Zwiehoff Rotrac: small powerhouse for heavyweight jobs
Linde Material Handling delivers electric drive for road-rail vehicle

 When most people hear the word “draisine” they tend to think of old-fashioned pedal-less bicycles or hand-operated rail trolleys. Although these images are not entirely wrong, modern draisines are driven by motors rather than muscle power and play an essential element in rail operations. Produced by the Rosenheim-based Zwiehoff company, the Rotrac E2 is a very special example of one of these machines, also known as a road-rail vehicle. It may not be as glamorous as a high-speed train, but the Rotrac E2 is capable of effortlessly pulling a freight train. Perhaps rather surprisingly, the heart of this compact powerhouse consists of drive and control technology by Linde Material Handling.

The role of the Rotrac E2 is to move locomotives and carriages, for example in loading stations or repair yards. This requires high tractive force, and the vehicles must also be able to move on and off rails - hence the name "road-rail vehicle“.

The Rotrac E2  meets these requirements more successfully than previous vehicles. Thanks to the amount of torque generated by the electric four-wheel drive and the perfectly adjustable contact pressure on the rails due to its moving guide rollers, the extremely compact vehicle can tow 250 tonnes without any difficulty. And when off the rails, the electronic four-wheel/live-axle steering enables it to manoeuvre freely on asphalt with a turning radius of only 0.9 metres.

Rotrac E2

This innovative drive concept, unique in the railway technology sector, can be realised with serial equipment manufactured by Linde Hydraulics. Two type
AE 18-05 48 V drive axles, 2 x 4.5 kW S2-60, with an AC S10 48 V converter are used. Their regulated braking characteristics allow for high levels of energy recovery through recuperation. The fully synchronised single-wheel drive is controlled by two LINC 1 control units , one per axle, which function in master-slave mode.

The system is completed by a sluice board, DC/DC converter  and charging circuit with components that have already proven their reliability in series applications. Even individual wiring harnesses originate from truck series production. Zwiehoff uses a 48 V/420 Ah traction battery as an energy source; the removable battery is sufficient for one shift. The system is optimised by the company's own control software and LinDiag diagnostic software, which allows the relevant drive parameters to be "read out", thereby speeding up the diagnostics process in the event of a fault.

The development and production of the prototype as well as the production of the small series has taken place at Linde subsidiary Proplan Transport- und Lagersysteme GmbH, which in addition to industrial trucks for explosion-hazardous areas also develops and manufactures other special vehicles for intralogistics. The series production of Rotrac E2 has started with significantly larger numbers than originally planned, as many companies in the railways and chemical industry sectors have been extremely impressed by the performance of this innovative road-rail vehicle, which Zwiehoff presented during a Europe-wide roadshow .

Rotrac E2 in action