Axle vs. Shaft
Both serve the purpose of supporting rotating machine parts.
- Axles do not transmit torque.
- Shafts transmit torque.
Examples on a bicycle: The wheel hub sits on an axle, and the pedal crank sits on a shaft.
Sliding vs. Rolling bearing
Both serve the purpose of guiding moving components against each other.
- In sliding bearings is a lubricant between both components.
- In rolling bearings are rolling elements between both components.
The abrasion in rolling bearings is lower than in sliding bearings.
Gear vs. Belt drive
Both serve to transmit torque between multiple shafts.
- In gear drives, the shafts are directly connected through their gears.
- Cog wheel drives: form-fit → no slip
- Friction wheel drives: force-fit → with slip
- In belt drives, the shafts are connected by a belt.
- Cam chain & Cam belt: form-fit → no slip
- Flat belt & V-belt: force-fit → with slip
Belt drives allow larger shaft distances, but gear drives require less space.
Globe vs. Plug valve
Both control the flow of gases and liquids.
- In a glove valve, the closure element is moved more or less onto a sealing surface.
- In a plug valve, the closure element has a passage opening only in one direction.
The typical cold water tap is actually a glove valve and not a plug valve.