One potential technological breakthrough in aerospace could hail from the automotive world, according to David Holland Smith who heads "horizon scanning" within the UK Defence Science and Technology Laboratory (Dstl).
He spoke at a recent Royal Aeronautical Society conference on the technology challenges of a future operational environment and the E-spring is a key area to which some of the MoD's brightest boffins are turning their attention.
E-springs are according to their inventor - Salah Elmoselhy, a postgraduate researcher at Cambridge University's Department of Engineering - set to shape the next generation of vehicle suspension systems. And industry tends to agree with his vision too, electing Salah as a laureate of the 2006 SAE Transactions Honor from the Society of Automotive Engineers, in recognition of his research into E-springs.
Here is his take on suspension design: traditionally a compromise between three conflicting requirements: passenger comfort, road holding and load carrying, vehicle suspension springs absorb road shock by compressing or extending when vehicle wheels encounter bumps and dips in the road.
The weight needed to depress a spring a certain amount is called the spring rate. A spring with a low spring rate is soft and can absorb a lot of energy, so generally increases passenger comfort. However, it can decrease road holding and carry only light loads. A heavy, stiff spring with a high spring rate performs well under a heavy load, but can make for a bumpy ride with a light load.
A spring rate can be chosen to achieve a compromise, but a better result can be gained if the spring rate of the suspension can be tailored to increase with deflection.
The sections in Salah's E-shaped spring can be designed to produce the required variation in spring rate. Some sections can be profiled to flex easily under light loads and others to provide greater stiffness as the load increases. This can be done without any part of the spring being subjected to undue stresses, which increases the spring's longevity compared with conventional solutions. Two E-springs can be combined in a compact space to create further options for tuning the suspension. Watch the video to get a better idea of what is involved.
The benefits?
- Weight reduction of 85% leading to reduce fuel consumption
- Space requirement reduction of 75% leaving additional space which could be used, for example, for wider tires, snow chains or storing a spare wheel in automotive applications
- Adjustable spring-rate in the same compact space allowance allowing the suspension system to deal with variable loads and increasing passenger comfort
- Eliminating the cost of a heavy duty hydraulic damper
- Improved fatigue performance.
And don't be tempted to limit the E-spring's application to vehicle suspension systems, think also about their scaled use in tiny mechanical devices such as valves, gears, and actuators embedded in semiconductor chips....
