Winch is a crank with a handle for giving motion to a machine. Winch gears are used to convert the high speed, low force input of the handle into low speed, high torque output at the drum. These are quite highly developed and use tooth forms that are significantly different from those found in other gear applications such as car gearboxes and power transmission.
The loads on winch gears are actually high while the speeds they turn at are relatively very low. This results in thick strong teeth that resist high loads as well. The winch gears are not long lasting and have low efficiency. The winches turn few thousand times in their entire lives and they never go fast enough to get hot.
There are three common gearing systems in winch gear system, spur gear, worm gear and planetary gear. They all do the same job, gear down the high-speed motor to a low speed high torque winch drum. The gear reduction ratio is by how much the motor's output revolutions are reduced for the spindle. The greater the reduction, the more revolutions the motor has to turn for one spindle revolution and less the motor has to work for that revolution. The worm gear has a transfer efficiency of 35-40% which causes the winch to be self-breaking even under heavy loads. The spur and planetary gear systems have efficiencies of 75% and 65% respectively. They have a tendency to free spool when loaded; therefore a braking mechanism is needed.
Maintenance and Care
A broken winch cable can have enough force in its whiplash to cut through a truck's roof and windshield. A cable that hits a small tree will tear the tree down. If a cable breaks, solid objects such as hooks and snatch blocks will fly. People should stand well out of range of the cable and never stand downhill of any vehicle being winched.
Winch should be maintained on a regular basis. All required points should be lubricated well. All mounts, pulleys, straps and clevis pins must be inspected and checked that they are not damaged and free from moisture. Cable must be lubricated with a chain and cable lubricant.
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