Today's Message Index:
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1. 05:57 AM - Re: Dynamic propeller balancing sensor. (Eric M. Jones)
2. 08:16 AM - Re: Re: Dynamic propeller balancing sensor. (Robert L. Nuckolls, III)
3. 11:38 AM - Re: Dynamic propeller balancing sensor. (Eric M. Jones)
4. 12:16 PM - Re: anderoid tablets (bob noffs)
5. 03:03 PM - Re: Re: Dynamic propeller balancing sensor. (Robert L. Nuckolls, III)
6. 07:04 PM - Re: Dynamic propeller balancing sensor. (Roberto Waltman)
7. 08:18 PM - Re: Dynamic propeller balancing sensor. (Robert L. Nuckolls, III)
8. 08:24 PM - Dynamic propeller balancing sensor. (Paul Millner)
9. 08:55 PM - Re: Dynamic propeller balancing sensor. (Roberto Waltman)
10. 10:14 PM - Re: Dynamic propeller balancing sensor. (Robert L. Nuckolls, III)
11. 10:38 PM - Re: Dynamic propeller balancing sensor. (Dave Saylor)
Message 1
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| Subject: | Re: Dynamic propeller balancing sensor. |
Bob's inputs here are great.
Here's my two-cents:
GovernmentLiquidations.com frequently has complete Chadwick Helmuth vibrex and
strobex units for cheap. A business in a box! These are very professional units
that are still used (for helicopters mainly...but hey, they still use propellers).
Alternatively, pick up stuff from Ebay.
Failing this, if you still want to roll your own, at least grab some C-H Strobex manuals to see how they do this, online: http://www.scribd.com/doc/40565507/Strobex-Manual .
BTW: I knew and worked with Jim Helmuth personally when I worked on Endoscopic
Strobo-Laryngoscopy for vocal cord vibration analysis. He was a brilliant, gentle
and greatly admired man (Chadwick was the biz man, Jim Helmuth the engineer.)
We all watched helplessly as he smoked himself to death far too young because
he couldn't break his cigarette addiction. Damned shame.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382587#382587
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| Subject: | Re: Dynamic propeller balancing sensor. |
Failing this, if you still want to roll your own, at least grab some
C-H Strobex manuals to see how they do this, online:
http://www.scribd.com/doc/40565507/Strobex-Manual .
Looks like a valuable addition to the archives.
Do you have a membership to download this?
BTW: I knew and worked with Jim Helmuth personally when I worked on
Endoscopic Strobo-Laryngoscopy for vocal cord vibration analysis. He
was a brilliant, gentle and greatly admired man (Chadwick was the biz
man, Jim Helmuth the engineer.) We all watched helplessly as he
smoked himself to death far too young because he couldn't break his
cigarette addiction. Damned shame.
The guy had an impressive resume. He's referenced
a lot in the arena of lightning-in-a-jar.
Bob . . .
Message 3
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| Subject: | Re: Dynamic propeller balancing sensor. |
Sorry Bob,
But the whole PDF appears to be there. The download is $9. An enterprising person
could image grab it all some rainy Sunday.
C-H's manual called "Smooth Propeller" and the Vibrex 2000 manuals are good too.
I can't believe the military doesn't have free downloads on all this stuff.
Maybe some AeroElectric lister can find them.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382630#382630
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| Subject: | Re: anderoid tablets |
rumen,
i have had the tablet for a week to play with it and am trying garmin and
avilution apps on it. the airport directories and briefing abilities on
each are very good. the navigation programs on both do have a few glitches
though. i would lean toward the garmin for the nav part if it would just
have a split screen to show the moving map and the nav. info at the same
time. right now that isn't available for nexus tablet, just 10'' screens. i
have read some forums and that is at the top of the list of gripes. as i
already have 2 gps's in the plane i would probably use one of those to fly
with for now. but like i said the other parts of the app. is very good. if
you are in wi-fi coverage you can get a radar overlay on the sectional
showing precip.
anyway , for a 7'' tablet $200 is a great deal and i expect garmin will
make improvements right along.
bob noffs
On Mon, Aug 27, 2012 at 1:56 PM, bob noffs <icubob@gmail.com> wrote:
> hi rumen,
> yea, i thought the revelance was aviation but oh well. i will keep you in
> on what i think after i get it. fwiw it has a gyroscope ans there must be
> an app out there for an artificial horizon!.
