At first Knight tried making the entire engine cylinder reciprocate to open and close the exhaust and inlet ports. Though he patented this arrangement, he soon abandoned it in favor of a double sliding sleeve principle. Backed by Chicago entrepreneur L.B. Kilbourne, an experimental engine was built in
Oak Park, Illinois in 1903. Research and development continued until 1905, when a prototype passed stringent tests in
Elyria, Ohio. Having developed a practicable engine (at a cost of around $150,000), Knight and Kilbourne showed a complete "Silent Knight" touring car at the 1906
Chicago Auto Show. Fitted with a 4-cylinder, engine, the car was priced at $3,500.
Knight engine Knight's design has two cast-iron sleeves per cylinder, bronze in some models, sliding inside the other, with the piston inside the inner sleeve. The sleeves are operated by small connecting rods actuated by an eccentric shaft and have ports cut out at their upper ends. The cylinder head (known as the "
junk head") is like a fixed, inverted piston with its own set of rings projecting down inside the inner sleeve. The heads are individually detachable for each cylinder. The design is remarkably quiet and the sleeve valves need little attention. It was, however, more expensive to manufacture due to the precision grinding required on the sleeves' surfaces. Continental declared the Single Sleeve-valve engines were cheaper and easier to manufacture than poppet valve motors, even though it used more oil at high speeds and was harder to start in cold weather. The engine's design allows a more central location for the spark plugs to provide a better flame path, large ports for improved gas flow and hemispherical combustion chambers that in turn allows increased power. Additionally, the sleeve valves required very much less maintenance than poppet valves of the era, which needed adjustment, grinding and even replacement after only a few thousand miles. However, the adiabatic and isothermal characteristics accompanying the increased power afforded by the large (relative to contemporary poppet valve designs) port areas in the sleeves proved the double-sleeve valve concept's Achilles heel. Much of the advantage to be gained from increased volumetric efficiency could not be realized due to the inability to transfer resultant heat in a sufficiently steep gradient to avoid excessive internal temperatures, however, Harry Ricardo pointed, about the single
Sleeve-valve, Burt-McCollum type, that as long as oil film between Sleeve and cylinder wall is kept thin enough, sleeves are transparent to heat. As a consequence of these thermal conditions, and contrary to conventional practice, the induction port area was reduced to substantially less than that of the exhaust port. Later engines having thinner, steel and white-metal coated sleeves possess improved levels of heat dissipation, but thermal transfer problems remain characteristic of the design, thus limiting development of the potential inherent in the double-sleeve valve engine. Improvements in design and materials of the more usual poppet valve engine eliminated most of the advantages initially held by the sleeve-valved variant, so that by the early 1930s manufacture of the Silent Knight had ceased, with only a couple of French automobile makers continuing to the end of the 1930's. Knight and Kilbourne had hoped to interest US automobile manufacturers in the engine so that they could grant licenses for its manufacture, but initially there were no takers.
Pierce-Arrow of
Buffalo, New York tested the engine against one of their own and found that it was more powerful at speeds above and would also go faster. However, they dismissed it as unsuitable for their range of cars because they believed that anything over was unsafe. They also considered the oil consumption (about 2 quarts/litres per ) excessive. Knight also received some bad publicity at the same time when a prototype car was entered in the 1906
Glidden Tour, only to drop out on the first day due to mechanical failure.
Daimler-Knight Having virtually ignored two written approaches by engineer
Edward Manville, a director of
Daimler, Knight changed his mind and decided to try to interest English manufacturers in his engine. In 1907 Knight went with one of his cars to London where he managed to see fellow-American
Percy Martin, also a director of Daimler. Daimler's engineers tested the engine and the results were sufficiently encouraging for Daimler to set up a secret team to fully develop Knight's concept. engines would be installed in some of its 1909 models. To combat criticism from its competitors, Daimler had the
RAC (Royal Automobile Club) carry out their own independent tests on the Daimler-Knight. RAC engineers took two Knight engines and ran them under full load for 132 hours nonstop. The same engines were then installed in a touring car and driven for on the
Brooklands race track, after which they were removed and again run on the bench for 5 hours. RAC engineers reported that, when the engines were dismantled, there was no perceptible wear, the cylinders and pistons were clean, and the valves showed no signs of wear either. The RAC was so impressed that it awarded Daimler the 1909
Dewar Trophy. The RAC reports caused Daimler's share price to rise, £0.85 to £18.75, European rights were purchased from them and used by
Panhard et Levassor and
Mercedes. Attracted by the possibilities of the "Silent Knight" engine, Daimler's chairman had contacted Knight in Chicago and Knight settled in England near Coventry in 1907. Daimler contracted
Dr. Frederick Lanchester as their consultant for the purpose and a major re-design and refinement of Knight's design took place in great secrecy. Knight's design was made a practical proposition. Daimler dropped poppet-valve engines altogether and kept their silent sleeve-valve engines until the mid-1930s. gaining an earlier start in Europe, where it also lasted longer. Mercedes built their 4-litre Knight 16/50 until 1924, while the
Simson Supra Knight of 1925-26 was probably the last German Knight-engined car. In France, besides
Peugeot and
Mors, two brands of luxury automobiles used the Knight engine as standard equipment between 1923 and 1940:
Avions Voisin and
Panhard et Levassor. Voisin also built an air-cooled
radial engine using the Knight principle in 1935 which was their last use of Knight technology. The
Panhard et Levassor Dynamic, produced until the summer of 1940, was the last Knight-engined passenger car to be built in series. ==Some Knight engine powered automobiles==