CranialRectosis' Alien 4" Build

[cranialrectosis]

I have been building smaller and smaller copters since I chopped the booms down on my FliteTest Knuckle H Quad back in 2013. My yard is small and the dogs carve little tunnels beneath the bushes and trees and I want to fly them. I also wanted a copter potent enough to lift a GoPro.

The Alien copters are simple, robust builds. We all know how they can fly in the right hands. Aliens also take a good cratering well. While I can't fly like FGA, I can crater with the best of 'em. :applause:

The Parts:
The frame is the 4" Alien frame from Impulse RC.
Motors are DYS 1806 3000kv from AsiaTees Hobbies.
ESCs are the ZTW Spider 20A Pro Opto F390s rated for 2S - 6S.
The flight controller is the Brain FPV board running the latest dRonin firmware.
This frame was designed for the HS1177 camera.
My video transmitter is the Mini 5.8ghz from Surveilzone.
The props for this are the HQ 4045s BN.

First thoughts:
Aliens are beautiful frames and are packed intuitively so as to make them simple to assemble. They are heavy and tough. The booms will handle 1806 motor spacing as well as 2204s. The carbon fiber is very nice and very sharp on the edges. You must file the edges down or they will slice your wires, fingers and lipo straps. You can purchase the files at ImpulseRC or use your own, but file the edges. :black_eyed:

Soma is the wizard behind this frame. His work is top notch and he provides video instructions on his RC Groups page here.

Current PIDS:


Current Build Weight:
467 grams including Turnigy 45-90C 4S 1300mAh lipo.

Current Photo:

 

[cranialrectosis]

Parts and Frame Assembly

Aliens are simple. If it's hard to assemble your Alien frame, you are likely overthinking it. The 4" is the most difficult of the lot due to space constraints, but if you can solder and have a good, adjustable temperature iron with a mix of tips, these are some of the simplest copters to assemble. Even for a butthead like me.

Start with the packaging. Everything is wrapped in groups. DO NOT just cut open the hardware bags and dump the parts in a pile unless you build these often. The booms, top and bottom plates are pretty self explanatory as are the 'top of the stack' X plate, the rubber lipo cushion and the camera mount carbon fiber parts. I ended up not using the short video extension at all.

The hardware is in 4 pouches plus the 3 pouch bag with the PDB parts. Open them when you get to that segment of assembly. In my photo below the top hardware pouch is for top plates. The next pouch down is for the camera mount. Below that is for main frame hardware. The bottom pouch is for motors and props.


I started with the PDB. The first decision is to hard solder the XT60 directly to the PDB or not. I decided to solder directly to it to help keep wires out of the way of props. It takes some heat. Use the 1mm G10 plate to protect the XT60 plastic from the hot PDB. I like to keep the XT60 halves together while I make this joint as the female side keeps the male side straight when there is this much heat. Coat the leads with liquid electrical tape at this point.

After the pads are tinned, I pulled the little metal threads (I have no idea what these are called) into the holes in the center of the PDB. Do this after you tin the PDB and you won't have to heat them. Draw these in by placing the cutting edge on the top of the PDB and drawing it into the PDB using the one silver cap screw and washer in the main frame hardware bag. Place the finished side of the washer against your PDB, thread the screw through the washer, through the PDB from the bottom side and into the thread gizmo on the top of the PDB and draw the threads into the PDB by tightening the screw.


Once the PDB is ready and since you have the hardware pouch for the main frame open, the next step I take is to assemble the main frame. The short screws go in the middle. Booms have a top and bottom so be sure you line up the holes correctly and run the purple screws up from the bottom of the frame and secure them with purple stop nuts or, for the center set of screws, the short black standoffs.


I had these blue washers from an old build and decided to add them here just 'cause. Eventually I do coat those exposed XT60 leads with liquid electrical tape. I wish I had done so before I had assembled the frame but oh well. They should have a butthead emoticon on this site. :black_eyed:

 

[cranialrectosis]

Motors, ESCs and the Brain

I went with the Cobra 1806 2800kv motors for a few reasons. I like Altitude Hobbies and the service I get from Garret is the best ever. I get free shipping and I usually get parts tomorrow or the day after because I live in Colorado. The other big reason is the Rotor Riot 180mm quad build episode. Ummagawd explains the difference between the 1806s and 2204s and recommends kv ratings higher than 2500 to give you enough umph.