> spent an hour reading reviews and they were very positive. google
> doesn't have their sights set on i pad but rather kindle.
> bob noffs
>
> On Mon, Aug 27, 2012 at 6:58 AM, R. curtis <mrspudandcompany@verizon.net>wrote:
>
>> mrspudandcompany@verizon.net>
>>
>> Don't see the relevance of the question now since you already ordered it
>>> before asking.
>>> ? ? ?
>>>
>>
>> The relevence, INMHO, is that there are at least a couple of us on
>> the list that may be interested in the Garmin App, and may or may
>> not own an Anderoid. Any info on this might be helpful.
>>
>> Roger
>>
>>
>>
>>
>>
>>
>
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| Subject: | Re: Dynamic propeller balancing sensor. |
At 01:37 PM 9/7/2012, you wrote:
>
>Sorry Bob,
>
>But the whole PDF appears to be there. The download is $9. An
>enterprising person could image grab it all some rainy Sunday.
No problem. Next time I have enough wishes in
the que, I'll pay the one-day feed and go grab
some stuff. But if I get flush (got a couple
of $jobs$ on the back burner) I'll get a year
subscription. Scribd is a fantastic resource.
Bob . . .
Message 6
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| Subject: | Re: Dynamic propeller balancing sensor. |
Robert L. Nuckolls, III wrote:
> ...it won't tell you which blade is heavy.
> But test weights will quickly reveal whether adding
> some small weight made things better (light blade)
> or worse (heavy blade).
Not being a mechanical engineer, that's all I could think.
Fortunately, other peoples are. [Mech engineers, physicists,
etc.]
See slides 36 to 42 in this presentation:
sem.org/PDF/Suri_Rotor%20Balancing.pdf
Roberto Waltman
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| Subject: | Re: Dynamic propeller balancing sensor. |
>Not being a mechanical engineer, that's all I could think.
>Fortunately, other peoples are. [Mech engineers, physicists, etc.]
>
>See slides 36 to 42 in this presentation:
>sem.org/PDF/Suri_Rotor%20Balancing.pdf
Cool! That's a flashback to and engineering graphics
course I took way back when . . . The dudes that
figured out that process had some pretty twisted
grey matter. One of those cases where a protractor,
compass and ruler can be used to yield some interesting
results. There's a process using similar tools whereby
you can use star sightings to draw circles representing
lines of possible position (each star sighting has
an infinite number of possible positions which inscribes
a circle on the surface of the earth). Plot LOP from
three stars and the intersection of three circles
is pretty close to where you're at. Love it . . .
Hmmm . . . I wonder if this would adapt to a
two bladed system? Anybody out there with sufficient
twist in the cognitive neurons?
Bob . . .
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| Subject: | Dynamic propeller balancing sensor. |
>> This setup will only give you gross unbalance data . . . it won't
tell you which blade is heavy. But test weights will quickly reveal
whether adding some small weight made things better (light blade) or
worse (heavy blade).
Typically with dynamic balancing, though, one isn't just adding weights
to one blade or the other, but rather just the right amount of weight at
just the right circumferential point on the hub... Typically, NOT at the
blade attachment location.
Perhaps your technique will give you sufficient resolution for that, I
haven't investigated... but your heavy/light blade reference concerns me
in that regard.
Paul
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| Subject: | Re: Dynamic propeller balancing sensor. |
Robert L. Nuckolls, III wrote:
> Hmmm . . . I wonder if this would adapt to a
> two bladed system? Anybody out there with sufficient
> twist in the cognitive neurons?
