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Cannondale's New Full-Suspension X-C Scalpel
 
03/25/2001
Cannondale's New Full-Suspension X-C Scalpel Cannondale has finally taken the wraps off their new lightweight full-suspension cross-country bike. Dubbed the Scalpel for its light weight, precise handling, and “cutting-edge” technology, the new bike weighs just 23 lbs – even with dual disc brakes and tubeless tires. The Scalpel also boasts 2 ½” of fully useable rear wheel travel, remote front and rear lock-out, and a cross-country-specific geometry with a relatively low, 12 ¼” bottom bracket height.
The new bike was designed with substantial input from the cross-country racers on the Volvo/Cannondale team, including two-time World Cup Champion Cadel Evans and Sydney Olympic Bronze Medalist Christoph Sauser. Evans, Sauser, and the team’s other cross-country racers will compete aboard the Scalpel at most 2001 World Cup events.

FRONT TRIANGLE
The Scalpel’s front triangle is hand-welded, heat-treated 6061-T6 aluminum, and features Cannondale’s Power Pyramid downtube. The Power Pyramid simultaneously increases in diameter and decreases in wall thickness throughout its length. As a result, the down tube has a weight-saving thinner wall and a super-rigid, oversized profile at the bottom bracket shell to resist pedaling forces. At its upper end, the Power Pyramid has a slimmer diameter for compatibility with the head tube and a beefier wall for added strength.

One of the performance criteria specified by the Volvo/Cannondale athletes was easy portagability, so the Scalpel’s front triangle has an open, uncluttered design with all of the suspension components located aft of the seat tube. And for enhanced stand-over clearance, the Scalpel’s top tube has a downward bend just forward of the saddle – a feature that Cannondale fittingly calls the Crotch Notch.

EPO REAR SUSPENSION
By far the Scalpel’s most notable feature is its EPO (Engineered Pivot Orientation) linkage rear suspension, and the suspension’s most innovative components are its carbon fiber, fiberglass, and nylon composite chainstays. The stays have a nearly rectangular cross-section, with the major (longer) axis oriented vertically at both ends. But along the central portion of their length, the stays temporarily flatten out so their major axis is horizontal. Along this same section, the stays’ lower edge gradually arches so the stays become noticeably thinner, top-to-bottom, at the center of their length. The ends of the stays are bonded within fixed collars that are part of the rear dropouts and bottom bracket shell.

The key to the EPO’s performance is how the seatstays’ unique shape, and the careful orientation of their fibers during fabrication, forces the stays to bend at a precise point mid-way along their length. (As opposed to other designs with flexing chainstays, where the stays bend throughout their length.) By isolating the point at which the stays bend – in reality, the pivot point around which the swingarm rotates – Cannondale engineers are able to dictate the performance characteristics of the rear suspension.

Before the EPO stays ever bend upward, though, they are bent downward. Preloading the Scalpel’s shock absorber also preloads the chainstays, bending them downward at the pivot so the suspension is extended an additional 1” at the rear dropouts. The natural inclination of the stays to spring back to their resting (unloaded) state functions as an integral negative spring that dramatically enhances small bump response.

Preloading the stays also moves the rear wheel’s axle to a level just below the Scalpel’s mid-stay pivot. The result is that, through the first part of its travel, the rear wheel is able to move back out of the way of impacts as it also moves upward. In the latter part of the travel the pivot is below the rear axle, eliminating chain growth, pedal feedback and bobbing.

As the swingarm goes through its travel, the suspension also morphs from using the chainstays’ decreasing negative spring (for plush initial response) to using the shock absorber’s ramping, positive air spring to add greater progressivity toward the end of its travel (to prevent harsh bottoming out).

HARDWARE
The Scalpel’s EPO suspension uses top-quality parts throughout. The EPO shock links and dropouts are machined from magnesium and coated with ceramic to prevent corrosion, and teflon-impregnated brass bushings are used at most pivots. One exception is where the two shock links mount to the Scalpel’s seat tube. At this highly-stressed point, Cannondale engineers have opted to use slightly heavier needle bearings (with a double-contact lip seal and external labyrinth seal) to eliminate flexing.

The EPO’s Fox Float RL shock absorber mounts at its lower end to a linkage axle suspended between the system’s two shock links. The linkage axle is crafted from hardened, 4130 cold-drawn nickel-plated steel, and provides a hard bearing surface for the shock bushings and high torsional stiffness between the links. At its upper end, the shock attaches near the top of the seat tube between two beefy mounting tabs. For strength and durability, the upper shock mount, the lower shock link mount, and the upper length of seat tube are all actually one forged part. (On smaller frame sizes, the seat collar is also part of this forged part.) The forging is reinforced with a V-shaped rib on the back side of the seat tube that adds significant strength with only minimal weight.

COMPONENT SPECS
Many of the Scalpel’s components are as innovative as its frame, particularly its integrated Hollowgram bottom bracket and crankset, and its Lefty Carbon ELO fork. The Hollowgram system features a lightweight bottom bracket (patent pending) with an oversized, hollow spindle inside a correspondingly oversized bottom bracket shell. The system also includes a super-light crankset with hollow crankarms. Combined, the Hollowgram crankset and bottom bracket weigh just 641 grams, or 25% lighter than Shimano XTR parts at 855 grams.

The single-sided Lefty fork has 80 mm of travel, a lightweight thermoset carbon fiber telescoping assembly, and a unique electronic lock-out feature (ELO) activated by a handlebar-mounted push-button. By locking out the front fork, riders are able to eliminate suspension bobbing to sprint and climb with greater efficiency. The rear suspension can also be locked-out through the use of a thumb lever that is also mounted to the handlebars. The Scalpels raced by the Volvo/Cannondale riders will also feature Magura Louise disc brakes, Mavic tubeless rims and tires, and Shimano XTR derailleurs.

COMING TO BIKE SHOPS!
Although only available to Volvo/Cannondale riders at present, the new Scalpel is scheduled to arrive in bike shops in late spring. At least two models featuring the Scalpel frame with EPO suspension are currently planned, including a Volvo/Cannondale team replica edition. Customers interested in more information should call Cannondale at 1 800 BIKE USA, or visit the company’s web site at www.cannondale.com

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