Battery positioning on F550 clone

[Cyberdave]

Hi guys,
I bought a used F550 clone from the sales page on this forum a few months back.  It had retractable gear, I didn';t like it so I';ve just changed it for a fixed setup (see photo).  I';m not into racing around like a maniac so the bird is a bit of a compromise, I want to carry a camera but still be capable of some brisk sport flying.
I have a question...  looking at Multirotors in general Quads/Hexes it seems that most people mount their batteries on top of the frame, why?  wouldn';t it be better from a stability point of view to sling them beneath the frame?  Having the battery right on top must surely make things top-heavy?  Whilst I appreciate that I need to reposition the battery fore and aft depending on whether I';m carrying a gimbal/camera to keep things balanced surely this can also be achieved with the battery beneath the copter?  BTW just watched the video showing the 3.2 firmware and was very impressed with POS HOLD mode for camera work with plenty of response to inputs!

[guest325]

What you really need to do is find out where the cog is in 3D, if you put your battery below the true cog you will get a pendulum effect which will spoil the stability.

[bunnygirl80]

Hi dave,

A lipo underneath is a lot better, but that said many frames cannot accomodate a lipo underneath as the gimbal takes up that space. Also, most flight controllers have a setting for the CoG and irrespective of where your lipo is, you can adjust this figure to ensure it flies okay. Either way, the FC will compensate for this.

Stef

[flybywire]

Hey Dave, take a look at my hexa lipo tray in the hexa section, maybe of use to you?

[guest325]

Hi dave,

A lipo underneath is a lot better, but that said many frames cannot accomodate a lipo underneath as the gimbal takes up that space. Also, most flight controllers have a setting for the CoG and irrespective of where your lipo is, you can adjust this figure to ensure it flies okay. Either way, the FC will compensate for this.

Stef

That';s interesting,  I didn';t know that this could be compensated for - possibly down to me being a cheapskate on fc';s ::)

[richardg6paj]

Dave,
It';s your choice, put it at the top, put it at the bottom, it really doesn';t make that much difference. Just experiment, that';s what multi';s are all about. Each multi is different in many ways even if they look the same so listen to the advice and then do it your way.  You will learn much more. 

Richard

[Hands0n]

Not wishing to appear overly heretical but ... it barely matters unless you get it hopelessly wrong!  Given the construction of that 550 hex of yours, mounting it on top plate or bottom plate will have almost no appreciable impact.  As others have said, the FC will sort things out for you.

If you totally overcook things, however, the effect will be to cause the motors to work unequally. As such, there will probably be some noticeable impact to flight performance.

That said - the other week I loaded up Old Planky with a 4000mAh solid cased LiPo, mounted to the extreme rear of its H-frame. The COG was shot to pieces. I swear you wouldn';t have known to witness it fly!    In engineering terms it defies all logic! Intentionally   

[Cyberdave]

Thanks to all!  I';ve decided to put it underneath as I have loads of room, I';m going to cut a GF plate with slots for velcro straps and screw it to the CF tubes on the underside.  I';ll be able to move the battery backwards or forwards depending on what camera(s) I have on the front mount.  Ive also ordered some of these dashboard sticky pads to fit between the battery and the GF plate for added security.....
http://www.ebay.co.uk/itm/231048024207?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT