Vibration Monitor (Hyde, Wanttaja?)

[RST Engineering]

Necessity, as they say, is a mother.

I am in the process of reinventing a square wheel called a vibration
monitor. The electronics is relatively trivial IF the input and output
parameters are known.

What we know is that the engine is going to have a fundamental frequency at
cruise RPM. Let's take the math-simple engine RPM of 2400. This gives us a
fundamental frequency of 2400/60 or 40 Hz.

But wait, he said. There are going to be other (sub) harmonics of that
frequency that will be of some interest. And, those harmonics will change
as a function of the engine being a two or four stroke, four or six
cylinder.

So, oh wise and noble gurus of engine stuffings, what (sub) harmonics are
going to be of most interest to us and what is their mathematical
relationship to the fundamental?

As an extra bonus question, my sensor is going to be an old phonograph
cartridge. Should I use the lightest weight "needle" that I can find? How
about a tiny little ball of lead at the tip of that needle? Would that help
the sensor? Or hinder it?

Lastly, once I get this sucker up and running with you all's good ideas, is
anybody game to bolt it onto their flying machine and report results? I can
do it for the 182, but I'd really like some other real-world reports.

Jim

[Robert Bonomi]

In article >,
RST Engineering > wrote:
>Necessity, as they say, is a mother.
>
>I am in the process of reinventing a square wheel called a vibration
>monitor. The electronics is relatively trivial IF the input and output
>parameters are known.
>
>What we know is that the engine is going to have a fundamental frequency at
>cruise RPM. Let's take the math-simple engine RPM of 2400. This gives us a
>fundamental frequency of 2400/60 or 40 Hz.
>
>But wait, he said. There are going to be other (sub) harmonics of that
>frequency that will be of some interest. And, those harmonics will change
>as a function of the engine being a two or four stroke, four or six
>cylinder.
>

*most* of the stuff 'of interest' is going to occur at the frequency of
ignition in the #1 cylinder.

You'll have "similar things" happening at the appropriate phase delay for
each cylinder.

*IF* everything is behaving exactly the same, that _should_ give you a
composite signal at (no. of cylinders) * (cyl #1 ignition frequency).

One also has to consider any drive-shaft powered 'accessories', that
may be operating at a _different_ speed than the main engine. (gear ratio,
and/or belt drive with different pulley sizes)

One form of 'bad news' is something that is going on in one cylinder that
is _different_ than what is happening in the rest of 'em. This may be
merely 'different amplitude', or it may be 'different wave-form.

Another form is something "recurring" at a frequency _other_ than what
can be explained. e.g., a flat spot on a roller in a roller bearing,
will have a characteristic frequency based on how many times the roller
rotates, per shaft rotation. Which is likely to be some "weird" ratio.

>So, oh wise and noble gurus of engine stuffings, what (sub) harmonics are
>going to be of most interest to us and what is their mathematical
>relationship to the fundamental?
>
>As an extra bonus question, my sensor is going to be an old phonograph
>cartridge. Should I use the lightest weight "needle" that I can find? How
>about a tiny little ball of lead at the tip of that needle? Would that help
>the sensor? Or hinder it?

Oh Lordie!

To get an _accurate_ measure of vibration, the 'system under test', and the
'testing system' must be *isolated* (mechanically, "vibrationally") from each
other. Then you detect the vibration in the system under test, by measuring
the instantaneous differences in position, relative to the testing system.

When the 'testing system' is mounted _on_ the 'system under test', there
is a complication of 'signal' being transferred *through* the mounting, which
is then *not* detected by the pick-up, because _both_ components are affected.

You can 'approximate' isolation with some sort of a 'suspension' system --
e.g. springs. This, however, ends up "complicating" things, because what
it does is just introduce a 'delay' in the transfer through the suspension
mechanism, *and* a probable, delayed, induced "negative" component restoring
'equilibrium'. Theoretical analysis can get *really* hairy real quick.

To accurately track vibration, you have to have a sensor that will _move_
as far as the maximum 'excursion' of the system under test. It has to
have enough structural strength that the sensor, itself doesn't "flex",
yet inertia has to be low, to enable it to 'mimic' every motion of the
system under test.

You've got two *entirely* different kinds of 'sensor' possible:
1) something 'firmly attached' to the airframe, with a "Cats whisker"
in contact with the engine, this measures engine movement relative
to the airframe.
2) something 'firmly attached' to the engine, using a cat's whisker against
a 'suspended' (as supported by a suspension) mass to compare against.
This measures the 'movement' of the sprung mass, relative to the engine.
Which is "more or less" equivalent (though opposite in sign, naturally :)
to the movement of the engine relative to the "surround".

In either case, the "cat's whisker" should be as light and rigid as possible
In the latter case, "bigger is better" for the 'reference mass', subject to
the suspension mechanism, and resonances, etc. in *it*.

[jc]

RST Engineering wrote:

<snip>
> As an extra bonus question, my sensor is going to be an old phonograph
> cartridge. Should I use the lightest weight "needle" that I can find?
> How
> about a tiny little ball of lead at the tip of that needle? Would that
> help
> the sensor? Or hinder it?

A lot depends on the range of frequencies, any sensor will have its own
fundamental frequency- multiple sensors may be a good idea. Geophones seem
to be good up to a few hundred Hz, cheap but difficult to get qty one. For
the application a speaker may be the clue (as a second sensor).
--

regards

jc

LEGAL - I don't believe what I wrote and neither should you. Sobriety and/or
sanity of the author is not guaranteed

EMAIL - and are not valid email
addresses. news2x at perentie is valid for a while.

[Brian Whatcott]

On Mon, 07 Mar 2005 13:07:25 +1100, jc > wrote:

///
>A lot depends on the range of frequencies, any sensor will have its own
>fundamental frequency- multiple sensors may be a good idea. Geophones seem
>to be good up to a few hundred Hz, cheap but difficult to get qty one. For
>the application a speaker may be the clue (as a second sensor).


Building on this idea - it appears that piezo speakers with a loaded
wafer have done well in this application.
I'm guessing that loading the ceramic to a natural frequency well
below 40Hz would be good. The output is a function of acceleration
of the casing, I imagine.

Brian Whatcott Altus OK

[Frank van der Hulst]

RST Engineering wrote:
> Necessity, as they say, is a mother.
[snip]
> As an extra bonus question, my sensor is going to be an old phonograph
> cartridge.

And you *need* to use that phonograph needle?

Analog Devices sells cheap MEMS-based accelerometers (e.g. ADXL202). You
could even use two or 3 axes. The output a 5V square wave whose duty
cycle is proportional to acceleration.

Frank

[Joerg]

Hello Jim,

>What we know is that the engine is going to have a fundamental frequency at
>cruise RPM. Let's take the math-simple engine RPM of 2400. This gives us a
>fundamental frequency of 2400/60 or 40 Hz.
>
>

Just a thought: Usually the time between the onset of a vibration and
some catastrophic failure is rather short. I believe what also needs to
be detected is the higher frequency stuff that can happen well before
this. Such as friction sounds from a bearing or cam not getting enough
lubrication.

Regards, Joerg

http://www.analogconsultants.com

[Ernest Christley]

RST Engineering wrote:

> Lastly, once I get this sucker up and running with you all's good ideas, is
> anybody game to bolt it onto their flying machine and report results? I can
> do it for the 182, but I'd really like some other real-world reports.
>
> Jim
>
>


I should be able to volunteer a rotary by the end of the summer.

Since you won't know what frequencies should be there, could you make it
a sort of historical tracking system, with maybe some sort of alarm that
goes off if something starts going out of whack from historical data?

[Stuart Fields]

Well Jim if you are inventing a vibration monitor, then you need a vibrating
platform to test it on. I have a Safari helicopter that qualifies. I also
have an electronic balancer and accelerometer transducers to provide some
cross checking at engine frequencies of 45hz, rotor frequencies of 8 and
16hz. and possibly with a little fooling, harmonics of all of the above.
Stu Fields

"RST Engineering" > wrote in message
...
> Necessity, as they say, is a mother.
>
> I am in the process of reinventing a square wheel called a vibration
> monitor. The electronics is relatively trivial IF the input and output
> parameters are known.
>
> What we know is that the engine is going to have a fundamental frequency
at
> cruise RPM. Let's take the math-simple engine RPM of 2400. This gives us
a
> fundamental frequency of 2400/60 or 40 Hz.
>
> But wait, he said. There are going to be other (sub) harmonics of that
> frequency that will be of some interest. And, those harmonics will change
> as a function of the engine being a two or four stroke, four or six
> cylinder.
>
> So, oh wise and noble gurus of engine stuffings, what (sub) harmonics are
> going to be of most interest to us and what is their mathematical
> relationship to the fundamental?
>
> As an extra bonus question, my sensor is going to be an old phonograph
> cartridge. Should I use the lightest weight "needle" that I can find?
How
> about a tiny little ball of lead at the tip of that needle? Would that
help
> the sensor? Or hinder it?
>
> Lastly, once I get this sucker up and running with you all's good ideas,
is
> anybody game to bolt it onto their flying machine and report results? I
can
> do it for the 182, but I'd really like some other real-world reports.
>
> Jim
>
>

[mindenpilot]

> Yes, IMHO accelerometers are a better way to go initially.
>
> This sort of thing has been done in commercial products, years ago
> although I don't know the details.
>

Stangely enough, this is what I do for a living. No kidding.
I am an engineer at Bently Nevada, Corp, the industry leader in machinery
diagnostics.
Most of our claim to fame is for rotating machinery; however, we do quite a
bit of work with reciprocating engines as well.

