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Piaggio’s New Old-Fashioned Alternative to Telescopic Forks

Look close at this Piaggio illustration and you’ll see their latest single-sided suspension brainwave. Interesting.

Look close at this Piaggio illustration and you’ll see their latest single-sided suspension brainwave. Interesting. (US Patent Office/)

For decades the telescopic fork has dominated motorcycle front suspension design, easily batting away challenges from an array of alternatives over the years. But attempts to develop a better system never end, and the latest comes from Piaggio.

The Italian company is working on a front suspension system based on a variation of Watt’s linkage concept, approximately replicating the linear movement of a sliding telescopic fork but allowing the freedom to alter the geometry to create a pro-dive or anti-dive effect as well as providing a single-sided setup, rather like the leading-link or trailing-link suspensions used on some scooters.

Watt’s linkage has been around for centuries, being first patented in the 1800s by James Watt, the new patent from Piaggio appears to be the first time it’s been applied to a motorcycle’s front suspension setup.

The Watt’s-type linkage in extension and under compression.

The Watt’s-type linkage in extension and under compression. (US Patent Office/)

The system itself uses three links, joined end to end and forming a Z shape. The front axle is in the middle of the center link, and the free ends of the upper and lower cranks are attached to the steerable “fork” section extending down from the steering head. While Piaggio illustrates several variations on the design in its patent, the most detailed pictures show this support structure made in cast aluminum, giving the appearance of a production-style component.

At a glance, the setup doesn’t look radically different to the sort of trailing-link suspension used on Vespa scooters, with a single coilover strut providing the springing and damping. But a trailing-link (or leading link) design would force the wheel to follow an arc through the suspension travel. That’s avoided on the new Piaggio design thanks to the additional two links; with a trailing link at the bottom and a leading link at the top, joined by a near-vertical center link that holds the wheel, the axle moves very much like it would if attached to a conventional telescopic fork. The motion isn’t quite straight, but it remains within around 3/64ths of an inch of the movement that a telescopic fork would follow. That potentially bodes well for the bike’s handling, though the layout of the linkages and the position of the brake caliper (mounted, like the axle, on the vertical center link) will impact the pro- or anti-dive characteristics of the design.

If the system replicates the movements of a telescopic fork so closely, one might ask, why not simply use conventional forks instead? The answer lies partly in that ability to tailor the dive characteristics, but also in the weight and rigidity of the Piaggio system. Forks have to withstand substantial stresses, particularly under braking, and since they have a circular cross-section, they’re similarly resistant to sideways flexing. That’s not always good, since a bike that’s leaning over in a corner can benefit from lateral flex when it comes to absorbing midcorner bumps. Systems like the “6D Flex” forks developed by MotoCzysz aimed to overcome that issue by having different flex characteristics laterally and longitudinally.

A pair of inboard-mounted Watt’s-type linkages shown on one of Piaggio’s trademark tilting three-wheelers.

A pair of inboard-mounted Watt’s-type linkages shown on one of Piaggio’s trademark tilting three-wheelers. (US Patent Office/)

However, a bigger advantage for Piaggio in adopting the system might be the fact it’s compact and single-sided, as it lends itself to the sort of tilting three-wheelers the company pioneered. The new patent shows that an identical fork can be used on both a two-wheeled bike and, with the addition of a mirror-image second unit, to a tilting trike. The trike itself closely resembles designs the company published some time ago for a large-capacity Yamaha Niken-style three-wheeler.

On the two-wheeled version, the front wheel looks unusually small, presumably to ensure enough suspension travel. But on the three-wheeler, the smaller front wheels somehow look less jarring. Perhaps that’s because, since the whole machine’s layout is relatively unfamiliar, we don’t have preconceptions about its proportions.

Another variation of the Watt’s linkage suspension is shown on a scooter based on the existing Piaggio Beverly design. Piaggio’s patent also illustrates a variety of more prototype-style tubular versions, with different layouts for the linkage.

As usual, a patent can’t be taken to be a guarantee that a design will reach production, but this one seems to have some genuine potential, particularly in the three-wheeled niche that Piaggio is keen to make its own.

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