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In the Spring 2006 Issue of

The Ramp-Head Merlin
Sometime
in the latter half of 1933, George Albert Elliott, Rolls-Royce Chief Engineer,
informed the PV-12 development team of his decision to change the engine’s
cylinder heads to the ramp type. This announcement would have been greeted with
astonishment, amazement and probably, dismay by the engineers involved. They
already had major problems to contend with and the introduction of an untried,
untested modification to a brand new engine had the potential to add
significantly to their woes.
Images Courtesy of Auckland War Memorial Museum and Jerrry Wells
Additional Images Courtesy of Bill Bishop
The MASM Gnome Omega Engine
Early
in the 20th century James Shannon Stephens and his engineer son Ralph became
interested in designing an aircraft, a common interest of engineers in the first
decade of the century. They subsequently designed the Steco (Stephens
Engineering Company) aircraft which has been variously described as a
hydroaeroplane or Aerohydroplane. Stephens was granted a patent on his aircraft
and its design inventions in 1915.
As with many aircraft designs of the era, the designer tried unique control
systems to get around the Wright patents. Also, the science of aircraft
stability and control was poorly known at the time, and while we have no
detailed data from the flight tests, we can surmise that the Steco was a
handfull to handle. Like many early aircraft, the plane was set up to be
neutrally stable in both pitch and yaw.
The aircraft and its Gnome Omega engine have been restored by the Minnesota Air
& Space Museum.
Turbocompounding the Wright Way
Engine
designers have a long history of trying to extract as much power as possible
from a given engine, and this is especially true of aircraft engines since there
is a large penalty for carrying extra weight, be it fuel, engine, or airframe
mass. There is significant energy in the engine exhaust stream, and it is an art
form trying to put that energy to efficient use. Stanley Hooker reported that
the jet efflux from a Rolls-Royce Merlin engine was worth up to 150 hp (10% of
power output) at high power settings. While this is a valuable and relatively
simple way to put exhaust energy to work, turbo-supercharging, which uses the
pressure of the exhaust gas, and turbocompounding, which uses primarily the
velocity of the gas stream, are other ways to boost efficiency.
As large-displacement piston engine technology peaked in the
late 1940s and early 1950s, turbocompounding was studied by a number of
manufacturers including Allison, Pratt & Whitney, and Napier, to increase
horsepower, but even more importantly, specific fuel consumption (sfc) of their
engines. More power on less fuel meant larger loads carried over longer
distances for the same-size airplane, an efficiency mantra that drives design
even today.
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Power Recovery Turbine
Assembled |
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Power Recovery Turbine
Outlets |
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Power Recovery Turbine
On Stand with Parts |
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Power Recovery Turbine
With Cap |
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Power Recovery Turbine
Without Cap |
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Power Recovery Turbine
Hood, Cap and Clamps |
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Power Recovery Turbine
Underside of Cap |
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Power Recovery Turbine
Buckets and Guide Vanes |
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Power Recovery Turbine
Turbine Wheel Showing Cooling Holes and Knife Cuts |
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Power Recovery Turbine
Underside |
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Aero Engine Drawings by Frank Munger
The Impact of the Engine on the Airframe
Schedule Effects—German Jet Engine Development in WWII
Part 2: The Aircraft
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| The Heinkel 280 was the company's dream for jet
production. It first flew with the von Ohain S-8 engines, but later
prototypes flew with 003 and 004 engines. It was too small to carry
adequate fuel and armament; hence, there was no production contract. (A.L.Kay,
Crowood Press) |
Aircraft
engine development requires more time than does airframe development, usually
about 60 percent more. This truism is sometimes forgotten in the desire to
achieve program goals. Perhaps the most dramatic example of the consequence of
such forgetfulness occurred in Germany in World War II when the jet engine
not-so-quietly arrived on the scene.
Part 1 of this series discussed German jet engine development during WWII.
Part 2 covers the manned turbojet-powered aircraft that actually flew in Germany
before WWII ended. Jet aircraft that flew in wartime Germany used
first-generation engines, and many aircraft were on the drawing boards using
second-generation engines such as the He 011, BMW 018,
BMW 028, Jumo 012, Jumo 022, and ramjet engines.
Conceive, Construct, Configure, then Run Your
Demo Engine
Or, How I Got My V-1710 Running
Most
of us have a favorite engine, one that we have always wanted to get “close and
personal” with. In many cases such engines are only operable in rare and
expensive Warbirds, airplanes whose owners will not willingly let just anyone
into the cockpit, let alone operate the engine. This is where the committed
enthusiast will look for an alternative, for me that meant one that was
affordable and restorable.
Those of us who are running and demonstrating old aircraft
engines are often asked, sometimes incredulously, “Why?”, others want to know
“How?”, and some others say, “I’ve always wanted to run one of these things.”.
This article intends to give the reader some insights as to how I got my V-1710
up and running, along with some of the lessons learned.
Table of Contents

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