Motorcycle Sport & Leisure

Every so often, we are given stories that we're simply not able to squeeze into the magazine.

TRIUMPH
ROCKET III

TOURING TECHNICAL: Bigger is Best

 

The Touring member of Triumph’s flourishing family of Incredible Hulks follows its Rocket lll/Classic forebears in employing an identical version of the British manufacturer’s unique all-aluminium 101.6 x 94.3mm liquid-cooled three-cylinder in-line 12-valve mega-motor, mounted longitudinally in the frame and measuring 2294cc - or a crucial 140 cu.in. in American terminology, a nice round number which, three years after its debut in the summer of 2004, still says "Beat that!" to Triumph's showroom rivals for the customer dollar. In fact, the Touring’s engine has been retuned to deliver just 107 bhp at 5400 rpm against the rortier Rocket III’s claimed 140 bhp at 5750 rpm, a power reduction and smoother power delivery offset by a humungous 209Nm/154 ft.lb of increased torque peaking at just 2000 rpm, against 200Nm/147 ft.lb at 2250 rpm for the Rocket III. 90% of this massive grunt is already on tap at a mere 1600 rpm, allowing the Touring to accelerate away from 20 mph in top gear with zero transmission snatch and no sign of a hiccup. This is a tractor turned tourer.

To achieve a low centre of gravity for what by bike standards is a massive powerplant weighing a hefty 125 kg., including the five-speed gearbox offset to the left of the crank and fitted with R1-style stacked shafts so as to reduce the overall width of the motor, the liquid-cooled Triumph engine is a dry sump design, with the lozenge-shaped six-litre oil tank mounted halfway down the left side of the engine, beneath the intakes for the three 52mm Keihin dual-butterfly single-injector throttle bodies. Doing without a conventional wet sump has the effect of making the vertical-block Rocket III's cee of gee even lower than on Honda's flat-six Valkyrie boxer, with the crank mounted just 205mm above the ground. To the rider sitting in the seat, the engine turns in a clockwise direction from left to right, with the forged crankshaft which features even 120-degree throws for perfect primary balance so heavy at 17.7 kg that a dedicated production line had to be installed in the Triumph factory at Hinckley three years ago to build the motor, equipped with a crane to lift each crank into place on the assembly line! To eliminate vibration as well as minimise torque reaction from the lengthways engine, there's a substantial balance shaft set alongside the crank, which rotates in the opposite direction to it, as does the five-speed transmission with its multiplate oilbath clutch. As before, you can balance a coin on the fuel tank with the Rocket III engine running at idle, without it falling over. That's smooth.

The same 101.6mm bore as a V-10 Dodge Viper sports car’s slugs, the Rocket III's three-ring pistons are mounted on forged conrods running on the plain-bearing crank and delivering a low 8.7:1 compression. The 12-valve cylinder head has double overhead camshafts chain-driven up the front of the engine, with paired 37.9mm inlet and 32.3mm exhaust valves, and dual ignition employed to take account of the large bore size in maximising combustion and enhancing emissions control. Aside from the long 10,000-mile/16,000 km. service intervals for what is a comparatively low-stressed engine, the Rocket III is also surprisingly frugal, delivering what the onboard trip computer forecast would be a 185-mile range from the just filled slightly smaller 22.3-litre (24-litre on the Rocket III/Classic) seamless fuel tank. That’s thanks to the efficient combustion of the dual-ignition cylinders, and the optimised mixture flow and fuel mapping obtained via the twin butterflies in each throttle body, one of which is operated normally by the light-action twistgrip, the other by the Keihin ECU according to gear selected, engine load and road speed. This also provides for the engine's massive torque output to be backed off by 7% in the bottom two gears via the ECU mapping, as is commonplace today with high-performance car engines in order to avoid placing too great a load on the transmission, and especially the drive shaft.

Because space was at a premium in installing such a big engine as a fully-stressed component of the Rocket III Touring's all-new massive tubular steel dual-spine frame, and room had to be found not only for the reasonably large fuel tank, sturdy 1.5 bhp starter motor, and high output alternator, but also for the massive 7 kg./18ah battery needed to prime the fuel pump and crank such a large engine into life (as well as deal with the larger electrical load entailed by fitting the copious accessories available via Triumph's dedicated aftermarket catalogue), the main airbox and air filter are located beneath the rider's seat. Fresh air is drawn in through an intricate ducting system moulded into the seat base, then fed from the main airbox through to a second plenum chamber beneath the chrome cover on the left side of the fuel tank, which in turn feeds the three throttle bodies. The Rocket III Touring engine is Euro 3-compliant thanks to the pair of large volume catalysts in the 3-1-2 stainless steel exhaust system's collector mounted just in front of the rear tyre, still without the use of secondary air injection, as Triumph engineers originally thought would be necessary.

The Touring follows its Rocket III family forebears in employing shaft drive via a bevel drive box manufactured in Italy for Triumph by Graziano, the same firm which builds transmissions for Ferrari, Maserati, Lamborghini and Aston Martin. The stacked-shaft five-speed gearbox employs a cable-operated clutch, delivering those acres of torque to the Touring’s more rational 180/70-16 rear tyre (well, compared to the Rocket III’s 240/50-16 design statement), complemented by a 150/80 16-inch front against the Rocket’s 17-incher. Both are shod with newly developed Bridgestone Exedra rubber making its market debut on the new Triumph, fitted to 25-spoke cast aluminium wheels. Rear suspension is taken care of by a pair of Kayaba twin shocks, which are adjustable only for preload, while the shrouded non-adjustable 43mm Kayaba upside down forks with 120mm of travel are set at a 32-degree rake, with a gi-mormous 185mm of trail combined with a 1708mm wheelbase, to deliver the rangy build determined by the lengthways engine, and the space and stability demanded by serious touring customers. The pair of 320mm Sunstar front discs are gripped by four-piston Nissin calipers, while the substantial rear 316mm disc and twin-piston caliper were instead developed especially by Brembo for the Rocket III family, helping to haul down a behemoth weighing a claimed 362 kg. dry from speeds of up to 140 mph, at which point the electronic speed limiter kicks in. So you should be able to go with the flow on German autobahnen aboard the Rocket III Touring, then….

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