X550 Quadcopter

UPDATE 28.6.2016:

• I've been busy last few months, hope to find time for this hobby and to finalize this project page
• Motor mount holes are rotated 90° in ARM_ALT.STL

X550 is a Work-In-Progress - here's my To-Do list:

• upload some video
• more details on wiring (requires adjusting some cable lengths i.e. soldering and crimping new connectors)
• APM:Copter-3.3 parameters I use with this setup

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This is a remix from Brendan22's T4 Quadcopter

Soon after building my Prusa i3, I started printing T4 parts but found problems especially with arms because of heavy ABS warping and deforming. I started designing arms with more bonding surface and that meant the body needed changes too. While waiting for all the electronics I decided to redesign the whole frame. First frame was asymmetrical like T4 but I found problems when tuning it to stable hover. So I moved to X-style frame. Later I learned that center of thrust (CoT) needs to be coincident (or close enough) with center of gravity (CoG). Still wanted to stay with X-style frame as it felt better.

After a lot of tweaking and testing I found frame design that seems to work great.

• 550mm motor-to-motor distance allows to use 10-12" propellers (I use Gemfan 11x5" CF+Nylon props) and gives a bit more stable flight and better wind resistance.
• The body has minimal unused space and has few dividing walls to make it more rigid.
• FPV video Tx is located front left corner and receiver's antennas are positioned opposite to minimize possible RF-interference.
• Battery compartment's end cap is held in place with screws as it makes frame more rigid and handles possible crashes better (the flight battery weights about 400g). The end cap has also place for velcro straps that are holding an auxiliary battery.
• ø5mm carbon fiber tubes are used as GPS mast and long feet (required with gimball) for overall better performance. Feet are fixed to body with the same screws as arms.
• For additional cover to Pixhawk and it's vulnerable cables and connectors I designed canopy mold that can be used with a vacuum forming machine.

CoG tends to be few mm's behind CoT when flying without G-3D gimball and GoPro - yet copter performs great.In fact I just got the G-3D gimball and made few adjustments to get it mounted properly.

As I found the frame performing excellent, I wanted to share it.Anyhow, most of the geometrical and mechanical design choices are copied from Brendan22's T4 Quadcopter. I give my respects.

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This frame is designed to work with following gear:

• Motors: NTM Prop Drive Series 28-30S 900kv or equivalent.

12x6E - 11.1v - 195W - 17.8A - 1.01kg thrust 11x7E - 11.1v - 188W - 17.0A - 0.89kg thrust 10x5E - 11.1v - 133W - 12.0A - 0.75kg thrust

• Propellers: 10x4.5" - 11x5" (haven't tested 12" props yet)
• Electronic Speed Controller (ESC) / BEC: Q Brain / Hobbywing Skywalker 4x25A
• Flight Battery: Turnigy 3S 5000mAh (146x50x27mm compartment size)
• Flight Computer: 3DR Pixhawk
• GPS / compass: 3DR uBlox
• Receiver: FrSky D4R-II

Optional gear:

• 3S auxiliary battery for LEDs, gimball and FPV gear (I use this)
• 4 x Super Bright 3W LED with Aluminium Heatsink (+ constant current driver)
• Walkera G-3D 3-Axis Brushless Gimball + GoPro3 / iLook
• Fatshark 600/700TVL CMOS FPV camera
• MaxBotix MB1242 I2CXL-MaxSonar®-EZ4™ Ultrasonic sensor
• ImmersionRC 25mW 5.8GHz A/V Tx
• MinimOSD
• Bluetooth Data Link for Pixhawk at least when using canopy

Required hardware:

8 x M3 40mm machine screw (arms) 8 x M3 nut + washer (arms) 20 (+2) x ø3mm 12mm self-tapping screw for plastic (body, deck, bottom, gimball) 1 x ø5mm 120mm carbon fiber tube (GPS stand) 4 x ø5mm 140mm carbon fiber tube (feet) 2 x ø3mm 135mm antenna tube (Rx) 2 x small rubber bands (A/V Tx and Rx) few cm's double-sided tape, eq. Scotch® VHB™ (fixing electronics)

