Evaluation of a new narrow and tiltable electric tricycle (e-trike) concept

Rapport, 2016

The great need for safer cycling should start with improvements of the cycle itself, of its stability. The vast majority (70-80 %) of cycle accidents are single accidents. The cyclist falls to ground, when he/she no longer can balance the cycle. A conventional bicycle is an unstable two-wheel vehicle at speeds up to about 15-17 km/h and therefore needs to be balanced by the cyclist. A cycle with a third wheel, a tricycle (trike), should be much more stable under most cycling conditions (for example when entering the bike, slippery road conditions, cyclists want to keep momentum and don´t want to stop when crossing a street or at red light, need to suddenly avoid impacts with pedestrians). A first prototype of a safer and a more stable three-wheel electric cycle concept has been developed with Cycleurope, with its subsidiary Monark Exercise AB (a manufacturer of specialized cycles as postal bikes). The concept is a narrow cycle, less than 700 mm wide, with two front wheels (about 500 mm between the wheels) and one rear wheel with electric motor support (250 W, 25 km/h max speed). This cycle, an e-trike, is tiltable when you make turns. The narrow e-trike should not take more space in traffic than a normal bike. The space needed for parking should be about the same as for a conventional bike. A source of inspiration for this new concept is the three-wheel scooter Piaggio – MP3. You can drive this scooter with “just” a driving license for a passenger car, because it is easier to drive than a normal two-wheel scooter. For a first evaluation of the e-trike concept it was decided to do it experimentally by a number of cycling tasks inspired by cycling studies done in the Netherlands. The e-trike was evaluated and compared with an e-bike and a conventional bike. The experiments took place at SAFER. There were 17 cycling participants with a mean age of 29 years. Most of the participants were students. The four cycling tasks were performed over a distance of about 120 m: - Accelerate safely to 17 km/h, stay above 17 km/h, brake safely before line. - Accelerate fast to 17 km/h, stay above 17 km/h, brake fast but safely before line. - Accelerate to your own pace, when you hear the bell - look over your left shoulder and count how many hands I show (0/1/2), afterwards ride slalom around 2 cones (5 m distance between), brake safely before line. - Accelerate to 7 km/h and try to stay above, ride slalom around 4 cones (3 m distance between). The three cycles were instrumented to measure steering angle (deg), steering angle rate (deg/s), roll rate (deg/s) and cycle speed (km/h). The e-trike was the most stable (of the three cycles) from start to 10-12 km/h cycling straight forward. The three cycles were then rather equal at speeds up to about 20 km/h. The E-trike had the best braking capability. However, the e-trike was the worst at avoidance and slalom maneuvers. The e-trike prototype steering system was confusing for several participants. The cycle tilt (roll) angle influences the front wheel angle. The maximum steering angle was found to be too small in the slalom maneuvers. It needs to be increased. The participants were asked to answer a number of questions in a survey to further evaluate the cycling tests with the tree different cycles. The safety dimensions stability, maneuverability and comfort were covered by the questions as well as the overall safety impression. The e-bike came out as the best in this survey.The pre-study has shown that there is a safety (stability) improvement potential with the new e-trike concept, but the steering system must be adjusted. An encouraging comment by one of the participants in the experiment was: “The e-trike is really fun while riding, the maneuvering is easy. I think I would rank the e-trike the best for control and safety. It took some practice to learn to control the e-trike, but I still find it better than conventional bikes”.