An accelerometer will work well.
So will proximity (vibration) probes.
We do all kinds of little tricks like putting a notch in the crankshaft to
use as a phase reference.
Then we can determine at what point in the cycle an anomaly occurs, which
can lead to different diagnoses.
We do a whole lot more, but I can't give away all of the trade secrets ;-)

Adam
N7966L
Beech Super III

[Morgans]

"mindenpilot" > wrote

> We do all kinds of little tricks like putting a notch in the crankshaft to
> use as a phase reference.
> Then we can determine at what point in the cycle an anomaly occurs, which
> can lead to different diagnoses.

How does the notch help in telling the rotational position?
--
Jim in NC

[Rich S.]

"Morgans" > wrote in message
...
>
> "mindenpilot" > wrote
>
>> We do all kinds of little tricks like putting a notch in the crankshaft
>> to
>> use as a phase reference.
>> Then we can determine at what point in the cycle an anomaly occurs, which
>> can lead to different diagnoses.
>
> How does the notch help in telling the rotational position?
> --
> Jim in NC

It takes a little nick out your finger as it goes by?

Rich "Ow ow ow ow owow ow ow ow ow owow" S.

[Brian Whatcott]

On Fri, 11 Mar 2005 20:25:16 -0500, "Morgans"
> wrote:

>
>"mindenpilot" > wrote
>
>> We do all kinds of little tricks like putting a notch in the crankshaft to
>> use as a phase reference.
>> Then we can determine at what point in the cycle an anomaly occurs, which
>> can lead to different diagnoses.
>
>How does the notch help in telling the rotational position?

A little magnet and associated coil sees a difference in flux as the
slot goes by. This is a variable reluctance sensor.
Your auto engine may be timed from something like this, any more.

Brian W

[Frank van der Hulst]

Morgans wrote:
> "mindenpilot" > wrote
>
>
>>We do all kinds of little tricks like putting a notch in the crankshaft to
>>use as a phase reference.
>>Then we can determine at what point in the cycle an anomaly occurs, which
>>can lead to different diagnoses.
>
>
> How does the notch help in telling the rotational position?

It adds a known vibration to the system? ;-)

Presumably, it gets used as a timing mark of some kind. I guess that
monitoring the spark time to the No 1 cylinder would almost give you the
same. "Almost" because of course the spark can be advanced/retarded.

Frank

[mindenpilot]

"Morgans" > wrote in message
...
>
> How does the notch help in telling the rotational position?
> --
> Jim in NC
>

Without giving too much away...
The notch depth is more significant than any vibration. If using a
proximity measurment, it is easy to determine when the notch occurs.
The notch is aligned with a known position (engineer inserts notch when
pistons/crank is in known position). This gives a phase reference. You can
compare where in the cycle a disturbance (knock, rub, etc) occurs with
relation to the notch. On recip applications, often a multi-tooth wheel is
used in addition to a phase reference for more accuracy.

Adam
N7966L
Beech Super III

[sleepy6]

In article >,
says...
>
>
>"Morgans" > wrote in message
...
>>
>> How does the notch help in telling the rotational position?
>> --
>> Jim in NC
>>
>
>Without giving too much away...
>The notch depth is more significant than any vibration. If using a
>proximity measurment, it is easy to determine when the notch occurs.
>The notch is aligned with a known position (engineer inserts notch whe
>n
>pistons/crank is in known position). This gives a phase reference. Y
>ou can
>compare where in the cycle a disturbance (knock, rub, etc) occurs with
>
>relation to the notch. On recip applications, often a multi-tooth whe
>el is
>used in addition to a phase reference for more accuracy.
>
>Adam
>N7966L
>Beech Super III
>

I love puzzles.

Start out with a picture in your mind of a perfectly round crank flange
with a dial indicator rideing on the outside edge at the top as you
slowly rotate the crank. The indicator will not move because the
flange is perfectly round.

Under viberation, the crank will move up and down (within the limits of
the bearing clearance) and the dial indicator will show how far the
crank moves.

Now replace the dial indicator with a precision proximity detector.
You get a steady flat line electronic signal until you get movement up
or down. Then the signal will change at the same frequency as the
movement and change amptitude with the amount of movement.

Now add a notch across the edge of the flange so that the notch is seen
by the sensor when #1 piston is at top dead center.

That notch causes a much larger timing blip in the signal than any
crank movement will cause. By measureing the time between the timing
blips you can determine the amount of rotation after a timing blip that
you see an up or down crank movement event.

In other words if you see a minor blip exactly midway between timing
blips then you know the crank moved up or down when #1 piston was at
bottom dead center in our example. The amptitude of the minor blip
will tell you how far it moved. It could even be set up to tell you if
the crank moved up or moved down by the polarity shift of the signal.

Of course this simple setup will not show side to side movement. That
would require a second proximity detector 90 degrees from the first
one. The 2 signals would require integration but would then show all
movement in the rotational plane with the proper signal processing and
calibration.

[Morgans]

"sleepy6" > wrote
>
> That notch causes a much larger timing blip in the signal than any
> crank movement will cause. By measureing the time between the timing
> blips you can determine the amount of rotation after a timing blip that
> you see an up or down crank movement event.

What sort of technology does a proxomity detector use? Magnetics, sonic,
radio waves?
--
Jim in NC

[Fly]

Without giving too much away............ (yuk yuk yuk)

One can always post your questions at:
http://www.vibinst.org/default.htm

and usually somebody will be happy to answer.

Phase indicators can be a variety of schemes or devices. Proximity
probes, and notch. Strobe light. Magnetic interrupter. Photocell.
Even the old proverbial pencil and masking tape!

Kent Felkins
Tulsa

[George A. Graham]

Jim,

I have a Memsic demo board, which displays LEDS on two axis with
their tilt and motion sensor.

I am done with it, would you like to play with it?

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[RST Engineering]

Strangely enough, that is what I *DID* for a living when Spectral Dynamics
was the industry leader in machinery diagnostics. Unfortunately, my job was
the circuit design, not the diagnostics itself, so all I concerned myself
with was the black box that took a defined input and produced a defined
output. There are times I wish that I had transferred to the applications
department. They were the ones that seemed to have the most fun (and the
most three martini Friday lunches).


Jim


">>
>
> Stangely enough, this is what I do for a living. No kidding.
> I am an engineer at Bently Nevada, Corp, the industry leader in machinery
> diagnostics.

[RST Engineering]

Yes, all of the below.

Sometimes you drill a hole in a small magnet and use a small screw to hold
it to the propeller backing plate. Sometimes you use a strip of reflective
tape on the prop itself. Sometimes you use a pulse from the #1 magneto
lead.

Jim




"Morgans" > wrote in message
...
>
> "sleepy6" > wrote
>>
>> That notch causes a much larger timing blip in the signal than any
>> crank movement will cause. By measureing the time between the timing
>> blips you can determine the amount of rotation after a timing blip that
>> you see an up or down crank movement event.
>
> What sort of technology does a proxomity detector use? Magnetics, sonic,
> radio waves?
> --
> Jim in NC
>
>

[RST Engineering]

Love to. You got my address?

Jim




"George A. Graham" > wrote in message
...
>
> Jim,
>
> I have a Memsic demo board, which displays LEDS on two axis with
> their tilt and motion sensor.
>
> I am done with it, would you like to play with it?
>
> George Graham
> RX-7 Powered Graham-EZ, N4449E
> Homepage <http://bfn.org/~ca266>
>

[mindenpilot]

"RST Engineering" > wrote in message
...
> Strangely enough, that is what I *DID* for a living when Spectral Dynamics
> was the industry leader in machinery diagnostics. Unfortunately, my job
> was the circuit design, not the diagnostics itself, so all I concerned
> myself with was the black box that took a defined input and produced a
> defined output. There are times I wish that I had transferred to the
> applications department. They were the ones that seemed to have the most
> fun (and the most three martini Friday lunches).
>
>
> Jim
>


LOL.
I've been an engineer designing in the dark many times.
Fortunately at Bently, there is a large effort to train engineers in
diagnostics.
Then we can use personal experience in addition to requirements documents
when designing a new product.
Or, at least, we can determine if requirements make sense!

