2.3. Dynamic positions
Front suspension travel: 200 mm
Rear suspension travel: 55 mm
2.4. Weight
Mass: 38 kg (without driver), 118kg (with driver)
Weight: 441 N; 48% on the front axle, 52% on the rear axle
Centre of the gravity without driver apportioned approximately in equal parts to the front and rear axle. But if there is a driver on the bike, force on the rear axle is higher than at the front. For distribution of the force equally between front and rear axles, we placed in front of the user a battery and a box for pizza.
3.1 Chassis frame
Exploring a lot of frame structures and materials, we chose duplex titanium frame structure.
The main advantages of the duplex titanium frame structure are lightness, simplicity and ruggedness. By using tubes with the bigger diameter on 10 mm than steel tubes we reached the goal to make our frame rigid as a steel frame (because strength limit of titanium is less than it has steel). The larger diameter - the larger contact area among tubes in a welding place, means the larger ruggedness of the frame structure. But titanium tubes are lighter on 43% than steel tubes. Consequently, by using titanium tubes we made rigid and light frame. Let’s watch the simulation frame video about axial stress and bend.
Minimum coefficient of the strength margin=1.9
Static analysis
3.2 Rear suspension
For analyzing rear suspension geometry we use Linkage Personal Version software. Also we explored the rear suspension geometry of MIG-1 and MIG-2 and we decided that applying of only one pendulum and rear spring are not enough for stiffness of the frame structure.
If we will make more difficult structure of the pendulum, bike’s weight will rather increase. That’s why we decided to use rear single hinge suspension. It consists of the pendulum, the cross slide extension, the rocker actuator and the spring. This kind of suspension is more effective for moving on the road through the obstacles. The pendulum is made of steel sheets, which depth is 2 mm, bended for achieving needed shape. The torque from the pendulum is transmitted to cross slide extension and then it goes to rocker actuator through the hinged connections. Thanks to the device as cross slide extension we can use lighter spring, which will has an equal spring stiffness as a hard and strong spring. The rocker actuator has leverage 1:1. It is made from aluminum. It changes line of action force for ride quality. Finally, changed torque turns into the compressibility of the rear spring. In such way, bike’s rear suspension is not heavy, and it is effective for city roads because of the ride performance.
Front suspension
In front suspension we use Marzocchi 888 RC3 EVO V2'14 fork. RC3 EVO has an adjustable rebound, high speed compression, volume and stiffness. The fork has an adjustable compression rate, which allows you to configurate the plug so it`s in all conditions the wheel will have constant contact with the ground, leaping backward over rocks and roots, and consequently will improve the handling of the bike and your safety. An adjustable high speed compression (is automatically adjusted during adjustment of the speed of compression) is triggered during a sharp impact and triggered on the last 3-4 cm of stroke, preventing a hard blow, and as a consequence loss of control.
