Powered Tag-Axle Traction Assembly

Gonzalo Garay-Romero, University of Portland

Copyright for this work is retained by the author.


Project P'TATA involves the concept and prototype development of a selectively-powered tag axle for 6X2-configured Class-8 on-highway tractors that would aid the vehicle in regaining traction during reduced-friction (slip) events. For increased fuel savings, 6X2 (1 driving axle, two unpowered axles) configured tractors are preferred over their 6X4 (two driving axles) counterpart. Because only one rear axle is powered in the 6X2 configuration, these tractors are susceptible to loss-of-traction events, where the amount of torque required to maintain non-slipping contact with the road exceeds the abilities of the single drive axle. For this and other reasons (accelerated tire wear, reduced resale value), the 6X4-configured tractors are chosen despite the fuel efficiency benefits of the 6X2 configuration. The purpose of the selectively-powered tag axle is to decrease or eliminate the 6X2 tractors' susceptibility to loss-of-traction events, improving driver safety while enhancing the competitive edge of 6X2 tractors in the market. At present, the P'TATA team plans to employ an electro-mechanical system that will satisfy the following identified design criteria. This system should provide sufficient power to the tag axle, while remaining lightweight and cost-effective. It also should not require significant alterations to the existing tag axle design.