TechArchive

Original article date: May 1998

Early composite springs foundered on manufacturing costs. But can they make a comeback. Dr RAYNER MAYER of Sciotech thinks they can.

The sprung suspension is vital to the ease of ride and safety of road vehicles yet the design of the spring has changed remarkably little over the years. Traditionally suspension springs have been made of steel a strong inexpensive material the properties of which are well understood. Its disadvantages are its weight and its inflexibility unable to bend very far for a given amount of energy absorbed.

Given that transport usage is increasing throughout Europe resulting in higher levels of noxious emissions vehicle weight is becoming even more of a major issue. The Eurosprings solution to the problem is to make the springs from glass reinforced polymer (GRP) a lightweight versatile material that possesses the strength of steel but is one-fifth the density.

A spring made from GRP can be moulded to its final shape in a single operation unlike one made from steel which requires multiple forming and heat treating operations. The lighter weight composite spring therefore offers the prospect of significantly reduced fuel consumption. Also because it is more flexible and resilient the spring absorbs more energy resulting in a more comfortable ride.

The original concept of GRP springs was first developed by GKN but the design and manufacturing process proved too expensive and the company went out of business in 1991. It was at this point that the Eurosprings project’s lead partner Sciotech entered the scene. The company concentrated on developing a flexible manufacturing method which would lower the production costs.

Within a EUREKA project the company gathered together a team of materials suppliers GRP moulding companies research specialists and end users who between them possessed the expertise and resources to design and test the prototype springs devise a cost-effective manufacturing method and develop a product which would be received enthusiastically.

According to Dr Rayner Mayer Sciotech’s chief consultant: “The major breakthrough came in developing a process which allowed one of the partners Fleming Textiles to pre-form the spring reinforcements by producing a glass pre-form package of identical shape to that of the spring. All the quality control can be carried out on the pre-form and when you mould it you simply cast the resin around the reinforcement rather like reinforced concrete.”

Eurosprings is a complex project to run. Mayer has the challenging role to keep all 16 partners on track with an ambitious production and testing schedule. The project has only one academic research member Reading University the others being involved in industrial development and applications.

The springs are currently being developed for London taxis and road haulage trailers prior to commercial production. Then logical next phase is to develop a composite GRP spring for passenger and freight rail vehicles. The DTI has contributed 50% of the costs towards a feasibility study for the new project designated Eurobogie enabling Mayer and his team to travel throughout Europe to evaluate existing technology mark out the potential market and start shaping the project itself.

The team have already lined up the launch customer EWS which is a subsidiary of the American-owned Erie and Wisconin. This provides a valuable entree into the North American market.

* Tractor suspensions from Reyco Industries can now be spec’d with lightweight composite springs. The Model 102 suspension can be ordered with Liteflex composite springs from Delco Chassis Systems. The suspension is said to be 350 pounds lighter than comparable multi-leaf steel spring suspensions. The composite springs are said to last three times longer than conventional springs and provide better ride quality.

* Readers wishing to study the subject further are encouraged to reviewAutomobile Ride Handling and Suspension Design With Implications for Low-Mass Vehicles by Robert G Riley

Rayner Mayer
Sciotech

01252 873564

Eurosprings:

Project Duration 4.5 years
Total Cost MECU 4.10
Participating members: UK, Czech Republic, Denmark, Hungary, Latvia, Netherlands

Main partner/project leader:  Sciotech Consultancy

Partners include:

Reading University
London Taxis International
Plastech Thermoset Tectonics
Polymarin BV
Polymath Engineering
Institute of Polymer Mechanics
Meritor HVS
Brecknell Willis Composites
SVUM
Vetrotex
Autokut
Culzean Fabrics
Don-Bur (Bodies and Trailers)
EM-Fibreglass A/S
Flemings Textiles
Scott Bader

Eurobogie:the next phase of the project is currently seeking new partners

May 1998