German manufacturing company Schaeffler ran its own Step2 electric car in the Silvretta E-Car Rally in Austria. The car is a Volkswagen Golf, stripped of its internal combustion guts and equipped with an electric powertrain supplied by one of Schaeffler's subsidiaries. The thing that makes the Step2 a little different, though, is the inclusion of a two-speed transmission.

Most electric cars use a single gear to transfer power from the motor to the wheels, but Schaeffler is re-thinking the status quo.

Tesla Motors famously started with a two-speed transmission but then ditched that strategy and today most electric cars use a single gear to transfer power from the motor to the wheels, and have no problems with drivability thanks to a relatively flat torque curve. This is great: smooth, comfortable driving, no costly transmission maintenance, no waiting for power while shifting, no added weight from the bulky gearbox. Plus, it's not ludicrous to think that including the unnecessary transmission with multiple gears would be less efficient due to mechanical losses. But Schaeffler is re-thinking the status quo.

In the E-Car Rally, the goal is not to complete the course in the least amount of time, but rather using the least amount of energy, and the alpine driving event allowed Schaeffler to put the Step2 to the test. The rally, as well as other driving tests and simulations, has shown that by using the two-speed transmission with a low and high ratio, the car is actually more efficient. The group reports the gearbox-equipped Step2 reduces energy consumption by about six percent.

With greater efficiency, obviously, the car also can drive farther on a single charge. Shaeffler's vice president of automotive research and development, Uwe Wagner, says, "With a two-speed gearshift system, a low ratio for high tractive force and a high ratio for good overall efficiency also at high driving speeds, we offer higher dynamics and at the same time we achieve a longer range of electric operation."

The Step2 sounds like a fairly simple conversion from a standard internal combustion car. Beyond replacing the powertrain, fuel tank and exhaust system with an electric motor, battery and the two-speed transmission, little else was changed. Schaeffler modified the front axle, but left the steering and brakes alone. No regenerative braking to boost the efficiency numbers here. In terms of power, its output peaks at 70 kilowatts (about 94 horsepower), with 50 kilowatts (67 horsepower) offered in continuous operation. Learn more about Schaeffler's Step2 in the press release, below.
Show full PR text
Schaeffler STEP2 Concept Vehicle Competes Successfully at Silvretta E-Rally
Transmissions increase range of electric mobility

Schaeffler was also represented by an electric vehicle in the E-Car Rally in Montafon (Austria), which was held for the fifth time from July 3 to July 5, 2014. After a prototype with an electric axle (2012) and the Fiesta E-Wheel Drive with an electric wheel hub drive (2013), the team lead by Uwe Wagner, Vice President R&D Automotive at Schaeffler, was competing this time with the Schaeffler STEP2. This is an all-electric vehicle with a drive from the Schaeffler subsidiary IDAM and a two-speed powershift transmission.

The E-Car Rally, which was established by the magazine „auto, motor und sport" and is held on the dream roads of Montafon and Vorarlberg, was not decided by the highest speed but the highest level of efficiency. Efficiency is also the driving force for combining an electric drive with a transmission. „With a two-speed gearshift system, a low ratio for high tractive force and a high ratio for good overall efficiency also at high driving speeds, we offer higher dynamics and at the same time we achieve a longer range of electric operation", concludes Mr. Wagner.

In simulations and test drives, the STEP2 concept vehicle has already achieved a significant reduction in consumption (as energy withdrawn from the battery) of around six percent compared to a comparable vehicle with only one gear. STEP2 is based on a volume-produced compact car. Schaeffler engineers removed the internal combustion engine, the manual six-speed transmission and the fuel tank. The front axle was also modified but the wheels, brake system and steering system were left in original condition. The electric motor was supplied by the Schaeffler subsidiary IDAM (INA – Drives & Mechatronics GmbH & Co. KG), the specialist for direct drive technology. As an electric vehicle, the Schaeffler STEP2 is now driven by an electric motor, which can be coupled with two ratios via a transmission. The transmission comprises a planetary gear set, wet multi-disk clutch, band brake and a lightweight differential. The first and second gear ratios are produced in the transmission by alternately closing the brake and clutch. The vehicle`s battery is located in place of the fuel tank and exhaust gas system below the passenger cell. The Schaeffler STEP2 has a system output of up to 70kW (peak) and 50kW in continuous operation.

Schaeffler`s engineers from the electric mobility sector gained further findings under actual alpine driving conditions during the three alpine stages and demonstrated in the field of mainly standard electric cars that the use of a transmission leads to even greater efficiency savings in terms of kilowatts, volts and amperes. The electric mobility sector at Schaeffler is involved in the development of solutions for all future mobility concepts and with its research and development work for and in collaboration with customers makes a valuable contribution to the mobility of the future.


