Hi guys,
Had a few queries regarding how I mounted my APM (mainly since I get a compassmot of 0%!). Well here it is. This will only work on side exit APM's!
Step 1:
Screw in 4 x 8mm risers in to the bottom plate, and add one sheet of moongel on top of the core (if you have no core, superglue some risers in the spot. Note: yes, that's moon gel stuck into the FPV camera slots.
Step 2:
Glue a 1mm fibre plate on top of the risers & two drops on the moon gel of the core. You can superglue the whole thing in place, but I chose to use 2 screws, for additional security. I use a battery tray plate from a spare set of quadframe legs.
Step 3:
Add you vibe solution. I've use moongel with good success, but I've decided to try out zeal corners (which i why I dismantled it)
Step 4:
Carefully place the APM in place. Take care to ensure nothing it binding; you don't want vibrations transmitted to the APM via the wires. Insert the battery to make sure it does not press the "out" servo leads. Also try and make sure the "in" servo cables don't torque the board too much, but this can be tricky.
Step 5:
Screw it all back together, but take not of the front starboard mount. This is where and how I placed the DJI riser. It's not exactly over the 4 holes - it only uses 2, This moves it outboard a few mm. Not much, but it might be this detail that separates a 0% compassmot from a 1%...
BUT...THERE'S A MASSIVE PROBLEM...
...take a look at where the USB port is.... You can still reach it with the standard USB cable, by pushing through the port front leg...but it's a really, really tricky, and you are in danger of pulling out a solder!
So find a USB cable with a 90' bend in it. And when you find one...let me know...before the logs fill up and I crash!
Comments
Federico, I think Michael means that the external GPS/compass is mounted on top and the APM is inside the Disco.
However, I have my APM 2.5 mounted on top of the Disco, it's sitting on Moongel pads with an elastic band holding it down. As I have just assembled this frame, I took it to my parking garage for some test flights (in Stabilize mode only) and was very impressed with how well it flew. I had no stability problems whatsoever.
Unfortunately, I can't seem to download my logs right now so I don't know what the vibe levels were.
Once my compass arrives I'll be installing the APM inside the Disco.
@micheal: no problem about stability with apm on top? how are vibration?
I have a TBS Disco, APM 2.6 w/ external GPS/compass mounted on the top plate with no mast. My compassmot is 8%. So no, you do not need a mast.
tbs disco support
I've designed and built a mounting system for the disco after some thought. it uses the kk holes on the frame and provide support for APM (Vr brain board in my case but it almost the same) .
Kyosho zeal is used for antivibration. Now its different from the image (6th prototype version) and i'm designing a pcb board for relaying radio signal from the left of the tbs to the front and 4 esc header at the corner. It's 3d printed in abs (very sturdy)
<a href="http://imageshack.us/photo/my-images/821/u3vq.jpg/" target="_blank"><img src="http://imageshack.us/a/img821/9181/u3vq.th.jpg" border="0"/></a>
That's good to know, thank you for sharing your build, Euan. I don't have my external mag yet, so I was just brainstorming ideas of how/where to mount the APM but still have room for a 5000mAh battery. Your blog post was very helpful.
You might be right Brian, but this one flies just fine, from my eyes. Maybe more experienced stick twiddlers can tell, but I can't! :-) I think Steadidrone has theirs forward and off to the side, so I don't thinks it's too much of a problem.
Rana: I don't doubt your experiences and in your case it does seem that, due to a misbehaving motor, you required a 30cm mast. But I don't think you can apply that as a rule - it sounds like you're saying that 30cm is required in all cases.
However, I think that we're both agreeing with Chris: the best test is to go out and fly the vehicle and see for ourselves what works and what doesn't.
Euan: Sorry, I didn't explain myself properly. I was under the impression that the APM had to be mounted as close to the CoG as possible for best results - that the IMU itself works best on the CoG.
UPDATE:
It's also possible to do this with 6mm risers as well - with 8mm risers, the APM is *very close* to the top plate, depending on your vibe solution.
Only difference is, you skip the moongel part, and glue the plate directly to the top of the Core RF shield.
Cheers guys! I'll look at these USB options today.
@ Brian: My vibe levels are good with moongel - +/-1 when loitering in slight breeze...+/-5 when pushing it around with full sticks in stabilize. I've not tried acro, but I suspect you'll exceed the recommended maximum of +/- 5. But since I never fly acro, that's ok for me!
I took this apart to try out the zeal squares; they are definitely more secure (when you consider the USB problem), and they are better in heat. I will let you know my vibe scores in the next flight. I will be re-running compassmot (since I've moved wires etc) while it's raining and I can't fly!
Re: CoG - Mounting the APM this far forward wasn't really that much of a problem, as it's not really that heavy - the problem was the battery. A 5000 3S is heavy, and it needs to be "right in" for good CoG. So by necessity you need to push the APM forward to allow the battery to move forward.
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