Auxiliary engine

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Bicycle "Friesenkönig" from East Friesland with auxiliary engine, built in 1945
Auxiliary motor for manual activation

An auxiliary engine is an engine that is not intended for permanent, but only for temporary use to drive a vehicle . The vehicle can also be used as intended without the engine.

Bicycles with auxiliary motor

Rex bike with auxiliary motor on the front wheel

A well-known example of the concept of a bicycle with an auxiliary motor is the Vélosolex . But this was more of a moped.

Another example is the Saxonette , which was once equipped with the wheel hub auxiliary motor of the same name, which was produced from the 1930s to the 1960s , and has been in production as a modern Saxonette since 1987 .

But there were also many other manufacturers such as B. Berini M13 ("The Egg") Rex ("Rex on the Belt") Victoria Vicky, Flink, MAW ("Hühnerschreck", GDR ) and Lohmann (FRG). The special feature of the Lohmann engine was that it was not a gasoline engine , but an 18 cm³ multi-fuel two-stroke compression-ignition engine.

The electrical system used in so-called pedelecs is relatively new .

Boats with auxiliary engine, lull slide

NSU KKM 150 built as a dump valve for sailing boats, single-disc
wankel engine , 150 cm³, 18.5 HP, Museum Autovision

From the 19th century onwards, auxiliary machines were occasionally installed on sailing ships as auxiliary drives. The first ship's steam engines at the beginning of the 19th century had efficiencies of one to five percent, i.e. H. for the exclusive steam operation (instead of sails), almost the entire hold should have been used to store the coals. Therefore they were not used for sea operations on long voyages. However, they were well suited for short-term bridging of lulls and especially for single propulsion during difficult maneuvers in narrow fairways and when berthing and casting off (maneuvering operations).

At the turn of the century, instead of steam engines, diesel engines were also used as an auxiliary drive on large sailing ships. The efficiency was significantly higher, there was no steam boiler and the diesel oil was bunkered in tanks (double floor) that were not suitable for cargo hold purposes. With a suitable arrangement, the liquid fuel could also be used for ballast , as it could be quickly transported to other tanks with pumps.

Auxiliary engines on small watercraft (colloquially sometimes laziness slide ) are usually outboard engines , which, unlike a built-in machine, are attached to the outside of the stern of the boat. Some larger sailing boats can also accommodate auxiliary engines in a specially reserved shaft ( shaft motors ). Outboard motors are available as two-stroke and four-stroke engines as well as battery-operated electric motors . Ships longer than about 10 meters, on the other hand, are built almost exclusively with built-in diesel engines.

The engines are mainly used when maneuvering in harbors or narrow entrances, in light winds, in current areas or, if time is short or the crew is impatient, in calm. Mooring and casting off maneuvers are rarely done under sail these days. Such maneuvers are very demanding and the smallest mistakes can lead to damage to your own or other ships. In many ports this is therefore prohibited or impossible due to the limited space available.

On motor ships, the term auxiliary engine (donkey engine) stands for all machines set up in the engine room or similar rooms, apart from the main engine, which, in some complex systems, guarantee the conditions for trouble-free ship operation. These auxiliary systems are used to generate electricity , ballasts, drainage, fire fighting, cold generation , air conditioning , ventilation, drinking water supply , fuel cleaning ( separators ), lubricating oil cleaning, waste water treatment, heating and preheating ( heating steam system ) and in the future also for exhaust gas cleaning and ballast water treatment . While on most sailing boats the engine is completely switched off while sailing, an additional generator is also used on large or luxuriously furnished yachts, which supplies the boat with the necessary electricity.

Gliders with auxiliary engines

Schempp-Hirth Ventus cT with unfolded auxiliary motor

The auxiliary engine in a glider ( homecoming aid , colloquially known among glider pilots as a turbo or lull slide ) is usually a two-stroke engine designed as a retractable engine. A four-stroke engine or a small turbine is also rarely used, but there are also projects in which an electric motor is to be used. The engine output is between 10 and 30 kW, depending on the size of the aircraft, and is sufficient for climb rates of approx. 0.5 to 1.5 m / s. A self launch on the airfield is therefore not possible; the engine is only used to avoid an outland landing if there is no thermal . Depending on the type of aircraft, the range in sawtooth flight is between 200 and 600 km.

There are such engines with foldable (e.g. the Schempp-Hirth T-models (after Prof. Claus Oehler), see picture) and rigid propellers (e.g. LS8-t , DG Flugzeugbau DG-1000 ). Many of these engines do not have a starter, but start the engine after being unfolded using the windmill effect .


  • Auxiliary engines, city slides and moped dreams. The history of small motorization . Podszun, 2003, ISBN 3-86133-320-1
  • Bicycle motors, chair wheels & scooter rarities. New stories of small motorization . Podszun, 2003, ISBN 3-86133-392-9
  • Stuttering bikes - street speedsters. German auxiliary bicycle engines from the 1950s . Isensee-Verlag, Oldenburg 12/2007, ISBN 3-89995-462-9

See also

Individual evidence

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