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  • 30 Comments
      Letstakeawalk
      • 8 Months Ago
      Edmunds sold theirs after they got their *fourth* drivetrain. "It seems like Edmunds’ Tesla Model S test vehicle has lived a pretty cursed existence, as many an issue has popped up over its 30,000-odd mile life…the most notable of which is now operating on its 4th drive unit. Now to be fair, a long term test in the hands of auto journalists is a true test of the limits for durability of any car. Still, when your Model S is immediately identified by a tech as needing a drivetrain unit replacement from just the sound of the car (and the service guys also have a catch phrase for the problem), you know this issue reaches to more than just one car." http://insideevs.com/edmunds-long-term-tesla-model-s-on-fourth-drive-unit-going-up-for-sale/ It's truly remarkable how quickly and easily Tesla will swap out an entire drivetrain (and/or broken motor mount)... but one must ask, what happens after the warranty runs out?
      Ricardo Gozinya
      • 8 Months Ago
      Most of the complaints you listed about transmissions might have applied as recently as the mid '80s, but modern transmissions are ridiculously good at what they do. Anyways, it's great that someone's actually thinking outside the box, isntead of just going with the status quo.
        EVSUPERHERO
        • 8 Months Ago
        @Ricardo Gozinya
        Agreed, transmissions are use to doing for ICE cars. Not EV's. It is a different critter. A ICE car takes 600-700 milliseconds to spool up, even then they are not at full tork, a EV takes 200 milliseconds. EV don't need all those gears and flywheel, clutch that would buffer the immediate energy on hand even more. Tesla could build a heavy duty drag racing gearbox but it has to be quiet and put around town as well as durable and low maintenance. Tesla is really a gearbox with a differential not many parts compared to a ICE transmission. If it was a larger transmission the energy could get spread out more equally among components. I am not a gear head so just a thought experiment.
          Ryan
          • 8 Months Ago
          @EVSUPERHERO
          It depends on the voltage of the motor. 300V-400V like OEMs use can be run without a clutch. 96-156V like DIY'ers convert benefit from more gears.
          JB
          • 8 Months Ago
          @EVSUPERHERO
          My guess is that is much more simple to design a transmission "shock absorber" for EVs then a intricate 8 speed transmission, clutch, ect. for ICE vehicles.
      DarylMc
      • 8 Months Ago
      I love the idea of electric drive with one fixed gear and no gear changes. Environment be damned, I lust after it like someone else might just want a V8 engine or a Porsche. But I suppose 2 speeds wouldn't be the end of the world. It's probably worth noting that poor acceleration from standstill is not a complaint you hear of in EV reviews or owners feedback.
      Joeviocoe
      • 8 Months Ago
      @ Letstakeawalk --"Edmunds sold theirs after they got their *fourth* drivetrain." Yes, I would call that an unfortunate lemon. It happens. Tesla needs to learn from that of course.
      Joeviocoe
      • 8 Months Ago
      @ Letstakeawalk --"but one must ask, what happens after the warranty runs out?" Auto techs and hobbyists need to get 'spun up' quickly on repairing these. As much enthusiasm as there is for Tesla, that should encourage many tinkerers to figure out the drive train. Essentially, it would be fewer "gear heads", and more Electronic folks that take on the mantle. Only problem is that, while most Tesla's (or most EVs) are under warranty, very few people will tinker... so there will be a knowledge gap for a few years and it will be expensive to get repairs out of warranty during that gap.
      jeff
      • 8 Months Ago
      The "More Efficient" claim is highly questionable. The answer really is based on how much voltage there is in the pack and how much current the pack can delver. All electric motors have a limit of operation called the "Back EMF". This is a force that is proportional to the amps that you feed the motor and works to prevent more amps from entering the motor. As you apply more and more amps to the motor this force rises in direct opposition. At the point when the voltage in the magnetic field in the windings is approximately equal to the pack voltage, you will not be able to put more amps in the motor and this limits it's ability to produce more torque. So, the lower the voltage of the pack, the more gears are needed to provide acceleration at any given speed. My EVThing has a 120V pack. It can provide about 100 ft-lb or torque almost linear from 0-3500 rpm. However, the saturation of the winding occurs at this point and the torque drops off sharply from 3500-4500 rpm. By 5000rpm the torque is almost gone. As a result, I need to shift gears to get the rpm of the motor down so that I can apply more torque. In my car this works out to 30mph in first, 45mph in second and about 60mph in 3rd. If I only had a single speed gear box, I would have to pick a gear ratio between 2nd and 3rd. This would cause slow acceleration (estimated 0-60 in about 30 seconds) and limit top speed to about 65mph on level ground and 10mph drop off on a steep hill.... However, my model S has a 400V pack and the motor in this car can generate it's torque up to about 15,000 rpm so it pulls hard from 0-100mph with a single gear of about 8:1. At about 100mph the back EMF starts to take it's affect. Now if I wanted a 150+mph Model S, the Tesla would definitely need a 2nd gear.... As for efficiency, this is where people get it wrong. There is little difference in efficiency between my driving my EVThing using four gears or just putting it in 2nd or 3rd and driving it. In fact the extra gearing probably causes a little drop in efficiency. The problem is that the performance would not be acceptable on most roads... So, when people say a multispeed transmission in an EV is more efficient, they are simply wrong...
