Reversing starter
A reversing starter is a mechanical pull-wire starting device for small combustion engines , in which the starter rope is automatically pulled back into the starting position (reversed) after the starting process.
commitment
Pull starters are used in particular for hand-held tools , such as chain saws and brushcutters , or other low-power combustion engines, such as smaller generators (up to around 2.5 kW), lawn mowers and maritime outboard motors , pocket bikes or certain glow-igniter motors . Pull starters were also occasionally used for larger motorcycles. Engines that are started with a pull starter usually have a displacement of up to 700 cm³. For single-cylinder industrial engines, reversing start is the standard starting method up to a good 0.5 l displacement and a maximum of 9 kW, for gasoline engines up to 11 kW.
The purely mechanically functioning reversing starter means that more complex on-board electrics with parts such as starter battery , starter and alternator can be dispensed with in the equipment, which meets the requirement for low weight and simple construction. A simple magneto ignition , which is usually integrated in the combined flywheel and cooling fan, is sufficient for gasoline engines .
functionality
The reversing starter consists of a pull rope with a finger grip as a termination, which is wound on a rope drum on a freewheeling hub on the crankshaft stub of the engine - usually opposite the power take-off side of the engine . To start the engine, the rope is first slowly pulled out using the finger grip until the freewheel is "meshed" in the engine, then it is pulled further vigorously. The winding spool, which rotates as a result, acts on the crankshaft via the freewheel and takes it with it until the end of the pulling process, after which the rope is automatically returned to its starting position by a spiral spring. If you pull at sufficient speed, the number of revolutions required to start is exceeded. A decompression device is required for larger engines . Rarely there are (or have been) pull-wire starters in which the power is transmitted via a gear on a thrust thread, which is first engaged in the ring gear of the engine's flywheel by means of the thread and then drives the crankshaft.
Differentiation from simple rope start
The simple rope start also belongs to the group of manual starting procedures for internal combustion engines. d. Usually a pulley is mounted on the front free end of the crankshaft. You will need a starter rope with a handle on one end and a knot on the other. In one of the flanks of the pulley there is a recess into which the rope is inserted with the knot facing outwards and wound up in the direction of rotation of the motor. Then the handle is pulled briskly to start the engine.
With a rope start, diesel engines up to around 20 kW can be started (according to the manufacturer's instructions), with petrol engines correspondingly larger due to the lower compression resistance. Large motors are turned against the compression resistance against the direction of rotation of the motor, then the rope is pulled until the motor runs against the next compression resistance. The motor bounces and runs back, the rope is released in a controlled manner so that it rewinds on the pulley. As soon as the motor has hit the first compression resistance again and bounces forward, this extra momentum is used to pull the rope with more speed. In this way the engine is rocked until you overcome the compression resistance with one last strong pull and start the engine.
Rope launch is cheap to manufacture because it requires minimal engine work, is quite dangerous and requires a lot of practice, especially with larger engines. At least in Europe, rope start is therefore banned (by employers' liability insurance associations) and is practically impossible to find. Especially at the recess in the sheave next to the knot, the rope is often damaged and can break, causing the operator to fall backwards. Often the rope was repaired unprofessionally, replaced by unsuitable other ropes, so that it could get stuck in the groove of the pulley and the rope was taken along by the running engine. In extreme cases, this can lead to the operator's hand being pulled into the running machine.
