Block rollers

Block rollers are used to change the direction of force when lifting loads. We also include various blocks with a rope fixation passing through the roller, tandem carriages for moving along anchor lines, and polyspast blocks.

Block rollers are a wheel (roller) with a groove around the circumference that rotates around its axis. The groove is designed for a rope, cable, rope, etc. The axis of the block is contained in a holder (cheeks). If the holder is attached to a beam or wall, such a block is called stationary (i.e., the axis of the block is fixed); if a load is attached to this holder and the block can move with it, such a block is called mobile.

In a real block, there are always some losses, so the efficiency (efficiency) of a block-roller is always less than unity. The efficiency of block-rollers (the ratio of the mass of the lifted load to the applied traction force) increases with:

increasing the diameter of the roller pulley (due to a decrease in the bending stress of the working cable/rope or the resistance of the rope stiffness brought to the block rim);

reducing the friction of the roller rotation on the axis due to the use of rolling or sliding bearings. (However, the maximum working load on a roller with a sliding bearing is often higher than on a roller with a rolling bearing);

rigidity of the cable: when the rope moves, the stationary block is driven into rotation by friction forces that arise between the ropes and the stream (groove) of the block. Due to the stiffness, the rope does not immediately enter its stream when it runs into the block, and does not immediately assume a straight position when it runs into it.

The pulleys and cheeks of the block rollers are made of steel or high-strength aluminum alloy, and the axles are made of high-alloy heat-treated steel.