Isaac

The planet gear bearings are the most critical lube point in the Hacker gearbox. I've found that they will wear and develop excess clearance on the pins over time - probably on the order of 700+ flights or so even when properly lubed. These are Timken drawn cup roller bearings and the gear side of the load is carried by the bearings "cup", which is where the wear occurs. These bearings are available at bearing supply places and are low cost (about 3 USD ea.) Press the old bearing from the gear and the new in - keeping the bearing position in the gear the same.

If solvent is used to clean the gearbox it can dilute/remove lube from the rear "prop shaft" bearing. The bearing will feel rough when rotated as it's failing. A little heat (heat gun) on the gearbox and the bearing will drop out with a slight tap, simply drop a new one in (there are snap rings between the bearings to position them properly). These bearings are also readily available, just search the web for the bearing number.

I've had one slight rotor separation (C50-14 Comp) which created end force on the motor bearings. The front motor bearing became noisey and rotated in the front case - ruining the case. When I lube the gearbox, I now check for rotor end play - a slight bit indicates that the rotor hasn't separated. Other than this rotor separation, I've not had any indication of rotor demag or weakening basis current draw / temp / power in over 1000 flights.

I use Shell Stamina RLS-2 lube for the gearbox, relubing every 100 flights. A "trick" is to fill excess space around the planet carrier with grease - do this by putting a large filet of grease in the housing before installing the prop shaft / planet carrier, then remove the excess displaced by the carrier. This prevents the grease in the gears from being displaced to this space, it then remains where it belongs - circulating through the gears. Like I mention first - the planet gear bearings are lube critical - be sure to pack grease well into these.