Greetings,
Below are the notes from today's
adventure. As you'll read, there are certainly some
vibration issues.
A question for Richard- Have you run
your single rotor with a realistic sized prop, or just with the drive
itself? Have you added any flywheel weight?
Rusty
Spent quite a
bit of time running the engine today, and tying some various tests. The good news is that the fluids all
stay inside the engine where they belong, so no more leaks. The bad news is that there are
certainly some vibration issues.
Running the
engine without the prop does not show any significant vibration, except for
the expected roughness at low rpms, below about 1800 or so.
Running the
engine with the 3 blade Warp
Drive prop, gives a few different vibrations. The best bet for “idle” is about 2200
rpm right now. Reducing rpm below
that point hits a pretty severe “rattle” at about 2000 rpm. This is the same
as the rattle I got with the redrive on the 13B, but it was around 1100 rpm on
that engine. Reducing below that
will get out of the severe rattle, but into the expected single rotor
roughness. It’s possible to idle
around 900 rpm, but you wouldn’t want to.
If you start
at 2200 rpm, and slowly increase the throttle, all is well until about 2500
rpm, then a high frequency vibration starts. The vibration increases in frequency,
and amplitude as the rpm increases, right up to 3100 rpm. At 3100, as you increase throttle,
initially nothing happens, but then the engine will suddenly jump to 3300-3400
rpm, and be smooth. It’s just
like someone flipped a switch to get rid of the vibration. This vibration is pretty severe, and
you can see things like the air filter shaking until they’re just a blur.
The
3rd problem is an odd “beat frequency” sort of vibration that
happens at all rpms. If you stand
directly in line with the prop arc, you can see the prop tips oscillating
forward and back about every second or so. I only watched this at idle, but other
observers said that it gets much worse at higher rpms, and I can certainly
feel it. I don’t really have a
clue what this is, unless it’s some sort of interaction between the 2.85
drive, and the ratio of eshaft to rotor rpm. 3 blade prop??? Gotta think about this some.