Left and right driven wheels are connected to a pair of continuously variable transmissions and independently driven. The driven wheels are increased or decreased in speed at the same rotational numbers by operation of a change lever so as to move a vehicle forward or backward. When a steering angle of a steering wheel exceeds a predetermined value, an inner wheel speed during turning of the vehicle is decreased and an outer wheel speed during turning of the vehicle is increased so as to turn the vehicle. If the steering wheel becomes greater than the predetermined value during forward running of the vehicle at a low speed, the inner driving wheels stop and the vehicle does a stationary turn. However, during forward running at a high speed or backward running of the vehicle, even if the steering wheel becomes greater than the predetermined value, the vehicle does not do a stationary turn. With this arrangement, it is possible to always obtain the optimal steering characteristic in accordance with variations of the vehicle speed or the steering wheel.

A transmission for working machines having a drive transmission mechanism and a working transmission mechanism which are operated by swinging a shift lever is provided. The transmission has a drive shift member for connecting the shift lever to the drive transmission mechanism and a working shift member for connecting the shift lever to the working transmission mechanism. The shift lever has a first protrusion constantly engaging the drive shift member and a second protrusion arranged to engage with or disengage from the working shift member. When the first protrusion engages the drive shift member with the second protrusion not engaged with the working shift member, only the drive transmission mechanism operates. When the first protrusion engages the drive shift member with the second protrusion also engaging the working shift member, both the drive transmission mechanism and the working transmission mechanism operate.

A tracked vehicle is provided for the transportation of loads and/or the supply of energy to areas having difficult access or to dangerous regions. The tracked vehicle is supported by an assembly of four banks of tracks, each driven by an independent hydraulic drive motor and directionally orientable. The vehicle includes an electronic control device for differential powering the four tracks in accordance with the distance travelled by each of the tracks.

A tracked vehicle produces a pressure no more than 3 psi on the ground by increasing the number of contact points on the inner surface of the track. The stiffness of the track is also selected to minimize bowing between the idler wheels or rollers. The track is therefore kept substantially straight between the rollers so increase the efficiency associated with transferring power to track. The drive sprocket is positioned above the ground so as to eliminate complexity in the design and yet effectively transmit power to the tracks. Positioning the drive sprocket above ground also prevents derailing of the track. The track is also held in a constant state of tension on the driver sprocket and the roller. This too prevents derailment. The undercarriage of the vehicle includes torsion axles and sealed bearings to provide for a lower maintenance track. Components associated with the undercarriage do not require constant greasing and cleaning of the idler wheels. The track is beveled so that it does not rip up surfaces. The drive sprocket is provided with roller sleeves that accommodate the changes in the pitch line of an elastomeric flat track. The sprocket does not "scrub" the areas between the driving lugs. The drive sprocket includes a pair of scrapers and a pair of conical shields which provide self cleaning and which remove debris from the sprocket area.

A riding lawn mower having zero turn capabilities has the engine mounted on the front of the frame. A drive system includes first and second hydrostatic transmissions for use in driving the back wheels. A grass bag may be mounted to the back portion of the frame and provides a counter balance to maximize the weight distribution. A discharge chute transfers cut vegetation from a mower deck to the grass bag and provides rear center discharge.