With the advent of the Diesel engine, which was correctly called petroleum engine, the gas machine of Otto was now referred to as the gasoline engine (Benzin Gasmaschine).

With the revocation of the four-stroke patent the four-stroke engine was widely adopted as the dominant as a guarantor for a smooth and shock-free operation. Apart from Benz & Comp, who were showing a two-stroke engine, all exhibitors were showing four-stroke engines.


Nine companies were exhibiting 27 gas engines in practically 10 different models. The smallest gas engine with 1/8 horse power and the most powerful, a twin cylinder engine, with 25 horse power.

The in every other way excellent Deutzer gas engine, the slide plate for controlling the intake of air and compositional gases and the exhaust of the combustion residues constitutes a serious disadvantage as the fine channels in the slide plate clog with dirt and need permanent cleaning. Also the slide plates inertia seems to limit the speed of the engine. Therefore, apart from a second exhibitor, the other seven exhibitors had equipped their engines with valves for intake, exhaust and ignition flame. 

Most manufacturers abandoned the sliding plate ignition system of Deutz and are now using valve ignition system. Also the oldest kind of ignition for gas machines, the electrical spark system is having a revival in form with a supply voltage generated by a dynamo.

Speed control is mostly performed according to the Deutzer gas machine by interrupting the supply with combustion gas for individual working cycles. Surprisingly the most obvious way of speed control, the reduction of the amount of supplied gas mixtures, is not used. 

Another manufacturer had made the experience that when air and combustion gas are not mixed well in the cylinder the pressure in the cylinder may be around 4 atmospheres. In contrast hereto an intimately mixed gas will yield a pressure of 10 to 15 atmospheres, which lowers the consumption. The intake valve was controlled such that it will only be opened if the engine requires gas. If this is not the case the exhaust valve is opened instead to allow the cylinder to suck in exhaust gases. With this method the consumption of a 4 horse power gas engine could be reduced to 0.885 cubic meter per horsepower and hour. The water consumption for cooling was only 31 liter per horse power and hour, whereby the water temperature was increased from 15°C to 60°C. This model propelled a piston pump that was connected by a reduction gear to the gas engine for pumping water.

The consumption of the mentioned double cylinder engine was advertised as 0.7 cubic meter illumination gas per horsepower and hour.

source: "Dingler's polytechnisches Journal" 1888, Band 270, pages 60-73


It is interesting that the competitors did not stop at copying the four-stroke engine, which was no longer under patent protection, but introduced various improvements to their engines to win market shares. Some of their ideas were also subject of patent applications. 



Market penetration of the four-stroke engine

Otto's four-stroke engine obviously dominated the market of small engines from 1877 to 1885. With the absence of patent protection they now had to face at least 17 competitors. According to a contemporary estimate in Germany  43,370 stationary steam engines were deployed in Germany in 1888. This compares with about 14,000 small steam engines to 28,000 gas engines.

An attempt to establish water (pressure) driven engines in the cities was less successful as apart from the water supply prices in Munich and Zurich the municipal water was too expansive. An installation in Hull delivered water at a pressure of 50 atmospheres for 1 Mark per cubic meter. Two installations in London deliver at the same pressure 1 cubic  meter of water for 1,80 Mark. 1 cubic meter of water at a pressure of 50 atmospheres provides per hour a power of 1389 Watt or 1.9 horse power. 1 horse power of provided energy comes therefore at a cost of 0.95 Mark in London. For a small motor the efficiency probably was not better then 75%, so that 1 horse power of usable energy cost around 1.25 Mark. On the other hand, one only had to pay for the energy used and not for the time no energy was consumed. Water engines were however simple to use as only the water valve had to be opened or closed to put them in action. In London and Hull they were mainly used for lifting devices as here the use of pressure was used in the most efficient way.  

Electrical motors were available form 1/2 horse power to 12 horse power. The costs for electrical energy was also still too high ( 0.38 Mark for a one horse power machine per hour) although the purchase prices for electrical motors are only half of comparable gas or steam engines. That should have made them at least compatible with gas machines, but probably the lack of central electricity power stations was the main reason that they were not used more often.

Since 1884 attempts were made in Paris, Birmingham and Leeds to centrally produce vacuum or high air pressure and distribute it via pipes. For example one installation of a vacuum supplier in Paris has a total length of 2500m  with 200 connected costumers. Another air pressure supplier uses 6 steam operated pumps of each 341 horse power to deliver 200,000 cubic meter in 24 hours.

source: "Ueber Kraftverteilung von Centralstationen" Dingler's polytechnical Journal 1888, Band 272, S.97-115.