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RE: Radius of Gyration
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- Subject: RE: Radius of Gyration
- From: "Conrad Harrison" <sch.tectonic(--nospam--at)bigpond.com>
- Date: Mon, 22 Jun 2009 12:13:47 +0930
Liaquat Ally Akhand wrote: <quote> The physical
interpretation : If a rotating fan is
pushed to right, the fan will rotate downward as well as righ. The downward movement is
about an axis having a radius. The radius is known as Radius of
Gyration. <end quote> I assume fan has horizontal axis and
rotating clockwise. An important point to note is reference to “an axis”:
not necessarily the centre of the fan drive shaft. Ideally, can locate the mass of the fan
blade and the mass of the drive shaft, at a distance equal to their radius of
gyration from their centres of mass. Hopefully their centres of rotation match. Since fan unlikely to be perfectly
symmetrical from material of uniform density, unlikely in practice to have
centre of mass where assume it is. The assumed symmetry and uniformity discarded
and each fan blade treated separately. The whole system dynamically balanced,
by adding mass or drilling holes, to remove excessive wobble and chatter of the
system. Or so as I recollect the theory. As for strength of materials the mass
moment of inertia is replaced by second moment of area: in essence the mass is located
in a flat plate of uniform thickness and density. Moments of area have other uses, such as
finding mean value from statistical distributions. And another balancing act is
the lever rule for liquidus curves, like the iron-carbon equilibrium diagram. To conclude: locate centre of mass, and
determine radius of gyration. If mass concentrated at distance of radius of
gyration from centre of mass and rotates about axis through centre of mass,
then have stability. If rotates about any other axis have instability. As for the mathematics Christopher Wright
covered that. Regards B.Tech (mfg & mech),
MIIE, gradTIEAust mailto:sch.tectonic(--nospam--at)bigpond.com |
- References:
- Radius of Gyration
- From: Richard Calvert
- Re: Radius of Gyration
- From: Liaquat Ally Akhand
- Radius of Gyration
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