Continental XR-1740-2
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| XR-1740-2 | |
|---|---|
.jpg) XR-1740-2 at the National Air and Space Museum | |
| Type | Piston aircraft engine |
| National origin | United States |
| Manufacturer | Continental Motors |
| First run | 1941 |
| Number built | Only one |
The Continental XR-1740-2 was an experimental American 14-cylinder, two-row, air-cooled radial aircraft engine developed by Continental Motors (later Continental, Inc.) in the late 1930s and early 1940s. It incorporated single-sleeve valves, direct fuel injection, and a single speed centrifugal supercharger. Rated at 875 horsepower (652 kW) at 2,600 rpm, the engine was built to a U.S. Navy contract but never entered production or flight testing. A single example, completed around 1941, is preserved in the collection of the National Air and Space Museum. The XR-1740 represented the final major effort in Continental's long but ultimately unsuccessful campaign to commercialize single sleeve valve technology for aircraft engines. Like many contemporary sleeve valve designs, it proved unable to compete with more mature poppet valve radial engines.[1]
In 1925, Continental a company already successful in automotive engines acquired the rights to the Burt McCollum single sleeve valve design. The firm believed the sleeve valve system, which replaced conventional poppet valves with a sliding sleeve, offered advantages in airflow efficiency, reduced maintenance, and higher power potential for aircraft use. Continental's first aircraft application was the R-790, announced in 1927. This engine adapted sleeve valves to a Wright 9-cylinder radial but was never fully tested or produced. In 1934 the U.S. Navy ordered five examples of a follow on 7-cylinder design, the R-794 (sometimes referred to as R-794S). These engines were built and tested but likewise did not progress to series production.[2] In February 1939 the Navy awarded Continental a contract for a more powerful 14-cylinder development, designated the XR-1740-2. The "X" prefix indicated its experimental status, while "1740" referred to its nominal displacement in cubic inches. The engine featured two rows of seven cylinders, air cooling, direct fuel injection, and a single speed centrifugal supercharger. It was intended as a high performance powerplant for naval aircraft. One XR-1740-2 was completed circa 1941. Despite the Navy's sponsorship of several unconventional engine projects in this period, the sleeve valve radial did not advance beyond the prototype stage. Continental ultimately achieved greater success with conventional poppet-valve designs. The XR-1740-2's fate mirrored that of other single sleeve valve efforts, including those by Britain's Bristol company under Roy Fedden: promising in theory but difficult to perfect for reliable, mass-produced service. The sole surviving engine was transferred from the U.S. Navy to the National Air and Space Museum (inventory A19710891000). It has never flown.
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