The ESCs were an odd thing. I went with the new ZTW Spiders with BLHeli on the new F390 chip. I like my Simon K ZTW Spiders and wanted to give these a shot. However, the parts I got are different than what are pictured. My 20A ESCs have a capacitor while the photo shows none. I have verified that I have the new F390 so these are the right part, but the capacitor makes them too long to fit on the top of the booms. UGH.

This is my first ever underside of the boom ESC build. I am a bit wary of it but I think it looks cool so I went for it!


I soldered the motor leads straight across to the ESCs on two opposing booms and crossed two leads (as pictured above) on the other two opposing booms. This way, I am either spot on for motor direction or exactly backwards. With dRonin it doesn't matter which is which so I just got to soldering. The clear heat shrink was removed and replaced with longer bits of black heat shrink. Since these are bottom mounted and prone to landing in snow and mud, there needs to be some extra protection.


I decided to remove the ground wires from the ESCs prior to reading Twitchity's explanation on another thread :black_eyed: because I wanted a single row of pins under the Brain. The bottom of the Brain boards is clear and smooth allowing for a very low mount. I also wired in a Pololu 5v 1A Step down voltage regulator and stuck it in place with a bit of two sided tape. I directly wired it to power and ground on the PDB and to power and ground on the Brain.


There is NO room under the Pololu but it doesn't sit on the PDB.

 

[cranialrectosis]

Receiver, camera, VTX and final assembly

With the main body of the quad assembled I turned to the receiver. Since I am using the X4R, I will be running S.Bus to the Brain's Main port. This harness is simple to make with the wiring included with the Brain board. I soldered directly to the pins on the X4R because taking the pins off is a royal PITA and I couldn't get the one without the pins from Aloft at the time.

I am also trying FrSky telemetry and have assigned the Brain's flex port. Again the wiring is simple given the wires provided with the Brain. Once the receiver is connected, a quick zip tie and the receiver is mounted.

About this time I connected the Brain board and flashed it with dRonin and smoke tested all my soldering. I also bound my receiver and set failsafe. Once the copter is smoke tested, I shrunk the heat shrink on the ESCs and mounted rubber feet cut from the foam packing of the Cobra motors under the ESCs to protect them and give my copter something to land on other than ESCs.


The camera mount and camera get assembled and attached next. You can find detailed video instructions for the 4" camera mount here. The Brain has an onboard OSD that gets wired into the mix. I am powering my camera and VTX directly from the PDB and have video out from the camera going to the Brain video port and video out from the Brain going to video in on the VTX. It's a gnarly harness but simple to build with the cables provided with the Brain board.


Now I mount the VTX and put the top plate on right?


Wrong. The 4" Alien frame is much shorter than the 5" and 6" frames. with my build, there isn't enough space between the 'top of the stack' X plate above the Brain and the top plate for the VTX. So I routed that gnarly harness under the Brain and put the VTX on top of the X4R receiver. I may play with this arrangement.
Oh look, the sun came out for a cameo!


Now the top plate and video antenna get attached.


and we have a copter!


dRonin is worth another whole post and I will get to it, but it is late and my CopterWidow wife wants me in bed on time tonight. As you can see I have been busy in the basement this weekend, but I will tease you all with this tidbit. Once the copter was assembled and configured correctly in dRonin, tuning took 30 minutes and with the help of the folks on the dRonin IRC, my copter is LOCKED in and flying fantastically in a single lipo.

 

[Crash and Burn RC]

Reserved 4

Ha-Just Joking. This looks like an awesome quad!
What is the motor-to-motor length? Looks tiny.
Also, What do you think of the Brain FPV Board? I have not seen many people using it and it looks really great.

 

[Twitchity]

Very nice start, Cranial. Is there a reason you went with mounting the ESCs on the bottom side of the arms? Did you decide to go with the 1806's to save weight on the build?