Adam

[mindenpilot]

"sleepy6" > wrote in message
...

> Of course this simple setup will not show side to side movement. That
> would require a second proximity detector 90 degrees from the first
> one. The 2 signals would require integration but would then show all
> movement in the rotational plane with the proper signal processing and
> calibration.
>

Exactly. This two-dimensional shaft path is called an orbit.

Adam

[RST Engineering]

Understood. What I started out to do (and still plan on doing) is to have a
device that will stay permanently mounted to the engine that can be
calibrated (adjusted, signed, pick a verb) when the engine is known to be
good and light a "your engine is about to come apart" lamp at the
appropriate time.

What this group seems to be leaning toward is a lab quality device that will
allow for sophisticated diagnostics. That ain't the thrust of my Kitplanes
columns. KISS and BURP.

Jim

[mindenpilot]

"RST Engineering" > wrote in message
...
> Understood. What I started out to do (and still plan on doing) is to have
> a device that will stay permanently mounted to the engine that can be
> calibrated (adjusted, signed, pick a verb) when the engine is known to be
> good and light a "your engine is about to come apart" lamp at the
> appropriate time.
>
> What this group seems to be leaning toward is a lab quality device that
> will allow for sophisticated diagnostics. That ain't the thrust of my
> Kitplanes columns. KISS and BURP.
>
> Jim
>

As is tradition, we tend to get off topic ;-)
I think you can accomplish this using the methods discussed.
Mount 2 proximity probes 90 degrees apart.
Calibrate the readings for normal low vibrations (be sure to account for any
nonlinearities in the probe).
Design the circuit to trip the buzzer/lamp when the vibration exceeds the
normal level.
You may need some analog circuitry to help (gain, etc).
But you don't need to get much fancier than that.

Adam

[RST Engineering]

Proximity probes? Or accelerometers?

I understand about the analog circuitry and actually plan on making a five
or six channel filter at each of the possible resonance points relative to
the fundamental ... and then strobing the filters to light a "normal",
"low", "high" lamp for each channel.

Jim



>
> As is tradition, we tend to get off topic ;-)
> I think you can accomplish this using the methods discussed.
> Mount 2 proximity probes 90 degrees apart.
> Calibrate the readings for normal low vibrations (be sure to account for
> any nonlinearities in the probe).
> Design the circuit to trip the buzzer/lamp when the vibration exceeds the
> normal level.
> You may need some analog circuitry to help (gain, etc).
> But you don't need to get much fancier than that.
>
> Adam
>

[Morgans]

"RST Engineering" > wrote in message
...
> Yes, all of the below.
>
> Sometimes you drill a hole in a small magnet and use a small screw to hold
> it to the propeller backing plate. Sometimes you use a strip of
reflective
> tape on the prop itself. Sometimes you use a pulse from the #1 magneto
> lead.
>
> Jim

This guy was talking about a notch and proximity detector for the phase
detection. I know about all of the things you mentioned, but the proximity
detector's workings are new to me.
--
Jim in NC

[mindenpilot]

I would use proximity probes if you are primarily going to measure
vibration.
They are also the best choice if you are going to notch the shaft and do
phase measurment.
I'm not sure about other venders' prox probes, but the one's I'm used to
have a linear range.
The phase measurment can be gained so that it rails one way when over the
notch and rails the other way when not, so you don't have to worry about the
linear range. As for vibration measurments, you will have to make sure that
you stay in the linear range of the probe.

I want to make sure I understand what you meant by having a filter at the
resonance points.
Are you only going to measure vibration at resonance (i.e. bandpass)?
Or, are you NOT going to measure at resonance (i.e. notch filter)?
Keep in mind other events may cause vibration, such as impulse, rub, etc,
which will likely occur synchronous to the shaft, and have nothing to do
with resonance.
This is where a phase reference may be handy because you could determine if
it is happening 1X/rev, 2X/rev, etc.
OR, are you assuming that an impulse/rub event will excite the case at the
resonance frequency?

At any rate, what you intend on doing is definitely do-able.
I recommend playing with probes a bit to see what you get.
Sounds like a fun project.
Let me know if there's anything I can offer...

Adam


"RST Engineering" > wrote in message
...
> Proximity probes? Or accelerometers?
>
> I understand about the analog circuitry and actually plan on making a five
> or six channel filter at each of the possible resonance points relative to
> the fundamental ... and then strobing the filters to light a "normal",
> "low", "high" lamp for each channel.
>
> Jim
>
>
>
>>
>> As is tradition, we tend to get off topic ;-)
>> I think you can accomplish this using the methods discussed.
>> Mount 2 proximity probes 90 degrees apart.
>> Calibrate the readings for normal low vibrations (be sure to account for
>> any nonlinearities in the probe).
>> Design the circuit to trip the buzzer/lamp when the vibration exceeds the
>> normal level.
>> You may need some analog circuitry to help (gain, etc).
>> But you don't need to get much fancier than that.
>>
>> Adam
>>
>
>

[Robert Bonomi]

In article >,
Morgans > wrote:
>
>"RST Engineering" > wrote in message
...
>> Yes, all of the below.
>>
>> Sometimes you drill a hole in a small magnet and use a small screw to hold
>> it to the propeller backing plate. Sometimes you use a strip of
>reflective
>> tape on the prop itself. Sometimes you use a pulse from the #1 magneto
>> lead.
>>
>> Jim
>
>This guy was talking about a notch and proximity detector for the phase
>detection. I know about all of the things you mentioned, but the proximity
>detector's workings are new to me.

Think of a proximity detector as 'ultra short-range radar'. <grin>
It may use reflected RF energy, or 'optical'.

where the 'excursions' you're trying to measure are smaller than the
wavelength of the measuring 'beam', you can use simple phase-shift
between outgoing and returning signal, to determine distance.

where the distance is much larger than the wavelength, you have to
impress a carrier on the beam, and measure phase-shift in the carrier
frequency. this gets an 'approximate' distance, that can be further
refined by phase angle measurements of the beam itself.

Capacitance tracking is also a possible approach.
and/or "Hall effect".

These can get 'messy', due to inherent non-linearity in the technology,
that has to be compensated for, in 'reading' the signals.

Capacitance tracking works best where there are *very*small* vibrations
involved, and a very _smooth_ surface to measure against. The technique
is capable of mapping individual atoms/molecules in a crystal lattice.
Scientific American had a write-up -- at least 15 years ago -- about
a new 'super microscope' (successor generation to the scanning electron
microscope) that worked in that manner. a _very_fine_ 'needle' was
carefully moved, raster-style, across the object being 'scanned', and
the capacitance changes between the needle and the object were mapped.

[mindenpilot]

"Robert Bonomi" > wrote in message
...
> In article >,
> Morgans > wrote:
>>
>>"RST Engineering" > wrote in message
...
>>> Yes, all of the below.
>>>
>>> Sometimes you drill a hole in a small magnet and use a small screw to
>>> hold
>>> it to the propeller backing plate. Sometimes you use a strip of
>>reflective
>>> tape on the prop itself. Sometimes you use a pulse from the #1 magneto
>>> lead.
>>>
>>> Jim
>>
>>This guy was talking about a notch and proximity detector for the phase
>>detection. I know about all of the things you mentioned, but the
>>proximity
>>detector's workings are new to me.
>
> Think of a proximity detector as 'ultra short-range radar'. <grin>
> It may use reflected RF energy, or 'optical'.
>
> where the 'excursions' you're trying to measure are smaller than the
> wavelength of the measuring 'beam', you can use simple phase-shift
> between outgoing and returning signal, to determine distance.
>
> where the distance is much larger than the wavelength, you have to
> impress a carrier on the beam, and measure phase-shift in the carrier
> frequency. this gets an 'approximate' distance, that can be further
> refined by phase angle measurements of the beam itself.
>
> Capacitance tracking is also a possible approach.
> and/or "Hall effect".
>
> These can get 'messy', due to inherent non-linearity in the technology,
> that has to be compensated for, in 'reading' the signals.
>
> Capacitance tracking works best where there are *very*small* vibrations
> involved, and a very _smooth_ surface to measure against. The technique
> is capable of mapping individual atoms/molecules in a crystal lattice.
> Scientific American had a write-up -- at least 15 years ago -- about
> a new 'super microscope' (successor generation to the scanning electron
> microscope) that worked in that manner. a _very_fine_ 'needle' was
> carefully moved, raster-style, across the object being 'scanned', and
> the capacitance changes between the needle and the object were mapped.
>
>

Actually, the proximity probes I am familiar with work on the "eddy current"
principle.
That is, RF energy is directed at the shaft through a coil. Some of the
energy is lost into the shaft in the eddy currents.
The energy that is coupled back into the coil is the measured signal.
Since the amount of energy dissipated in the shaft is proportional to the
distance between the shaft and probe, the result is a displacement
measurment.

