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Hub Cen­tre Steer­ing

Ba­si­cally a HCS has a wheel axle through the cen­tre of a very large di­am­e­ter hub, inside of which is a king pin about which the steer­ing oc­curs. There are two hubs, one sta­tion­ary and one ro­tat­ing. The sta­tion­ary hub is pre­vented from ro­tat­ing, usu­ally, by means of an up­right struc­ture which it­self is lo­cated by a link back to the main chas­sis. An­other link back to chas­sis from the axle com­pletes the link­age. Today the most known ex­am­ple is the Vyrus de­riv­a­tive of the Bi­mota Tesi.

4-bar link­age or dou­ble-link

BMW’S Duolever sys­tem, the Yamaha GTS1000 from the 90s, Hos­sack and the Cor­tanze ELF en­durance racers from the 80s are well­known ex­am­ples of this.

The Hos­sack and its many de­riv­a­tives (eg BMW Duolever) have both links above the wheel. The ELF type have both links within the cir­cum­fer­ence of the wheel, which re­quires the use of bent links for steer­ing clear­ance. My own de­signs and the Yamaha GTS have one link above the wheel with the other within the wheel and bent.

The Hos­sack is the only one which al­lows for the use of stan­dard wheels and brakes – which low­ers cost and sim­pli­fies con­struc­tion. The other two op­tions re­quire spe­cial sin­gle-sided wheels (ELF’S work led to the sin­glesided swingarm).

Slid­ing el­e­ments

Th­ese are funny front ends with slid­ing el­e­ments like tele­scopic forks, but with some form of piv­ot­ing link to pro­vide ex­tra stiff­ness and mod­i­fi­ca­tion to the ge­om­e­try of move­ment. In many ways this is a de­sign based on a de­sire for im­prove­ment in per­for­mance whilst re­tain­ing the familiar look of tele­scopic forks. BMW’S Telelever is an ex­am­ple, 20 years af­ter Bri­tish spe­cial-builder Saxon pro­duced lim­ited road bikes.

The ELF racer and its anti-dive char­ac­ter­is­tics meant that funny front ends were as­so­ci­ated with high­per­for­mance ap­pli­ca­tions. But tele­scopic forks have im­proved way be­yond what was thought pos­si­ble prior to the 1990s and racers use brak­ing dive to their ad­van­tage.

FFES also tend to be kin­der on tyres and gen­er­ate less heat which re­duces grip and rider feel.

Good de­signs have a lot to of­fer the road rider in terms of sta­bil­ity and con­fi­dence but for­get about them in top­class rac­ing at least for the near fu­ture.

There is a lot of in­for­ma­tion on var­i­ous funny front ends in my chas­sis book, details on www.tony­foale.com

BMW used Duolever for some of their K-se­ries ma­chines

Bri­tish firm Saxon came up with an early Telelever type

Hub cen­tre steered ELF 500

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