 

[cranialrectosis]

Reserved 4

Ha-Just Joking. This looks like an awesome quad!
What is the motor-to-motor length? Looks tiny.
Also, What do you think of the Brain FPV Board? I have not seen many people using it and it looks really great.

M to M on the 4" is 185mm. This is my second Brain board. I miss voltage detection and am looking into a solution. However, the Brain is no longer made. A new board is coming and rumor has it the new board will deal with voltage monitoring.

The Brain is awesome. The onboard OSD makes it a natural for tiny copters. If I want to, I could add GPS to this thing and fly waypoints or I can use the autotune to lock this copter in with custom PIDs and fly it like a WarpQuad.

 

[cranialrectosis]

Very nice start, Cranial. Is there a reason you went with mounting the ESCs on the bottom side of the arms? Did you decide to go with the 1806's to save weight on the build?

I used spider 12 A ESCs on my 3S WarpQuad and the capacitors stick up a bit because the ESCs are just a tad too long for the caps to sit on the boom. They stick up a bit on the frame. Every time I crater the quad upside down, a prop bends down and wipes a capacitor off an ESC. I think I have replaced 3 in 8 months.

Even a butthead like me can learn to get the caps out of the way of the props. :black_eyed:

The 1806s provide plenty of power for less weight. Ummagawd goes through that in a Rotor Riot episode. I'm pretty happy. The quad lifts off at 30% throttle and whips about smartly in my yard.

Hopefully the weather will give me a break. It started rain/sleeting yesterday and is supposed to be wet and cold all week.

 

[cranialrectosis]

dRonin, the sweet firmware with Autotune

This is my 3rd copter running the dRonin firmware installed with the dRonin GCS (Ground Control Station). dRonin is a fork of TAU Labs and is being actively developed by a team of brainiacs who respond to questions via an IRC channel here. I have found these folks to be more patient than TimeCop (and brighter) but I recommend you do some research on your question before you wander in and ask. These guys can quickly get over my head (not hard to do). The more research I do prior to a question, the more likely I am to understand the answers I get.

That is one big reason I decided to post this build. This is so I can remember and others can find answers and documentation of a build with pictures. I will invite the gents from dRonin to comment here and I will not be surprised to have someone with more brains than I contradict something I say here.

Once my ESCs, flight controller and receiver are all connected to power and ground and each other, my next step is to triple check polarity (it sucks to blow up a new board before it ever flies) and smoke test the rig. Once I know I have power I bind the receiver to the transmitter and set failsafe. IMO failsafe should always kill motors and shut down the copter.

Now that you can power the quad and have set failsafe, it is time to flash the board. If you are flashing a Sparky 2 or Brain, this is as simple as starting dRonin and connecting your PC to the board via USB. If you are flashing a Naze32, you have to use Cleanflite to flash dRonin onto the board and then you can connect dRonin.

When you start dRonin you will be greeted by the welcome screen. On the right side of the welcome screen is the configuration wizard (highlighted in the photo).

Use the wizard if that is an option for you. If you need to manually configure dRonin, continue reading.


I went into the configuration screen and set up my copter manually. I am running an X4R receiver and will be using S.Bus to communicate between the rx and Brain. I set up the Main port on the brain to run S.Bus and am not using the RX port on the Brain at all. I also, later, configure the Flex port on the Brain to run FrSky telemetry. Do this later. For now, leave telemetry off. Turning on telemetry turns on the Telemetry module. With dRonin, you cannot run the Autotune module and ANY other module on an F1 board like a Naze32. Turning on telemetry kills Autotune. So do this later after you tune the copter if you are running an F1 board. Lastly I increased the MPU rate to 1000 as the Brain can easily run that fast on my setup.


Now I need to tell the Brain what it is connected to. Do this in the Vehicle tab by setting vehicle type to multirotor and frame type to Quad X.


Now I need to use the Outputs tab to help configure the Vehicle tab. At the top of this tab is the Output update speeds. I am running Oneshot125 so my output speeds for channels 1-4 are SynchPWM with a resolution of 12MHz. My assignments are set up as PWM with a range of 125 to 250. At this point I need to test motor direction and pin assignment using the test outputs check box.