Adam

[Robert Bonomi]

In article >,
RST Engineering > wrote:
> Proximity probes? Or accelerometers?

The proverbial "it depends". _first_ you have do decide what your
'frame of reference' for vibration is. If you're looking for
excursions in the drive shaft, relative to the engine block, then
a pair of proximity sensors in quadrature to measure excursions from
the shaft axis, plus a strain gauge at a fore-to-aft thrust bearing
gives you complete data. Convert from XYZ to polar co-ordinates,
Fourier transform on the magnitude component, check each passband
against loading-corrected reference values, and illuminate corresponding
indicators.

If you're looking for things that might affect all parts of the engine
equally, then, can you use the airframe for reference, or not? If "yes",
then the same approach works, just on a different scale. If, "no", then
you're pretty much stuck with three _inertial_ accelerometers, mounted at
mutual right angles.

>I understand about the analog circuitry and actually plan on making a five
>or six channel filter at each of the possible resonance points relative to
>the fundamental ... and then strobing the filters to light a "normal",
>"low", "high" lamp for each channel.
>

Sounds like you're talking about using a group of narrow bandpass filters
and sampling the short-term average signal level out of each filter,
"Looking for" a marked increase vs a base-line reference (at that frequency),
as an indicator of problems.


I see a couple of difficulties -- not necessarily insurmountable, but
there, nonetheless. (1) Most, if not all, the 'frequencies of interest'
are dependent on engine speed. thus the filter 'center frequencies'
will have to track engine RPM. (2) "Normal" vibration _magnitude_ will
vary with the load on the engine. The trigger threshold would seemingly
have to adjust to compensate. 3,000 RPM in a 2,000 FPM climb is a
different engine environment than 3,000 RPM in level cruise. I don't
know enough engine mechanics to guess whether just the throttle setting
is going to be sufficient to determine the required adjustments. At
a guess, torque relative to the airframe would be a better indicator.

Lastly, I'd suggest one channel that is comparatively broadband. specifically
to catch unanticipated "out of band" goings-on.

>Jim
>
>
>
>>
>> As is tradition, we tend to get off topic ;-)
>> I think you can accomplish this using the methods discussed.
>> Mount 2 proximity probes 90 degrees apart.
>> Calibrate the readings for normal low vibrations (be sure to account for
>> any nonlinearities in the probe).
>> Design the circuit to trip the buzzer/lamp when the vibration exceeds the
>> normal level.
>> You may need some analog circuitry to help (gain, etc).
>> But you don't need to get much fancier than that.
>>
>> Adam
>>
>
>

[Robert Bonomi]

In article >,
mindenpilot > wrote:
>
>"Robert Bonomi" > wrote in message
...
>> In article >,
>> Morgans > wrote:
>>>
>>>"RST Engineering" > wrote in message
...
>>>> Yes, all of the below.
>>>>
>>>> Sometimes you drill a hole in a small magnet and use a small screw to
>>>> hold
>>>> it to the propeller backing plate. Sometimes you use a strip of
>>>reflective
>>>> tape on the prop itself. Sometimes you use a pulse from the #1 magneto
>>>> lead.
>>>>
>>>> Jim
>>>
>>>This guy was talking about a notch and proximity detector for the phase
>>>detection. I know about all of the things you mentioned, but the
>>>proximity
>>>detector's workings are new to me.
>>
>> Think of a proximity detector as 'ultra short-range radar'. <grin>
>> It may use reflected RF energy, or 'optical'.
>>
>> where the 'excursions' you're trying to measure are smaller than the
>> wavelength of the measuring 'beam', you can use simple phase-shift
>> between outgoing and returning signal, to determine distance.
>>
>> where the distance is much larger than the wavelength, you have to
>> impress a carrier on the beam, and measure phase-shift in the carrier
>> frequency. this gets an 'approximate' distance, that can be further
>> refined by phase angle measurements of the beam itself.
>>
>> Capacitance tracking is also a possible approach.
>> and/or "Hall effect".
>>
>> These can get 'messy', due to inherent non-linearity in the technology,
>> that has to be compensated for, in 'reading' the signals.
>>
>> Capacitance tracking works best where there are *very*small* vibrations
>> involved, and a very _smooth_ surface to measure against. The technique
>> is capable of mapping individual atoms/molecules in a crystal lattice.
>> Scientific American had a write-up -- at least 15 years ago -- about
>> a new 'super microscope' (successor generation to the scanning electron
>> microscope) that worked in that manner. a _very_fine_ 'needle' was
>> carefully moved, raster-style, across the object being 'scanned', and
>> the capacitance changes between the needle and the object were mapped.
>>
>>
>
>Actually, the proximity probes I am familiar with work on the "eddy current"
>principle.
>That is, RF energy is directed at the shaft through a coil. Some of the
>energy is lost into the shaft in the eddy currents.
>The energy that is coupled back into the coil is the measured signal.
>Since the amount of energy dissipated in the shaft is proportional to the
>distance between the shaft and probe, the result is a displacement
>measurment.

No doubt about it, there are *LOTS* of ways to measure proximity. :)

Eddy current detectors have somewhat limited application.
1) the material of the item measured must be uniform in composition where
it is 'presented' to the detector.
2) the material has to be electrically conductive to a degree. If the item
under test is a good insulator, you don't get eddy currents, If the item
is _too_good_ a conductor, you don't get eddy currents.

For engine shafts, etc. those items are a "non-issue", agreed.

They don't work worth a d*mn if you're trying to measure motion in a rubber/-
polyethylene/vinyl/whatever drive belt, though. <grin>

[Morgans]

"Robert wrote

> No doubt about it, there are *LOTS* of ways to measure proximity. :)

> > and some others contributed lots

And I think I'm almost sorry I asked! <g?>
--
Jim in NC

[RST Engineering]

Well, a Spectral Dynamics SD2001 FFT would be well received if you have one
laying around unused {;-)


Jim



"mindenpilot" > wrote in message
...
> At any rate, what you intend on doing is definitely do-able.
> I recommend playing with probes a bit to see what you get.
> Sounds like a fun project.
> Let me know if there's anything I can offer...
>
> Adam

[LCT Paintball]

"RST Engineering" > wrote in message
...
> Understood. What I started out to do (and still plan on doing) is to have
> a device that will stay permanently mounted to the engine that can be
> calibrated (adjusted, signed, pick a verb) when the engine is known to be
> good and light a "your engine is about to come apart" lamp at the
> appropriate time.


Excuse my ignorance, but couldn't you just feel the vibrations?

[Pete Schaefer]

If you wait that long, you're probably more concerned if the chain that's
holding the motor to the firewall is going to break after the motor cuts
loose from the mounts. All too often, the vibrations start to pick up
seconds or miliseconds before a catastrophic failure.

To do such a health-monitoring function properly, you really want some
seeded fault data to characterize what a "bad" engine spectrum looks like.
How many engines do you want to sacrifice to get the data? You can approach
it from the "anything different from a healthy engine signature" standpoint,
but that will likely result in a ton of false positive fault indications.

"LCT Paintball" > wrote in message
news:_Lq0e.14520$fn3.9681@attbi_s01...
> "RST Engineering" > wrote in message
> ...
> > Understood. What I started out to do (and still plan on doing) is to
have
> > a device that will stay permanently mounted to the engine that can be
> > calibrated (adjusted, signed, pick a verb) when the engine is known to
be
> > good and light a "your engine is about to come apart" lamp at the
> > appropriate time.
>
>
> Excuse my ignorance, but couldn't you just feel the vibrations?
>
>

[William W. Plummer]

RST Engineering wrote:
> Necessity, as they say, is a mother.
>
> I am in the process of reinventing a square wheel called a vibration
> monitor. The electronics is relatively trivial IF the input and output
> parameters are known.
>
> What we know is that the engine is going to have a fundamental frequency at
> cruise RPM. Let's take the math-simple engine RPM of 2400. This gives us a
> fundamental frequency of 2400/60 or 40 Hz.
>
> But wait, he said. There are going to be other (sub) harmonics of that
> frequency that will be of some interest. And, those harmonics will change
> as a function of the engine being a two or four stroke, four or six
> cylinder.
>
> So, oh wise and noble gurus of engine stuffings, what (sub) harmonics are
> going to be of most interest to us and what is their mathematical
> relationship to the fundamental?
>
> As an extra bonus question, my sensor is going to be an old phonograph
> cartridge. Should I use the lightest weight "needle" that I can find? How
> about a tiny little ball of lead at the tip of that needle? Would that help
> the sensor? Or hinder it?
>
> Lastly, once I get this sucker up and running with you all's good ideas, is
> anybody game to bolt it onto their flying machine and report results? I can
> do it for the 182, but I'd really like some other real-world reports.

