starapex
Active Member
NTSB Identification CH108LA274
Accident occurred Sept 3, 2008
Aircraft: Sadler Vampire powered with a Rotamax 1300 CG Rotary engine.
Accident occurred Sept 3, 2008
Aircraft: Sadler Vampire powered with a Rotamax 1300 CG Rotary engine.
- The NTSB determines the probable cause of this accident as a total loss of engine power due to the failure of the reduction drive.
- I have the strong opinion that accident was due to engine failure caused by excessive friction and heat due to the small diameter of the rollers in the bearing assembly.
- This bearing failure caused the engine turning 5,100 rpm to abruptly stop causing the PSRU failure.
- The Wankel design rotary engine has five distinct motions.
- 1- The spinning rotation of the drive shaft.
- 2- The orbiting motion of the e-shaft lobe.
- 3- The rotor held back a two thirds revolution as it orbits around the stationary gear.
- 4- The one third foreword motion caused by the full orbit.
- 5- The motion of the rotor around the e-shaft lobe.
A person standing on the center of a carousel, slowly turning two thirds of a revolution counterclockwise, as the carousel is rotated one revolution clockwise, will appear to advance one third clockwise by an observer.
The Mazda 13B rotary engine has a 2.91 inch diameter e-shaft lobe which should be the inside roller bearing race. We divide the 2.91 by two then multiply it by three and find that the outside bearing race must be a 4.365 inch diameter. The difference in size between the inner and outer race is 1.455 inches. This divided by two shows he required roller size to be a .7275 inch diameter.
This roller bearing configuration will in fact be an almost frictionless roller gear.
The needle bearings at the e-shaft lobe in the Rotamax 1300engine are about a .125 inch diameter.
The .125 inch diameter needle bearings would attempt to turn the rotor counterclockwise over nine tenths of a revolution and cause friction and heat and probable failure.
Ken
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