Actually, this model might be closer to
our disc on a shaft gearbox
http://www.mecheng.osu.edu/vibrations/files/vibrations/jva7-99b.pdf
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Thursday, March 25, 2010
3:03 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Rotating Disc
Vibration nodes was [FlyRotary] Re: Adaptor plate rivets
Have not gone out and checked my rivets on
my R1C, will do that this weekend. However, there is one possibility for
the cause of the smoking rivets that I have not heard addressed and that is
vibration nodes of a rotating disc. There is the possibility that if the
disc were in some oscillatory mode that the smoking rivets might be caused by
with the rivets being at the nodes of certain modes (like that?) of
vibration which could be causing the holes in the discs to be sliding up and
down the shaft of rivet.
In the end, it may be important to know
what is causing this. The 20Bs should be smoother than the 13Bs, on the
other hand, they do have a different firing frequency. For the same RPM
the number of firing pulses from the 20B are 1/3 higher than the 13B over the
same time period. That could possibly induce vibration nodes in the
disc that the 13B (which has longer duration between firings pulses). The
long time between firings in the 13B might permit the mass/structure of the
assembly to dampen the amplitude of any such induced vibration between
firings pulses – where not so for the more frequent pulses of the
20B. The higher the frequency of the input, the stiffer structure
that can be caused to vibrate. A vast over simplification, but thought I
would throw it out just incase somebody had a finite analysis package sitting
on their computer. Just a WAG.
Here is an URL that provides a drawing of
how such nodes might form on a disc
http://demonstrations.wolfram.com/NormalOscillatoryModesOfRotatingOrthotropicDisks/
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Thursday, March 25, 2010
2:25 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Adaptor
plate rivets
Al,
I had a bunch of AN-6A bolts, so I used them with two thick washers,
one under the head and one under the nut. I mainly wanted to ensure that
the shank went all the way through both pieces. You might be able to use
AN-5.5A or even AN-5A bolts if you use only one thin washer under the nut.
On Thu, Mar 25, 2010 at 11:22 AM, Al Gietzen <ALVentures@cox.net> wrote:
To answer your question about the washers, I used thick washers on both
sides. But I'll have to remove them all in order to replace the AN-6A
bolts with AN173-6A's. I'm hoping the bolts arrive by this weekend so I
can start putting everything back together.
Normally washers are needed only under the side that you’re turning
to apply the force; unless needed to provide shimming or a more uniform or
larger surface. The -6A length has a 3/8” grip length, and I
assumed the plate was 1/8” and the flange ¼”. If the
thickness is less I may have to get some more, or thicker, washers.
Al
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