Help wanted: questions on multi-speed, propeller reduction

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Help wanted: questions on multi-speed, propeller reduction

Post by aerovet »

The Scramble editorial team has received the following E-mail and hopes that there are readers that can give answers to the questions posed by Mr. Andre Rousseau:

"Dear Sir,
I am writing in the hope that either your readers or even perhaps, some of your technical contributors can assist in helping me to undertake an historical aviation technical research project.
The subject of my research is a very obscure technical development of the propeller airscrew. Specifically, the multi-speed, propeller reduction gear-box. I am not referring to variable-pitch propellers and by multi-speed I mean changing drive ratios in flight like changing gear in a car when you are about to climb up a hill.
I am interested in all parts of the chronological time-scale: from the earliest pioneering days through to the post-WW2 (for Russians, the great 'Patriotic War') period. So far, most of my research has discovered several developments that all seem to have occurred in either England or America. The subject seems to have been part of the general academic discourse amongst aviation experts at the time as variable-pitch propeller technology was still in its infancy.
By way of examples, there is the propeller reduction gearbox attached to the LYCOMING XR-7755 (i.e. mid-late 1940's). Also, one of the earliest references to the multi-speed type of propeller I've been able to locate concerns the test-flight of a research aircraft equipped with this type of propeller reduction gear by the US Army Air Corp at their McCook Field test-flight facility in 1924:- ... ld&f=false

.... and the 'hardware' description:- ... ne&f=false

For further technical insights you may also want see this Patent:

...... so you can see, there is a rich history of this most unusual subject initially applied to Fixed-Pitch propeller-driven aircraft then later to variable-pitch propeller driven aircraft with piston engines in the 3,500+Hp class (N.B. required in order to keep the propeller tip-speed beneath the speed of sound).
However, I am very surprised at the absence (or at least, so it seems) of similar work from other leading aviation nations, e.g. France, Italy, Germany, Japan and of course, Russia (or, the U.S.S.R. at the time). This is hard for me to understand because Russia has such a rich aviation history and its engineers were not afraid to experiment with radically new ideas afterall, the rules of physics and engineering are universal so the same technical hurdles were faced by all designers no matter what their nationality so it stands to reason that surely they must have investigated similar ideas and experimented with similar solutions. But perhaps I am wrong in my opinion so I am hoping that your experts and knowledgeable readers may be able to supply me with information on Russian and East European developments in this field of technology. Perhaps those who know their way around the Russian Patent system may also be able to discover new information on this topic? Therefore, would you be good enough to publish this letter in the editorial letters section of the magazine?

I can be contacted directly at:

............. however, I speak no Russian - only 'GOOGLE" Russian! So long as repondants can tolerate my apalling translation I will be more than happy to correspond."

Kind Regards,

[P.O. Box 72-425, Papakura 2244, Auckland South, NEW ZEALAND.
Phone; +64 274 767 925]
Proud to be a boomer!
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