It is not a three-blade system. It is a rotating mass, of
any geometry, measured/balanced by placing sample weights
120 degrees apart. I assume you need at least three to make
the intersection of the three circles unique.
Roberto Waltman
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| Subject: | Re: Dynamic propeller balancing sensor. |
At 10:54 PM 9/7/2012, you wrote:
>
>Robert L. Nuckolls, III wrote:
>> Hmmm . . . I wonder if this would adapt to a
>> two bladed system? Anybody out there with sufficient
>> twist in the cognitive neurons?
>
>It is not a three-blade system. It is a rotating mass, of any
>geometry, measured/balanced by placing sample weights 120 degrees
>apart. I assume you need at least three to make the intersection of
>the three circles unique.
aHHH . . . but of course. Guess it would be
pretty hard to make this work on a two bladed propeller
unless you could put the weights on the hub.
I suspect the professional chasers of propeller
shake use a methodology not unlike the old Bear
alignment systems that used a strobe to mark wheel
position when the heavy (or light) spot was straight
up or straight down. I remember my mechanic putting
a chalk mark on the tire and using the 'scope to
clock the chalk mark. The 'scope only located the
weight, he put his hand on the fender to judge when
he was getting close to the right weight . . . if
he overshot, the 'scope would report a swap of
the heavy/light sides.
Kinda crude by today's techniques but it sure
worked better than the static bubble balance
method.
Bob . . .
Message 11
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| Subject: | Re: Dynamic propeller balancing sensor. |
We balance props on a regular basis using an ancient Chadwick. It
usually takes about an hour.
The Chadwick system uses an accelerometer and a strobe. A black box
calculates when the acceleration reaches it peak and flashes the
strobe at that point. The box also indicates a quantity for the
vibration, in units of "inches per second", or IPS.
There's also a mag pickup system but that's more for helicopter main rotors.
Since the peak occurs when the heaviest part of the weighted disc is
adjacent to the accelerometer, you know where to add weight (opposite
the accelerometer, with the target positioned as it appeared in the
flash).
The user fine tunes the flash rate by watching for shift in the target
position while pushing a tuning button, and simultaneously adjusting
for RPM. It takes a little practice but once you know what to watch
for it's pretty easy.
Chadwick used to have an FAA-approved pamphlet called "The Smooth
Propeller" that talked about how and where to add weights. It's
pretty much trial and error until you get a handle on how much weight
has a resulting effect.
Dave Saylor
831-750-0284 CL
On Fri, Sep 7, 2012 at 10:12 PM, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com> wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 10:54 PM 9/7/2012, you wrote:
>>
>> <aero@rwaltman.com>
>>
>> Robert L. Nuckolls, III wrote:
>>>
>>> Hmmm . . . I wonder if this would adapt to a
>>> two bladed system? Anybody out there with sufficient
>>> twist in the cognitive neurons?
>>
>>
>> It is not a three-blade system. It is a rotating mass, of any geometry,
>> measured/balanced by placing sample weights 120 degrees apart. I assume you
>> need at least three to make the intersection of the three circles unique.
>
>
> aHHH . . . but of course. Guess it would be
> pretty hard to make this work on a two bladed propeller
> unless you could put the weights on the hub.
>
> I suspect the professional chasers of propeller
> shake use a methodology not unlike the old Bear
> alignment systems that used a strobe to mark wheel
> position when the heavy (or light) spot was straight
> up or straight down. I remember my mechanic putting
> a chalk mark on the tire and using the 'scope to
> clock the chalk mark. The 'scope only located the
> weight, he put his hand on the fender to judge when
> he was getting close to the right weight . . . if
> he overshot, the 'scope would report a swap of
> the heavy/light sides.
>
> Kinda crude by today's techniques but it sure
> worked better than the static bubble balance
> method.
>
>
> Bob . . .
>
>
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