Cycle News

VOL. 52 ISSUE 1 JANUARY 6, 2015 P77 twist your wrist, because they warm-up so much faster than any of their competition. The fact they are also the lightest available production tires is another benefit, because lowering the amount of torque needed to get the wheel rolling reduces "fuel" consumption, and so extends range, as well as delivering enhanced acceleration and braking by reducing rotational inertia, and offering en- hanced suspension compliance via reduced un- sprung weight. Electric motorcycles have been the next big thing in powered two-wheelers for the past sev- eral years, as they've progressed from the back- yard projects of amateur boffins, some of whose amp fuse, a 90 percent charge comes in 60 minutes, but the 20 minutes for the last 10 percent is the same, because it will automatically go to slower Normal recharge for that last 10 percent, to get the balancing of the cells correct." KTM has opted for the ubiquitous cylindrical lithium-ion 18650 laptop batteries, even though the flat-sided ar- chitecture of the next-generation lithium polymer cell batteries now available from its Korean supplier permits much denser packaging, a key issue on the Freeride E-SM. "We considered using these so-called coffee pack cells, but we had to think about how we can pack them, especially when they're heating up and getting warm under load," says Plöckinger. "But we decided maybe it's too early, so let's use standard cells, but develop our own battery management system as part of the battery package. The controller controls the engine, and communicates to the battery, but to manage the cells you need to have this BMS, especially in terms of balancing the charge." Balancing means accounting for the energy differences between the 360 individual cylindrical cells in the KTM battery pack, because by nature of the chemistry, it can happen after a few recharging cycles that one of the cells has more charge than another one. But the lowest one will determine when you have to shut off the battery, because there's a lower voltage threshold, so it's important to try to equalize the charge, in order to make full use of the storage capacity available. With the battery pack weighing 61 pounds and the motor 22 pounds, the resultant power-and-fuel package is nearly identical in weight to that of a 125cc two-stroke engine and a full tank of fuel (not forgetting the actual tank itself!) combined. While it's true that on an E-bike this doesn't get any lighter, as the fuel gets used up, the constant weight means that the 49/51 percent overall distribution of the E-SM's 238-pound weight remains the same at all times. That's a little more than the original target, mainly because of having to add the liquid-cooling. However, alongside the motor and battery, the key element in the trio of ingredients delivering motive E-power is the electronic controller, aka ECU, and with nothing available off the shelf, unlike with the motor, here KTM had to search for a partner to deliver a purpose-built product, and program it. They found one in British E-specialists TT Electronics, which conveniently already had an Aus- trian office in nearby Salzburg, together with whom KTM engineered the power section of the controller, both high and low voltage boards, and the packaging for all this to suit the bike's very compact layout. The key points on the control- ler were the performance range and packaging size, and the requirements for water tightness and protection against dust, vibration and shocks, especially in off-road riding on the two other mod- els in the Freeride E range. This must have represented quite a challenge in developing a suitable product, because electricity, water and dirt don't go so well together! Consequently, the complete electric system is dust- and water-proof, so KTM claims that cleaning the bike with a pressure washer is not a problem. And to provide impact protection, the battery is housed in a solid aluminum casing to protect it from external shocks or penetration. Plus, the chassis itself wraps around the battery, giving added protection. KTM believes its protective system actually makes the Freeride E safer from fire risk than a traditional bike with liquid fuel aboard. However, the protection provided by the Freeride E-SM's composite frame is ultimately secondary to its role in making it handle, and here KTM engineers took advantage of the fact there's no exhaust system, especially not a fat two-stroke one. They thus downsized the E-SM's physical dimensions to their 85cc entry- level motocrosser's, as part of their crucial weight-saving campaign to offset the weight of the battery, while also mak- ing it more agile and controllable. The chrome-moly steel frame spars which wrap around the battery pack are bolted into the aluminum rear upright forgings, comprising the pivot for the forged aluminum swingarm with a high-strength fiber-reinforced plastic subframe car- rying the seat. The whole clothed in Kiska Design styling. All the running gear comes from the 85cc KTM 'stroker, including 43mm WP upside-down forks delivering 9.8 inches of wheel travel up front, matched to the fully-adjustable WP shock with PDS progressive-rate link giving 10.2 inches of rear suspension movement. Chassis geometry is quite sharp, with a 23º head angle combined with a 55.8-inch wheelbase, and the pair of lightweight Giant wheel rims are the standard 17-inch sizes for a conventional streetbike, shod with 100/80 Michelin rubber up front and a 120/70 rear. The wave disc brakes are different from the 85cc MX bike's, though, with a four- piston caliper and 260mm disc handling stopping duties up front, and a 250mm disc and two-piston caliper in the rear, all supplied by Formula, a company already well known in the mountain bike arena. Here, it's entering the motorcycle sector for the first time on KTM's E-bike. The rear brake is operated by a hand-lever positioned bicycle-like on the left grip of the taper-section 28/22mm aluminum handlebar.

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