NoWingsAttached
Unobtainium Member
- Joined
- May 21, 2006
- Messages
- 4,871
- Location
- Columbia, SC
- Aircraft
- Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
- Total Flight Time
- >350
Attached is the data sheet for ball bearing life, 90% expectancy to last as long as shown. Two sizes are listed side-by-side: First, the 25 mm ID 6205 used in the Rotax C - the only PSRU that can be fitted to a Skytrax adapter, for YG4/ RX1 engines only. Gear tooth angle of contact has accurately been accounted for, though I took liberties with prop and gearbox harmonics as I have no hard data for that.
Next, the 40 mm ID 6208 - used in every PSRU (gearbox or chain drive) by Mohawk Aero to date, to include: Arrow, Air Trikes SPG4, Mohawk Silent Drive, and most recently the Mohawk AK7, which an SPG4 built to Mohawk Aero specs for the YG4 and YG4i.
The datum indicate the Rotax C is an inferior, if not unacceptable, choice for use on any Yamaha 4 powered, carbbed or EFI, experimental aircraft of any type. If is already in use, it should be rebuilt (new bearings) every 300 Hrs.
The Rotax C has no HP rating. The propeller mass inertia is limited to 6000 kg/sq cm, which is 3000 kg/sq cm less than Mohawk AK7, Silent Drive, Arrow, and Air Trikes SPG4 - all rated minimum 180HP or better. Check with your propeller vendor for proper loading spec of your particular prop.
Note that, by design, it is virtually impossible to axially load the two, drive gear shaft, bearings equally in the Rotax C. The gearbox must be disassembled for installation/removal, and therefore the accuracy required to equally load both bearings precisely is impossible to achieve and reproduce, mostly due to gasket thickness changing every time the cases are torqued together, plus micro warping due to mounting to the engine. It is not only possible to load only one of the two bearings fully, but has been shown to have happened even when the gearbox is attached to a one-piece adapter by even the most accomplished kit builders in the country. When one bearing bears the full axial load, it exceeds the maximum acceptable rating for even one hour of use at any speed that could result in flight.
In a perfect world, both bearings loaded exactly the same, Rotax C, 25 mm ID, 6205 bearings, has a 90% probability to last:
MOHAWK AERO IS THE ONLY SHOP ANYWHERE IN THE WORLD THAT SELLS AND DELIVERS EVERYTHING YAMAHA FOR PROP-DRIVEN CRAFT INCLUDING YG3 Nytro, YG4 RX1, YG4i APEX.
Other shops promote and sell but one type adapter, for one type engine (YG4/ RX1), for one type PSRU (Rotax C) - which speaks for itself, in light of the life expectancy life of those gearbox bearings under ideal conditions, let alone worst-case scenario; and at least 3 or 4 accounts found elsewhere on RF of bearing failures reported to us this past season, all under 400 hours, one in a as little as ~12 hrs.
MOHAWK AERO deals, fabricates, services, and sells everything you need to convert to EAB aircraft use your choice of YG3, YG4 and YG4i engines.
For any questions, advice, truly open-minded discussion on ALL available equipment for ALL Yamaha engines, including SALES of stacked adapters, one-piece adapters that replace the crankcase cover, additional vendors' contact info, ROLLER CLUTCHES, centrifugal clutches, hard-coupling flanges and flex shaft couplers, dimensionals & measurements, all known available after-market engine equipment, hard-to-find parts, used parts, new and used engines, after-market turbos & blowers, ECU mods, all the really serious stuff. We are a dealer for Luga, Warp Drive, and Whirlwind props, new aluminum dual-core radiators, Jake-Bilt SS custom exhaust headers, Air Command gyroplanes AND Tango Gyro...with more to come If you really want a Rotax C on your Yamaha, we can and will help you out with that, too, NP - just be prepared to rebuild it more often than the other equipment we sell, fabricate and deal in, new and used.
Let us help you build a hot-rod, Yamaha-powered aircraft, cuz THAT'S what we're here for!
