The resistance of telescopic tubes is calculated by verifying the maximal torsion that the tube can hold before the so-called yield point; therefore it is directly connected to the area of the section of the tube. The driveshaft must be chosen so that the torque required by the final application is lower than the hoop stress bearable by the tubes.
The telescopic tubes allow to adapt the driveshaft to the distance oscillations between the two PTOs; therefore the capacity to axially slip under pressure generating low telescopic thrusts is very important and, for this reason, the lubrication of the telescopic parts is essential to calibrate the wear and to reduce the axial thrusts.
Eurocardan offers a wide range of telescopic solutions that allows the motion transmission in several applications:
- Triangular tubes: they are the best solution for standard applications, that require a correct balance between torque and axial thrust. The coupling of the two tubes (internal and external ones) is allowed in just one phase position.
- York tubes: York profile allows the transmission for harder applications , characterized by more frequent torque peaks. Furthermore the particular profile with pipes for grease allows a better distribution of the grease between the external tube and the internal one; it also has the function to keep the grease for a longer time. The coupling between the two tubes (internal and external) is allowed in just one phase position.
- Grooved tubes and driveshafts: they are used for applications characterized by high torque peaks, as well as by significant extension of the driveshaft (more than other tubes) and by frequent axial slippages.
- Lemon tubes (German standard): they are the best solution for standard applications that require a correct balance between torque and axial thrust. The coupling between the two tubes (internal and external) is allowed two phase positions.
- Star tubes (German standard): thanks to a special section with 6 point of contacts, they grant a better torque transmission if compared with lemon profile. The coupling between the two tubes (internal and external) is allowed two phase positions.
Furthermore to improve the resistance to wearing and axial slippage, there are two kind of treatments:
- TEMPRA: this treatment is carried out only on the internal tube and it grant a better surface hardness as well as a better torsion resistance. Tempered tubes are particularly recommended for very abrasive conditions.
- RILSAN: rilsanized tubes allow to reduce the friction coefficient up to 50% if compared to the normal metallic surfaces and this also makes it possible to reduce the axial thrusts. These tubes are particularly recommended for applications requiring frequent axial slippages under load, like for example in the case of towed vehicles.