The self-tapping screws I used have been salvaged from broken stuff. http://de.screwerk.com/en/products/stp/stp32.html

Additional information:

*WEIGHT PRINT TIME FILAMENT USAGE (3mm)** Body 128g 11h 50min 20.45 m Deck 37g 2h 30min 5.45 m Bottom 46g 3h 20min 7.20 m Arm (1) 44g 3h 15min 6.75 m Feet (4) 25g 2h 20min 3.60 m

Canopy mold 4h 31min 12.15 m

TOTAL WEIGHT: (with gear listed above):

• without batteries (dry weight) 1170g
• with batteries 1675g
• with G-3D gimball and GoPro3 1975g

STABLE HOVER THROTTLE:

• with G-3D and GoPro3, 11x5" props about 52%

FLIGHT TIME: (using 4000mAh = 80% capacity):

• without G-3D gimball and GoPro3 ≤20min
• with G-3D gimball and GoPro3 ≤12min

MEASURED POWER CONSUMPTION: FPV-gear + LEDs 450mA = 1h 45min of safe usage time with 1000mAh battery FPV-gear + LEDs + G-3D 1.0A = 50min

(*) printed with E3D v6 Belt Driven Extruder.

Print Settings

Rafts:

No

Supports:

No

Resolution:

0.2 - 0.25 mm layer height

Infill:

30% honeycomb

Notes:

All files include necessary built-in supports.

Arms are printed with closed ends to minimize warping and deforming.

For testing purposes there's pre-cut piece of body's arm recess and stubby arm.

• Unfortunately even as these test parts seemed to fit perfectly, full parts (especially arms) tend to deform slightly during much longer print time. This makes minor adjustments with sanding necessary. I suspect this is ABS related problem.

I've printed all parts with ABS, 0.25mm layer height and 0.4mm nozzle. I used 100% infill for feet for maximum strength, 30% for all others. 3/3 solid layers, 3 perimeters. Default extrusion width is set to 0 = AUTO. Detailed parameters can be found on my E3D v6 Belt Driven Extruder page.

Feet base part have weak spot that can lead into problems. The part printed with Taulman's Alloy 910 feels unbreakable.

If you take up the challenge of printing parts with ABS, warping can be minimized with:

• heated bed (110°C)
• enclosed cabinet
• high quality filament (I used PrimaABS™, which is licenced from ESUN 3D)
• BuildTak™. With Kapton tape I didn't get reliable binding. BuiltTak™ also leaves a nice matte finish.

Post-Printing

Body

• arm recesses have "comb"-supports, that I found easiest to remove / cleanup while they give excellent support. Carefully remove all residues of these supports before installing arms.

*[optional] if MB1242 is used, glue sonar base part into body's bottom *[optional] if G-3D gimball is used, glue bracket's support pieces into body's bottom. It is recommended to glue them after ESC is fixed to the bottom with double-sided tape (see reference wiring pictures).

» I prefer plastic glue (e.g. UHU Allplast) as it gives some time to settle the pieces and a very strong bond.

Arms

• cut along small groove to reveal open end. I used small hack saw with fine tooth for cutting and knife to finish.
• if required, use 150-240 grit sandpaper to fine-tune the shape of arm's end and get snug fit into the body's recesses. If you find there's too much clearance, apply thin tape around arm's end.Design clearance is left to 0.25mm and I'm ready to make different versions if requested.

There's a weak spot on foot's base part. The upper part (printed with Taulman's Alloy 910) feels unbreakable.

MB1242 base and G-3D bracket's support pieces on the right place.

LED's with constant current driver

I salvaged constant current driver from cheap MR16 4 x 3W LED spot lamp.I measured the driver's output is 300mA. I soldered JST-connector in place of desoldered MR16 pins and thenconnected four 3W leds (2 red, 2 green) in series to DC-output. Finally covered the board with heat shrink tubing. The LED's are powered from the auxillary 3S 1000mAh battery that is also giving power to FPV gear and G-3D gimball.With 300mA current they are surprisingly bright without draining too much power. The heatsink gets barely warm.

