The big problem with gas turbine gearboxes is that they have to operate at such high RPM that only the best metalworking tech works.
Same with driveshafts and any kinds of transmissions. Any off-axis power diversion from turbines is extremely hard. Imagine a driveshaft spinning at 1/10 of the turbine RPMs, it will still require extreme stiffness or it will disintegrate from vibrations.
Very high RPM generators are not that efficient too because of eddy current losses. It's not so bad in big industrial turbines spinning at 5-7k RPM or so, but losses mount at 15k+ RPM.
This is why there is such a high interest in making superconducting generators for direct drive by turbines. They can be very efficient, and very small — two usually mutually exclusive qualities for an electrical machine.
And even with the best metalworking, materials, and lubricants, high speed gearboxes don't last long, and require frequent inspections for fatigue, and overhauls.
P&W 1000G series have 32000hp gearbox rated in excess of the core cycle life and hours, but still apparently needs mandatory defectoscopy.
Same with driveshafts and any kinds of transmissions. Any off-axis power diversion from turbines is extremely hard. Imagine a driveshaft spinning at 1/10 of the turbine RPMs, it will still require extreme stiffness or it will disintegrate from vibrations.
Very high RPM generators are not that efficient too because of eddy current losses. It's not so bad in big industrial turbines spinning at 5-7k RPM or so, but losses mount at 15k+ RPM.
This is why there is such a high interest in making superconducting generators for direct drive by turbines. They can be very efficient, and very small — two usually mutually exclusive qualities for an electrical machine.