Steering
Wire locking or Safety wiring
Safety wiring should be threaded though a hole in the head of a fastener, twisted on itself with a twisting tool and then around a fixed part that the fastener is retaining so that any movement of the fastener to loosen (rotate anti-clockwise for a right hand thread) increases the tension on the locking wire.
Two adjacent fasteners fixing the same component can be wired to each other provided the fasteners increase tension in the lock wire if either try to loosen. The locking wire should not be tied between the fastener and another component that can move relative to the fastener. In particular a shackle pin head should be fixed to the leg of that shackle and not to the component the shackle is attaching.
For a turnbuckle the screw should be fixed with a locknut before the turnbuckle eye or clevis is wired to the turnbuckle body (or hole through the rigging screw body) on both sides. The twisted wire between the eye and body should run in a spiral in the correct direction to prevent the eye from unscrewing - noting that the ends have handed threads - LH on end RH other end.
Chain and sprocket steering system
The chain and sprocket system uses a chain and sprocket to convert rotary motion on the steering wheel to a linear motion on the steering cable. Typically there is an angle of wrap on the sprocket of 180 degrees so provided the rope is tensioned the chain cannot jump as the chain would break before the chain and rope can stretch enough to rise up the teeth. The chain and sprocket is therefore limited by the load capacity of the chain. If there is a failure further down the line it is important to have a chain guide fitted to the sprocket. Many earlier production boats did not have this fitted at the time of manufacture and is an easy addition to early sprockets.
Steering cables and pulleys
The steel can either be a high carbon steel or 316 (Austenitic) stainless steel. The carbon steel is generally galvanised to prevent corrosion and is generally stronger than stainless steel. The stainless-steel wire is significantly more prone to fatigue than carbon steel. Rope fatigue failure is mainly caused by the rope bending and straightening as it runs over a pulley sheave or drum. As the outer strands need to stretch more than the inner strands the first indications of fatigue is always when the outer strands start to break. The smaller the bend radius the bigger the difference in stress between the bent state and straight wire or stress amplitude. The higher the stress amplitude the fewer cycles to failure. To limit this form of fatigue the sheave radius should be more than 28 rope diameters (for 7/19 wire rope) or 112 mm for 4 mm rope and 140 mm for 5 mm rope.
If the outer strands are seen to be broken or frayed the rope should immediately be replaced. It should be noted that the rope running around the thimble is only bent around the thimble when the ends are made and are not repeatedly bent, this area is not prone to fatigue. The thimble is principally there to prevent wear or fretting to the rope.
