----- Original Message -----
Sent: Wednesday, October 07, 2009 6:28
AM
Subject: [FlyRotary] Balls and
Springs
Lynn,
With balancing my single rotor, what would you
suggest that I allow ( percentage wise) for oil weight in the rotor - it was
suggested to me that I should allow full rotor oil weight.
This discussion suggests otherwise.
George ( down under)
George,
The process I saw
on the internet came from Down there. A rotor is spun up in the lathe with a
plastic shield around the outside. Oil is squirted in until it starts
spilling out. A pan is slipped under the rotor and the lathe stopped. (if
your lathe has a coolant system that would work as well with less mess) The
weights are close enough. Then the rotor is laid on a grill on the pan and
allowed to drain. Then weigh the liquid in the pan. I bet the balancing
people just have a number on the wall for rotaries that is close to that
weight. A balancer could do it backwards by spinning the shaft from a
factory built engine, with the counterweights mounted, and then add
bobweight until he gets a balance. Then subtract the rotor weight from the
bobweight and that difference would be the oil allowance.
The big name
builders all balance to a gnats butt weight, but I just get the rotor
weights the same. Never a problem. The single pulse per revolution will be
so big that a small balance error will go unoticed. But, its no sin to start
out with the balance correct. I have thought about singles and decided that
as big a diameter flywheel that you can fit but weighted only at the outer
edge. Like 4 sets of starter rings tiged to a flex plate. Even Mazda builds
with pieces two weight ranges apart. They have stamped the weights on
rotors, and have used colored paint dots. Of course the paint dots are gone
when we see a used rotor.
Richard Sohn can
tell you. He seems to be doing well with his.
Lynn E.
Hanover
Thanks for the comment Lynn.
For the 12A rotor I am using 360 grams, that is on the
analytical balancing. When my first engine went on the balancer at Racing
Beat, the first question was "who did the first balancing on that?" . I
think that only supports your comments on the sensitivity.
Here is the way I am doing it:
First I measure the moment of the rotor and the
e-shaft.
Next is calculating the moment required for the fly wheel and
the counter weight.
When the fly wheel fabricated I trim it to the calculated
moment.
next is measuring the moment on the counter weight and
calculating the correction.
Next trimming the counter weight to the calculated
moment.
The resolution I
achieve on each component is +- 15cmkg at a total of 5000cmkg.
I have not
done any nrs with the 13B setup.
FWIW
Richard
Sohn
N2071U
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