The easiest way to mount APM2 on ArduCopter.

You'll need 4 rubber rings ~1.5-2cm diameter, ( used on prop-savers ) and 4 M3x10mm Spacers.

Just squeeze it through the hole:

 and lock it on the spacer:

you can use 4 extra spacers and mount the top plate:Good flying to you all :)

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Comment by Anish on January 25, 2012 at 8:50am

guys, how about this, three sets of linear actuators, with three accelermeters, with an arduino to do some active dampening, did anyone consider this for camera platforms :)

Comment by Rob_Lefebvre on January 25, 2012 at 9:18am

Ian, yes, it's all really high frequency vibrations.  30hz for a big helicopter, to 200hz for a multi-rotor.  And don't forget that we can't even begin to respond to any dynamics faster than 50hz anyway. Yet these ranges work out where helis, or quads with harmonics will create aliasing on the sensors.  I have definitive proof that the vibes in my heli were totally messing up my sonar readings.

My next project, I'm going to make an alu plate on which to mount the APM, receiver, and sonar so that they can all be a single mass.  Good for dropping the natural frequency, and also good for eliminating as many wires as I can from jumping the gap.  Previously I made a super soft mount, but found that all the wires I had jumping the gap was pulling the APM out of alignment.  I've even gone so far as to move the magnetometer directly soldered to the Oilpan instead of remote mounted.  One more set of cables gone.  I'm even thinking of going so far as to run all the servo leads to a remote power header, so that the only servo wires jumping the gap will be the signal wires.  That'll leave me with only external power, Xbee and GPS wires jumping the gap.

I think there's a very good reason why the close-source guys have the IMU mounted remotely with a single wire coming out of it...

Comment by Rob_Lefebvre on January 25, 2012 at 9:23am

@Ellison: see, now I don't know if you're joking again, or if I'm just way under-educated.   {:o

Comment by Jim Solinski on January 25, 2012 at 11:18am

This a similar idea to the FeiYu Tech suspension mount.  That was fine for their gyro only FY20A because the vibrations are less of an issue for those sensors, but it gave problems to many who used it on their modules that used accelerometers to self-level such as the FY-90Q and FY-91Q.  They never should have provided that o-ring mount for those modules!  Those problems were a result of the mount not being able to maintain a level platform for the board,  Every hard-landing changed the level.  Only a degree out of level makes a difference in multicopter performance and when that is always changing you get the Toilet Bowl Effect(TBE), oscillations, etc. The o-rings change with temperature and rot with aging.  I agree with Robert above on the separate IMU.  Isolating the IMU and tuning the weight to isolate or change the harmonic vibrations that negatively affect the sensors is key to optimal performance in multicopters.  Having a Vreg that changes temperature next to these sensors also can cause poor performance.

Comment by Squalish on January 25, 2012 at 12:29pm

So my impression is that an ideal mount would be something along the lines of: four LIPOs mounted at the ends of a rigid cross for a large moment arm, with the PCB at the center, attached to the rest of the frame by tight rubber bands which have a bounded position (can't slip)?

Comment by Squalish on January 25, 2012 at 12:58pm

Something like this.

Comment by Sebastian Gralla on January 25, 2012 at 1:30pm

no, that adds way too much mass to the autopilot, it needs to be able to follow the movement of the frame

Comment by Gareth Rens on January 25, 2012 at 4:17pm

Hey Max, do you mind if I add your mounting method to the AC wiki?

Comment by Gareth Rens on January 25, 2012 at 4:28pm

@Ellison, An inertial dampener wouldnt work too well. It would have to be very specific.Dampening or removing inertia from the equation would remove the apms ability to sense where it is. With regards to putting the board in a sub space bubble. That would cause interesting effects relative to time compression with the rest of the copter. Perhaps a 3 space (temporally unpolarised) bubble around the entire copter would work better. Then again, propellers that move air wouldnt function in a temporally de-coupled environment. Perhaps a form of subspace projector would work better for movement. As far as navigation or spacial orientation in an "out of phase" environment goes... I'll have to ponder more on that... Direct vectors would work

Comment by Rob_Lefebvre on January 25, 2012 at 5:28pm

Ok Gareth, now please tell me all this sub-space talk is a joke.

Maybe we just need to use some flux capacitors to stabilize the mount?

Jim, so you're saying that that mount system doesn't work for units with accelerometers, only with gyros?  That's interesting. As I said I tried a super soft mount and found the wires pulled it all over the places (a number of my cables are shielded/jacketed and stiff).   I wonder then what is the ideal for us?  Maybe the heli gyro system where they have a layer of gel, a metal plate, more gel, then the sensor.  The plate in the middle absorbs much of the vibration.


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