Vertical card compass

[John M. Morgan]

Do vertical card compasses, like the Precision PA-700, work well in
sailplanes? Or do they need a bit of vibration to keep them from sticking?

bumper

[1M]

the PAI-700 is the best of the vertical cards....(others being the cheap
VC-100 and Hamilton). They do operate better in powered aircraft than in
gliders because of the added vibration in powered aircraft.
Though the vertical cards are stickier than liquid compasses the
presentation is much better and it's easier to visualize headings and
directions, and vise-versa because they are fluid the liquid compasses never
seem to settle down and are constantly moving making it equally hard to
determine your heading. I've used both....and personally prefer the Vertical
card compass...even though I sometimes have to reach up and tap the panel to
get the last few degrees to register...
tim
--
Visit our web site at : http://www.wingsandwheels.com

John M. Morgan <Flyb...@castles.com> wrote in message
news:7q6d9r$r...@enews4.newsguy.com...

[Sula]

John M. Morgan wrote:
>Do vertical card compasses, like the Precision PA-700, work well in
>sailplanes?

You need to take care that they are mounted in an area reasonably free from
magnetic influence (tightly-packed glider panels may not be).

[ChrisAtUpw]

Vibrator motors from dead pagers? Don't they have rather strong magnetic
fields?

[Robert W. Cunningham]

Sula wrote:

Nah, just wrap it in some mu-metal foil to eliminate most of the magnetic field. You can orient any residual leakage normal to the plane of the needle, and it won't affect the compass reading. If that doesn't do it (and it should) just mount the vibrator on a short arm and allow 1/r^2 to attenuate the field.

The mu-metal shield alone should do the job.

I just did an experiment with my pager and a digital compass (1 degree resolution, 2 degree accuracy), and it turns out the static field from the permanent magnets in the motor is massively larger than anything generated when the motor is running. Without shielding, the induced compass error dropped to less than one degree when it was just 4 inches away from the compass sensor, INDEPENDENT of orientation.

With care, I was able to orient the unshielded pager right against the compass with no noticeable effect on the bearing. Of course, since I don't have a second compass handy, I merely took several measurements at known bearings. This is hardly a scientific test, since I'm certain the magnetic inclination ("dip angle") has to have changed, and I'm not certain how that affects my compass.

Bottom line, it should be very doable. A 1mm layer of mu-metal should attenuate the magnetic field by about a factor of ten. Mount the shielded motor as far away from the compass needle as possible, oriented to minimize residual effects (if any), and all should work quite well.

Ideally, you'd want to induce only the minimum vibration needed to prevent the compass from sticking. To do this, you'll probably want to mount the motor on a piece of foam rubber. Some experimentation may be needed to determine the density and thickness needed.

Plus, the foam will drastically reduce any conducted and radiated sound.

-BobC

[Robert W. Cunningham]

Whoops! I clipped a bit too much of the prior message. I was replying to a response to my idea of using the vibrator motor from a broken pager to to keep a vertical card compass needle unstuck. The reply mentioned interference from the magnetic field of the motor...

[gareth johnstone]

How about their performance whilst thermaling, do they give a meaningful
reading?
Airpath type compasses give a totally meaningless reading and it is
impossible to come out on a heading just by using the compass. The Bohli
and similar work well in this mode of operation but you have to set them
up for the bank angle and so are good but not perfect.
1M <t...@wingsandwheels.com> wrote in message
news:7q6fdt$s...@enews4.newsguy.com...

>
> the PAI-700 is the best of the vertical cards....(others being the
cheap
> VC-100 and Hamilton). They do operate better in powered aircraft than
in
> gliders because of the added vibration in powered aircraft.
> Though the vertical cards are stickier than liquid compasses the
> presentation is much better and it's easier to visualize headings and
> directions, and vise-versa because they are fluid the liquid compasses
never
> seem to settle down and are constantly moving making it equally hard
to
> determine your heading. I've used both....and personally prefer the
Vertical
> card compass...even though I sometimes have to reach up and tap the
panel to
> get the last few degrees to register...
> tim
> --
> Visit our web site at : http://www.wingsandwheels.com
>
>
>
> John M. Morgan <Flyb...@castles.com> wrote in message
> news:7q6d9r$r...@enews4.newsguy.com...

> > Do vertical card compasses, like the Precision PA-700, work well in

[1M]

none of the compasses are very good here....
the PAI700 also stops and starts some during turns

tim
--
Visit our web site at : http://www.wingsandwheels.com

gareth johnstone <johnsto...@hotmail.com> wrote in message
news:7q8h20$2ev$1...@gxsn.com...

