1. The test stand oil system provided a fixed oil pressure to the engine,
which is even worse than an engine-driven pump in terms of "oversupplying"
oil to the engine because we typically would leave it set to regulate a
constant 60 psi regardless of engine speed. However, it is really the bearing
clearances, speeds, temperatures, and cooling jet sizes in conjunction with
the oil supply pressure (and viscosity) that dictate the amount of oil that
the rotor will receive. I maintain that for our systems the rig engines did
not supply significantly different amounts of oil to the rotors than did our
all-up engines. If anything, the rotors had more oil at lower speeds by
virtue of a constant 60psi source.

2. The people at Racing Beat and others should do what works for them. I only
tell what worked for us to add to the general knowledge base.

3. Yes, the engines were generally hard mounted, but vibration pickups were
constantly monitored to determine if there were driveline wear problems.
Small imbalances were easy to detect. The single rotor engines did not
vibrate more than the twins.

4. I have seen the films that were made by Curtiss Wright in the 1960's to
determine the oil flow into/out of the rotors. Yes, at times there is some
oil in the rotors. A very small mass, relatively speaking, and a variable one
as well. There is certainly some "best compromise" mass to use when balancing
an engine. We chose "no oil" as our compromise and it worked for us. You are
free to choose what works for you, but I feel that based on my experience,
your choice did not work for you, hence the vibrations.

5. We did also have single rotor engines on soft mounts (gensets, etc.) and
there again was no vibration issue. You may have had a torsional resonance
problem because of a mismatch in the mass-elastic system of engine / coupler
/ PSRU / propeller. Again, my experience is that a single rotor engine can be
made to work fine in many applications (I have no first hand single rotor /
propeller experience), providing very smooth power.

Jon Lauter
Rotary Power Marine Corporation
www.rotarymarine.com

 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org