Compact size, lightweight design and ability to accept directly-mounted standard wheel rims, are three of the major reasons why Brevini’s wheel drives were selected for use on an agricultural tea harvesting vehicle built in the UK. The wheel drive units permit a much neater design solution than axle drives and provide greater clearance for rough terrain vehicles.
Tea harvesting is a tough process that requires vehicles which are able to withstand damp, dirty and uneven conditions while operating reliably. Harvesting machines need to work in a host of inhospitable conditions ranging from rain sodden, muddy fields; to areas so dry that dust ingress poses a constant problem. These conditions mean that often traditional transmission solutions are not suitable for use; fortunately wheel drives provide a solution.
The wheel drives incorporate a simple, but robust gear design and are supplied in pairs with a built-in hydraulic motor and mechanical braking available in left and right hand configurations. They use a compact planetary drive system which is designed for self propelled vehicles and provides far greater ground clearance on rough terrain than conventional drive systems that require a fixed axle.
The wheel drives employ the highly efficient combination of a planetary gear unit and high-speed hydraulic motor. This combination is more economical than using large slow-speed hydraulic motors alone and offers significant operating advantages. In the event of hydraulic fluid contamination only the inexpensive package motor need be replaced, and this can be removed and refitted in minutes, without having to jack up the entire unit. The gearbox / motor combination is capable of producing extremely low speeds and high torque when required.
The wheel drive units provide drive torque capacities between 1,000 Nm and 38,000 Nm, and radial load ratings up to 200,000 N. The units supplied for the tea harvester were from the RF range. Each unit used a two stage reduction gearbox with a ratio of 25:1 and an SU2 plug in male shaft. The RJ series is ideal for use on self-propelled vehicles which have individually motorised wheels.
The drives incorporate a mechanical disconnect device. This is manually operated from the hub end-pate and enables a vehicle to be towed in an emergency. There are a range of braking options with the drives including double action drum brakes, hydraulic service braking and mechanically activated parking brakes; this functions as an emergency fail-to safe brake should the hydraulic pressure fail and is an important safeguard for any vehicle.