When you use the test motors option be sure your props are off the copter. The first time I did this I blew a setting and my NW motor started off at WOT. Save the stitches and take the props off your copter. This is the simplest IQ test ever. It stuns me how many smart people fail this simplest test.

Use the test motors option to figure out which assignment spins which motor. Set these assignments in the motor output channels on the Vehicle tab. This is also where I figure out that all my motors spin backwards. When building, I didn't care. All I did was be sure two motors are connected to ESCs straight and two have crossed leads. Now that pays off. I can simply check the reverse motors direction on the Vehicle tab and viola, the Brain now expects the motors to spin the direction they spin.

Once motor assignments are set and motor direction is correct, synch your ESCs and set Neutral. Neutral is the lowest rate the motors spin and are stable. My motors spin at 129 and are smooth and stable at 130. My motors will spin so long as the copter is armed because I have checked the box on this tab and they will spin at the 130 rate per the settings on this tab.

Now it is time to configure the transmitter. Here is where I love the wizard. Follow the steps and the wizard will set you up. Simply click the Start Configuration Wizard button on the Inputs tab with your radio in hand and the copter connected to USB and a Lipo. Before you start the wizard, ensure that you have set failsafe.


There are two more key elements on this tab. The next biggie are your flight mode switch settings. I have one 3 position switch I use for mode (SG on the Taranis). Top is for Horizon mode (for the kids at the high school). Middle is for acro and the last position is currently set for Acro Plus in this photo. You will want to select Autotune. DO NOT SELECT AUTOTUNE AS THE DEFAULT SWITCH POSITION.


When you select Autotune here, you also need to turn on the Autotune module or the GCS will return a critical config error. If you are running this on an F1 board like a Naze32 you can only run the autotune module by itself. On an F1, no other modules will work with the autotune module selected. Do that in the Autotune tab on the GCS by checking the box on the lower left.


Back in the inputs tab the last tab on the right is your arming settings. I still arm with stick movements and am set up to arm with 0 throttle and full right yaw.


Now that my controls are set up, I have a few tweaks left and it will be time to try an autotune. First I need to ensure the board is leveled and rotated correctly in the GCS. I have installed my Brain backwards (no surprise there eh?) and as a result, I need to set my virtual attitude relative to the board at 180 degrees. Do this in the Attitude tab. While in there, take the time to run automatic level detection, Automatic yaw detection and the 6 point calibration. All of these are in the Attitude tab.


The last thing I do on a little mini, is cut the default P gains down. I will need to fly in acro mode to get to autotune. If the copter wobbles like mad due to too high a P gain, it will be REALLY hard to fly in autotune mode. Too low a gain is hard to fly. Too high and it will toilet bowl wobble up into the sky before you ever get to autotune.

That's it. Now it is time to test arm the copter on the bench. If you have your props on at this point, you fail. Go sell your stuff on ebay and buy a Zyma toy from Amazon.

Once the copter arms without USB support and you can see that your ESCs all start at the same time and your motors all spin the proper direction it is time to test fly and autotune. This post is long enough so I will do that later and maybe have some video to show it all.

 

[Cyberdactyl]

Looks great.

My questions are, (and I know you're not ready at the moment), but do you ever plan to try 5 or possibly 6S down the road with those extremely high Kv motors? If you ever decide to try it, I would build a XT60 series coupler and use two smallish 3S instead of investing in a 6S.

That said, I suspect 5S and 6S would almost certainly desync, and would be over-the-top insane if they worked, in any case for anything other than an experiment, and you'd probably want some two-blade 0345s to not fry the motors.

 

[cranialrectosis]

Looks great.

My questions are, (and I know you're not ready at the moment), but do you ever plan to try 5 or possibly 6S down the road with those extremely high Kv motors? If you ever decide to try it, I would build a XT60 series coupler and use two smallish 3S instead of investing in a 6S.