Inside MR16 LED spot lamp there's small constant current driver (with bridge rectifier circuit).

MR16 pins desoldered and replaced with JST-connector. Pink wire is +Vout, white -Vout.

3W LED is fixed with small ø1.5mm 6mm self-tapping screws I had salvaged from broken stuff. NTM 28-30 motor is fixed with button head M3 6mm screws (with low strength threadlocker). Note the balancing tape piece on propeller's bottom face - don't forget to balance your props!

Making canopy

Additional canopy can be made with vacuum forming machine. Print model with 15% honeycomb infill and use it as positive mold. I used1mm thick white polystyrene, which transilluminates Pixhawk's status leds nicely. The canopy weights only 17g but it feels really tough when fixed into body.

For DIY vacuum forming machine plans, just use google.

I found ahooked carpet cutting blade very handy to get clean cut along canopy's curvy edges. 3mm fixing holes and 6mm hole for GPS mast and wires can be made with a leather hole punch.

Wiring

http://copter.ardupilot.com/wiki/advanced-pixhawk-quadcopter-wiring-chart/

https://code.google.com/p/arducam-osd/wiki/Specific_Hardware_Diagrams

Q-Brain / Hobbywing Skywalker ESCs havea bit too short input wiring for this frame. I de-soldered the original wires andreplaced them with 20cm long ones. ESC's circuit board need's to be removed for this job.

Pixhawk's power module has XT60 connectors that aren't compatible with the flight battery I chose. I soldered 5cm long 10AWG silicone wires with HXT 4mm bullet connectors to the modules input and ESC's power input wires directly to the modules output.

• 80W soldering iron is highly recommended for this job
• For Taranis TX users: input toFrSky Analog Battery Voltage Sensor can be soldered at the same time. Output from the sensor board goes to D4R-II's AD2 pin (white). You can also get digital voltage reading (along with the other data) from Pixhawk's telemetry output withFUL-1 adapter, that is connected to D4R-II's three other input pins (http://www.frsky-rc.com/product/images/pic/D4R-II.jpg). I have the both options available.

When using canopy use ≥15cm long DF13 cables with 3DR uBlox.

MB1242 can be connected with ≥10cm long 4-position DF13 wire to I²C splitter board. I cut the other connector off and soldered wires directly to MB1242.

• http://copter.ardupilot.com/wiki/common-rangefinder-maxbotixi2c/

Wiring on DECK before installing Pixhawk with Anti Vibration Foam pads. Note that A/V Tx need's to be removed when installing/removing arm bolts.

Wiring on DECK without connections to G-3D gimball. Telem 1 = MinimOSD. Telem 2 = FrSky FUL-1 adapter. Serial 4/5 = 3DR Bluetooth Module.

D4R-II's PWM RSSI output from CH2 to Pixhawk's SBUS port (signal = white, gnd = black). It will be shown on FPV video. G-3D's tilt (and roll) control signals are outputted from Pixhawk's CH6/7 OUT (for some reason I didn't get AUX outputs work).

Right-Click and select 'Open picture in new tab' to see it in full resolution.

G-3D gimball mount and CoG balancing

I wanted tomount G-3D gimball to the body instead of sluggish bottom piece. The solution is to use 2mm thick aluminum (or carbon fiber) bracket between bottom piece and body's G-3D support pieces.

• Print attached PDF-file and glue/tape it on aluminum/CF sheet. I cut the bracket with Proxxon DSH 2 Scroll Saw and made the holes with Micromot 50 Mini-Drill mounted on drill stand.

The bracket alsomakes possible to fine-tune G-3D's position = X550's CoG. I even made simple tool, which might come handy during adjustment.

After correct place for G-3D's mounting rail is found and bottom piece is fixed to body, install additional ø3mm 12mm self-tapping screw through bottom and the bracket to the body's mating support pieces.

G-3D's mounting rail fixed with M3 12mm hex socket screws to the bracket. Remember to use thread locker! Bottom piece is not shown.

When tuning CoG balance with G-3D's placing, this simple tool might come handy. Lift the quad from the center line (little notches).

Category: R/C Vehicles