle axle member is rotatable about an axis positioned substantially below a plane extending through the rotational axes of the two endmost axle members.

20. The undercarriage assembly according to claim 18, wherein the middle axle member is rotatable about an axis lying substantially within a plane extending through the rotational axes of the endmost axle members, and wherein the wheel member mounted on the middle axle member is relatively larger than the wheel members mounted on the endmost axle members.

21. The undercarriage assembly according to claim 18, wherein the elongate hollow frame is rectangular in cross section and is comprised of structural members around its entire periphery and along its entire length so as to facilitate the attachment of the mechanism at any point thereon.

22. The undercarriage assembly according to claim 18, wherein the means rotatably supporting each axle member comprises bearing means mounted on opposite sides of the frame and rotatably supporting the axle member with the axle member extending through the frame.

23. The undercarriage assembly according to claim 18, further including means for selectively varying the positioning of one of the axle members and thereby positioning all of the axle members for rotation in the same plane and thereby stabilizing the positioning of the mechanism.

24. The undercarriage assembly according to claim 1 further including a backhoe excavator mechanism, comprising:
a frame;
means supporting the frame on the elongate hollow load-bearing frame of the undercarriage assembly;
an articulated arm mounted on the frame at one end thereof;
a bucket mounted at the opposite end of the articulated arm for receiving, lifting and carrying materials therein;
hydraulic cylinder means for extending and retracting the articulated arm and bucket;
an operator's compartment mounted on the frame; and an engine mounted on the frame.