bryancobb
Junior Member
- Joined
- Aug 2, 2010
- Messages
- 5,045
- Location
- Cartersville, GA
- Aircraft
- Owned Brantly B-2b/Fly Kitfox III/Mini-500b
- Total Flight Time
- 1350
Here's the starting point and my goal.
Starting point is...
I have two complete Mini-500 gearboxes. One is a brand new, unmolested, never spun under load, factory assembled one. This one is an early Alpha that was shipped with Kit S/N 117. I assume it is identical to the one I installed in my other Mini-500 in 1997 since it was S/N 129. It is well known that factory gearboxes assembled during this time-frame had the preload set way high and they ran hot. Also the pinion has a 4-pack of bearings, one of which is an angular contact bearing (rearmost one). This setup was problematic. All of my 100 hrs of Mini-500 time was on helicopters that had this setup and I had no problems except the case got a little warmer than I would have liked.
The second one is out of my Texas parts helicopter. It was originally shipped in the kit (S/N 417) which was a factory Bravo model that was originally shipped without the Mast Support Upgrade. Mr. Dave Mealy, the original builder, flew it for 152.9 hours between March 1998 and Feb 1999 when he modified it per the Mast Support Upgrade. Between then and 10-20-2002, he flew it to a TTAF of 226.6 hours in the western PA area. Now there is 245.4 on the Hobbs and I have no idea about the circumstances surrounding those 19 hours on it. Bravo gearboxes had the correct preload and ran a lot cooler. I suspect it still has the pair of dual-row, angular contact bearings on the pinion. I have the complete maintenance records and for the first 153 hours, logbook entries are almost zero. Because of the frequency of entries in the flight log, and the nature of the flights (many short cross countries) with no long gaps, I can assume this gearbox was trouble free because the only logbook entries are lubricant flush and changes. After he did the Mast Support, logbook entries were very thorough and include several AD c/w entries were made. I feel like he flew this gearbox for the whole 227 hours without any major problems. The scab on the frame tube tells me that his frame DID crack like Alphas did, at about the 153 hour point, and then he purchased the expensive Mast Support Upgrade and installed it.
Starting point is...
I have two complete Mini-500 gearboxes. One is a brand new, unmolested, never spun under load, factory assembled one. This one is an early Alpha that was shipped with Kit S/N 117. I assume it is identical to the one I installed in my other Mini-500 in 1997 since it was S/N 129. It is well known that factory gearboxes assembled during this time-frame had the preload set way high and they ran hot. Also the pinion has a 4-pack of bearings, one of which is an angular contact bearing (rearmost one). This setup was problematic. All of my 100 hrs of Mini-500 time was on helicopters that had this setup and I had no problems except the case got a little warmer than I would have liked.
The second one is out of my Texas parts helicopter. It was originally shipped in the kit (S/N 417) which was a factory Bravo model that was originally shipped without the Mast Support Upgrade. Mr. Dave Mealy, the original builder, flew it for 152.9 hours between March 1998 and Feb 1999 when he modified it per the Mast Support Upgrade. Between then and 10-20-2002, he flew it to a TTAF of 226.6 hours in the western PA area. Now there is 245.4 on the Hobbs and I have no idea about the circumstances surrounding those 19 hours on it. Bravo gearboxes had the correct preload and ran a lot cooler. I suspect it still has the pair of dual-row, angular contact bearings on the pinion. I have the complete maintenance records and for the first 153 hours, logbook entries are almost zero. Because of the frequency of entries in the flight log, and the nature of the flights (many short cross countries) with no long gaps, I can assume this gearbox was trouble free because the only logbook entries are lubricant flush and changes. After he did the Mast Support, logbook entries were very thorough and include several AD c/w entries were made. I feel like he flew this gearbox for the whole 227 hours without any major problems. The scab on the frame tube tells me that his frame DID crack like Alphas did, at about the 153 hour point, and then he purchased the expensive Mast Support Upgrade and installed it.
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