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From CAD User Mechanical Magazine  Vol 22 No 4 - APRIL/MAY 2009

Leading Brake and Clutch equipment manufacturer, Alcon Components uses Ansys DesignSpace FEA integrated with Autodesk design tools to develop advanced clutch systems for performance cars

Well known for its brake equipment for competition cars around the world, Alcon has also been tentatively exploring the world of clutches - the fruits of their efforts being a new range of race quality units. Back in 1998 Alcon Components Ltd, although a distributor of Tilton clutches outside of the USA, started making its own carbon-carbon clutches to fill crucial gaps they had found in the market place (Racecar V8N9). From those early tentative steps has come a new range of sintered, cerametallic and carbon-carbon clutches to suit most professional and semiprofessional competition categories Alcon MD Alistair Fergusson explained the company's reasons for entering a tough market with its own range of products. "We felt there was an opportunity to supply a viable alternative. We have distributed Tilton clutches for some time, but they are products aimed primarily at US markets which are not perhaps ideally suited elsewhere. In 1997/8 we spotted a need for a 200mm carbon-carbon clutch, and Tilton didn't produce one. So we made one and sold it to Prodrive, which has used our clutches (on its World Rally Championship Subarus) since then. Indeed we are now an official technical sponsor to the Subaru World Rally Team. "Having made that clutch we decided it had some advantages over competitors products. We soon found, though, that not only did we have the necessary skills to make a full range of clutches but that we had also spotted some technical areas where we felt we could do better than the competition." A bit of an understatement, though, as company founder John Moore codesigned the worlds first diaphragm spring competition clutch during a long spell with AP Racing. That original design was, in essence, the ancestor of clutches now used the world over. To reinforce Moore's impressive credentials, experienced clutch design engineer Tony Bonser, who had a background in race and rally clutches following periods at AP Racing and Mitsubishi Ralliart Europe, was also recruited.

PATENT ADVANTAGE

Alcon started out with the proverbial blank CAD screen for the design of its new clutch range. With the benefit of the designers combined experience and the aid of Autodesk's Mechanical Desktop 3D CAD and ANSYS/DesignSpace finite element analysis software, supplied by Croydon based IDAC Limited (Integrated Design and Analysis Consultants). The company's aim was to produce the best available range of race and rally clutches. Tony Bonser: "We had a fresh start. This meant we could redesign and optimise each component in relation to all others, including the diaphragm springs which meant, in turn, that we could optimise the size of the clutches. "With the new 5.5in clutch we were further able to optimise the spring design to get the fulcrum point into the best position to prevent distortion, even when used in the most arduous conditions. The spring itself is the smallest around. And by reducing mass wherever we could, the clutches are lighter overall by as much as 17% compared to competitor's products. This offers reduced moment

of inertia, engines respond faster and gear changes may be made more quickly, and there is also a bit less mass on the crank line, which allows a little more ballast to be placed where it can offer some benefit.

"We were determined to make clutches that lasted well, offered the driver good feel (achieved with a stiff cover) and a well defined, consistent biting point (defined by the diaphragm spring) that allowed a degree of modulation, though not all drivers seem to require the latter. The cover and diaphragm designs benefited from ANSYS/DesignSpace, especially in optimising the strength and weight of the highly stressed cover.

"ANSYS/DesignSpace not only allowed a view of stress concentrations but also deflections. We were able to take off some mass but also design stiff covers."

Alcon has also designed a super light cover for use in some less demanding applications. Material has been removed from the cover periphery, where stress concentrations were low, so that the outside diameter is no longer circular, and lightening holes have also been cut near the centre, again where low stress meant that mass removal was not disadvantageous.

Alistair Fergusson explains: "With the carbon clutches we were also able to maximise the friction material contact area to achieve a good wear rate. Prodrive came to us partly because the clutches were more durable. Also with the carbon clutch we re-thought the hub retention method. We came up with a novel method for which we have applied for a patent, which incorporates a non-floating hub. This has allowed us to make a shallower, lighter hub, and as a result a more compact, thinner clutch assembly."

CAPITAL INVESTMENT The manufacture of the new clutch range has required investment in additional

people and equipment. Alistair Fergusson again: "Its our intention to do as much of the manufacture as possible in-house. Our experience is that it's the best way to maintain quality but also to retain the responsiveness and bespoke manufacturing capability that the motorsport market requires.

"We brought in some extra people on the shop floor to address production requirements, and invested in a Hitachi Seiki Hi-Cell powered-tool lathe costing around £140,000 plus tooling - primarily for machining covers, and driven by EDGECAM 5 software. The assembly area is currently being re-vamped, and we'll be installing the latest computer-controlled clutch test equipment.

“Some components you can't avoid having to buy in, and one or two production operations are performed outside. Diaphragm springs are bought in of course, but as these are the heart of a clutch, they're to our own designs and specifications. Hub splines are broached outside, but otherwise everything is made, assembled and tested in-house.

“Every clutch we make is tested for clamp load and release load and the data is retained on file. When carbon clutches come back in for reconditioning, we check the original data (via traceable etched serial numbers on the clutch components) and rebuild the clutches to achieve the same settings.”

THE PRODUCTS

Alcon's new range includes 5.5in (140mm), 6in (152mm), 7.25in (184mm) and 200mm clutches in sintered, cerametallic and carbon-carbon variants. The company is positioning its products principally at the top end of the market but will be able to supply to semi-professional and well-heeled amateur teams too. At present it supplies Subaru and Skoda in the World Rally Championship and all

Formula Renault 2000 championship cars. Furthermore, the Pescarolo-entered Courage-Peugeot C52, which placed fourth at Le Mans in 2000 used an Alcon clutch, clear evidence of the products durability. Ford is also set to use a new Alcon cerametallic clutch in its Puma Super 1600 rally car.

The different clutch types have different applications; the carbon units can be used for both racing and rallying, sintered devices for racing, and the cerametallic clutches are specifically for rallying. The latter have a higher thermal capacity, and are heavier than other types, but have to cater for road driveability as well as heavy duty demands of rally competition. Alcon's carbon clutches are between 8 and 16% lighter than competitive products, whilst the sintered units are up to 17% lighter.

All variants will be available with different numbers of driven plates from one to four (in the GT racing variant of the 5.5in carbon clutch), according to torque capacity and life requirements. Other options include a choice of spring load and spring ratio, and although most units utilise electro-less nickel plated high-grade alloy covers (some of the larger sizes replace the nickel plate with a hardanodised finish), metal matrix composite covers will also be available to special order for certain applications.

Currently all the clutches are push-type in operation, but pull-types will follow. The range doesn't at present include units in Formula 1 or Champcar sizes, but has been selected to meet the core applications in the clutch market and prices are said to be competitive.

www.idac.co.uk

Thanks to Alcon Components Ltd, Simon McBeath (Freelance Motorsport Writer) and Racecar Engineering Magazine for their cooperation in allowing this article to be used.

CaseStudy

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