Sometime ago someone published a program that runs on a PalmPilot. It
uses the microphone to listen to a plane engine and will tell how many
RPM it is turning, even from a half mile away (IIRC). Could you do your
engine vibration analysis through the microphone rather than
accelerometers and other sensors?

[LCT Paintball]

> If you wait that long, you're probably more concerned if the chain that's
> holding the motor to the firewall is going to break after the motor cuts
> loose from the mounts. All too often, the vibrations start to pick up
> seconds or miliseconds before a catastrophic failure.
>
> To do such a health-monitoring function properly, you really want some
> seeded fault data to characterize what a "bad" engine spectrum looks like.
> How many engines do you want to sacrifice to get the data? You can
> approach
> it from the "anything different from a healthy engine signature"
> standpoint,
> but that will likely result in a ton of false positive fault indications.


Are you suggesting that a bad engine will give clues to it's demise enough
in advance that you could actually do something about it? Clues that a
monitor could pick up on, but an experienced pilot wouldn't?

[Pete Schaefer]

Of course. It has been done. Depends on the failure mode, of course. There
are some failure modes that take a long time to develop that give early
indications, and some that don't. A ton of work has been done in this area
for military jet engines. Seeded fault test data is the key to this.
Unfortunately, that might mean wrecking a bunch of engines to get the data.
It's not a project for the average home-builder.

Personally, I wouldn't bother trying to get a vibration caution together for
a home-built. Doing right would be just way too expensive. It would be
cheaper to just buy something that's turbine-powered and get rid of the
hazards that way. Besides, a huge number of failure modes already show up in
CHT's, EGT's, RPMs, etc. You have to weigh the cost of covering additional
failure modes against the hazards. This is really a job for engine
manufacturers. Additionally, you have to take complexity and reliability of
the sensing and processing into account. A monitor that is always going
haywire on you would be worse than nothing at all.

I'm actually looking at some stuff like this for possible inclusion on a
future project right now for a different type of powerplant. If you can
reliably predict RUL (remaining usable life) for a critical component, it
could be possible to reduce the amount of redundancy in a complex system and
rely on health monitoring functions to let you know when it's time to
replace the part.

PHM (prognostics and health management) has been a big focus in the military
aircraft world in recent years. I'm hoping that some of this technology will
trickle down to us in the GA world. Hmm...maybe I should get with an engine
manufacturer and work something out... SO, how much would people pay for an
engine health monitoring system package as an option for a new engine (i.e.
one of the new generation...maybe a DeltaHawk)? My guess is that it would be
too expensive to ever sell.

Pete


"LCT Paintball" > wrote in message
news:ipA0e.102105$Ze3.20828@attbi_s51...
> Are you suggesting that a bad engine will give clues to it's demise enough
> in advance that you could actually do something about it? Clues that a
> monitor could pick up on, but an experienced pilot wouldn't?

[nafod40]

Pete Schaefer wrote:
>
> PHM (prognostics and health management) has been a big focus in the military
> aircraft world in recent years. I'm hoping that some of this technology will
> trickle down to us in the GA world.

One useful technology that keeps getting more real are self-powered
sensors that communicate via bluetooth or other wireless, so you could
just stick them on various places and not have to worry about cabling
and all those other points of failure.

[Pete Schaefer]

Cool. Maybe we should do entire airplanes around bluetooth. That way, any
geek with a PDA can hack our planes when we fly by. Yeah, **** all these EMI
worries!

Sorry, but that idea sounds like an awfully inviting drive-by target.

"nafod40" > wrote in message
...
> One useful technology that keeps getting more real are self-powered
> sensors that communicate via bluetooth or other wireless, so you could
> just stick them on various places and not have to worry about cabling
> and all those other points of failure.
>

[mindenpilot]

> Are you suggesting that a bad engine will give clues to it's demise enough
> in advance that you could actually do something about it? Clues that a
> monitor could pick up on, but an experienced pilot wouldn't?
>

My company makes ~200MM/yr on this premies.

Adam
N7966L
Beech Super III

[mindenpilot]

oops... I meant "premise".

"mindenpilot" > wrote in message
...
>> Are you suggesting that a bad engine will give clues to it's demise
>> enough in advance that you could actually do something about it? Clues
>> that a monitor could pick up on, but an experienced pilot wouldn't?
>>
>
> My company makes ~200MM/yr on this premies.
>
> Adam
> N7966L
> Beech Super III
>

[Frank van der Hulst]

Pete Schaefer wrote:
> Cool. Maybe we should do entire airplanes around bluetooth. That way, any
> geek with a PDA can hack our planes when we fly by. Yeah, **** all these EMI
> worries!
>
> Sorry, but that idea sounds like an awfully inviting drive-by target.

Bluetooth has a limited range -- about 10m absolute max. Do you often
fly overhead geeks at 36ft AGL?

Not only that, but Bluetooth also allows closed networks to be set up --
no access to anyone outside the selected group of devices.

Sorry, but you shouldn't get all sarcastic about someone suggesting a
technology that you clearly don't have a clue about.

Frank

[LCT Paintball]

"mindenpilot" > wrote in message
...
> oops... I meant "premise".
>

Was that a Freudian slip? ;)

[nafod40]

Pete Schaefer wrote:
> Cool. Maybe we should do entire airplanes around bluetooth. That way, any
> geek with a PDA can hack our planes when we fly by. Yeah, **** all these EMI
> worries!
>
> Sorry, but that idea sounds like an awfully inviting drive-by target.

The idea that some sensors sending their signals via bluetooth to a data
recorder instead of cabling could be "hacked", whether from a PDA
standing outside the plane or from 5,000 feet AGL is silly. The EMI
argument is an open one, but the FAA rule says...

"a) Except as provided in paragraph (b) of this section, no person may
operate, nor may any operator or pilot in command of an aircraft allow
the operation of, any portable electronic device on any of the following
U.S-registered civil aircraft:


(1) Aircraft operated by a holder of an air carrier operating
certificate or an operating certificate; or
(2) Any other aircraft while it is operated under IFR.

(b) Paragraph (a) of this section does not apply to--

(1) portable voice recorders;
(2) hearing aids;
(3) heart pacemakers;
(4) electric shavers; or
(5) any other portable electronic device that the operator of the
aircraft has determined will not cause interference with the navigation
or communication system of the aircraft on which it is to be used.

It's coming to aircraft. In fact, it's already there via people that
don't turn off their cell phones and laptops etc., just uncontrolled.
Good article.

http://developer.intel.com/technology/itj/q22000/articles/art_4.htm

[Blanche]

I've always wanted 100T ethernet thru the entire avionics stack.
Adding Bluetooth to the portable devices makes perfect sense!

[Pete Schaefer]

OK, if all you want is to record data, then yeah, whatever you want to use
is just fine as long as you can keep it from interfering with any critical
functions on your plane. However, debugging all the potential EMI stuff
could be hell just to get things to work. I was being sarcasting about the
hacking comment....yeah, it was silly.

There are already enough other decent options that will work just fine
without the hassles of dealing with radio frequency stuff. Look at the
aviation versions of CAN. Well supported, cheap, and really easy. There's
also 1394, which is used a bunch in some new aviation systems.


"nafod40" > wrote in message
...
> It's coming to aircraft. In fact, it's already there via people that
> don't turn off their cell phones and laptops etc., just uncontrolled.
> Good article.
>
> http://developer.intel.com/technology/itj/q22000/articles/art_4.htm
>
>
>
>
>

[Pete Schaefer]

Frank:

I do have quite a clue about EMI, and clearly have a better clue than you
about systems engineering in general. Here's a question for you:

Why bother?

If you're trying to cert bluetooth for aviation, maybe with the thought of
selling some other bluetooth product that you think you can make a big chunk
of cash with, then, yeah, maybe going off to play with bluetooth on your
airplane makes sense. Personally, I can't see it. Maybe it makes sense for
using it to reprogram boxes on your airplane, but to go to the extent of
making it useful/safe in flight....nah. Way too much effort for too little
return, given that the inclusion of an RS-232 port is so freakin' easy.

