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What's new? Radical RXC
Radical's first fixed-head "roadable track car" has a highly adjustable chassis and electric power steering
by Graham Heeps
UK-based Radical Sports Cars has taken the wraps off its first closed-cockpit design, the Radical Xtreme Coupe (RXC). It’s a race car that will also be certifiable for road use and has been engineered since April 2012 to finally bring to reality a concept that the company first considered several years ago.
The RXC is built around a carbon-steel spaceframe in typical Radical fashion. Radical designer Mark Cousins explains, “From the front end back to the roll hoop, there’s a definite similarity to previous chassis. But we have a completely different engine and gearbox, so from the roll hoop backward it’s a very different car.”
The powertrain in question centers on a Ford V6 (cradled by the spaceframe and rubber-mounted, not a stressed member) and a Quaife seven-speed ’box. Because the transmission and differential are in front of or on the rear axle line, weight is kept within the wheelbase and the car’s dimensions remain compact. A casting over the gearbox bellhousing attaches the rear end – including the suspension – to the front, so in the event of an accident, the rear end can be quickly changed.
The rear-suspension pickup points are on the spaceframe rather than cast into the gearbox casing, for additional flexibility in changing the suspension geometry, says Cousins. The suspension itself is a steel double-A-arm pushrod setup to inboard, Intrax dampers, plus an inboard, pushrod-activated anti-roll bar. The dampers have remote reservoirs and four-way adjustability. Intrax also supplied the springs, although they are made by a third party.
There are double-wishbones at the front too, again with a pushrod to rockers and a pushrod-activated anti-roll bar. The front pickups are not as adjustable as at the rear, although in theory, the welded spaceframe means they could be moved if necessary. A rear-end-style, quick-change detachable structure is not currently fitted, but is apparently being considered.
“We’ve moved the steering system outside the cockpit – on previous Radicals it was inside – so that’s changed the shape of the chassis at the front a little bit,” says Cousins. “But apart from that it’s very similar [to previous cars].”
The electric power steering has a column motor and is modified from a donor road-car system. There is cockpit-adjustable assistance to adapt to different track conditions and according to Cousins, it could be developed into an ECU-driven system that would allow different settings at different corners.
The RXC has yet to see a four-post rig but the suspension geometry was extensively simulated during the design phase. The initial simulation was done using Mitchell software and then this was verified and continued using OptimumG kinematics. Mike Rowe is a resident race engineer at Radical and was responsible for running most of the simulation program.
The priority for the car now is to get some track running time to debug the powertrain and get the reliability right, while also developing the handling. To this end, the first prototypes will head to warm-weather test tracks (Spring Mountain in Nevada is reportedly one of the destinations) very soon. The first customer cars could be ready by mid-summer.
Tech spec – Radical RXC
Dimensions: 4,300mm (L) x 1,960mm (W) x 1,127mm (H)
Engine: 3.7-liter Ford V6; 380bhp, 434Nm
Gearbox: Quaife seven-speed sequential with paddleshift
Brakes: Hi Spec. Front 360mm discs, six-pot calipers; rear 330mm discs, four-pot rear calipers. Upgrade packages under consideration.
Wheels: Braid 9.5J x 17in (F); 11.5J x 17in (R)
Tires: Dunlop SP Sport 215/45 (F), 255.40 (R)
Estimated performance: 175mph, 2.8 sec 0-62mph (100km/h)