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Car-development engineers are invariably discontented with the status quo. That''s especially true in ride-and-handling development, where twin-tube shock absorbers-more accurately called suspension dampers-are now under scrutiny. These 100-plus-year-old devices are finally prime candidates for replacement by more sophisticated hardware.
Twin-tube dampers are inexpensive to manufacture, serviceable for tens of thousands of miles, and entirely suitable for mainstream use. That said, they''re susceptible to wear, which deteriorates their performance over time, and they lack the tuning flexibility offered by newer damper designs.
Enter Multimatic, a Canadian enterprise that strives to be every car company''s problem solver. This suspension-systems and composite-body specialist is currently Ford''s ally forconstructing its GT supercar. In addition, Multimatic''s Motorsports division has a lengthy history of designing, engineering, constructing, and campaigning race cars for top-series competition around the globe.
In 2010, Multimatic applied for a patent on an innovative suspension damper. Code named DSSV, for Dynamic Suspensions Spool Valve, this design initially proved its merit by helping Newman-Haas Racing win seven of the 19 races and the driver''s championship in the 2002 CART series. DSSV hardware became mandatory equipment in five other major racing series between 2006 and 2015. Red Bull Racing used them to win four consecutive Formula 1 titles (2010–2013) and nearly half of this year''s Le Mans 24 Hours competitors swear by DSSV dampers.
Conventional dampers use multiple thin discs covering ports in the piston moving up and down within a tube containing hydraulic oil to generate the forces that control body and wheel motion. The flexibility tuned into these discs-and the size and shape of the ports they cover-determines how fluid flows between the chambers above and below the piston. The greater the flow restriction, the higher the damping force.
While that principle is sound, problems arise with mileage. The steel disc material is subject to fatigue, which diminishes its strength and stiffness. Bits of debris from the damper seals, piston, and shaft become trapped between the disc layers, altering their damping qualities. Anyone who has owned a high-mileage car with clapped-out shocks knows that the term "handling" no longer describes its dynamic behavior.
The other shortcoming with conventional dampers is that they can''t be tuned to cover the full scope of road driving, track lapping, and off-pavement excursions that ambitious manufacturers are striving to cover.
Multimatic''s DSSV dampers retain basic components such as a sealed tube filled with hydraulic oil and a piston that moves within that tube in sync with suspension motion. The difference is that the thin discs are replaced with a pair of hollow cylindrical sleeves nested concentrically within each other and held apart by a coil spring. Suspension motion forces damper oil inside the sleeve cavity. When that internal pressure is sufficient to overcome the spring force, one sleeve moves slightly with respect to the other, uncovering apertures, which allow oil to move to the opposite side of the piston. One sleeve valve regulates compression damping; another controls rebound damping.
The beauty of this arrangement is that the sleeve valve components are not susceptible to wear or fatigue. The stiffness of the coil spring and its preload and the shape of the apertures facilitate three distinct damping curves. A linear "curve" provides damping forces directly proportional to the velocity of the suspension movement. Progressive damping characteristics mean that the force rises gradually with suspension velocity. Digressive damping is a steep initial rise in damping followed by the force curve leveling off at some specific suspension-travel velocity. Multimatic has software called SpecFinder that allows ride-and-handling engineers to quickly and easily pick spool valves that deliver the damping curves they desire.
-The 18th China(Guangzhou)Int’l Spring
Industry Exhibition
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