If you have some other goal in mind, maybe some other sensing or data fusion
tech (e.g. may you have a huge array of air data sensors for some advance
stall detection method), then you have to look at whether or not the tech
risk buys you something that you can't get otherwise. Why bluetooth rather
than the 1/2 dozen other wired data communication protocols (e.g. 1392, .
422, 232, 485, CAN, etc.) that are out there?

I get rather frustrated with people who get really !@#$ing enamored with
technologies for implementation and loose sight of what their goals are. All
too often, risk variables get introduced where none is warranted, resulting
in zero or negative value added. I beat on my guys daily about issues like
this. (Kelly Johnson (...yeah, I work at that place.....) had a lot to say
about where it was acceptable to take project risks..too bad so much of it
never got captured in "the rules").

So, back to Blue Tooth....

Why bother?

For data collection, I've already got a half-dozen options in my hip pocket
that I know will work just fine with very well understood EMI issues that I
know how to mitigate. What's my goal? Blue tooth airplane or getting the
data for some other purpose?

I have very little room for Geek Factor on any airplane that I'll ever
build. If it can't buy it's way on (I'd lump Blue Tooth in here), then !@#$
it.


Pete

P.S. I just got done with a 5 hour drive and am tired as all !@#$. I've got
4 beers in me to diffuse stress. Please forgive my abbrasiveness. I'm not
really that bad of a guy. I just don't want people to pursue ideas that
will get them killed.


"Frank van der Hulst" > wrote in message
...
> Sorry, but you shouldn't get all sarcastic about someone suggesting a
> technology that you clearly don't have a clue about.

[Pete Schaefer]

Frank:

P.S. Your're right...I don't know **** about the specifics of Blue Tooth.
I'm glad to admit it.

"Frank van der Hulst" > wrote in message
...
> Sorry, but you shouldn't get all sarcastic about someone suggesting a
> technology that you clearly don't have a clue about.
>
> Frank

[nafod40]

Pete Schaefer wrote:
> OK, if all you want is to record data, then yeah, whatever you want to use
> is just fine as long as you can keep it from interfering with any critical
> functions on your plane. However, debugging all the potential EMI stuff
> could be hell just to get things to work.

I hate cables. They are a gawdawful pain to manufacture, install, even
worse to troubleshoot, and hell to fix. Installing new ones to odd
points on a plane is sometimes impossible. I flew the E-2C (whistling
s%$# can) and most of our class alphas were due to cables abrading and
causing shorts, wandering signals, fires, etc. Obviously the bad things
came from the power-carrying cables failing, but everything in the
bundle went south when they did.

EMI is obviously an issue, in ways I don't understand since I'm not a
tron-bender, but the idea that you could plunk down a sensor and have
*no* additional wiring whatsoever appeals to me. I wonder how much wire
weighs and costs in the typical airplane? What are the EMI issues for
your Mark I Mod 0 homebuilt? Nav system, obviously. What else? Sounds
like an experimental airplane kind of thing to me.

A company a friend of mine owns is developing the self-powered sensors,
so I'm familiar with the work. The ones they sell now are bigger and (I
think) battery-powered, but they are installing them on Navy ships,
which have emmisions and EMI concerns too.

http://www.rlwinc.com/

[Frank van der Hulst]

Pete Schaefer wrote:
> Frank:
>
> I do have quite a clue about EMI, and clearly have a better clue than you
> about systems engineering in general. Here's a question for you:
>
> Why bother?

For the same reason that we build planes instead of buying them.

> If you're trying to cert bluetooth for aviation, maybe with the thought of
> selling some other bluetooth product that you think you can make a big chunk
> of cash with, then, yeah, maybe going off to play with bluetooth on your
> airplane makes sense. Personally, I can't see it. Maybe it makes sense for
> using it to reprogram boxes on your airplane, but to go to the extent of
> making it useful/safe in flight....nah. Way too much effort for too little
> return, given that the inclusion of an RS-232 port is so freakin' easy.

I agree totally. except maybe about RS-232. I suggest that some sort of
current-based rather than voltage-based signalling would be more
noise-immune. Bring back 20mA current loop! :-)

> If you have some other goal in mind, maybe some other sensing or data fusion
> tech (e.g. may you have a huge array of air data sensors for some advance
> stall detection method), then you have to look at whether or not the tech
> risk buys you something that you can't get otherwise. Why bluetooth rather
> than the 1/2 dozen other wired data communication protocols (e.g. 1392, .
> 422, 232, 485, CAN, etc.) that are out there?

The TWO key ideas in the proposition (wasn't mine, BTW) were wireless
comms and self-powered. If you can do BOTH of those, then wired comms
and power is best. Wireless comms has been pretty much solved. For
example, I saw a projection in an engineering mag that within 25 years
wireless will replace wired as the cheapest comms technology to the home.

But without "self-powered" it is pointless. Are there any devices out
there that can turn (e.g.) vibration into *useful* amounts of electricity?

> I get rather frustrated with people who get really !@#$ing enamored with
> technologies for implementation and loose sight of what their goals are.

Hmmm... so what are *my* goals? Maybe I want the geekiest plane on the
block? I suggest that one or other of your 4 beers has introduced some
patronisation (as well as abrasiveness) into your system.

> All
> too often, risk variables get introduced where none is warranted, resulting
> in zero or negative value added.

I'll choose what risks are warranted on *my* project, thanks.

> I beat on my guys daily about issues like
> this. (Kelly Johnson (...yeah, I work at that place.....) had a lot to say
> about where it was acceptable to take project risks..too bad so much of it
> never got captured in "the rules").

This is fine where *you* get to set the goals.

> So, back to Blue Tooth....
>
> Why bother?

*With* self-powered devices, it gives options not available via wired
systems.

> For data collection, I've already got a half-dozen options in my hip pocket
> that I know will work just fine with very well understood EMI issues that I
> know how to mitigate. What's my goal? Blue tooth airplane or getting the
> data for some other purpose?
>
> I have very little room for Geek Factor on any airplane that I'll ever
> build. If it can't buy it's way on (I'd lump Blue Tooth in here), then !@#$
> it.
>
>
> Pete
>
> P.S. I just got done with a 5 hour drive and am tired as all !@#$. I've got
> 4 beers in me to diffuse stress. Please forgive my abbrasiveness. I'm not
> really that bad of a guy. I just don't want people to pursue ideas that
> will get them killed.

Hey, I prefer to talk straight too. And also don't want people to kill
themselves. But if people don't experiment with Experimental category
aircraft, then nothing is going to change.

Frank

[nafod40]

Frank van der Hulst wrote:
>
> *With* self-powered devices, it gives options not available via wired
> systems.
>

Couple of sources. This is a hot research area.

http://www.sandia.gov/media/NewsRel/NR2002/vibepoweredsensor.htm

http://www.perpetuum.co.uk/

[Ernest Christley]

Frank van der Hulst wrote:
>>
>> Why bother?
>
>
> *With* self-powered devices, it gives options not available via wired
> systems.
>

Even if you have to run 12V to it, in a metal airplane that will only be
one wire and one connection. Assuming they can build a wireless device
that can stand up to typical airplane abuse for a while*, this would
make for a much simpler and safer installation. At these power levels,
the EMI issue is a red herring that would be easily defeated with a
$0.98 roll of aluminum foil, and once defeated on the ground the
problem isn't likely to pop back up in flight (like loose cabling will).

IMHO

*It seems that your standard store bought router is designed to die
after a few years. I wouldn't trust this quality control with my
comfort. I barely trust it with my ability to read this newsgroup.


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[Pete Schaefer]

So, what things on the airplane are you guys going to replace with
self-powered blue tooth devices?


"Ernest Christley" > wrote in message
om...
> Even if you have to run 12V to it, in a metal airplane that will only be
> one wire and one connection. Assuming they can build a wireless device
> that can stand up to typical airplane abuse for a while*, this would
> make for a much simpler and safer installation. At these power levels,
> the EMI issue is a red herring that would be easily defeated with a
> $0.98 roll of aluminum foil, and once defeated on the ground the
> problem isn't likely to pop back up in flight (like loose cabling will).
>
> IMHO
>
> *It seems that your standard store bought router is designed to die
> after a few years. I wouldn't trust this quality control with my
> comfort. I barely trust it with my ability to read this newsgroup.

[Frank van der Hulst]

Pete Schaefer wrote:
> So, what things on the airplane are you guys going to replace with
> self-powered blue tooth devices?

First thing would be Bluetooth headsets... no more cords tangling round
the cockpit.

Next would be various engine instruments... EGT, CHT, etc.

