Mar 05, 2012, 02:15 PM Registered User Lakewood, Colorado Joined Aug 2002 30,541 Posts You trust everything you read in Chinese manuals as a fundamental truth? ian
Mar 05, 2012, 02:20 PM
Registered User
United Kingdom, England, Cumb
Joined Sep 2011
62 Posts
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

# Images

Mar 05, 2012, 02:27 PM
Registered User
Old Blighty
Joined Apr 2010
1,718 Posts
Quote:
 Originally Posted by ojala1 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.
 Mar 05, 2012, 02:32 PM Registered User Calgary Canada Joined Jun 2006 5,159 Posts 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
 Mar 05, 2012, 02:46 PM Registered User New Zealand, Auckland Joined Oct 2010 452 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?
Mar 05, 2012, 02:53 PM
Registered User
The Netherlands, OV, Oldenzaal
Joined Jul 2010
355 Posts
Quote:
 Originally Posted by Ian Davidson 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.
Mar 05, 2012, 04:02 PM
Registered User
Belgium
Joined Aug 2005
225 Posts
Quote:
 Originally Posted by ojala1 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 ?
Mar 05, 2012, 04:10 PM
Registered User
Old Blighty
Joined Apr 2010
1,718 Posts
Quote:
 Originally Posted by D-OCHO 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.
Mar 05, 2012, 04:19 PM
Registered User
Didcot, UK, OX11
Joined Sep 2003
653 Posts
Quote:
 Originally Posted by Ian Davidson 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
Mar 05, 2012, 05:25 PM
Registered User
Austria, Wien, Vienna
Joined Feb 2012
320 Posts
Quote:
 Originally Posted by Daemon 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!!
 Mar 05, 2012, 05:29 PM Registered User Austria, Wien, Vienna Joined Feb 2012 320 Posts another video from our fy31ap installation flight - Vmax: 156km/h!! http://youtu.be/3hdTtIRLm2w
 Mar 05, 2012, 08:40 PM Registered User Redmond OR Joined Dec 2009 39 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..
Mar 05, 2012, 08:49 PM
Hawk Fanatic
United States, KY, Louisville
Joined Jul 2008
8,143 Posts
Quote:
 Originally Posted by jet72 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!
Mar 05, 2012, 09:02 PM
Registered User