Tom Shelley reports on fastening and joining components for motorsport and other demanding applications.
Where winning is all, often decided by tiny improvements in technology relative to that available to competitors, motorsport is one of the best places to test and find optimum solutions, and this applies to fastening and joining just as it does to almost every other aspects of engineering. First to catch our eye at this year's Autosport Engineering was a new latch for sports car body panels, the 'Aerocatch 3'. Peter Boote, managing director of Specialty Fasteners and Components told us, "Sports cars use a lot of tension latches, these are put into pockets. Hence we decided to come up with a tractor latch that would look neat, and not require the forming of pockets in body panels."
What he showed us was a device that had a tongue in one half which located in a housing with tapered edges in the other half so as to provide rigidity in shear, combined with a draw hook. A secondary lock with a button release provides added security. It is designed to be mounted in a panel cut out, and can be mounted from either the top or underneath the panel. It has already been race proven during 2010 with development undertaken in conjunction with the S2000 Duratec championship winning car, Loaded Gun TS11. Like the other products in the range, it is made by the vendors at Totnes in Devon.
Next to come to our attention were brightly coloured anodised aluminium alloy bolts offered by Pro-Bolt, which is based in Tewkesbury. Joint owner Nick Bailey told us that historically, the company was in the business of supplying race specification bolts for motorcycles but they now supplying bolts to customers with cars, karts and boats.
The attraction of aluminium bolts over steel is that they are 60% lighter. While the alloy used has a yield strength of 505MPa, and the bolts have cold formed heads and roll formed threads, they are mainly recommended for non safety critical areas such as mudguards, screens, fairings, engine casings, huggers, fuel caps, number plates, lamp units, exhaust cans, heel plates, exhaust manifold brackets, fuel cap surround, air filters and car rocker covers. For those who require strength, the company also supplies quality bolts made in 316 stainless steel and 6Al 4V titanium.
Aerocatch 3 is a new tractor latch for sports cars that does not require the forming of pcckets in the body panels. It has already been proven during 2010 and is from Specialty Fasteners and Components.
The bolts are made in Bristol. Also present at the show, were Automotive Racing Products, whose bolts are made in Santa Paula in California. Our attention was caught by some molybdenum disulphide coated wheel studs. The purpose of the coating is to reduce friction so that when tightened to the correct torque, exactly the right amount of tension will be induced in the stud, no more and no less. Wheel studs on racing and rally cars suffer even greater shock loads than on heavy goods vehicles, and as on HGVs, we were told that the usual cause of failure is over tightening of nuts rather than under tightening.
We then asked Hansell Composites what fasteners they recommended to use to hold their constructions together and was told that they preferred not to use mechanical fasteners at all but favoured bonding with adhesives. Their favourites turned out to be 3M Scotch-Weld Epoxy Adhesive 9323 and DP490.
They added that to get a good bond, surface preparation is key, and said they found best results were achieved by using peel ply. Henkel has recently brought out wet peel plies for this purpose, supplied in film form. Hysol EA 9895 WPP is a pre-impregnated polyester product which is specially designed for curing at 177°C while nylon Hysol EA 9896 WPP enables best performance at 121°C. Both products are said to be compatible with all composites and provide minimal residual peel ply fibers at the bond surface after curing and removal.
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