        EVSUPERHERO
        • 8 Months Ago
        @jeff
        Thanks for the info Jeff. I have a little Yaris conversion that maxes out at 85 with it's single speed gear box.
        karlInSanDiego
        • 8 Months Ago
        @jeff
        Jeff, imagine halving the size of your 1 speed motor in order to make it more efficient. Smaller motor turning same speed with less drag should result in less power needed to operate, at least in theory no? This is one of the reasons ICE motors have had gearboxes. We size the motor smaller, reduce the gearing to start off with and allow the little motor the chance to get the car moving, then continue to gear up with the benefit of your car's inertia meaning your power demands are smaller. You end up turning your engine slower in the higher gears which results in fuel savings because less cycles always means less fuel in ICE. Now the electric motor is far from a direct parallel to an ICE motor. For example it can attain its peak torque straight away. Modern ICE DI turbo motors need 1400 rpm and some spooling to be in peak torque. And in theory, your electric motor is ok spinning at 10k or more, arguably without sacraficing its peak efficiency (in reality this is a compromise), whereas an ICE engine might make peak HP at 6-9k but it is far from peak efficiency when turning that fast, and it's not particularly reliable at sustaining that rpm. But I propose it is entirely possible that given the design edict of maximum range with a limited battery, a very small electric motor plus the benefit of exaggeratedly long mix of gear ratios could result in a marked increase in efficiency and therefore range. We may not know because it may not have been tried yet. If you look at 2 stroke Gran Prix 50cc motorcycles of the 1960s, this is how they achieved wins, with 14 speed gearboxes: http://2strokebiker.blogspot.com/2010/01/1968-suzuki-50cc-grand-prix-roadracer.html So could we build EVs with cruising motors of tiny size with massive gearing, and maybe a second motor for hills of much greater spec? This could be the untapped future of BEVs. We are in its infancy, so try not to naysay all possibilities untested. I've often read that sustaining cruising speed takes a minimal amount of energy, if your car enjoys a good Cd and low frontal area, and minimal rolling resistance (poor RR could be a by-product of bloated 4785 lbs. coupled with extra wide tires to control a heavy car in corners) The greatest problem I see with this model is the need to climb hills at speed.
          protomech
          • 8 Months Ago
          @karlInSanDiego
          "This is one of the reasons ICE motors have had gearboxes. We size the motor smaller, reduce the gearing to start off with and allow the little motor the chance to get the car moving, then continue to gear up with the benefit of your car's inertia meaning your power demands are smaller." There are two primary reasons not to install an overly large ICE motor: 1. ICE engines are both larger and heavier per unit power delivered. Multi-gear transmissions are not small, but you probably can get more wheel torque with a fixed weight / volume budget with a multi-gear transmission and a smaller engine than a single-gear or two-gear transmission and a large engine. 2. ICE engines are very inefficient at low load, such as at highway speeds, where the oversized engine is likely spinning fairly quickly. Imagine a V8 sedan spinning at 4000 RPM at 70 mph. Neither of these are necessarily problems for EVs. The Tesla motor / gearbox unit is very compact, but can produce more than 400 hp, and it seems to be fairly efficient at highway speeds even when geared for 4 second 0-60 dashes.
      Ben Crockett
      • 8 Months Ago
      Personally I enjoy driving my PHEV with the equivalent of only the one gear, much smoother than anything with a transmission. The claimed increased in efficiency could be better achieved in other ways. If I read the article right it says the vehicle uses the standard brakes which infers that it doesn't have regen braking - that right there is a huge potential gain in efficiency as braking energy is recovered.
      PeterScott
      • 8 Months Ago
      It depends on how good your EV motor is, and how wide an operating range it maintains efficiency over. I am betting that most good EVs will have wide operating range that doesn't drop even by 6% enough of the time to make this useful. I would rather just see more high quality EV motors, that better efficiency over a wider range to make the added complexity of a transmission redundant.
