Bicycle wheel To accomplish this, wheel designs are employing lighter rim materials, moving the spoke nipples to the hub or using lighter nipples such as aluminum. Note however that rotational inertia is a factor only during acceleration (and deceleration/braking). At constant speed, aerodynamics are a significant factor. For climbing, total mass remains important. See Bicycle performance for more detail. The hub flanges of modern tension-spoked bicycle wheels are always spaced wider than where the spokes attach to the rim. When viewed in cross section, the spokes and hub form a triangle, a structure that is stiff both vertically and laterally. In three
Reaction wheel temporary changes in its speed result in small changes in angle. The wheels therefore permit very precise changes in a spacecraft's attitude. For this reason, reaction wheels are often used to aim spacecraft carrying cameras or telescopes. Over time, reaction wheels may build up enough stored momentum to exceed the maximum speed of the wheel, called saturation, which will need to be cancelled. Designers therefore supplement reaction wheel systems with other attitude control mechanisms. In the presence of a magnetic field (as in low Earth orbit), a spacecraft can employ magnetorquers (better known as torque rods) to transfer angular momentum