Rapid success and good bonding at TVR

UK-based sports car manufacturer TVR is using the latest rapid prototyping technology and adhesives to cut costs and improve the structural integrity of its cars, writes Dean Palmer

TVR Engineering is quite a unique car manufacturer in that it is both British and, unlike so many car producers these days, it also manufactures around 95% of car parts in-house at its main manufacturing site in Blackpool.

The company has a long tradition of this and clearly doesn’t believe in outsourcing its manufacturing expertise or design intellectual property to third party subcontractors. This policy may seem alien to many manufacturing firms but the result is a unique car design that feels very different to any other car on the road. Many car OEMs share the same Tier One suppliers and so some car parts in different vehicles feel the same. But at TVR, things like seats and seat covers are made and assembled in-house, along with speedometers, electronic devices, pushbuttons for dashboards and even the engine is manufactured at the Coventry plant, then assembled from ‘kits’ at Blackpool. The only system currently being made abroad is the powertrain (including the gearbox) which is manufactured by a company in Mexico. But even the gearbox will be manufactured by TVR as from next month.

There are 400 employees at the Blackpool site, five in vehicle design and styling, 10 in development, eight in engine development, the remainder work in the machine shop, body shop, paint, tooling, assembly and general production. The strange feeling when you walk around the plant is that most processes are manual, not the high volume automated environment of a major car producer such as Ford or Toyota. It’s not a high volume production plant – around 600-700 cars of various models are produced annually – and so the emphasis is on styling and unique design, not maximising throughput using the latest robot technology (although of course throughput is still measured!).

The design team uses Autocad and Solidworks for all its 3D CAD modelling of metal parts and assemblies.

Chris Runciman is project manager of the company’s new Typhon car at Blackpool. He told Eureka: “For prototyping, we wet lay up in fibre glass and produce all the moulds here. All metal parts on the car are designed at Blackpool and we then laser cut them. We have two CNC machines for prototype work.”

According to Runciman the interior of TVR cars are normally produced in injection moulded pre-preg [pre-impregnated epoxy resin] but the Typhon is now being produced in carbon fibre. He explained: “All the other cars have a one-piece polyester resin body because carbon fibre is a nightmare for one-piece without having to super glue everything. TVR did two-thirds of it using carbon fibre but to get that complete egg shape you need prepreg. Hence we used Araldite adhesive.”

Araldite, manufactured by Huntsman Advanced Materials (formerly Vantico) is a high performance polyurethane and epoxy range of adhesives. TVR uses the Araldite AV 4076-1 opaque epoxy adhesive and HV 5309-1 hardener to bond a variety of substrates in key components on the Typhon. These include pre-preg epoxy carbon fibre panels and powder coated steel.

During construction of the Typhon, the transmission tunnel and floor pan are bonded to the floors and then the main body is bonded to the transmission tunnel, floors and chassis. As Runciman told Eureka: “Bonding rather than welding was the original design solution we chose for the Typhon. The main benefits of this for us are its better fatigue performance and it distorts less under stress, has good corrosion resistance and greater load distribution, all critical in a high performance sports car.” The adhesive is also resistant to engine and exhaust by-products such as water, fuel and oil.

He said TVR chose Araldite AV 4076-1 for the Typhon because of the product’s proven track record in SMC bonding. “This showed the adhesive’s performance was dependable through its entire lifecycle and that the bonded joints would be able to withstand extremely hard road and track use of the car.”

TVR is also benefiting from advanced prototyping technology which it is using for producing its Tuscan model. It’s using a rapid setting polyurethane called ‘parts in minutes’ (PIM) from Huntsman. This material simulates the properties of thermoplastics and is able to withstand extreme criteria for elongation, stability and temperature. It is therefore being used for the low to medium (10 to 20 cars per week) production runs required by TVR.

The company is using Huntsman’s RenPim 5215. This polyurethane is used to make a range of plastic parts fitted in the engine bay of the Tuscan as well as the pillar trims and seat backs which are painted in the finish colour specified by the customer. It is also being used to produce the steering wheel which is then coated in leather.

TVR first trialled the products three years ago for pre-production purposes only. But then the company realised that they were suitable for final production in the quantities it required. So the firm invested in the necessary machinery to mould the parts in-house.

At present, tooling is using PIM to produce the air cover/box for the engine. The reason for this is because the material produces a smooth surface on both the inside, for good airflow, and outside, for good aesthetics, of the cover. Previously, TVR had used fibre glass but this proved very rough and extra grinding was necessary to achieve the same surface finish.

John Reid, tooling manager at TVR told Eureka: “We can now produce injection moulded engine air covers in three minutes. I reckon it now costs us 70 pence per unit rather than several pounds before. We can also inject rubber for the door seals now rather than using expensive aluminium tooling.” Although John Reid conceded that the company had to spend around £12k on an injection machine, he said the benefits more than outweighed the investment.

The real benefit of using rapid setting polyurethanes is that it reduces costs and lead times for parts by eliminating expensive tooling. It also enables TVR to develop novel component designs without the constraints of conventional manufacturing techniques. As Runciman told Eureka: “In short, PIM brings total flexibility in design and production planning.”

He added that tooling modifications at TVR are frequent because of the firm’s insistence on ‘perfect’ styling and can sometimes run to 10 separate changes such as moving the headlights.

Tom Shelley

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