TUBE NEWS TN December 2017 - Page 9

The early years were dominated by European cars, primarily Lola, McLaren and Porsche with drivers including Bruce McLaren, Mario Andretti and John Surtees. By 1969 a revolutionary car designed by Peter Bryant from the UK and built in the USA made a significant impact on the sport. Bryant recognised that weight and lack of ground effect was holding back advances and a car emerged that used lightweight titanium body parts for the first time. Titanium components are stronger than the steel equivalent and are barely half the weight. Called the Ti22 (chemical symbol and atomic number of titanium) the car set new standards in performance. Bryant built two cars, the MkI in 1969 and the MkII in 1970. They achieved several podium finishes and over their lifetime scored more points in Can-Am racing than any other American built car. Recreated car, the Ti22MkII, manufactured by Bob Lee. Image courtesy Melinda Stewart The success of the Ti22 cars was short lived because of funding constraints. Both cars were destroyed in the Can-Am era In 2015 Bob Lee in the USA acquired original Ti22 MKII drawings and rights to the MkII history. He assembled a team of fabricators led by Ilia Burkoff and began work to build a new car employing his Burkoff’s expertise in fabrication of titanium. It became apparent early in the construction that a major hurdle to be overcome was welding. The fundamental problem in welding titanium alloys is the elimination of atmospheric contamination1 from the weld zone. Contamination of the weld metal and the adjacent heat affected zones will increase tensile strength and hardness but only at the expense of ductility loss. This can lead to cracking even in conditions of only moderate restraint. The most likely contaminants are oxygen and nitrogen, picked up due to air entrained in the gas shield or from impure shield gas, and hydrogen from moisture or surface contamination. The molten weld pool can be protected by the normal gas shroud but the cooling weld and its HAZ will need additional protection. The underside of the weld also needs similar protection through the provision of an efficient gas purge. Atmospheric contamination however is best avoided by the use of a welding Flexible enclosure purged with argon in use during welding of titanium components for the Ti22 Mk II. The enclosure is a Huntingdon Fusion Techniques 1.2 metres diameter standard model and the welder used a GTAW torch with MultiStrike® electrodes for arc stability and longevity. chamber or glove box that can be filled with inert argon. Metal glove boxes are available but these can be very expensive. Lee solved the problem by using a flexible welding enclosure together with an oxygen monitor. This combination allowed him to weld all the sensitive titanium components in his car, the Ti22 MkII. They included roll bars and braces, front and rear sub- frames, suspension parts, brake throttle and clutch pedals, engine firewall and mirror mounts. » TUBE NEWS December 2017 9