The mechanical transmission is the complex of organs able to transmit the engine power in mechanical systems.
Some of these power transmission components (like trees, couplings and joints …) convey the power without changing the laps numbers, or by keeping constant and equal to one transmission ratio: are coaxial shafts.
Other transmission organs, by the contrary (sprockets or smooth wheels, chains, belts), can achieve transmission ratios other than one, icrementale variables continuous (continuous variable) or step by step (change).
The reasons why a machine needs to transmit a varied are manifold: for example, is the case of reciprocating endothermic motors four-stroke, where the cam shaft must be rotate with speed equal to the half of the one of crankshaft.
The choice of the type of power transmission components to use is determined by the specificity of individual applications; the variables that most influence the choice are:
– distance between the trees
– end-outline marker
– power to be transmitted, speed of operation,
– gear ratio to be achieved,
– motor characteristic
– user characteristics
– cost
– maintenance needs.
For example, is typic the case where lesser ratio transmissions are necessary to connect a fast engine to a slow user: is often convenient and necessary that the engine developing power at high speed, while the speed of the user is lower and not editable for functional needs.
Among the transmission components, friction wheels are best suited to convey small powers (few kW) between parallel or incident shafts, but not too far away from each other.
If used in optimal conditions, the friction wheels can have high efficiency; however the transmission is limited by the material that composed them.
The need for a high grip imposes the use of rubber or leather, that have a high coefficient of friction; the need to endure high pressure forces the use of metallic materials, with less friction coefficients.