The SIT VARIO belts are used for high power transmission on variable speed drive systems.
The variable speed pulley is a well established drive; designed to give continuous speed variation at a comparative low cost. Unfortunately, it is well known that this design is subject to excessive flange wear due to the type of drive systems employed.
The hub is made from induction hardened steel, hard chrome plated and ground to give uninterrupted slide fit with flanges. Keys are not used with this application. Moving flanges give a wide contact area therefore eliminating uneven belt pressure. The pulley flanges are coupled by means of nylon (6,6) sleeve couplings to the outside of the flanges and by two flats machined on each end of the pulley hub. Two springs situated inside the nylon coupling give the desired pressure.
Fixed driven pulley have been specifically designed to be used with VAR pulleys. They are manufactured in grey cast iron (GG20 -GG25) and are treated with a black manganese phosphating process.