The names of both neutral transmission and those discussed below are quite clarifing. So in relation to this type, the main parameters - rotation speed and torque remain unchanged. To get a neutral gear, just use the same and equal parts. If we are considering a gear, then both gears should have the same number of teeth. If we consider a belt drive - the pulleys should be the same diameter.
In the case of a gear transmission, the direction of rotation changes to the opposite (subject to the use of two gears), but if we are talking about a belt driving, then the direction of the driving and driven pulleys will coincide. If the task is to change the direction of rotation of the pulleys - it is necessary to make the belt cross (in the form of a figure eight).
Speed up gear
The speed up gear got its name due to the fact that the rotation speed of the driven axis and the actuating element on it (for example, the wheel) increases compared to the rotation speed on the driving axis. Simply put - we increase the speed. It is easy to notice that the number of teeth of the driving gear is greater than the number of driven gear, which is why the effect of increasing speed arises.
However, with increasing speed, the value of the torque decreases (the value of the force and traction). Therefore, if we want to make a racing car, then we apply a speed up gear.
Speed down gear
In turn, a speed down gear is the case when we are talking about a decrease in the speed of rotation of the driven axis compared to the driving axis. Simply put, we are reducing speed. The theory of the number of teeth is valid in this case as well - the driving gear has less of them.
However, as the speed decreases, the value of the torque increases (the value of the force and traction). Therefore, if we want to make a tractor, then we apply a speed down gear.