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nuckolls.bob(at)aeroelect
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 Posted: Tue May 11, 2010 6:15 am Post subject: IVO Prop System Brushes |
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At 04:20 AM 5/11/2010, you wrote:
To clarify things.....
Bob, it is the brushes that transfer the power to the prop motor on the hub,,, not the actual pitch change motor itself.
THAT is a very difficult set of components to optimize to
design goals. Brushes on alternators run on the smallest possible
diameters and smooth surfaces. Smoothness reduces wear, diameter
controls surface speed under the brushes. Brushes in tiny
motors benefit most from their tiny commutators . . . in spite
of having to run over a segmented surface.
Brushes that carry power to a moving prop hub DO benefit from
smooth surfaces . . . but they run 100% of the time, are exposed
to environmental contaminants, and have high surface speeds. A
de-ice slip ring for a three bladed prop . . .
[img]cid:.0[/img]
can be about 10" in diameter and has three slip rings.
Brushes are a high-maintenance item on these systems
too.
When the first motor failed I did discuss this with Ron (at) Ivo and he was insistent not for me to open the motor and do an autopsy on it but to just send it back. Which I did and he promptly replaced it back then. I don't know if it tricky to open up, or there is some proprietary stuff in it he doesn't was people to see or what.
Probably nothing sinister here. The clues that lead to
good failure diagnosis can be subtle . . . they can also
be fragile to the extent that they are destroyed or
missed by someone opening up a device under study
for the first time.
I don't think I've ever encountered a situation where
a supplier was attempting to keep his "dirty laundry"
a secret. I've encountered many instances were well
meaning but unskilled investigators trashed or missed
an important data point during a teardown inspection.
Bob . . .
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n801bh(at)NetZero.com
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| Posted: Wed May 12, 2010 3:05 am Post subject: IVO Prop System Brushes |
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Ben Haas
N801BH
www.haaspowerair.com
Please note: forwarded message attached
From: "n801bh(at)netzero.com" <n801bh(at)netzero.com>
To: aeroelectric-list(at)matronics.com
Subject: Re: Re: IVO Prop System Brushes
Date: Tue, 11 May 2010 16:14:06 GMT
Your explaination and picture clearly shows the reason for high wear rates for those brushes..Surface speed is the main culprit and at the diameters the brushes ride against is a built in evil that cannot be reduced much.
I fabricated everything on my experimental and in a earlier life I spent 25 years in the racing arena, building motors mostly. I am very familier with non destructive testing, ie, magnaflux, zyglo, dye penetrant, eddy current,sonic testing for wall thickness, Xray among other methods. I also did extensive destructive testing because that shows the real outcome of system failures, building expensive motors only to blow them up does get expensive but the remains of said motors are invaluable for analysis.
I can see your thoughts on a lay person dissambling a componant only to destroy any evidence to use to explain that failure.... I would like to think I am capable of exceeding the lay persons ability of that task.
I would like to share my thoughts on the first motors failure; My application is unique in that I am transferring ALOT of horsepower through the Ivo prop and its related componants. I also started with the largest diameter blades Ivo offered, 84". My first 25 hours of test flights were using the Magnum Paddle series blades too and they are substantially bigger and stiffer then the regular magnum blades. My guess is the increased forces needed to twist those blades took out the motor, even though Ron at Ivo knew and sold me that set up. Hey,,, we are experimenting here and both Ron and I may have learned something by my initial failure. He is a real nice guy too. By the lack of others responding of their motors failing my gut feeling as of this morning is that my 84" paddle blades hurt the motor, not a inherent design flaw. I never suggested something sinister, sorry it seemed to come across that way.
In closing I truly want to say THANK YOU for sharing your vast knowledge of electrical experiences throughout the years. I for one have gained a ton from it.
Tailwinds,,, and do not archive
Ben Haas
N801BH
www.haaspowerair.com
Please note: message attached
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Subject: Re: IVO Prop System Brushes
Date: Tue, 11 May 2010 09:15:01 -0500
____________________________________________________________
$12/Month Auto Insurance
Drivers in your area are paying as low as $12/m. Free Quote instantly.
