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It’s not the interior of a helicopter gearbox. It’s the workings of the Pantigo windmill in East Hampton built in 1804 but it is a demonstration of the technology used in modern gearboxes. There have, in recent years, been a number of accidents because of the failure of this system either through failing structurally or not having the correct lubrication. Future designs suggest that this system, which has been in use since the 15th Century, is going to be persevered with even though the stress management and manufacturing standards required are reaching their practical limit.
It is time to look at an alternative system?
Mechanical System. Rubber bands or chains. Has been proven in a small way in 10,000 R22/44s. It has a lot of history as a prime means of keeping the components of an automobile’s internal combustion engine apart. 50k miles is the normal operating time of a cambelt and the failures during that period are virtually unknown. It is quiet, can be made to handle a large amount of energy and, if required, can be doubled up as a safety measure. Properly designed it can be flexible enough to run around a pulley system so that it can transfer energy through right angle drives. Whether it can handle thousands of kilowatts of mechanical energy is to me, unknown.
Electrical System. Generators and motors. Thousands, soon to be millions of cars are going to be propelled this way. Even helicopter manufacturers are toying with it. It has been around for over a century with electrically powered trains with a large number generating their own in situ. The Turmo IIIC, the Puma helicopter’s first engine, started off this way, To convert 1,000 kw of gas turbine power via a generator to a motor capable of reproducing that power within a reasonable weight frame is a different problem but is it within the bounds of possibility. Electric motors, receiving a controlled frequency can rotate at a fixed RPM therefore negating reduction gears with their weight and lubrication problems.
Hydraulics. The construction industry show how much energy can be moved around with very little quantities of oil. The source of the pressure is generated by a rotating engine so that pressure needs to converted back to rotary motion. Chrysler invented the fluid drive in the 1930s and that led to the almost universal use of automatic transmission in the USA. The transmission itself is not the answer as that incorporates planetary gears which is what we are trying to avoid but the fluid drive itself is a possibility. The kit that controls in-flight refuelling gear is an example. That uses a variable level of fluid to control the torque on the drogue to keep it neutral for the receiver. The amount and the cooling requirements for the hydraulic oil would be a problem but not necessarily insurmountable. Alternatively hydraulic motors could be designed to rotate at high torque and low r.p.m..
Like all things that break with tradition any alternative system has to overcome the prejudice and suspicion of those that are going to use it. It is possible. Operations now use equipment that would be considered science fiction fifty years ago. I know damn all about the finer points of design and manufacturing so I cannot fathom my own questions. However I will throw it in so people can think about it and come up with any dreams or ideas.