Please visit our Facebook group (you don't need a Facebook account to read it) "Yamaha Aircraft Engines" soon.
Next, the 40 mm ID 6208 - used in every PSRU (gearbox or chain drive) by Mohawk Aero to date, to include: Arrow, Air Trikes SPG4, Mohawk Silent Drive, and most recently the Mohawk AK7, which an SPG4 built to Mohawk Aero specs for the YG4 and YG4i.
The datum indicate the Rotax C is an inferior, if not unacceptable, choice for use on any Yamaha 4 powered, carbbed or EFI, experimental aircraft of any type. If is already in use, it should be rebuilt (new bearings) every 300 Hrs.
The Rotax C has no HP rating. The propeller mass inertia is limited to 6000 kg/sq cm, which is 3000 kg/sq cm less than Mohawk AK7, Silent Drive, Arrow, and Air Trikes SPG4 - all rated minimum 180HP or better. Check with your propeller vendor for proper loading spec of your particular prop.
Note that, by design, it is virtually impossible to axially load the two, drive gear shaft, bearings equally in the Rotax C. The gearbox must be disassembled for installation/removal, and therefore the accuracy required to equally load both bearings precisely is impossible to achieve and reproduce, mostly due to gasket thickness changing every time the cases are torqued together, plus micro warping due to mounting to the engine. It is not only possible to load only one of the two bearings fully, but has been shown to have happened even when the gearbox is attached to a one-piece adapter by even the most accomplished kit builders in the country. When one bearing bears the full axial load, it exceeds the maximum acceptable rating for even one hour of use at any speed that could result in flight.
In a perfect world, both bearings loaded exactly the same, Rotax C, 25 mm ID, 6205 bearings, has a 90% probability to last:
- 365 hrs at (less than) < 7200 ERPM - minimum cruise speed (conventional setting for light loads and nominal speed).
- 310 hrs @ 7200 > 9000 ERPM - fast cruise, to take off, and excellent climb
- 270 hrs @ > 9000 - extreme climb
- 3300 hrs @ < 7200 ERPM
- 2900 hrs @ 7200 > 9000 ERPM
- 2300 hrs @ > 9000 ERPM
MOHAWK AERO IS THE ONLY SHOP ANYWHERE IN THE WORLD THAT SELLS AND DELIVERS EVERYTHING YAMAHA FOR PROP-DRIVEN CRAFT INCLUDING YG3 Nytro, YG4 RX1, YG4i APEX.
Other shops promote and sell but one type adapter, for one type engine (YG4/ RX1), for one type PSRU (Rotax C) - which speaks for itself, in light of the life expectancy life of those gearbox bearings under ideal conditions, let alone worst-case scenario; and at least 3 or 4 accounts found elsewhere on RF of bearing failures reported to us this past season, all under 400 hours, one in a as little as ~12 hrs.
MOHAWK AERO deals, fabricates, services, and sells everything you need to convert to EAB aircraft use your choice of YG3, YG4 and YG4i engines.
For any questions, advice, truly open-minded discussion on ALL available equipment for ALL Yamaha engines, including SALES of stacked adapters, one-piece adapters that replace the crankcase cover, additional vendors' contact info, ROLLER CLUTCHES, centrifugal clutches, hard-coupling flanges and flex shaft couplers, dimensionals & measurements, all known available after-market engine equipment, hard-to-find parts, used parts, new and used engines, after-market turbos & blowers, ECU mods, all the really serious stuff. We are a dealer for Luga, Warp Drive, and Whirlwind props, new aluminum dual-core radiators, Jake-Bilt SS custom exhaust headers, Air Command gyroplanes AND Tango Gyro...with more to come If you really want a Rotax C on your Yamaha, we can and will help you out with that, too, NP - just be prepared to rebuild it more often than the other equipment we sell, fabricate and deal in, new and used.
Let us help you build a hot-rod, Yamaha-powered aircraft, cuz THAT'S what we're here for!
Please visit our Facebook group (you don't need a Facebook account to read it) "Yamaha Aircraft Engines" soon.
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