Hi Colyn,
I've flown in a Harmon Rocket 2 with the Lyc. 540 engine. There was
some vibration with a 2 blade Hartzell propeller.
We installed a 3 blade Rocket propeller (the MTV-9-B/198-52 MT
Propeller), and the engine seemed to have been replaced by an electric
motor.
We then installed a different 2 blade Hartzell propeller, and the original
vibration was back.
John Harmon has flown both the same MT 3 blade propeller and a 4 blade
propeller on his Harmon Rocket 3. John said the 4 blade propeller was
slightly smoother than the 3 blade propeller.
MT Propeller says there is a 2nd order harmonic present with a 2 blade
propeller that is not present with the 3 blade propeller. I believe there
is a 3rd order harmonic with the 3 blade propeller that isn't present with a 4
blade propeller.
Regards,
Jim Ayers
Less Drag Propucts, Inc. - An MT Propeller distributor and FAA MT Propeller
repair station.
Custom Aircraft Propellers - MT Propeller sales of custom designed
propellers
PS I will have a 4 blade counterweighted blade MT propeller on my Harmon
Rocket 2.
In a message dated 03/15/2006 9:46:15 PM Pacific Standard Time,
colyncase@earthlink.net writes:
Kevin,
I have no experience with the MT.
However, some observe that a 6-cylinder engine makes 3 pulses per
revolution and so does at 3 blade prop.
So a 4-blade
might be less apparent noise and vibration. I have not
personally experimented with this but maybe some on the list
have.
Colyn