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Old Mar 05, 2012, 02:15 PM
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Daemon's Avatar
Lakewood, Colorado
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You trust everything you read in Chinese manuals as a fundamental truth?

ian
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Old Mar 05, 2012, 02:20 PM
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United Kingdom, England, Cumb
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I could be mathematically declined but surely do the nose and tail not move at a greater angle than the C of G. See attached
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Old Mar 05, 2012, 02:27 PM
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Old Blighty
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Originally Posted by ojala1 View Post
I could be mathematically declined but surely do the nose and tail not move at a greater angle than the C of G. See attached
No, the angle is the same, but the acceleration will be different as the nose/tail are having to travel a further distance (compared to the CoG) in the same period of time.
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Old Mar 05, 2012, 02:32 PM
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Calgary Canada
Joined Jun 2006
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come on kids it's going to work at its theorectical "Best" at the C of G no doubt. But it can also work just fine off the c of g too... let's get back to the X8

there is a 31AP thread if you want here http://www.rcgroups.com/forums/showthread.php?t=1575919

Steve
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Old Mar 05, 2012, 02:46 PM
Opt
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New Zealand, Auckland
Joined Oct 2010
388 Posts
I'm thinking of getting one of these two motors, since bevrc doesnt seem likely to deliver their promised motor any time soon.

http://www.hobbyking.com/hobbyking/s...er_770kv_.html
http://www.hobbyking.com/hobbyking/s...ner_Motor.html

To be used with a 12x8 prop or similar. Does anyone have any opinion on either? Or a good alternative motor/prop combo?
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Old Mar 05, 2012, 02:53 PM
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The Netherlands, OV, Oldenzaal
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Originally Posted by Ian Davidson View Post
e.g. putting an accelerometer on the outside of a bicycle wheel would read different than were it closer to the rotational centre/axle.
You think so.
An accelerometer measures changes in acceleration.
So when you keep the wheel turning the accelerometer will only measure something when you move the wheel slower or when you change the angle of the wheel.
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Old Mar 05, 2012, 04:02 PM
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Belgium
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Originally Posted by ojala1 View Post
I could be mathematically declined but surely do the nose and tail not move at a greater angle than the C of G. See attached
Hey ojala1, you're right and not mathematically declined ! As you, Daemon and I stated, the angle is the same, so an ideal gyro will measure the same when placed at the CG, nose, or tail.

The problem is that while an ideal gyro is not sensitive to linear acceleration, a real one will be somewhat. Hence, a non-ideal gyro placed at the nose will be slightly disturbed by the linear acceleration as the nose accelerates up or down due to the plane pitching around the CG. The same non-ideal gyro placed at the CG will not.

Practically you can place today's high quality gyro's anywhere you like if you don't need or care about the lowest possible drift.

Now back to the X8. Are we going to be able to get an EPO one from the next batch or is it going to be sold out immediately ?
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Old Mar 05, 2012, 04:10 PM
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Originally Posted by D-OCHO View Post
You think so.
An accelerometer measures changes in acceleration.
So when you keep the wheel turning the accelerometer will only measure something when you move the wheel slower or when you change the angle of the wheel.
Well off topic, so my last comment on this, but acceleration has both time and velocity as a component and velocity has both distance and direction. As the wheel is rotating the direction is always changing, so as is the velocity and therefore so is the acceleration. In short, a mass on a rotating wheel experiences constant acceleration.
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Old Mar 05, 2012, 04:19 PM
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Didcot, UK, OX11
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Quote:
Originally Posted by Ian Davidson View Post
In short, a mass on a rotating wheel experiences constant acceleration.
Or more precisely if the acceleration sensor is not mounted on the center or rotation (not the CoG though the two are likely to be close) it will see centrifugal force / acceleration when the aircraft is rotating around one of its axes. The good news is that this isn't going to be much to affect the attitude estimation unless you are doing several rolls at crazy speeds and even then a good algorithm could predict what's going on and ignore it.

I have been working on a similar system (auto level) for helis and I have seen the effects of fast piros on the accelerometers and how they confuse the attitude estimator if you don't have specific rules added to cope with it.

-Angelos
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Old Mar 05, 2012, 05:25 PM
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Austria, Wien, Vienna
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Originally Posted by Daemon View Post
You trust everything you read in Chinese manuals as a fundamental truth?

ian
i don´t trust everything i read in a chinese, japanese, or korean manual....but i trust THE DEVELOPER of the FY31AP...yes, they´re from china....but i think they are NOT stupid!!
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Old Mar 05, 2012, 05:29 PM
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Austria, Wien, Vienna
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another video from our fy31ap installation flight - Vmax: 156km/h!!

http://youtu.be/3hdTtIRLm2w
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Old Mar 05, 2012, 07:49 PM
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Lakewood, Colorado
Joined Aug 2002
28,204 Posts
Threw an ezOSD on my X8 and did some test FPV piloted flights. Unfortunately I lost the last vid, due to
shutting the Tx off before the recorder (didn't like sustained static), but the gist of it was this.
Current power setup 3S batt 1110kv motor 12x8.5 prop. Sources of drag include GoPro embedded
in the nose, flight cam on pan servo sticking up off the top of the fuse, half my UHF antenna sticking outside
vertically inside a straw, a cloverleaf video antenna outside the fuse, and a not totally smooth canopy.
Min sink level flight speed is about 31mph at 8A
35mph requires about 10A
45mph takes 17-20A.
Maxes out in level flight somewhere around 70mph at 65A.

To put that in practical terms, if we ignore wind, and some loss in efficiency due to added weight (to be
determined later), I should be able to load up with 8Ah (couple 4Ah batts) and fly for 1 hour, covering a total of about 30 miles.
Or, for a faster flight, start with same 8Ah of batt and fly for 24 minutes at 45mph at 20Amps
giving me a total range of about 18 miles. Should be able to repeat the 6 mile (nearly 10km) out and back flight I did
with my SW in about half the time.

Landing this thing in a tight space on level ground is going to be a bear.
All my FPV flights have had an uphill landing area and it still usually goes longer
than I expect.

ian
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Last edited by Daemon; Mar 05, 2012 at 08:04 PM.
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Old Mar 05, 2012, 08:40 PM
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Redmond OR
Joined Dec 2009
38 Posts
Bev RC

Has anyone been getting bev RC to answer there emails? I emailed them three times in the last month and no reply..
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Old Mar 05, 2012, 08:49 PM
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United States, KY, Louisville
Joined Jul 2008
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Quote:
Originally Posted by jet72 View Post
another video from our fy31ap installation flight - Vmax: 156km/h!!

http://youtu.be/3hdTtIRLm2w
Get lower!!! Thread the needle next time, between your car and the barn. This is FPV right? Awesome Vid and loved the music!
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Old Mar 05, 2012, 09:02 PM
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Lakewood, Colorado
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Originally Posted by SkylineFlyer View Post
This is FPV right?
Looks LoS piloted.

ian
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