A frequent visitor at home (and vice-versa) was Eric Lewis and his family and when my father and
he got together the conversation often turned to weird and wonderful engineering projects, possibly
many were ‘pipe dreams’ at the time but I can recall discussions ranging from gas
turbine powered cars and fuel cells to improved designs for razors. Enthusiasm for Gillette,
Wilkinson Sword and Rolls Razor waxed and waned as each companys technology leap-frogged the
others. Sometimes elaborate back of the envelope sketches were made practically
all of which have not survived. However one has been found (see above) among his personal papers
which to my unskilled eye looks like any other jet engine but presumably to those in the know means
rather more. What became of this flight of fancy I have no idea but it is interesting to note that
the Americans patented a contra-rotating gas turbine in 1994.
Notes by Malcolm Knight.
The hand written note stapled to the sketch says
“This design though mechanically complicated could have considerable advantages for reducing rotor stresses for a given power output. The relative rotational speeds between contra-rotating elements would be the same as for conventional gas turbines of a given design performance. For single shaft engines the rotating elements would be suitably geared together through fixed or variable ratio systems. For the pure jet type it is likely that the rotors would run in the matched state without gears unless synchronising is necessary. The ratio of rotational speeds could be be varied to optimise the rotor stresses or developed power from one or other of the rotating elements.
The intake, combustion system and exhaust would be part of the static main casing which would absorb the torque reaction as per conventional engines. The main design problems would appear to be the gas sealing and gearing. These will affect efficiency but are unlikely to off-set the advantages.