Basics
If the chain expands and contracts with temperature, the system needs some means to absorb it. When you use a chain in a high-temperature envi- ronment or to convey high-temperature objects, the chain becomes hotter and the length increases at about the same ratio as its coefficient of linear expansion. When the temperature is between 0˚ and 300˚C, and 1 m of chain is heated by a value of 100˚C, the chain elongates by about 1 mm. If you want to allow for this elongation with take-up, you must be careful about the following points or the chain may fail: • In the case of chain temperature increase, adjust take-up after the temperature increase. • In the case of chain temperature decrease, adjust take-up before the decrease. In the case of chain temperature change, the take-up should be designed to absorb the elongation or the contraction of the chain. If you don’t drive the chain in reverse, it is more convenient to design a catenary section and collect the elongation in that part. In that case, it is also beneficial to design a take-up. Figure 2.25 shows an example of a design with catenary and take-up. It is very annoying to continuously adjust take-up. Sometimes it is possible to use self-adjusting take-ups by hanging a weight or using a hydraulic power cylinder instead of adjusting the take-up. However, the chain receives addition- al tension by doing this (sometimes the motor capacity is also influenced), so don’t forget to check the chain strength as well as the motor capacity. Another point about take-up is that if you drive the chain in reverse while carrying objects, the take-up receives the load as if it were a driving part. In this situation, you must select and design take-up with consideration for its strength.
Driver Sprocket
Take-Up
Roller Catenary Support
Figure 2.25 Catenary Take-Up
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