Jointly developed between Swiss tractor maker Rigitrac, Dresden’s technical university and a specialist electronic engineering firm, the EWD 120 diesel-electric tractor is a truly novel concept.
A 120hp Deutz four-cyl provides power for an 85kW generator which in turn powers four hefty wheel motors built into the tractor’s hubs. The lack of mechanical drive means there is no need for true axles and so the team has employed an independent double wishbone arrangement at each corner.
Not only does this mean there is height-adjustable hydro-pneumatic suspension front and rear but also all four wheels can be steered. In addition, there is a clever traction control system that senses when one wheel starts to spin faster that the others and slows it, applying more torque. The same system acts as an ‘electronic differential’ when cornering, slowing the inner wheels while speeding up those on the outside. While tractive power might come via the electrics, the pto and hydraulics use a direct mechanical drive.
Key advantage of such a setup is said to be that the transmission runs at 85% efficiency compared with the 65%-70% of the hydrostatic units used on Rigitrac’s standard hillside tractors. While other such concepts have a tendency to disappear out of sight after they appear at shows, the company tells us that the EWD 120 is set to go into production, albeit in a few years time.