The Diesel-Zarlatti locomotive was a prototype railway locomotive, built in Italy in 1929, which adopted a hybrid diesel-steam transmission system.
History
In the 1920s, there was a search for alternatives to the
steam locomotive for railway traction, to reduce cost and improve efficiency. The main alternatives were
railway electrification or the use of an
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal c ...
, such as the
diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...
.
A disadvantage of the internal combustion engine was the need for a transmission system. One option to be explored was the conversion of an existing steam locomotive by fitting a diesel engine and an
air compressor
An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces m ...
to supply compressed air to the existing steam cylinders. This was the constructive principle on which the Zarlatti locomotive was based. It may be seen as a development of the earlier
Mekarski system
The Mekarski system was a compressed-air propulsion system for trams invented by Louis Mékarski or Louis Mékarsky (the correct spelling is uncertain) in the 1870s. He worked in France, was born in 1843 in Clermont-Ferrand (center of France) ...
.
Between 1928 and 1929, FS steam locomotive number
910.042 was modified at the Royal Arsenal of
La Spezia to test the system, which was based on the patents of the inventors Fausto Zarlatti and Umberto Simoni. If the system had been a success, it could have led to the modification of a large number of FS steam locomotives and the avoidance of the need to build new locomotives.
The tests took place on the
Rome–Lido railway
The Roma–Lido railway is an urban railway line connecting the Porta San Paolo Station in Rome to Lido di Ostia, Rome's seaside neighborhood.
The railway is long, stops at 13 stations and carries on average over 90,000 passengers per day.
Hi ...
from 6 April to 25 April 1929 with 16 round-trip pairs. The maximum speed reached with a tail load of 101 tonnes was 74 km/h.
[http://www.trenidicarta.it/pdf/13/13637.pdf ] The experiment had some success but there were problems: On 17 April, the piston of the engine water circulation pump broke and on 23 April a pipe attached to the
Westinghouse brake compressor became detached. The experiment, for these reasons, was not pursued.
Technical features
The boiler and superstructure were removed from the locomotive in the arsenal workshop at La Spezia but the original compound expansion steam cylinders were left in place. A six-cylinder,
two-stroke
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...
, diesel engine built by
Fiat-San Giorgio was installed. This engine produced 325 hp at 450 rpm and drove a rotary compressor, built by a Swiss company in
Winterthur
, neighboring_municipalities = Brütten, Dinhard, Elsau, Hettlingen, Illnau-Effretikon, Kyburg, Lindau, Neftenbach, Oberembrach, Pfungen, Rickenbach, Schlatt, Seuzach, Wiesendangen, Zell
, twintowns = Hall in Tirol (Austria ...
, which delivered compressed air at 8 bar pressure. A small
naphtha
Naphtha ( or ) is a flammable liquid hydrocarbon mixture.
Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ' ...
-fired boiler with a heating surface of 52 square metres was also installed for the production of steam. Cooling water from the engine and compressor was fed into the boiler at about 70 °C. For cold starting, the boiler was used to preheat the diesel engine. When the locomotive started from rest, the original steam cylinders were fed with steam alone, but when running they were powered by a mixture of steam and compressed air. The steam was needed to prevent the cylinders icing up, because compressed air cools when it expands.
See also
*
Steam diesel hybrid locomotive
A steam diesel hybrid locomotive is a railway locomotive with a piston engine which could run on either steam from a boiler or diesel fuel. Examples were built in the United Kingdom, Soviet Union and Italy but the relatively high cost of fuel oil, ...
References
{{reflist
Experimental locomotives
Hybrid locomotives
Italian inventions
Scrapped locomotives