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nuckolls.bob(at)aeroelect
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| Posted: Wed May 12, 2010 6:51 am Post subject: IVO Prop System Brushes |
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I can see your thoughts on a lay person dissambling a componant only
to destroy any evidence to use to explain that failure.... I would
like to think I am capable of exceeding the lay persons ability of that task.
Sure, but IVO probably didn't know that. Further,
given that they probably knew more about their
product's design, development and field history,
it seems likely that they are the most qualified
to do failure analysis . . . presuming that their
grasp on the simple-ideas and critical thinking
was up to the task.
I've always desired that field failures of my
products be returned to me for analysis . . .
irrespective of the $time$, talents and resources
of individuals who discovered the failure.
At least for the FIRST time. As you are no doubt
aware, failures arise from a host of stresses
impressed upon weaknesses. The best understanding
of a product's overall performance comes from
a central repository of all data points. This
is best kept with the honorable manufacturer.
However, second and subsequent failures of the
same nature are up for grabs. For a single customer
or some small cluster of customers to experience
the same failure suggests a high-risk stress/weakness
couple that would probably benefit from analysis
by many.
I wasn't suggesting that you were not qualified
or even within your rights as owner of a piece of
failed hardware to do with it as you wish. But
from the perspective of one who has been intimately
attached to dozens of products from conception all
the way through development, qualification, manufacturing,
evolution of design and decades of field service
history, I can empathize with IVO's desire for
conducting their own failure investigation.
I would like to share my thoughts on the first motors failure; My
application is unique in that I am transferring ALOT of horsepower
through the Ivo prop and its related componants. I also started with
the largest diameter blades Ivo offered, 84". My first 25 hours of
test flights were using the Magnum Paddle series blades too and they
are substantially bigger and stiffer then the regular magnum blades.
My guess is the increased forces needed to twist those blades took
out the motor, even though Ron at Ivo knew and sold me that set up.
Hey,,, we are experimenting here and both Ron and I may have learned
something by my initial failure. He is a real nice guy too.
I suspect he is also honorable and that your
joint efforts will do much to advance the value
of his products.
By the lack of others responding of their motors failing my gut
feeling as of this morning is that my 84" paddle blades hurt the
motor, not a inherent design flaw. I never suggested something
sinister, sorry it seemed to come across that way.
Not a problem . . . and it wasn't intended to be
an accusation . . . only an observation based on
my own experiences and intended for 1800 others
who read this List. It's all too easy . . . and
too common for innocuous assertions to morph in
directions that the speaker never intended.
In closing I truly want to say THANK YOU for sharing your vast
knowledge of electrical experiences throughout the years. I for one
have gained a ton from it.
Its a two way street. I AM THANKFUL that the List
offers me opportunity and a reason to be
both curious and constructively critical of
the collections of simple-ideas that drive
performance and value of our airplanes.
I agree with your impressions of the IVO concept
for prop-pitch management. It's a novel idea with
a VERY low parts count but comes with a new set
of challenges. The FORCES involved are, shall we
say, significant? First you have to build a blade
that will survive and perform it's intended task
while still being flexible enough to allow this
pitch-adjusting philosophy to be applied. At the
same time, you need a mechanism that can not only
produce those forces in a controlled fashion but
be able to HOLD against those forces while
vigorously thrashing the air with an energetic
engine.
Achieving the combination of features that meets
design goals while remaining free of hazardous
failure is no simple task. Anything we can do to
be helpful in refining those processes seems
a useful and valuable thing to do. It may
be that a change of gear reduction for the larger
propellers would reduce stresses on the motor.
His product may also be a candidate for a
brushless motor design. Brushless motors can
operate with VERY fast design points and get
a whole lot more horsepower from a small
package. The brushless technology is
so prevalent that prices are now a fraction
of what they were 20 years ago. Further,
the electronics associated with brushless
motor drives is easily integrated into
sophisticated controllers that would limit
both current spikes and servoing pitch for
constant speed operation.
Bob . . .
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