[Armand A. Medieros]

I purchased two of these compasses from Wings & Wheels and they have worked
perfectly for several years now. One in my Centrair 101A and one in my
Cessna 152-II. The Cessna mount had soft rubber and it was replaced with
stiffer stuff to prevent leaning so much -obviously an attempt by the makers
to allow vertical orientation during turns- and I am very happy with them.

The metal surrounding the instrument panel interfered a bit in the glider
but the adjustments brought it into perfect alignment.

And I might add, except for helping to figure out the winds aloft, I don't
use it! I fly using pilotage as my main means of navigation with the compass
as a general backup to the sectional and roads while the GPS I use as a
kinda DME device.

The one huge advantage is instantly being able to read the heading and the
face doesn't degrade like the whisky compasses do.

Armand

1M wrote in message <7q8o4g$16...@enews1.newsguy.com>...

[John M. Morgan]

> Ideally, you'd want to induce only the minimum vibration needed to prevent
the compass from sticking. To do this, you'll probably want to mount the
motor on a piece of foam rubber. Some experimentation may be needed to
determine the density and thickness needed.

> -BobC

Okay, this sounds interesting. But there's gotta be a simpler way to
introduce a small amount of vibration to the aircraft's panel. This would
have the added advantage of keeping the ASI and altimeter unstuck too?

Sometimes "simpler way" turns out more complicated . . .

How about some sort of small air motor (paddlewheel or turbine) device to
power the vibrator weight. This could be driven off the ventilation air
duct. Advantage no current draw and no magnetism. Anyone know of a suitable
device?

--

John "Bumper" Morgan <bump...@castles.com> S10-VT "ZZ"
To REPLY please remove aviation part of address.
"Eagles may soar, but weasels don't get sucked into jet engines."

[Dan Marotta]

... or you could fly with the dive brakes open... That would add a
little vibration! <g>

Dan

[John M. Morgan]

>
> How about some sort of small air motor (paddlewheel or turbine) device to
> power the vibrator weight. This could be driven off the ventilation air
> duct. Advantage no current draw and no magnetism. Anyone know of a
suitable
> device?
>

It's pretty bad when you respond to your own post . . .

Might be possible to modify one of the small muffin fans like those used for
cooling CPU's in computers. Disassemble, remove motor parts (or grind off
enough to create imbalance) and insert weight. Fabricate small plenum (maybe
out of ends from two plastic Gatorade bottles or similar) to put motor in
line with air duct.

bumper

[Sula]

John M. Morgan wrote:
>How about some sort of small air motor (paddlewheel or turbine) device to
>power the vibrator weight. This could be driven off the ventilation air
>duct.

When a proposed compass starts needing mu metal and a vibrator turbine, it
might be time to look for something simpler. Given that you only rarely
need a compass, the ball-style (e.g. PZL) works great - compact, reliable,
inexpensive, put it anywhere.

[Robert W. Cunningham]

Sula wrote:

> When a proposed compass starts needing mu metal and a vibrator turbine, it
> might be time to look for something simpler. Given that you only rarely
> need a compass, the ball-style (e.g. PZL) works great - compact, reliable,
> inexpensive, put it anywhere.

Hey! We were Rube Goldberg-ing here! Do you mind?

I mean, if we wanted to get dead simple, just get a $50 digital compass. You may need to spend $70+ to get one with high accuracy and fast response. Or $300 to get a 3-axis unit that indicates correctly even during loops.

And, so I hear, they can't get stuck!

-BobC

[Luke Dodd]

I purchased a PAI700 vertical card compass from tim recently
for my glider. Its a great compass, quality is excellent,
easy to read and does not continually jump around as with
liquid compasses. The slight sticking is not a problem,
there is plenty of vibration in a glider courtesy of
thermals to overcome this very minor problem. Very rarley on
a cross country task do you encounter smooth air long enough
to require a slight tap on the instrument panel cover.

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[Al]

How many of you actualy use a compass anyway!!

I use mine as a backup if my GPS (two gps's) poops out!!
Even it I was left with only a mag compass I would not be too alarmed if it
were a bit sticky.
As long as you get in the rough direction of where you are going the rest is
down to basic map work (or knowing your soaring area.)

Now if you really want to add a vibrator to your panels might I suggest
www.goodvibes.com
Then after you have gone flying the wife/girlfriend can borrow it when your
finished.
I am sure she would appreciate the exspense being lashed out on her.

Al