Lexicon DIY-Knowledge

Transmission, mechanical

Getriebe, mechanisch

Reductora mecánica

Engrenage, mécanique

With mechanical transmissions you can influence the power tool speed as well as its torque. Several types of transmissions are available:

Single-speed transmission
The relatively high motor speed of a universal motor is reduced to match the desired operating speed. Just about all power tool transmissions reduce motor speed in accordance with the following formula:

If the desired spindle speed cannot be obtained in one step (for constructive reasons), a two-speed transmission is used. Slow spindle speeds of, for example, powerful drills or stirrers can often be obtained only by using a three-speed transmission. Transmissions with several speeds are more complex, but often the only possibility to obtain high reduction ratios in narrow spaces.

Two-speed manual transmission
The number of transmission steps is increased by adding another gear pair with a different transmission ratio to serve as second speed. The torque is calculated by using the formula (EWL-G008/G).

Three-speed manual transmission with two forward speeds and one reverse speed
The existing first and second forward gears are complemented by a reversing gear with mechanical change of the direction of rotation. Rotational speed and torque are approximately those of the first gear.

The types of transmissions mentioned so far can only be used to change gears during standstill or when the machine is coasting. Synchronised transmissions or draw-key transmissions must be used to change gears at full speed and under full load.

Draw-key transmission
are manufactured with two or three speeds; however this special construction allows only gear shifting under load from the higher to the lower speed, and not vice-versa!

Synchronised transmissions
are also made with two and three speeds. Synchronised transmissions allow gear changes at high speed and under full load.

Fully synchronised transmissions
allow gear changes at any speed, and also under load and during standstill.