Slight snag to beware of with Aimdroix arms on TBS Disco

[Big Island Guy]

I discovered that the metal Aimdroix arm that attaches by the battery pig tail (arm #4) has to be insulated from the metal pads used for fastening it to the bottom plate. They're hot and will short the system when they contact the metal arm. What I've done is first, after cleaning with alcohol, paint the metal attach points on both sides of the bottom plate with liquid tape. I applied in a couple of thin layers, allowing drying in between. After curing, this is then covered with a single layer of electric tape to provide abrasion resistance. In addition, a very thin plastic washer I cut is put under the screw head to prevent it cutting through the insulation when torquing it down. To prevent contact with the hex screw, I shrunk a little piece of heat shrink around it where it passes through the plate. I'm confident this will work and keep working, but if anyone has a better way to do this, I'd be delighted to hear it. I really do want to use these arms.

[clouseau]

Bummer! This is the first I've heard of this issue. What spacers did they give you with the arms, I know the have both aluminum and plastic ones. There is a lot of guys flying these arms on their discos and i've never heard any mention of this before.

[CircleH]

I could make those arms... any length or such.... any color too..

so.... how about....... a T-shaped nylon insert that completely isolates the AL arms from the board???

(did you catch my little pun re: Al arms?)

[Big Island Guy]

Originally Posted by clouseau

Bummer! This is the first I've heard of this issue. What spacers did they give you with the arms, I know the have both aluminum and plastic ones. There is a lot of guys flying these arms on their discos and i've never heard any mention of this before.

They gave me the aluminum ones. I mentioned this to RMRC where I got the arms, just as a heads up not complaint, and they were quite surprised too. They don't carry TBS, but they too said they'd never heard of this and that it'd be shockingly poor design if there's a mounting point that's hot and I agree. Too poor in fact to come from the likes of TBS I'd think, so between that and what you've just told me, I'm wondering if I just got a bad sample. The first thing I did was make sure there were no solder bridges by accident and all was good, so it's definitely inside the board.

[Big Island Guy]

I finally and reluctantly have decided to go back to the plastic DJI arms. It just felt too dicey knowing that one little contact could sent the thing down and I wanted to get on with the build so I could start exploring the marvelous Pixhawk instead of futzing with this issue. The Aimdroix are really beautiful arms and I'm sure I'll find a use for them elsewhere, perhaps my first Disco, if its attach point isn't hot too.

[CircleH]

are the attach points all generic or do you have to make your own holes?

[Big Island Guy]

Originally Posted by CircleH

are the attach points all generic or do you have to make your own holes?

They're plated through holes provided by TBS and apparently, somewhere in the board, one of them is making contact with the hot lead from the main battery lead, which is just mms away. I don't know if this is common to all the Disco Pros or just my bad luck to get a bad sample. As Ready Made RC points out, this would be egregiously bad design to have an fastener sticking out that's hot. (Maybe someone reading this with one could see if theirs is to?) I checked my regular Disco (the non Pro version) and it doesn't have this problem, so now I'm torn about replacing it's DJI arms with the lovely Aimdroix arms. I'm torn, because it involves a major tear down of a bird that flies really nicely already and I'm sort of loathe to "fix" something that ain't broke. On the other hand,.... Sigh.

[CircleH]

yeah.. nothing like doing the same job twice...
yeah.. nothing like doing the same job twice...

Can you "sleeve" the fastener in question.. and if you remove that particular fastener are there any others that a hot?

[Big Island Guy]

Originally Posted by CircleH

yeah.. nothing like doing the same job twice...
yeah.. nothing like doing the same job twice...

Can you "sleeve" the fastener in question.. and if you remove that particular fastener are there any others that a hot?

It's just that one next to the main supply lead. I tried home brewing a sleeve with heat shrink, but the fit is really tight and while I did get it to work sitting on the bench, I just don't trust it to the rigors of flight when the slightest contact would be catastrophic. If one had access to the right materials or better yet, a 3D printer, I'm sure a little fixture could be made that would safely isolate them.

[CircleH]

I could probably turn something for you on the lathe or make something on the mill.
send me a drawing of what you need.. if your interested. I have nylon rod on hand as well as a plethora of other non conductive high strength materials.

In my mind I have an image of what you are dealing with but I could be wrong..

anyway as an internet buddy who has provided me with lots of good advice.... Im willin' to help you solve this.

[Big Island Guy]

Originally Posted by CircleH

I could probably turn something for you on the lathe or make something on the mill.
send me a drawing of what you need.. if your interested. I have nylon rod on hand as well as a plethora of other non conductive high strength materials.

In my mind I have an image of what you are dealing with but I could be wrong..

anyway as an internet buddy who has provided me with lots of good advice.... Im willin' to help you solve this.

Hey, that's really nice of you. I'll take some pics plus do a careful measurement if you'd like to give it a crack.

[CircleH]

You bet!! we have to be like a band of brothers Brah!

I have another idea, but it would better be explained with a short video. I'll see if I can put something together today.. CAUTION!!! my video puttin' together skills are a far cry from even a C+!

[Kingacp]

When I was installing my AIMDROIX Aluminum Extended Arms and the one piece aluminum spacer I saw this could be a problem, so I unsoldered the Leeds, carefully cleaned area, used two pieces of electrical tape to keep new solder from getting to close to edge, modified the spacer and added a piece of shrink wrap tube to insulate.

[CircleH]

how are you making out with your measurements?

[Big Island Guy]

Originally Posted by CircleH

how are you making out with your measurements?

I'll get those to you tonight. I was at my son's girlfriend's birthday shindig at their new house last night. Never came home till late and trashed.

[Big Island Guy]

Originally Posted by Kingacp

When I was installing my AIMDROIX Aluminum Extended Arms and the one piece aluminum spacer I saw this could be a problem, so I unsoldered the Leeds, carefully cleaned area, used two pieces of electrical tape to keep new solder from getting to close to edge, modified the spacer and added a piece of shrink wrap tube to insulate.

Thanks, but thinking the same thing, I cut a channel there with a Dremel and cutoff wheel, which makes it very nicely clear the wire, but the attachment point where you insert the screw is actually hot with the battery voltage. Only on my Disco Pro though, so I'm sort of thinking about using the arms on the plain old Disco I also have, but I'm kind of loath to completely tear down a bird that flies so nicely already. I'll probably just save them for another project unless CircleH can make the right fixture for me to insulate it with.

[CircleH]

I can give it a shot.. This is the sort of thing that I am good at. mechanical problem solving.
I really need to make that video I said I was going to do.. It may be the solution you are looking for.... But we wont know until I get it done and posted. Soooooooo... pitter patter.
I will add this to the list of thing to do tomorrow.. I think I have all the material on hand to record a possibly useful demonstration.

speaking of B-days.. mine was just a few days ago. 27th.

[truraza]

Originally Posted by Big Island Guy

I'll get those to you tonight. I was at my son's girlfriend's birthday shindig at their new house last night. Never came home till late and trashed.

Sounds like a good time to break out small hand tools and caliper...

[andythilo]

Would these not solve the problem?

http://www.readymaderc.com/store/ind...oducts_id=1932

[CircleH]

I think the problem is that the screw goes through a "hot" part of the trace that is embedded in the board. I have to make some time to make a shorty video of a possible solution, but in my world lately, making video is like trying to find diamonds in a coal fire.

Sorry BIG. I will do this thing.. I promise. : )