Alternative traction system for road-rail vehicles

Abstract: Excavators have traditionally been diesel driven with hydraulic actuators, but with the ongoing electrification of vehicles, smaller electric excavators are getting more common. Larger electrical excavators are still in a prototyping or early production stage but can be expected to grow. The electrification of construction equipment creates new possibilities to replace previous hydraulic- with electric actuators. This thesis covers the product development of an electric tractive system for a road-rail excavator using Ulrich and Eppinger ́s method for product development. Current hydraulic actuators have different speed, torque and size characteristics while following other safety regulations compared to electrical motors. These differences create the need for a product development project to investigate potential problems and possibilities in the change from a hydraulic- to electric tractive system. The project was made at CE Engineering Solutions (CEES). Different technical standards were studied to simplify a possible CE-marking of the product and the technical specifications were set using comparative data from competitors as well as data and knowledge from previous projects within CEES. The solutions were restricted to the use of components available today in small order quantities since the initial target was building and verification of a prototype. In the thesis, multiple concepts were generated and three different concepts with two different working principles are presented more in detail. A final solution was selected by concept scoring with weight factors decided together with CEES. The final solution consists of a single motor, inverter, and reduction gear per wheel axle due to cost efficiency, differing from the more recent solutions at CEES with two independent motors per axle. The limitation of using “off the shelf” products available today resulted in a solution using an industry standard gearbox not fully adapted for the high-speed electrical motors often used in mobile applications, restricting the traction performance but resulting in a more cost-effective solution.