        Ricardo Gozinya
        • 8 Months Ago
        @PeterScott
        Actually electric motors have a much sharper drop in efficiency than ICEs do. Yes, the electric starts off way, way more efficient, when you get it going, even for just highway driving, that efficiency takes a massive drop. ICEs start lower, but when pushed, drop less. Part of that, a large part, is the fact that they use transmissions. It's the nature of electric motors. They'll always have that steep drop.
          Aaron
          • 8 Months Ago
          @Ricardo Gozinya
          You must be referring to DC motors. Most production EVs use AC (brushless) motors. They don't have the drop-off that you're referring to.
          PeterScott
          • 8 Months Ago
          @Ricardo Gozinya
          Untrue: http://www.coppermotor.com/wp-content/uploads/2013/09/CR-IM-hi-speed-improvement-project-ARMI-final-report-11Jul13.pdf EV motors have lower starting efficiency, but throughout the middle range they are VERY efficient (~90%). Only at VERY high RPM do they start to lose efficiency and this will depend strongly on how good the design is. Typical numbers in the PDF above, were dropping about 2% going from 8000RPM, to 10000RPM (91% down to 89%). These are not number to bother chasing with extra gears.
      nbsr
      • 8 Months Ago
      The driver wouldn't have probably noticed such transmission. Switching the gear (mode?) is not required like it is in ICE, it just improves comfort, performance and efficiency. Typically it would only be needed twice - when entering and leaving a motorway. Not harder than switching the lights or wipers on/off. The EV performance is pretty good but the designers still have to choose between the top speed, the torque, and the size of the motor. Currently the solution is to assume a modest top speed and to scale the motor size until it produces satisfactory torque. A mass-produced two-speed transmission would be both better and cheaper but it simply does not exist yet and it costs money to develop (chicken egg problem). The efficiency. While the torque curve is mostly flat from zero to max speed, the efficiency curve does have at least two points where it falls all the way to zero. In a (fairly broad) mid-range the efficiency is high but when driving close to min or max speed this is no longer the case. There are many practical situations (start-stop city traffic, motorway speeds) where the low-speed or high-speed mode would have helped. Every EV (without hub motors) already has one set of gears in the drivetrain so the obvious solution would be to make that gear ratio switchable. That wouldn't incur any extra losses and would still do the job. The simplicity isn't necessarily helping here as gearbox manufacturers would have rather preferred a more advanced/traditional design.
        PeterScott
        • 8 Months Ago
        @nbsr
        The Model S does 0-60 in 4 seconds, and has a top speed of 130 MPH. Exactly how is it lacking in either Starting Torque or Top speed? Why move from a virtually indestructible simple reduction gear, to a transmission introducing a new point of failure? This is a "solution" trying to pretend there is a problem here that needs solving.
          Tweaker
          • 8 Months Ago
          @PeterScott
          It isn't "indestructible", Tesla is quietly replacing thousands of drivetrains, strongly rumored to be over the reduction gear. Instant torque is much more destructive than spooled torque.
          nbsr
          • 8 Months Ago
          @PeterScott
          With two speed transmission Model S could do 0-60 in 3 seconds, have top speed of >150mph, more range and more effective regenerative breaking. Or it could use a smaller, cheaper and more efficient drivetrain to achieve the same performance. This is not an issue for a car in the price range of Model S but such brute force solution won't scale to mass market. Transmissions are coming but since in EVs they are seen as an optimization and not an essential part of the drivetrain, we have to wait for the scale effects to kick in and pay the development cost.
      Aaron
      • 8 Months Ago
      I'll keep the elegant simplicity of my EV. I don't have to worry about the transmission, nor feel its shifting as I accelerate. Remember: The first Tesla Roadsters had a two-speed transmission. Due to the high failure rate, Tesla replaced those transmissions with a single-speed reduction gear (as most EVs use today).
      Joeviocoe
      • 8 Months Ago
      Fun Fact: Tesla's original limitation was the Motor Controller (not the motor or battery).. that led them down the 2-speed transmission path. According to Elon and JB... when the newest IGBTs came out... they finally had the components to build a motor controller with enough power and efficiency to meet their targeted 125 MPH on a single reduction gear. So far from "status quo"... but really single speed is the "new hotness". (now, if you want to keep going faster than 140 mph... then maybe an extra gear would do well, but really not needed for any EV not on a race track) Autoblog Comments Enhancer (ACE) v1.0.0 - bit.ly/Autoblog_Comments
      JB
      • 8 Months Ago
      Whatever the best balance of SWAP-C. My guess is that a single speed is fine.
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