Seamless Gear Change

A comment wasmade that this had a previous incarnation and that makes sense. It just nevergot into the mainstream, possibly because the need was not compelling.

Whatever itshistory, here it is and it nicely simplifies the drive train while eliminatingmuch of the weaknesses of the dual clutch assembly.  This is another incremental improvement intraditional transport technology which we will hopefully soon see of in favorof electrical configurations.

In a way itis remarkable that we should be squeezing improvements out of the drive trainafter a full century of intense development that has never let up.  Perhaps someday we will have perfection.

Xtracshows seamless gearchange alternative to dual clutch transmission
21:41 December 1, 2010

Xtrac IGS is applicable to a two speed EVtransmission

Aftertwo years secret development in motorsport competition, Xtrac unveiled animportant new driveline technology this week in the form of an InstantaneousGearchange System (IGS). It does exactly the same thing a dual clutchtransmission achieves with less weight, cost, and complexity. The secret toXtrac IGS is the integration of a ratchet and pawl mechanism between each gearhub and the main shaft so that two consecutive gear ratios can be selected andengaged simultaneously, but with only one set of gears driving.

Conventionalgearboxes have always had some serious problems associated with needing tointerrupt engine torque in order to change gear. Apart from increasing fuelusage, hydrocarbon and CO2 emissions, momentarily cutting power delivery to therear wheels obviously also reduces performance.

Porschewas the first to develop an answer to this problem with itsDoppelkupplungsgetriebe (dual clutch transmission - DCT) and the DCT is now incommon usage in cars and has just been applied to motorcycles for the firsttime by Honda.

Size,weight and complexity are the main drawbacks of the DCT. Now motorsporttransmission specialist Xtrac has applied its high performanceengineering skills to design and develop a seamless gearchange known as IGS orInstantaneous Gearchange System. IGS is small, lightweight, and is now readyfor commercial development in motorcycles, electric vehicles, cars, trucks andbuses. IGS was unveiled this week in Berlinat the International CTI Symposium “Innovative Automotive TransmissionsHybrid & Electric Drives”.

Thesecret to Xtrac IGS is the integration of a ratchet and pawl mechanism betweeneach gear hub and the main shaft so that two consecutive gear ratios can beselected and engaged simultaneously, but with only one set of gears driving.

“Whenintroducing new technology to the automotive mainstream it’s important to haveprogressed beyond the initial research and development phase,” said XtracTechnical Director Adrian Moore.

“Carmakers like to see practical demonstrations to show that the technologyactually works and is more than a concept. With our motorsport experience wehave the advantage of two years of racing IGS with professional teams.”

IGS isprotected by worldwide patents, and the company reports that initialdevelopment will focus on improving the efficiency of electric vehiclepowertrains. Xtrac has considerable experience in the design and manufacture oftransmission systems for experimental, prototype, pre-production and specialistlow volume vehicles, and a study is already underway to implement IGS into atwo-speed EV transmission with the aim of ensuring the optimum performance ofthe vehicle.

Xtrac is based in Berkshire,UK, with satellite motorsport operations in located at Indianapolisand North Carolina in the United States. Its gearboxes,differentials and driveline components are used in Formula One, IndyCar,Touring Car, Rallying, Rally Raid, GRAND-AM and Le Mans sportscar racing.

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