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Hi Fred,
Attached are a couple of pix of it all happening. You are correct in all
you wrote. The counterweights have to counteract the mass of the rotor (and
all seals except the apex seals), the eccentric lobe, and the oil capacity
inside the rotor. Additionally, the rotor is not dead symmentrical on the
lobe as it has a gear on one side. So there is a bit of an unbalanced
dynamic couple.
So I can only agree with you that balancing a "WunLunga" is not easy - a bit
of a black art - especially working out how much PERCENTAGE allowance to
make for the oil! (See pix:. Using soluable machining oil to see just how
much volume there is in a rotor - tip: each model rotor has a different
internal capacity!). You only know if you have got it really right once you
have had one running!
BTW, the drawing you attached is NOT originally from the hand of my really
good "friend" Paul Lamar. He fliched it, without due credit, from the
original author. Someone ought to have a go at him for being of double
standard about this copyright thing - I've seen dozens of drawings etc
published on ACRE without due credit given to the original authors.
Mazda produced a book many years ago called "The Rotary Engine" (as you
would), a fairly slim silver publicastion, but choc a block full of
information. The author was the head of Mazda's rotary development,
oneYamamoto San. So it is to him that the credit for the drawing should go
.
Enjoy!
Leon
----- Original Message ----- From: "Fred Osborn" <fosborn@infowest.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, April 21, 2005 2:40 AM
Subject: [FlyRotary] Single Rotor Balance
In a message dated 04/15/05 21:39 EDT Lehanover@aol.com writes:
"In the single rotor, the whole rig is going to be dynamically balanced,
so the
two counter weights will equal the weight of the rotor exactly."
Please forgive my delay in commenting on the above. It took several days
for
me to work up the courage to dispute anything posted by Lynn Hanover whose
experience and knowledge place him at the very top level of the Rotary
Gods.
How's that for kissing up (;-)?
In a single rotor the counter weights must statically balance out the
unbalance
of the eccentric shaft PLUS the rotor, its attachments, and cooling oil.
IN
ADDITION, they must do so without creating a longitudinal or rocking
couple that
will generate a dynamic unbalance. In other words, the CG plane of the
counter
weight combination must fall exactly on the CG plane of the unbalance
they are
correcting. If not, the spinning assembly will try to wobble.
I realize this is a bit of a quibble but with the increasing interest in
single rotor
engines there should be adequate recognition that balancing one is not
easy.
Balance Diagram courtesy of PL's ACRE NL.
With all due reverence, Lynn.
Fred O.
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