The future of EV bus design is already here

Introduction

Zemtec (Zero Emission Technologies) is a new player in the rapidly-evolving electric bus industry. Zemtec was born out of a strong bias for innovation, seeking to design, create, and build an electric bus with greater efficiency than other e-buses available on the domestic market.

The challenge

The key to achieving industry-leading efficiency for Zemtec was to minimise weight in the design. This involved disrupting the traditional methods of construction by innovating in both structural design and material selection. Zemtec designed a fully composite vehicle, starting with a completely flat floor, up to windows, and roof construction, with a fibreglass shell, and stainless-steel frame.

Consultation

Sabre's technical application team began working with Zemtec in 2019, reviewing the bus design and looking at how adhesives could be incorporated to bond the lightweight composite materials that Zemtec were hoping to use. When using composite materials, it is important to use joining methods that will deliver structural properties, yet have the flexibility to distribute stress and absorb the movements that occur across the structure of the bus. Zemtec's goal was to offer an industry-leading warranty on their buses, so it was crucial the adhesives used would have high durability and not lead to premature failure or breakdown, which would shorten the service life of the bus.

The Sabre solution

Sabre assisted Zemtec to incorporate optimum bonding joint designs in their bus design and construction, helping reduce mechanical fastenings and spread stress distribution evenly throughout the body. This allowed the use of lighter composite components resulting in optimum weight efficiency and ultimate durability. SabreBond 055 was selected for window glazing for its balance of high adhesive strength coupled with exceptional flexibility, which was particularly important for the large windows on the front of the bus, as the adhesive needs to absorb stress. SabreBond SMP60 was used for structural bonding of the sidewalls and roof sections, and SabreBond SMP50 was used for all other general bonding and assembly applications. The versatility of the SabreBond MS Polymer range allowed for consolidation down to just three core bonding products. As part of the validation process, Sabre conducted extensive adhesion and mechanical testing specifically on Zemtec's materials and substates, giving confidence around the structural integrity and durability of the adhesives specified. The result was a bus that is 30% more energy-efficient than any other e-bus on the New Zealand market, allowing it to carry more passengers at a much lighter weight than its competitors.