Cycle News

KTM FREERIDE E-SM FIRST RIDE P76 The WP suspension eats up quite substantial ridg- es and ruts (and curbs!), giving added confidence. It's tuned for road use, so while the wheel excur- sion is nominally the same as on its off-road breth- ren, it feels more firmly damped. It's fully adjust- able, so you can dial up practically any setting you like. But I didn't care for the Michelin tires the bike comes fitted with, which took a while to warm up on this cool evening, and didn't have much feed- back, which essential for twist-'n'-go sportbiking. I'm guessing Pirelli or Metzeler rubber would have been a better bet in terms of the kind of immedi- ate grip you need to have on a motorcycle, which instantly delivers maximum torque the moment you E-TECH 101 Before starting development in 2008 on its prototype electric bike, KTM first established its dynamic objectives. "We began by determining which gasoline-engined traditional product the final version should be comparable to in terms of performance," says Harald Plöckinger, Chief Operating Officer of KTM, with overall responsibility for product development at Europe's largest motorcycle manufacturer. "We set a maximum weight target of 220 pounds, and decided the benchmark perfor- mance should be the same as or better than a 125cc two-stroke. But it was also clear to us that it should be a KTM, so no compromises, even with a different propulsion system, and it must be fun to ride! Then we contacted the Austrian Institute of Technology/AIT research institute in Vienna, who are well-known specialists in electric drive and battery technology, and they agreed to collabo- rate with us. The project has been par- tially funded by the Austrian government as an experimental development project, although this only happened once it was well under way, when we thought we may as well apply for whatever money they'd care to give us. It's not often that the applicant presents a running prototype for such a project, as we did in demonstrating it publicly to them!" The first step for KTM was to deter- mine the overall strategy for its electric bike's power pack, and Plöckinger & Co. quickly settled on a high voltage 300V motor developed by German suppliers Heinzmann's PERM subsidiary, already well known for its high power, high- efficiency, but very slim double-sided brushless double-stator DC electric motors. Such a compact design comple- mented the projected architecture of the bike, and matched the 125cc two-stroke dynamics sought by KTM, using lithium- ion batteries, which were also a key ele- ment in the weight issue and in energy capacity, were chosen. The high-voltage system permits downsizing the entire package, crucial in a motorcycle where weight and bulk are key issues. In elec- tricity, power is the multiple of current times voltage, so the higher the voltage, the lower the current needs to be in at- taining a target output, and the lower the current, the smaller and therefore lighter the components that need be used. This was a vital element in making the KTM Freeride E-SM light and compact, while maintaining an acceptable level of performance. So the resultant brushless, syn- chronous, water-cooled motor, with the permanent magnets sitting inside a narrow disc armature, is extremely slim and compact, and in production guise delivers 16kW/22bhp at 4,400 rpm, with maximum torque of 42Nm available from 1 rpm upwards. That's around twice the torque of a 27bhp KTM 125cc EXC two-stroke, while not quite comparable in output—the air-cooled Freeride-E prototype that I rode three years ago gave 22kW/30 bhp at 6,000 rpm, but had significant heat issues because of the power produced, according to KTM's Electrical Drive Engineer, Nina Deitermann. She, incidentally, joined the company three years ago on gradua- tion from university, after converting a conventional combustion-engined KTM dirt bike to electric power as the design project for her Mech.E course! "Because of the heat, we reduced the power output slightly without sacrificing torque, and switched to a liquid-cooled ECU—what we call an E- box—because it's a very small controller for this amount of power," said Nina. "We also decided to liquid-cool the motor, employing one combined system for both units, although the batteries are still not water-cooled. The reason is that if we combined doing so together with the ECU and motor cooling system, their temperatures are much higher than the batteries, so we would need either a separate system for those, or to make this one larger. That would mean extra weight, extra cost and especially extra bulk. Where to put all this without making the bike much bigger would be a real problem. We did consider fitting supplementary cooling fans to cool the battery pack, but we managed to avoid the extra weight and complication of this by employing sheets of heat-transfer material, instead." The E-SM's motor is powered by a 2,600Wh lithium-ion battery pack containing 360 cells and weighing 61 pounds, which I timed a KTM engineer in taking one minute and 38 seconds to remove for recharging. He did so by unbolting the four thick bolts attaching it to the top of the motor and replacing it with another fully charged pack. Claimed complete recharging time is one and a half hours, including balancing the cells, using KTM's own charger supplied with the bike. You're basically limited by how much current you can transfer via the plug, so it's not the battery that limits recharging speed, it's the socket itself. "For recharging with a 240V outlet from a conventional household socket, we have two modes, Fast and Normal," says Nina Deitermann. "The difference is in the fuse—in some older houses you have only a 10 amp fuse, in which case you can only use 2,400W Normal mode for charging. This way, recharging from completely empty to 90 percent full takes 70 minutes, or 90 minutes to 100 percent charge. Using 3,000W Fast recharge with a more commonplace 13

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