That said, I suspect 5S and 6S would almost certainly desync, and would be over-the-top insane if they worked, in any case for anything other than an experiment, and you'd probably want some two-blade 0345s to not fry the motors.

99% of my flying is done in my yard, under the 6' fence level. I rarely fly as high as 20' and I haven't flown a machine over 50' since 1986.

I just don't have the room to go that fast and unless another flying field opens up I don't see that changing any time soon.

For those of you who can fly over grass. Thank your lucky stars. They may not be able to 'take the sky from me', but they danged sure can take away the land under the sky and force me to fly in the desert.

5S or 6S would be fun. I would love to build a big hex or octo and volunteer with the local FD but I have no place to fly something like that so instead of going large, I go small. Small enough to fly in my yard under the radar and out of sight of LEOs.

 

[Darkback2]

I was looking at how you mounted your ESCs and had a few questions...How does the foam hold up in rough landings? Would it help to shrink wrap the foam onto the arms or would that trap too much heat in the ESCs?

More generally, what makes people choose one type of ESC over another? (How did you pick this particular ESC vs any other?) I always just get something with the right amps that fits...

I've been having great success with the DYS 20amp ESCs. They are super tiny and I am sure I will find out the downside at some point, but given my current skill level that point is pretty far off.

I have them on my current blade 150 and now on my martian 230. I'm about to rebuild a ZMR with a set of them also.

Also...Cool looking quad! I like this form factor.

DB

 

[cranialrectosis]

Thank you Darkback2. The foam peels off in rough landings. I don't want to use the foam as a lever to apply pressure to the ESCs and I went with 2 blade props and not covering the cap on the ESC with foam specifically to prevent overheating.

If you buy 4 Cobra motors you can make 8 such pads and a few camera tilt pads for a GoPro.

These ESCs are the new BLHeli 20A from ZTW Spider. ZTW Spiders have a good reputation, I have used them in the past. They are small and fast and cheap and I can get them from Altitude Hobbies in a day or two with free shipping.

If Altitude stocked KISS 24A ESCs for a reasonable cost I would have chosen them. I tend to buy electronics I can replace in days instead of weeks and I prefer local or domestic small time vendors for purely altruistic reasons.

 

[jhitesma]

Few nit picky comments/clarifications about dRonin setup.

The vehicle setup wizard makes most of this much easier - really bummed that it didn't work for Cranial. Especially the board/ESC configuration - manually configuring the ESC's is still pretty confusing but the wizard will do that for you on most setups.

The comment about enabling failsafe before running the setup wizard refers to setting up failsafe on the RX if your RX needs to have that configured. With my RX's there's no setup so I forget about that step. Configuring failsafe on the FC is done as the last step of the input wizard and is pretty simple as long as your RX is working (basically it just has you turn off your TX to confirm failsafe is detectable.)

Few notes about modules and autotune:

1) The limitation of only having the autotune module enabled by itself is unique to F1 boards (Naze32/CC3D) due to their limited memory. It does not affect newer F3/F4 based boards.

2) However on all boards if you setup the autotune flight mode you must enable the module or you'll get a sysconfig error since you've setup an invalid flight mode. The errors about this have been recently improved - if you click on the red "sys config" error in the PFD (Primary Flight Display - the status box deal.) it's now much more likely to give you a meaningful error. (I found a bug that was preventing this error from displaying just before this last release but it's now fixed: https://github.com/d-ronin/dRonin/issues/906)

Basically there are two parts to autotune - there's a "module" which is code that gets dynamically loaded and there's an "autotune" flightmode which activates the module.

The overall way that autotune works is that when you enable the module and put the quad into autotune mode the FC tries to model the system of the quads "actuators" (think motors/ESCs together). That's what the wobbling is for. Right now this happens fairly unintelligently, the quad just does it's wobble dance for a fixed number of iterations. Eventually they want to make autotune smart enough to detect when a good tune is found and stop - but that will probably never happen on F1 targets. Anyway, once it's done that dance and determined the system model you connect back up to the GCS where that data is crunched and you're given an actual tune.

