Dodge Tomahawk

The Dodge Tomahawk was a non–street legal concept vehicle introduced by Dodge at the 2003 North American International Auto Show. The Tomahawk attracted significant press and industry attention for its striking design, its use of a large-capacity 10-cylinder automobile engine, and its four close-coupled wheels, which gave a motorcycle-like appearance, and fueled debate on whether it was or was not actually a motorcycle.The Retro-Art Deco design's central visual element is the 500-horsepower (370 kW), 8.3-litre (510 cu in) V10 SRT10 engine from the Dodge Viper. The vehicle has two front wheels and two rear wheels, which are sprung independently and theoretically allow it to lean into corners and countersteer like a motorcycle.

Dodge's claims of a hypothetical top speed of 300 to 420 miles per hour (480 to 680 km/h), probably based on horsepower and gearing calculations, were debunked by the motorcycling and automotive media. No road tests of the Tomahawk have ever been published. Hand-built replicas of the Tomahawk were offered for sale through the Neiman Marcus catalog at a price of US$555,000, and up to nine might have sold. As they were not street legal, Dodge called the Tomahawk a "rolling sculpture", which was not intended to be ridden.

The Tomahawk was a resounding success in its true purpose: to generate media buzz, and send the message that Chrysler was a bold, ambitious company, unafraid to take risks.

Inception

The idea for a Viper-engined motorcycle started with two lower-level Chrysler Group employees, Bob Schroeder, a design office modeler and motorcycle rider, and Dave Chyz, vehicle build specialist and drag racer. According to designer Mark Walters, himself not a "motorcycle guy", the question asked was, "What if we had a Viper engine and a Champion chassis? Something like a Boss Hoss."Schroeder and Chyz took the proposal to Senior Vice President of Design Trevor Creed, who initially said, "we don't build bikes" but still allowed some design sketches to be created, which were "mind blowing" enough to bring Creed on board.They eventually took the idea to Freeman Thomas, DaimlerChrysler VP of advanced design, who assigned Walters to join the effort.Thomas suggested using two front and rear wheels because a single wheel would look thin next to the unusually wide engine, inspired by the four-wheeled light cycles in the film Tron.Walters anticipated howls from bikers that this would make it not a motorcycle, but he felt uniqueness was more important, and imagined the appearance with only a single wheel in front of and behind the engine would have been visually unbalanced, saying he would like to see it made that way for comparison. By the spring of 2002, Walters had prepared a full scale design presentation, with sketches along a 20 ft (6.1 m) wall and a borrowed Viper engine resting on an engine stand with two wheels placed fore and aft as a visual aid. This was presented to Chrysler Group COO, Wolfgang Bernhard, and CEO, Dieter Zetsche, who gave their immediate approval.

Design

The design was the work of Chrysler staff designer Mark Walters, who built the vehicle around the Dodge Viper 8.3-litre (510 cu in) V-10 engine. Once approved by Bernhard and Zetsche to build not just a full-scale mockup, but a running, workable concept vehicle, the design and fabrication process took six months.The engineering, as well as the fabrication, was outsourced to RM Motorsports, a Wixom, Michigan specialty shop that fabricates one-of-a-kind parts for rare and vintage race cars.[4][9] Walters said Kirt Bennett at RM handled the task of making Walters' sketches a physical reality that was mechanically sound. Walters' early sketches had a front suspension that looked something like an Elf-Honda racing motorcycle's hub-center steering, from which RM designed a new, patented front- and rear-swingarm suspension that allows both parallel wheels to lean together, keeping all four in contact with the ground and allowing countersteering. The Tomahawk was intended, unlike many concept vehicles, to be a "functional runner" that "had to work" as well as have a finished appearance, since the mechanical parts would be exposed to view.

The V-10 engine needed several design changes. To position the engine lower to the ground, the lubrication system was changed from wet sump to a dry sump type, moving the under-engine oil sump to a tank located in front of and to the left of the engine. The car-style single radiator out in front of the engine was changed to two smaller radiators and fitted into the V-shaped space above the engine, where cooling air is force-fed using a belt-driven fan sourced from a Porsche 911

Suspension

The Tomahawk has an independent suspension on all four wheels designed to allow the rider to countersteer and lean into turns like a tilting three-wheeler.There is a hub-center steering style swingarm connected to the outboard side of each of the two front wheels, with a steering link connected to the handlebar shaft. There is very little lock-to-lock steering range, only about 20° on either side of center, so the turning radius of the Tomahawk is large; "only a little tighter than an SR-71", said Motorcyclist's Jeff Karr. A low center of gravity, accomplished by situating the engine as low to ground as possible, is intended to provide greater control at low speeds, and a low saddle allows riders to place both feet on the ground when stopped, for greater stability. The two rear wheels also each have an independent swingarm, but on the inboard side, along with an inboard chain drive for each wheel. The rider can engage a rear suspension lock, which hydraulically holds the two wheels' relative positions, letting the vehicle stand on its own, without using a side stand.

According to computer imaging, the suspension would allow a lean of up to 45° with all four wheels maintaining contact with the ground before one of the swingarms contacted the ground, although attempting to actually corner at such extreme angles is not safe given the Tomahawk's 1,500 lb weight. Test rides for the purpose of photographing the Tomahawk in action revealed that there were still stability issues to be worked out, given that it rides, "like two motorcycles riding in ultraclose formation, coupled with the weight of three and the horsepower of four," in Karr's words, meaning that, "some disagreement is inevitable."