For motocross racing fans, the prospect of their sport being revitalized by “green” propulsion technology is exciting. A new prototype motocross bike developed by IAV GmbH and on display at IAV Engineering Inc.’s 2013 SAE World Congress booth (no. 819) aims to prove to interested motorcycle OEMs the benefits of a nearly silent competition machine with zero tailpipe emissions.
IAV’s E-Crossbike presents a battery-electric alternative to the dirt-bike-world's ICE hegemony, while sacrificing none of the performance that gives the sport its appeal. Development began in late 2011, with the IAV engineering team in Germany using a stock Husqvarna TC250 that is a mainstay of the MX2 racing class. The engineers, led by Christian Wanner, removed the combustion engine (a 250-cm3 liquid-cooled, fuel-injected, single-cylinder four-stroke) and began with the bare chassis. Enlisting resources from IAV’s Vehicle Division and supported by TR Engineering (IAV’s in-house race vehicle development group) as well as suppliers Freudenberg and HERMS, they mapped out the bike’s specifications and began development of the powertrain.
The project bogey was to create a race bike with handling and acceleration at least equivalent to current 250-class race machines. IAV engineers first defined the bike’s requirements “by taking a look at various real-life racetracks, going on test rides with GPS data loggers, and evaluating data from Husqvarna. In a simulation we also worked out what kind of power output the different sections demand and what speeds the bikes go at on them,” Wanner noted.
Analysis of major motocross tracks showed an average racing distance of nearly 32 km (20 miles) and an average speed of 50 km/h (31 mph). A duty cycle of 30 min plus two additional laps called for a 30-cell lithium battery pack rated at 2.5-kW·h. The air-cooled pack weighs 25 kg (55 lb).
The traction motor produces a claimed 15-kW continuous power, with 25 kW peak power available for a maximum 10 s.
The bike’s electrical architecture also was designed to include a Bluetooth/WLAN interface so that telemetric data (battery SOC, motor output, fault codes, etc.) can be transmitted to personal mobile devices. This allowed development engineers to constantly monitor the motorcycle’s performance remotely. Wanner noted that the overall development challenge proved difficult.
IAV developed the e-motor, power electronics, and battery pack, the latter being contained in a watertight module. It is connected by two short cables to the electric drive system that combines the power electronics and e-motor in a compact, integrated unit. To fit the electric powertrain, engineers made complex modifications to the TC250 frame, including removing the entire front downtube. This was replaced with a box section made of high-strength steel. Concealing the E-Crossbike’s powertrain are exterior body panels made of GRP, CRP, and ABS plastics.
While IAV had shown the prototype to Husqvarna late last year, prior to BMW selling Husqvarna in late January to Pierer Industrie AG, owner of rival bike maker KTM, there are no production plans yet. It remains a prototype exercise aimed at proving the electric-drive technology is competitive in a 250-class dirt racer.