So enabling the module without the flightmode will waste memory but doesn't hurt anything. On the other hand enabling the flight mode but not the module results in a configuration that can't fly so the board goes into error mode.

3) You can increase the MPU rate on the hardware tab on F3/F4 boards for better performance. Have to leave F1 boards at 333 for autotune though as they can't keep up at any higher speed

I'll let Cranial tell his autotune story before I go any further...don't want to spoil any surprises

 

[cranialrectosis]

Not nitpicky, Jhitesma. You are spot on for all comments you made.

FrSky receivers have their own failsafe. You set two failsafes with a FrSky receiver with a Naze32 in Cleanflite too. One failsafe works when the rx loses rssi, the other works when the fc loses connect with the rx (crash hard enough and it happens).

Autotune is the big enchilada here. The wizard to set up your copter is excellent. The wizard to set up your transmitter is awesome. But the wizard to tune the PIDs is the real time saver here.

More a bit later.

 

[cranialrectosis]

Autotune

Autotune takes a bit of setting up to do right. Done right, you will have a solid tune in a few minutes. Here are the steps to get an good tune after you have dRonin set up on your copter.

1. Autotune is an autoleveler program. If horizon mode doesn't keep you level, autotune won't work well. You need to get your flight controller leveled so that Horizon mode is easy. If when you switch to Horizon mode, the copter pitches or rolls, you need to fix that FIRST.

2. Autotune won't be flyable if you have toilet bowl wobble due to too high PID settings. Yes to tune autotune, you have to do a manual tune first! Ok Ok I know this sounds horrid but it is really simple. The default PIDs are too high for my minis. I reduce the P gains by 50%. If the default Roll P gain is 20, I set it to 10. Flying a copter with P gains too low isn't nearly as challenging as flying a copter with toilet bowl wobble. Lose the wobble first. It is easier to tune up than down.

3. Autotune like you will fly. If you fly with a GoPro, tune with a GoPro. If you fly with HQ props and change to Gemfans, you will want to re-tune. Dramatic changes in weight, power, thrust will alter your tune. Autotune is completely custom to how your copter is right now. If you change how your copter is, you want to change the tune.

4. Autotune on a fresh lipo. Autotune takes 1 minute. If your lipo starts sagging at 30 seconds your tune is gonna suk big time.

5. Outside influences mess with autotune. If you have to use the sticks a lot to control the copter, your tune is gonna suk. If you are autotuning in the wind, your tune is gonna suk. If you have your copter all off level so that horizon mode makes the copter pitch or roll and you use stick to control that pitch or roll your tune is gonna suk.

Let's put this in perspective. I have done autotunes where the wind was going and I had to use a ton of stick to hold the copter in my yard. The tune sukked but the copter was infinitely better tuned than it was on defaults and flew well enough for the day. Later when the wind died down, I could re-tune and got a much better tune.

This video shows me trying to autotune with thundersnow hitting Monument in the distance. There is a breeze from my right to my left pushing the copter. We may get snow/lighting/hail this afternoon. The weather is wicked. This tune is gonna suk but in reality, it is better than I can do in Cleanflite in an hour so I'll take it.

Once autotune has been recorded, set it down, disarm, disconnect the lipo and re-connect to the GCS with USB. Open the autotune tab and select the Autotune setup tab. There you will see your autotune results. You may apply them or if you don't like them you can chuck them and try again.


If you choose to keep them, you will be re-directed to the stabilization tab where you may apply and save them to your board.


While I am on the stabilization tab, I need to point out the roll and pitch and yaw rates in the stick scaling and expo coefficients in the center of this screen. I have mine set to 600, 600, 750 which will flip with authority. Default is 150 which is marshmallow mode. I put my expo on my Taranis but if I wanted expo on the flight controller I would set it here.

Autotune can reveal problems with your copter. If autotune is not working well, you can get help. On the bottom left of the Autotune setup tab is an option to 'share results'. This sends your settings to the guys at dRonin and they can look at these numbers and tell a HUGE amount about your build.

Really, it is stunning how bright some of these guys are and the things they can tell by looking at the numbers. I highly recommend you share your results. It helps everyone and can provide you with really useful information.