Maybe move the entire radio receiver out to a wingtip or somewhere well
away from the engine's RF noise. But I can't see that being
self-powered. Perhaps we could use Tesla's beam-power technology to run
those.

Frank

[Ernest Christley]

Frank van der Hulst wrote:
> Pete Schaefer wrote:
>
>> So, what things on the airplane are you guys going to replace with
>> self-powered blue tooth devices?
>
>
> First thing would be Bluetooth headsets... no more cords tangling round
> the cockpit.

That's a good one. Keep an old pair if wired sets stuck in an
accessible hole someplace...just in case.

>
> Next would be various engine instruments... EGT, CHT, etc.

Perfect. If the signal dies, the plane won't know it. The Cherokee I
trained in didn't even have a working EGT.

>
> Maybe move the entire radio receiver out to a wingtip or somewhere well
> away from the engine's RF noise. But I can't see that being
> self-powered. Perhaps we could use Tesla's beam-power technology to run
> those.
>
> Frank

Oooh. You just lost me on that one. To much complication with the radio
to human interface there. You've got a device in front of the pilot to
select a station, which must transmit it to a device out on the wing,
which has to recieve and interpret it correctly, then transmit the
correct station's signal back over bluetooth. You'd still have to run
signal wires for the physical backup. I just don't see the advantage
when remoting the antennae is all that's necessary to avoid the engine EMI.

How about stress monitors built into the prop (I have no idea if anyone
makes such a thing). Would help you to carve a perfect prop.

Miniature temp probes and air pressure sensors that you can stick all
over the place. Would make it real easy to map out the pressure regions
on the airplane and design a better cooling system or decide if wing
modification would be necessary/beneficial.

Vibration sensors stuck inside control surfaces and different parts of
the skin. Early warning system for flutter. Might only give you time
for a short prayer, but it may save your butt if you can react quick enough.

Nothing is stopping anyone from doing any of this with wired sensors.
It would just be cleaner and easier if the wire can be left on the spool.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[Frank van der Hulst]

Ernest Christley wrote:

>> Maybe move the entire radio receiver out to a wingtip or somewhere
>> well away from the engine's RF noise. But I can't see that being
>> self-powered. Perhaps we could use Tesla's beam-power technology to
>> run those.

> Oooh. You just lost me on that one. To much complication with the radio
> to human interface there. You've got a device in front of the pilot to
> select a station, which must transmit it to a device out on the wing,
> which has to recieve and interpret it correctly, then transmit the
> correct station's signal back over bluetooth.

This kind of stuff is bread-and-butter for Bluetooth. Remember that one
of its original design goals was moving (high-quality stereo) audio in
real time from a player to headphones. Sending channel-select signals in
the opposite direction isn't a biggy either... Bluetooth devices are
continually communicating digitally amongst themselves.

> You'd still have to run signal wires for the physical backup.

Why? The airplane will keep flying if the radio fails. Granted that,
depending where you live and fly, losing access to your radio could be a
bit, um, difficult. But, for many, a radio isn't a necessity.

> I just don't see the advantage
> when remoting the antennae is all that's necessary to avoid the engine EMI.

You said it yourself in your last sentence: It would just be cleaner and
easier if the wire can be left on the spool.

> How about stress monitors built into the prop (I have no idea if anyone
> makes such a thing). Would help you to carve a perfect prop.

Prop blade pitch control... a motor in the spinner to adjust pitch,
controlled via Bluetooth. No hollow crankshafts and oil pressure
systems, no slip-rings.

Frank

[Scott Skylane]

Frank van der Hulst wrote:
/snip/
> Prop blade pitch control... a motor in the spinner to adjust pitch,
> controlled via Bluetooth. No hollow crankshafts and oil pressure
> systems, no slip-rings.
>
> Frank

Eh? How would the motor be powered, batteries? I'm not sure how long
reasonably sized batteries would work. And what about centrifugal force
issues?...

Happy Flying!
Scott Skylane

[Pete Schaefer]

"Frank van der Hulst" > wrote in message
...
> First thing would be Bluetooth headsets... no more cords tangling round
> the cockpit.

That would be pretty nice. But now you need batteries in your headset to
power the audio amp.

> Next would be various engine instruments... EGT, CHT, etc.

I guess you'd need some devices (i.e. wires) for routing the signal through
the firewall or around it. How much lighter would this be than, say, a
twisted pair for CAN?

> Maybe move the entire radio receiver out to a wingtip or somewhere well
> away from the engine's RF noise.
> But I can't see that being self-powered.

The receiver could be, but not the transmitter. An antenna wire is probably
a lot lighter than running power out, so I guess that would need to stay in
the cockpit.

[Pete Schaefer]

"Ernest Christley" > wrote in message
om...
> How about stress monitors built into the prop (I have no idea if anyone
> makes such a thing). Would help you to carve a perfect prop.

How much would someone pay for the software to analyze this data? Also,
you'd probably need structurally integrated sensors, which would have to be
strong enough to support the loads. This would be a pretty tough engineering
problem in itself.

> Miniature temp probes and air pressure sensors that you can stick all
> over the place.

More software. Sure it could be done, but cheaply enough for the average
home builder?

> Vibration sensors stuck inside control surfaces and different parts of
> the skin. Early warning system for flutter.

Might be really expensive to get the signals characterized well enough for a
warning system.

> Nothing is stopping anyone from doing any of this with wired sensors.
> It would just be cleaner and easier if the wire can be left on the spool.

There's a ton of stuff stopping people from doing this right now. It's
money. None of the stuff you've mentioned is even remotely innexpensive. I
know people who've researched this stuff with the wired sensors for several
years, and haven't gotten much of it out of the lab. Yeah, with steady
improvements in computational fluids, finite element, mems tech, sensing
tech, etc., this stuff will be eventually packaged into something us
home-builder types can afford to use. However, most of it is still too
damned expensive, manpower intensive, and technically immature for even the
military to employ on huge aircraft development programs like JSF. By the
time this stuff really becomes generally available, I'm sure there will be
something better than blue tooth around.

[Frank van der Hulst]

Pete Schaefer wrote:
> "Frank van der Hulst" > wrote in message
> ...
>
>>First thing would be Bluetooth headsets... no more cords tangling round
>>the cockpit.
>
>
> That would be pretty nice. But now you need batteries in your headset to
> power the audio amp.

Yeah. I wonder whether head movement would produce enough power... like
the 'self-winding' watches of the 1970s.
>
>>Next would be various engine instruments... EGT, CHT, etc.
>
> I guess you'd need some devices (i.e. wires) for routing the signal through
> the firewall or around it. How much lighter would this be than, say, a
> twisted pair for CAN?

Not necessarily... I guess you're talking about a metal firewall
shielding the signals, right? But, assuming a fibreglass cowl, mount a
self-powered repeater someplace where the engine instruments can see it,
and where the instrument panel can see it (e.g. a bump on top of the
cowl, on a wingtip, on the leading edge, on the landing gear perhaps).
An extra benefit is that you no longer need (as many) penetrations
through the firewall.

>>Maybe move the entire radio receiver out to a wingtip or somewhere well
>>away from the engine's RF noise.
>>But I can't see that being self-powered.
>
>
> The receiver could be, but not the transmitter. An antenna wire is probably
> a lot lighter than running power out, so I guess that would need to stay in
> the cockpit.

Well, I did suggest (kinda tongue-in-cheek) using RF to power the radio
transmitter, as Nicola Tesla proposed way back in the (IIRC) 1930s.

Yeah, I know that none of these things is quite right, right now.
There's lots of engineering to be done to make it workable. But I think
we *probably* have enough technology to be able to begin implementing
this kind of stuff.

Frank

[Frank van der Hulst]

Scott Skylane wrote:
>> Prop blade pitch control... a motor in the spinner to adjust pitch,
>> controlled via Bluetooth. No hollow crankshafts and oil pressure
>> systems, no slip-rings.
>
> Eh? How would the motor be powered, batteries? I'm not sure how long
> reasonably sized batteries would work. And what about centrifugal force
> issues?...

If I was totally serious about this, I wouldn't tell you... I'd go and
make a huge fortune. Or lose a small one.

How about this... mount some permanent magnets on the front of the cowl,
right behind the spinner. In the rear face of the spinner, embed some
coils. In effect, the spinner becomes a generator. This electricity is
used to run the motor inside the spinner that adjusts blade pitch.
Probably include a small battery to allow pitch adjustment when the
engine isn't running.

Feasible? Dunno. But if you use this idea to make a large fortune, could
you please just send me a small fortune? In advance?

