The story on this gearbox is:
The contract was for Titan to install a new LS3 engine and gearbox on a T-51 Mustang airframe, replacing Rotax engine. To upgrade the gearbox from the Suzuki 150hp to the 300 hp engine the needle bearings on the idler shaft were changed to roller bearings at the Titan factory. The bearings used were reportedly ones sourced from China rather than their usual source in an effort to save money.
The gearbox suffered two “traumatic events” during the work, 1) a prop strike which shredded all 4 composite blades when the plane was started at full throttle in the hangar, and 2) sudden stoppage when the first engine threw a rod due to an error in installation by Titan.
At 34 hours on the gearbox (with a new engine,) the governor started sticking and the gearbox oil was found to be full of fines. The gearbox was returned to Titan and it was discovered that a bearing on the idler gear shaft had disintegrated. It was reportedly replaced. It was explained to me that to save time, instead of hardening the shaft where it had been damaged, the bearing was press fitted onto the shaft.
The gearbox then was shipped back to me ($600 shipping) and remounted on the airplane. After approximately 8 minutes in the air the governor began to stick again so the plane was landed. Examination showed the gearbox oil to be full of fines.
Under the theory that the gearbox had not been adequately washed of fines at the time of the bearing replacement, it was run several times without the governor on it for a few minutes and the oil then drained and replaced. The fines decreased in number but did not disappear.
A new gearbox was purchased to put the plane back into airworthy condition and I just recently had time to take the old one apart.
See photos. What appears to be the plastic cage of the rear idler shaft bearing has disintegrated, damaging the shaft. The gear surfaces all look the same- tiny pock marks where fines have gotten between them. One pic shows a small crack in the surface of the gear arising from a particularly big divot.
Are these gears usable? If so, can they be considered to give the same service life as new, undamaged gears? AFAIK no parts have been subjected to examination for cracks or other damage.
Thank you for your opinions,
Jim
![IMG_8342[1].jpg](https://cdn2.imagearchive.com/homebuiltairplanes/data/attachments/96/96473-7b46815fe9d390d62b81707c1133f557.jpg "IMG_8342[1].jpg")
The contract was for Titan to install a new LS3 engine and gearbox on a T-51 Mustang airframe, replacing Rotax engine. To upgrade the gearbox from the Suzuki 150hp to the 300 hp engine the needle bearings on the idler shaft were changed to roller bearings at the Titan factory. The bearings used were reportedly ones sourced from China rather than their usual source in an effort to save money.
The gearbox suffered two “traumatic events” during the work, 1) a prop strike which shredded all 4 composite blades when the plane was started at full throttle in the hangar, and 2) sudden stoppage when the first engine threw a rod due to an error in installation by Titan.
At 34 hours on the gearbox (with a new engine,) the governor started sticking and the gearbox oil was found to be full of fines. The gearbox was returned to Titan and it was discovered that a bearing on the idler gear shaft had disintegrated. It was reportedly replaced. It was explained to me that to save time, instead of hardening the shaft where it had been damaged, the bearing was press fitted onto the shaft.
The gearbox then was shipped back to me ($600 shipping) and remounted on the airplane. After approximately 8 minutes in the air the governor began to stick again so the plane was landed. Examination showed the gearbox oil to be full of fines.
Under the theory that the gearbox had not been adequately washed of fines at the time of the bearing replacement, it was run several times without the governor on it for a few minutes and the oil then drained and replaced. The fines decreased in number but did not disappear.
A new gearbox was purchased to put the plane back into airworthy condition and I just recently had time to take the old one apart.
See photos. What appears to be the plastic cage of the rear idler shaft bearing has disintegrated, damaging the shaft. The gear surfaces all look the same- tiny pock marks where fines have gotten between them. One pic shows a small crack in the surface of the gear arising from a particularly big divot.
Are these gears usable? If so, can they be considered to give the same service life as new, undamaged gears? AFAIK no parts have been subjected to examination for cracks or other damage.
Thank you for your opinions,
Jim
