The split-single, colloquially referred to in the United States as a twingle, is a variant on the two-stroke engine with two cylinders sharing a single combustion chamber. Externally, the "single-cylinder" version looks much like a regular single cylinder two-stroke engine with a single carburettor, single exhaust and single sparkplug. "Twin cylinder" versions with four bores have been made, working on the same principle.
Contents |
Principle of Operation
The split-single system sends the intake fuel-air mixture up one bore to the combustion chamber, sweeping the exhaust gases down the other bore and out of the exposed exhaust port.[1] The split-single two-stroke thus delivers better economy than the common forms of two-stroke (and runs better at small throttle openings) at the cost of an engine that is heavier.[2] The lubrication weaknesses of the two-stroke remain, as does most of the pollution.
History
Origin
The first split-single engine was patented in 1912 by Alberto Garelli and he produced a 346 cc version to use in motorcycles. His Italian Garelli Motorcycle company is a successful modern manufacturer but it quickly moved to more familiar versions of the internal combustion engine.
Puch
In 1923, Austrian manufacturer Puch started using this layout, with the same Y-shaped connecting rod that Garelli had used. In 1931 they won the German Grand Prix with a supercharged version, though in subsequent years they were somewhat overshadowed by DKW.[3]
In 1949 Puch switched production to a design by Giovanni Marcellino that used a more complex system of two connecting rods and they continued making these engines until 1970.[4] This system benefits from asymmetrical port opening (without con-rod flexing), not available to regular two-strokes.[5] The Puch was sold briefly in the US as the "Allstate 250 1967" where Sears called this engine system the "Twingle".[6]
DKW
In 1931 split-single engines produced by Ing Zoller were used in motorcycle racing and helped DKW dominate smaller motorcycle racing classes between the wars.[3]
TWN
The German Triumph (TWN) company produced the BD 125H, BDG250,BDG250H,(H standing for Hinterung suspension)BDG250 S (Sport) and BDG250L (Luxus) 200cc Cornet and 350cc Boss . They also produced a double up version of the 125! now that is a 4 piston (kolben) 4 cylinder ,2 carb, 2 plug motor ,but its performance was only slightly better than a confentional 250 so with more cost for the same performance it was only a prototype and never went into production. using Garelli's original Y-shaped connecting rod but ceased production in 1957 after only a few years.
Trojan
The famous Trojan two-stroke, as used in the British Trojan car is effectively the same thing. It was first produced in 1913, photos of a 1927 "twin" model at the Science Museum show the V-shaped connecting rod - the "fore-and-aft" layout of the cylinders mean that this conrod had to flex slightly with each revolution, a quite unusual mechanical feature.[7] Unlike the motorcycle variants, this one was water-cooled.
Regulation implications
In some countries, for vehicle taxation purposes the split-single suffers no penalty and offers no advantage, as only the swept volume is considered, not the number of cylinders or spark-plugs. (This remains true even if the two pistons are not the same size and have slightly different strokes).
Notes
- ^ Diagramatic split-single Fuel-air circulation and the Y-shaped connecting rod.
- ^ Sammy Miller Museum Split-single torque and economy rival that of a four-stroke.
- ^ a b Puch split-singles from 1923 and racing success with the Monza.
- ^ Puch Classic Motorcycles 1960 Puch Split Single 250cc, four-speed manual.
- ^ Puch's two-stroke double-piston engines Diagram of the asymmetric port opening obtained by both Garelli and Marcellino systems.
- ^ Sears Allstate 250 1967 Puch sold in the US, engine system called "Twingle".
- ^ Trojan Two-stroke 1927 Science Museum photo of split-single with V-shaped Connecting Rod.
See also
|
||||||||||||||||||||
|
||||||||||||||||||||
External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
