Seamless Shift Gearbox

Changing Strategies

At last we can reveal the revolutionary principle behind the ZeroShift gearbox and how the company has progressed since it was last featured in these pages

It was in February last year that we broke thestory about ZeroShift’s revolutionaryseamless gearchange system. At the time itwas agreed with the company that wewouldn’t reveal how the design worked oncondition that we could break the story when itwas able to go public. It has taken a while butnow, for the first time in any magazine in theworld, we can reveal the secret of how theZeroShift system operates. Unless you areextraordinarily patient, you have probably readthe panel explaining already. If not, then we urgeyou to read it and experience that eurekamoment, then we can bring you up to date on thecompany and the latest progress with the system.When we first visited ZeroShift in late 2003 toresearch that first feature, the company was verynew and very small. It had been founded todevelop an invention by one of its founders, BillMartin. The technology allowed different gearratios to be selected without any break in thetorque delivery from the engine to the wheels.This was ZeroShift and that same principle is stillat the core of everything the company is workingon today. However, in the intervening period,much else has changed. Initial interest frominvestors has been turned into a firm financialfooting that allows the company to take a morethorough approach to developing the system,rather than rushing to market with a hastilyproduced product in order to generate funds. It has also enabled the recruitment of a very wellqualified and able team of people to take the ideaand transform it into something marketable.Having read the panel, you may be wondering,with such a simple and elegant principle to workwith, what is there to develop? In fact there arecertain issues that come about during the transferto the real world. The most obvious one is whathappens to all that inertia in the engine when youengage a higher ratio? You cannot dissipate 500 to1000rpm in a millisecond without producing a bigimpact and ZeroShift’s aim is to achieve a flatacceleration curve on a graph.Current transmissions break the torque duringchanges, however briefly, resulting in a hole in thecurve, while a raw ZeroShift system produces a spike as the inertia in the engine delivers amomentary increase in torque while the revs dropto match the road speed in the higher ratio. This isobviously undesirable due to the load it puts onthe drivetrain and the tyres. But smoothing out aspike is something that is achievable, unlike fillingin a hole which is not.The team at ZeroShift is working on a numberof strategies for smoothing the spike, the simplestof which uses the clutch. By briefly reducing theclamping torque on the plates during the shift, itallows a moment’s slip that dissipates theunwanted energywithout breaking thetransmission of torqueto the rear wheels.Other techniquesinvolve cutting the fuel,or spark, or both duringa change creating ahole in the engine’storque delivery that can be filled by the unwantedinertia. In addition the company is investigatingin-line, driveshaft dampers that can absorb theextra torque, smoothing its impact on theacceleration curve.The engineers also showed us otheridiosyncrasies with the system and varioussolutions to other issues that appeared duringtesting that, in the interests of competitiveadvantage, we have been asked not to reveal. Allthis may seem a little daunting, but the companyhas assembled a team of bright, enthusiasticengineers to tackle them. Their backgroundsinclude Xtrac, Ricardo, Cosworth, Jaguar Racingand Prodrive, and the issue is not so much a lack of solutions but a question of choosing whichones to follow. Head of design is Miles Ashcroftwho has served time at Xtrac, BAR, Nissan and cuthis teeth on jet engines. He has been overseeingturning the concept into a practical reality with aview to bringing a product to market.But in our original feature, we reported that bynow the company would already have its firstproduct, an aftermarket version of the T5 gearboxon sale. So what went wrong? Bill Martin ispragmatic and refreshingly honest. ‘Whathappened was two things. First, at that time wedidn’t know what wedidn’t know. Secondly,we have taken a morelong-term approach todoing things that willtake the companytoward seriesproduction.’ Theresponse frominvestors has put them in a much strongerposition and the need for a marketable product isnot as pressing as was first envisaged. ‘We havebeen spending a lot of time on automating thesystem and developing control systems.’ Work iscurrently focusing on NVH and FMEA. ‘It’s beenexciting because we’re learning quickly.’The original concept of ZeroShift was for apassive manual system that worked like anordinary stick-shift gearbox. That was fine untilthey started to incorporate systems to smooth outthe torque spike. Trying to synchronise theseelectronic shift management systems with themechanical input from a gear lever proved moredifficult than managing the whole process electronically, so the plan now is to operate thefirst generation of ZeroShift electronically.To develop this the company has recruitedAndrew Bowyer, an engineer with expertise inindustrial automation for manufacturing. LikeMartin, he does not have a background intransmissions or even automotive applications sohe brings no preconceptions about how thingsshould be done. ‘Most car companies are doing itas open loop,’ he explains, ‘our system is based onclosed loop control so it is self taught. The clutchsystem will be self taught and the cut to theengine will be self taught so it will be constantlychanging.’ Normally thecost of torque sensorsmakes this strategyprohibitive, but Bowyerhas developed a way oftackling it without one.This is anotherunexpected feature ofthe company, as the coreproduct drives numerousspin-off technologies thatZeroShift is registeringwith the intention oflicensing in the future.The team obviously has a great deal of talentand experience within it, but the burning questionis are they turning ZeroShift into a workablesystem? Our experience of the company’s longsufferingTVR test bed suggests it is. Even with thebare minimum of smoothing strategies inoperation the change is only betrayed by asubdued clonk and a barely perceptible surge. It really is a seamless change with no break intorque delivery, the big giveaway being the lack ofacceleration reversal at any point in the change.In fact, when demonstrating ZeroShift to potentialcustomers, the subject of luxury carsas suitable applications is often raised byrepresentatives of car manufacturers. The guestswill also ask to be shown the system without thecontrol systems to gauge its appeal to the sportsmarket in its raw form.So, when can we expect a ZeroShift gearbox onthe market? With less need to generate revenuethan originally anticipated, the company is takingmore care over its firstretail product. The fivespeedT5 originallyintended as a base is nowconsidered less suitable.Instead work is switchingto a production six-speedunit, and the team nowexpects to have anaftermarket ZeroShiftversion on the marketlate in 2006.And what about itsapplication inmotorsport? The company is currently in talkswith a number of outfits and while we were there,Ashcroft gave us a glimpse of a concept for aFormula 1 gearbox. This demonstrated the abilityto provide seamless selection of all seven gears ina unit as restricted as the smallest currently in usein F1 today. It seems this dynamic new companyhas some exciting times ahead.

[Source：Racecar Engineering Magazine June-2005]