I'm currently dreaming up a super simple, square aluminum tube, welded H-Octo airframe. Since it's made of aluminum, and welded, the electric path should be pretty good.
Any electronic gurus have any idea if I could use the frame itself as the ground connection for the battery? The ESC's will be mounted very close to the motors, so if I could do this, I'd only have to run a single positive wire to each ESC.
Cars are built this way.
But I don't know, what with the high power and frequency of the ESC's operate at, will it just become a giant flying Yagi antenna and cause more trouble than it's worth?
It sounds like a good idea but dont do it, you will have a accident waiting to happen.
Electrically heres why :-
1. If you make the frame (-) Battery and power everything form (+) Battery then eventually you will drop a live wire to the frame or wear through some heatshrink and let the smoke out of the bottle!!.
2, If you electrically connect anything to aluminium you need to be aware that dissimular metals (Alu/ copper/ steel) will all cause corrosion and bad joints, it can be prevented buts its not easy.
3, motor currents flowing in the frame will give an offest to the controllers and so they may run at different speeds with the same Rx signal.
4, more radiation of interference,
5, A heavy landing and broken or loose Arm could give undesired operation.or a short circuit to the frame from a cut wire.
Yes, cars can get away with most of these issues ( at a weight penalty)
6, Dont laugh buts its also illegal to connect a battery system of more than 12 v nominal to the ground side in a vehicle in USA/Can. . .
Aluminum is darn hard to weld, isn't it?
No, it's actually quite easy.
Well, I mean, I have a TIG welder. Obviously you need the right equipment, but it's not a big deal.
1. Good point, I'd like to say that would never happen, but I can't.
2. How do they do this in cars? My Land Rover has an aluminum body, and it's a ground. Yes, it's an endless string of ground faults causing much hilarity, but then it's also 10 years old and has seen a lot of salt. Hit the brakes, and the rear wiper runs! Wee!
3. I don't understand this one?
4. That's what I'm really afraid of.
5. Yeah, that's probably the biggest risk. Thinking about it, a car only has one place where this is a risk. If the battery positive, going between the battery, and the fuse panel were to short, you'd have a fire. But after the fuse panel, all the circuits are protected. In my scheme, of course I wouldn't be fuse protected so... boom.
6. Really? That's interesting. I didn't know that. Are you saying that 24V vehicles don't use chassis ground?
item 2, they use either passive material for screws and tinned cables ot remeve the different metals from each other , or they can use gold terminals, they aslo use aluminium screws and fastenrs, it can be done but a lot of effort.
item 3 if all of your (4) escs are receiving the same Rx signal then they will give the same % of the supply voltage to the ESC, = same speed as same rpm /volt.
but if the supply voltage to motor 1 ESC is using the common ground then the volt drop in the frame can be different to each motor depending on the route the current will take back to the battery. therefore you will have the same % of power but the supply voltage will be different = differnt speed.
item 6, Yes, all (recent) electric vehicles use 2 wire systems trucks,,Buses boats, etc 24v,36,48, 72v
Some are even equipped with ground fault monitoring for additional safety.
someone got fried at a university electric car competion and they (UL and CSA) changed the rules.
Hi, I once got some solder for aluminium. I guess from the LiPo battery industry, they have alu. terminals. It works quite well for soldering on wires and for joining alu. pieces where the electric properties are more important than the physical ones. I now build antennas etc all out of aluminium, no more copper of brass needed. It probably only works on soft alloys though.
I was learning GMA Aluminium Welding, certainly as many others around here, without having "Pulsed Mode(s)" available. Mentioned by the way and not to forget - it was a BOC Murex. Due to the heavy wall thickness parts we were required deploying "spray droplet transfer" - the root cause also for my one and only but the more painful photokeratitis.