We talk to Chris Staunton about how light weight bodies are the answer to heavy batteries
From Tokyo to Stuttgart to Detroit to Hangzhou there is a common enemy in the electric car world. Weight is the one of the chief enemies of car designers and engineers across the world. With electric vehicles the problem is compounded by the weight and often bulk of the battery pack required to power the car. “Geely Intelligent Power” strategy calls for the launch of 30 new energy vehicles by 2020. Spearheading the drive to reduce weight in such vehicles is a small band of experts at Emerald Automotive Design (EAD), a wholly owned Geely company, housed in Coventry in the United Kingdom.
Chris Staunton heads up the Body Structures group at EAD. With the company for two and a half years he is one of a specialised team of around 250 people that is leading Geely’s design and development of light-weight, low-emission and long-range advanced hybrid commercial vehicles. Many of the people at EAD have come from sports car backgrounds. “It’s effectively a hand selected team to work on fast moving programmes” Chris states.
One of the team’s earliest projects was to reduce the weight in a new London taxi that is fit for the 21st Century, or as Chris puts it to “replace an icon with an icon.”
The chance to work on such an icon allowed EAD to recruit some of the best talent in the business. New environmental standards meant that the taxi had to be electrified and that means housing a 350kg battery pack. The team however wanted to create a new taxi that was no heavier than the outgoing TX4.
“Conceptually there is something called a weight spiral and it is a problem that all manufacturers are facing as everyone goes towards EVs. In theory what happens is you end up with a vehicle and you put a big battery in it and you need to stop that vehicle so you have bigger brakes to stop it because it is heavier.
And because you have bigger brakes you now need bigger wheels and tires. But because these are now bigger you then have to make the structure stronger and therefore because you’ve made all those things bigger it’s got heavier and therefore it has to be stronger to meet safety requirements” says Chris. The danger is that you end up with a four ton car – a beast few would likely want to drive.
“The answer was we light-weight and that’s where the technology that we’re using comes in” says Chris. Most of the body structure is made from anodised aluminum which is lighter than steel. Much of this is in the form of extrusions where each wall is precisely the required thickness for the loads on that part. Instead of welding the pieces together which not only adds weight but also changes the mechanical properties of the aluminium, glue is used. “Those mechanical properties are what makes the structure work. You don’t want to create weak points within the system” explains Chris. The adhesive used is stronger than the aluminum itself and only breaks after the point the aluminum yields.
For the painted body panels the taxi uses a composite material – SMC. This was first used in volume car productions with the 1980s era Renault Espace. “It’s a proven technology that has an advanced supply chain that’s available globally and delivers for lower and niche volumes a very high level of surface finish and quality” explains Chris. Panels also can be changed within two hours in the event of an accident – an important consideration for London taxi drivers who are constrained from operating a damaged vehicle and need to maximise vehicle utilization.
Light-weighting doesn’t come at the cost of safety. Aluminum behaves in a better way than steel in an impact. “An aluminum structure will absorb energy in a really progressive manner as long as you keep things together while its happening, which is how we use the adhesive, so we end up with progressive control” explains Chris. The new London taxi is a much safer vehicle than the car it replaces.
The team managed the near impossible. Not only did they deliver a new London taxi that is only slightly heavier than the old one but they did it in what would normally be considered an impossible time frame.
The taxi had to be ready by January 2018 when the new Transport for London standards including emissions went into force.?Normal car programmes take between 48 and 60 months depending on the changes needed. “We’ve done it from the ground up including the factory in 30 months” says Chris. The team is now turning its expertise to other commercial vehicle applications which will find their way onto roads around the world.