Thanks

Frank

[Gord Beaman]

Frank van der Hulst > wrote:

snippo

>> "Frank van der Hulst" > wrote in message
>> ...
>>
>>>First thing would be Bluetooth headsets... no more cords tangling round
>>>the cockpit.
>>
>>

Not to change the subject but where did they come up with
'Bluetooth anyway?... (just lucky maybe?) :)
--

-Gord.
(use gordon in email)

[Pete Schaefer]

"Frank van der Hulst" > wrote in message
...
> Yeah. I wonder whether head movement would produce enough power... like
> the 'self-winding' watches of the 1970s.

Probably not, but you don't need a lot. I guess it depends on how long you
need it to operate. Using modern digital amp chips (which are amazingly
efficient), you can keep consumption down. A couple of gumstick batteries
might be alright.

> Not necessarily... I guess you're talking about a metal firewall
> shielding the signals, right? But, assuming a fibreglass cowl, mount a
> self-powered repeater someplace where the engine instruments can see it,

That kinda goes against my "as few possible components between the source
and the destination" philosophy. I think you'd have to just locate the
receiver on the firewall and put an antenna through.

> Yeah, I know that none of these things is quite right, right now.

If you don't keep working through the possibilities, you might miss an
opportunity to invent that new gadget that everybody just has to have.
Personally, I'm not hopeful that there's a big opportunity for blue tooth on
home-built airplanes, but there might be a couple of really good
applications.

Pete

[nafod40]

Pete Schaefer wrote:
> So, what things on the airplane are you guys going to replace with
> self-powered blue tooth devices?

I'm typing out loud here...

When I suggested bluetooth the other day, what I had in mind was a kit
that you would temporarily hang on an airplane for specific tests, much
like we hang all the orange on Navy aircraft for flight tests. Much more
accurate pitot-static, vib sensors, postion sensors, data loggers, etc.
You could, for example, have a kit for flight testing an RV-8. Pop it
on, do the tests, and remove it. Or it could be used for "external
stores" such as a camera.

Afterward, I contemplated replacing all signal wires with wireless. So
any wire not carrying power could be replaced. This might be especially
useful for a refit, where access is far more difficult than during
initial construction.

Other harebrained ideas...two planes in semi-close formation could
network via bluetooth. Why? Could be low prob. of intercept comms on a
private channel, sharing of nav data, text messaging, ipod music files.

There's an ongoing thread on rec.aviation.soaring on bluetooth and
cellphones aboard planes.

[William W. Plummer]

nafod40 wrote:
> Pete Schaefer wrote:
>
>> So, what things on the airplane are you guys going to replace with
>> self-powered blue tooth devices?
>
>
> I'm typing out loud here...
>
> When I suggested bluetooth the other day, what I had in mind was a kit
> that you would temporarily hang on an airplane for specific tests, much
> like we hang all the orange on Navy aircraft for flight tests. Much more
> accurate pitot-static, vib sensors, postion sensors, data loggers, etc.
> You could, for example, have a kit for flight testing an RV-8. Pop it
> on, do the tests, and remove it. Or it could be used for "external
> stores" such as a camera.
>
> Afterward, I contemplated replacing all signal wires with wireless. So
> any wire not carrying power could be replaced. This might be especially
> useful for a refit, where access is far more difficult than during
> initial construction.
>
> Other harebrained ideas...two planes in semi-close formation could
> network via bluetooth. Why? Could be low prob. of intercept comms on a
> private channel, sharing of nav data, text messaging, ipod music files.
>
> There's an ongoing thread on rec.aviation.soaring on bluetooth and
> cellphones aboard planes.
>
Bluetooth: a solution in search of a problem

[Ernest Christley]

Pete Schaefer wrote:
> "Ernest Christley" > wrote in message
> om...
>
>>How about stress monitors built into the prop (I have no idea if anyone
>>makes such a thing). Would help you to carve a perfect prop.
>
>
> How much would someone pay for the software to analyze this data? Also,
> you'd probably need structurally integrated sensors, which would have to be
> strong enough to support the loads. This would be a pretty tough engineering
> problem in itself.
>


??? analyze ???
What analysis would you want to do other than to look a the relative
strains at a few distinct points. You'd like a bell shaped lift curve
on the prop, same as for a wing. I would pay $0 dollars for software
analysis, and opt for plotting the values on a sheet of graph paper with
a pencil. Well, that's not EXACTLY true. I'd probably use Gnumeric
(open source spreadsheet), as it would produce a much prettier graph
that I would.

Mind you, I'm talking a home carved wood prop here. Build in a little
pocket for the probe. Keep carving until one gives you the perfect profile.

>
>>Miniature temp probes and air pressure sensors that you can stick all
>>over the place.
>
>
> More software. Sure it could be done, but cheaply enough for the average
> home builder?

Why the software again. Danm, man, what do you think people did before
Intel came along with their little 4-bit wonder. You're engine isn't
cooling like you want it to. The way to see what you need to fix is to
map out pressures in and around the radiator system (I'm building a
water cooled auto-conversion. Please be patient with the radiator
thing.) The current way is to run water lines all over the place, duct
taping them to the side of the plane to get them back to the cockpit so
that you can measure all the relative water columns. No fancy analysis
is needed. Either you have a few inches of pressure across the radiator
cores, or you don't. Move the sensors around to find out where the high
pressure areas are.

>
>
>>Vibration sensors stuck inside control surfaces and different parts of
>>the skin. Early warning system for flutter.
>
>
> Might be really expensive to get the signals characterized well enough for a
> warning system.

Do you have a squelch knob on your radio? Do you have to run incoming
signals through a laborious data analysis before you decide where to set
said squelch? No! You just turn it up till the background noise stops.
Same here. If you hit flutter, the intensity will increase
dramatically, just like the occasionaly noise gets through the squelch.

As I said in my original post, it will probably give you just enough
time to kiss your butt goodbye, but flutter isn't always noticed for
what it really is and it does't always catastrophically destroy the
airplane. Sometimes it beats the airplane to death slowly. If the
'flutter squelch' from the t-tail always goes off as you hit 140kts and
dies back down as you pass through 150kts, it might be a clue that you
should rebalance the t-tail or avoid 145kts as a minimum.

>
>
>>Nothing is stopping anyone from doing any of this with wired sensors.
>>It would just be cleaner and easier if the wire can be left on the spool.
>
>
> There's a ton of stuff stopping people from doing this right now. It's
> money. None of the stuff you've mentioned is even remotely innexpensive. I
> know people who've researched this stuff with the wired sensors for several
> years, and haven't gotten much of it out of the lab. Yeah, with steady
> improvements in computational fluids, finite element, mems tech, sensing
> tech, etc., this stuff will be eventually packaged into something us
> home-builder types can afford to use. However, most of it is still too
> damned expensive, manpower intensive, and technically immature for even the
> military to employ on huge aircraft development programs like JSF. By the
> time this stuff really becomes generally available, I'm sure there will be
> something better than blue tooth around.
>

I say those people are asking for too much. If you want the computer to
tell you exactly what's wrong, I'll agree with you all day long that
it's not economically possible with todays technology. If all you want
is a little information about what's going on around you (with the human
doing the divining), the cost is well under $500 (for wired sensors,
don't know about BlueTooth).


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[nafod40]

William W. Plummer wrote:
> Bluetooth: a solution in search of a problem

So was the internet for a while.

I'm thinking of just wireless in general, of which bluetooth is an
implementation (with a really catchy name.)

[William W. Plummer]

nafod40 wrote:

> William W. Plummer wrote:
>
>> Bluetooth: a solution in search of a problem
>
>
> So was the internet for a while.

Not at all. TCP, the original name for "TCP/IP" that we know today,
was designed to meet certain military needs but the bigger issue of how
to communicate through widely-disparate networks was _THE_ problem.
You can look up the IEEE Trans. on Communications paper by Kahn and
Cerf. 1974 as I recall.

[nafod40]

William W. Plummer wrote:
> nafod40 wrote:
>
>> William W. Plummer wrote:
>>
>>> Bluetooth: a solution in search of a problem
>>
>> So was the internet for a while.
>
> Not at all. TCP, the original name for "TCP/IP" that we know today,
> was designed to meet certain military needs but the bigger issue of how
> to communicate through widely-disparate networks was _THE_ problem. You
> can look up the IEEE Trans. on Communications paper by Kahn and Cerf.
> 1974 as I recall.

Yea, I guess I meant the Internet as in meaning the http protocol and
WWW, which took what was a nifty way of hooking computers together and
turned it into an incredible way to hook people together. In short, the
"killer app".

Bluetooth is still waiting for the killer app. I think as ubiquitous
computing continues to grow (everything will have computers
embedded...everything) the ability to form networks on the fly will be
needed. But I digress from airplanes...