Dale,
You are correct about rotating assembly. All high speed rotating parts need to be balanced.
Bill Jepson
Connected by DROID on Verizon Wireless
-----Original message-----
From: Dale_R <dale.rog@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, Aug 2, 2011 20:45:21 GMT+00:00
Subject: [FlyRotary] Re: Flywheel Machine Work
Bill,
Dunno how that one slipped past me; I could blame my 30 year old
R-S calculator, but ultimately, I'm the responsible party -- I
should have run the numbers twice. And it isn't just a misplaced
decimal, either; although would have been close.
But that just shows how much ~more~ important it is that the
flywheel balance be done correctly.
Best regards,
Dale_R
On 8/2/2011 1:27 PM, wrjjrs@aol.com wrote:
Dale,
I think you got a term wrong there. I get 807.34 rpm @ 60
mph. 25" x 3.14=78.53in
78.53/12=6.54ft. 60mph=1mile per minute. 5280'/6.545= 807.34 RPM
Bill Jepson
Connected by DROID on Verizon Wireless
-----Original message-----
On 8/2/2011 5:05 AM, David Leonard wrote:
> ... I am starting to think that the whole science of
balancing is
> just a gimmick. Despite the old balance hole being mostly
drilled
> away, the new balance holes are on the opposite side of the
flywheel. !??
>
Dave,
Balancing is a procedure that falls right on the edge between
science and black art. At high RPMs, changes "out of plane" can
become
critical.
As an example, when I started balancing wheels all we had were
bubble (static) balancers, and - because the weights had to go
on the
rim edges - we would find the amount of weight, then split it,
e.g. two
half ounce weights, one on the inside and one on the outside.
~Most~ of
the time it would put give good freeway speed balance.
Sometimes,
though, we'd still get an out-of-balance wobble in the wheel due
to the
imbalance being off center of the c.g. plane of the wheel.
Then affordable (for a small shop) dynamic balancers came along,
and
we discovered that, most of the time, less weight was required
on one
side of the wheel than the other, often not even opposite each
other, to
bring the center of balance the same as the center of rotation.
Drilling balance divots on only one side of something like a
wheel
can create a similar situation - where the static balance is
correct but
the center of balance is no longer the same as the center of
rotation.
It takes sophisticated equipment and an equally sharp operator
to get it
right.
BTW, FWIW ... For an average car tire with 25" diameter at the
tread, at 60 MPH, the wheel is turning ~7950 RPM.
--
Dale_R
Cozy MKIV #497
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Dale_R
Cozy MKIV #497
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