The shared tunes appear here and you can look at yours and compare with others. This one is mine from yesterday. I am not keeping today's tune as the wind and storm gave me results that due to the wind and all my stick adjustment probably won't work as well.

Here is what autotune looks like through the FPV video feed. Here you can see the thunderstorm in the background and the Brain OSD in action. You can also see that I am rolling right to keep the copter level. It does the Hula pretty well doesn't it?

Unless you already have toilet bowl wobble or a real problem with your quad, autotune is safe and simple to control. It isn't hard to control autotune. The point here is that if you do it right, you don't have to exert much control at all.

 

[jhitesma]

One thing Cranial didn't mention. After tuning you can change the aggressiveness sliders to adjust the tune without having to redo a systemident (the wobble flight thing.) Just hook back up to GCS, change the sliders, then save your "new" tune to try it out. The defaults work well for most situations but if you prefer something more or less aggressive you can adjust to get something more to your liking.

You try hangtime yet Cranial? Going to tell them about trying curve fitting

 

[cranialrectosis]

One thing Cranial didn't mention. After tuning you can change the aggressiveness sliders to adjust the tune without having to redo a systemident (the wobble flight thing.) Just hook back up to GCS, change the sliders, then save your "new" tune to try it out. The defaults work well for most situations but if you prefer something more or less aggressive you can adjust to get something more to your liking.

You try hangtime yet Cranial? Going to tell them about trying curve fitting

Do you mean the sliders in the autotune page? I'll have to play with that once the storm blows over.

Hang time.


Lemme get FrSky voltage monitoring working first so I don't torch any of my lipos.

Curve fitting if you have warble. If no warble, IIABDFI. :applause:

 

[jhitesma]

Do you mean the sliders in the autotune page? I'll have to play with that once the storm blows over.

Yeah, it lets you adjust how aggressive the tune is so if you prefer it snappier or softer you can adjust for it.

Hang time.

I tried half a battery of it the other day LOS and liked it. Not a huge difference (other than having to learn to arm/disarm with a switch instead of stick commands) but when I chopped throttle things were noticeably more stable. It's IMHO a much better approach than airtime and works more like FGA's throttle up - only on an adjustable timer so it only stays up for as long as you set it to not indefinitely. It also works at the top end to increase stability when you're at a high enough throttle there isn't any more power available for additional stabilization.

Lemme get FrSky voltage monitoring working first so I don't torch any of my lipos.

Curve fitting if you have warble. If no warble, IIABDFI. :applause:

[/quote]

Curve fitting is basically what TPA wants to be While TPA uses a straight line to correct a non-linear problem curve fitting actually uses a curve to achieve the same thing - whodathunk? I haven't had to use it yet so I can't give any details...but I remember you saw improvement with it on this little beast so thought you may want to share details of how you enabled it since it's not well documented yet.

 

[cranialrectosis]

This copter has been a ton of fun for me in my backyard.

However, there has always been a bit of trouble with the OSD and flight controller. I could never get a good autotune and now I think I know why.

You see, when I fly this copter, sometimes the OSD goes a bit wonky. The artificial horizon sometimes tilts to the left during a level hover. I have finally isolated the issue. The problem is excessive vibration from the motors thrashing the flight controller. This explains also why autotune didn't work well for me as autotune is an autolevel algorithm and as such uses the accelerometers.

The problem gets worse the more throttle I run. Balancing props can help but sometimes the problem exists with 4 new props.

A few weeks ago after an odd crash where the copter just seemed to lose thrust I noticed a loose bell. The C clip had fallen off the motor shaft. The motor shaft was still attached to the bell but the bell could be lifted right off the copter. I replaced the C clip with one from my spare Cobra motor. Yesterday, two more C clips fell off mid flight. The shafts are still connected to the bell, but the clips are no where to be found. Without props the motors spin fine. With props you can hear the motors ticking and buzzing in the air.

This is the cause of my vibration and probably has been since day one.

I am now in the market for a set of 1806 motors in the 3000kv range that can handle a 4" prop. Any suggestions are welcome.