New quad lives... sort of. Motors get hot, and pitch is reversed.

[Hugh Hemington]

After all the configuration in APM, fixing MODE 1 vs 2, then fixing having reversed the throttle (because Turnigy's UI is a bucket of suck), I finally got the props on today.

First a word about Turnigy motors. I have four D2836/8 motors (1100kv). They have grub nuts, two of which slid right down on the shafts and two which didn't -- sliding down leaving about twice the motor shoulder/prop mount gap. So Turnigy is using or contracting "conical drill bits" (worn out drill bits). Also, don't I ideally want two of the prop hubs to screw down counter-clockwise? These are all the same. Later on that.

I screwed the quad to a stand I made from a champagne box so it wouldn't fly away in testing -- it tried to anyway. After weighting the box down with my SCUBA weight belt, I tried again and found that the pitch is reversed. Push stick away causes quad to pitch back and I'm not in "simple mode" having walked around it.

The second issue is that my parts selection is proving to be sub-optimal. I'm running a 4S LiPo on 45amp ESCs into these 1100kv motors, and at the end of a brief test, the motors were too hot to touch. I'm thinking that's not a good sign. Here's the motor on HobbyKing http://www.hobbyking.com/hobbyking/...r_Motor_USA_Warehouse_.html?strSearch=D2836/8
A guy suggested I use a 3S battery but I'd already bought two 4s batteries, and as usual, the HobbyKing info was about as clear as tar. I have a hard time believing my ESCs are wrong. How do you over-buy an ESC? And I want to keep the 4s batteries in the mix, so I think I'll look for different motors (and wait another two weeks).

What I can't figure out is, wouldn't HIGHER voltage produce REDUCED current draw for the same power and generate LESS heat?

If anyone wishes to chime in with a motor suggestion that will turn 11" props off a 4s battery through 45amp ESCs I'm all ears. Oh, and of course, I need to address this pitch reversal issue too. And anything on the merits of counter-rotating prop hubs would be of great interest. Thanks!

 

[Hugh Hemington]

I visited a VERY smart friend last night who explained to me that, motors work a bit differently than other power systems, due to the additional element of torque to produce "work". Apparently, using a 3S lipo works where using a 4S lipo gets too hot because the motor derives/produces torque from current, so driving the motor with lower voltage, causes it to draw more current furnishing it with more torque driving my 11 inch blade while putting less strain on the motor, producing less heat.

So, the solution I'm going to pursue first, to my motor heat problem is dropping back to a 3s lipo. Still working on why my "pitch" controls are reversed.

 

[Hugh Hemington]

While HobbyKing stares at my battery order, with their fingers in their noses, I'm still working this pitch reverse issue. Anyone have an idea how I can isolate it?

I guess I can plug the ESC leads directly into the receiver and see if the pitch is still reversed, huh?
And I've noticed that my props start turning all at once and very fast. They don't run up from slow. Is this normal? Is it a PID tuning issue?

After all this time building and ordering and waiting, I'd really like to see this thing get into the air, or just bounce off something really hard. Thanks.

 

[Hugh Hemington]

I ran my battery, prop and motor numbers through eCalc and it confirms that my motors are being roasted to death by the 4S lipo. That may also explain why the thing tries to blast off like a rocket -- too many watts running through it. I have 3S lipos on order from HobbyKing (US warehouse) for flight, ground FPV, and the radio, but naturally I paid extra for faster shipping, and HobbyKing dumped my order to the back of the queue -- using all the time I paid extra for! So the shipment will bump into the weekend and I won't see the batteries now until NEXT week. I also ordered the backlight for the Turnigy 9x! That display is HARD enough to read without the hassle of having to get a nuclear blast set off behind your head! I'm also going to modify it with a switch, so the backlight is only on when I need it.

I tried connecting the receiver directly to the ESCs to see if my radio was reversing pitch. One motor ran all the time, and they rest went insane. Not a very useful test.

 

[Hugh Hemington]

The 3S lipo battery runs the motors much better, but they were still scrambled as to channel, and didn't work right connecting receiver directly to ESCs. Scrap Turnigy, in comes Taranis. Things working better, but these Turnigy motors are far out of balance, or the grub nuts are defective (or both). I'm trying to figure out how to use an old automotive ignition timing light, connecting the trigger lead to one of the ESC wires, to strobe the motor/prop and determine where the imbalance is. To me, it makes more sense to use a strobe than a laser and a mirror. I think I can draw a red and blue line down the prop hub and actually SEE which line is closer to facing me when the prop hub is deflecting.

 

[Mike]

Wow - Not sure how I missed all this, but it sounds like you're working through all of the issues. Haha - your posts are always so entertaining. HobbyKing/Turnigy stuff is real hit or miss on the quality and handling and shipping consistency is a worse story. The price is always pretty good though, so I remain a customer. I just usually order extra of everything and pick the best parts out of the bunch I order as far as quality (and lack of defectiveness) goes.

When you connect your rx directly to the ESC, you'd typically connect one at a time to the throttle channel - not all of them. That's probably why the others went insane. Did you verify that all of your motors spin in the correct direction based on your configuration when you have the board plugged in and you're just giving it throttle? The reverse pitch issue could also very well be a tx programming issue. I believe there should be settings in the 9x or taranis to reverse the outputs of the stick position for pitch.

I'm not sure about the timing gun. That would be an interesting test though. With my NTM Prop-Drive motors, I had a crash and a few of the motors were kind of wonky after. I was able to change out the shafts and then I threw new bearings in them.

The shafts were from HobbyKing and the bearings were from Avid RC. I'm not sure if you'd know the specs to do that for those motors, but it might help. In fact, people on messages boards were saying HK motors sometimes come with bent shafts and/or bad or inferior bearings.

 

[Hugh Hemington]

So, updating... After switching from 4S to 3S, the QuadLugs 610 frame "tested" yesterday, but as with the Turnigy 9X, the Taranis X9D radio appeared to have reversed pitch/elevator. When I reversed that, the aileron seemed to act as pitch (too)! Basically all the controls are screwed up. The throttle is too touchy -- a small touch flipped the quad, which means the controller sent power to the motors unevenly.

At this point, I'm considering the possibility that my APM 2.5.2 board is fried, damaged or malfunctioning for some other reason. It should NOT be this hard to get a quad into the air! I considered that Mission Planner had not or was not sending my configuration down to the board, and this still might be the case. It would be exactly like dweeby nerds to hide the "transmit configuration" function nine levels deep in some obscure menu and not document it anywhere, just to dick with people.

Anyway, as I suspected, I might get my Alien in the air before my QuadLugs. The SunnySky motors arrived today from Banggood (there is no real "tracking" of packages from them), and the rest of the parts are "out for delivery" according to Swiss Post (a Hong Kong order from HobbyKing). I'm encouraged by "out for delivery" because they don't say that when they dump the package off at USPS, and the USPS guy delivered the motors today, so it wasn't in his bag. Typically the non-USPS deliveries are just left at the door -- they don't need a stool sample!

With the HK Mega 2.7 in hand, I may wire it into the QuadLugs to see if the 2.5.2 board is indeed the culprit before installing it in the Alien. If it isn't, I can't believe I won't have ALL the same issues with the Alien, in which case, I'll dump this stuff in the trash can, get drunk and order a DJI Phantom!

(I keed! I keed!)