Wazowski upgrade

Wazowski upgrade

With 2205 motors, this weighs 232.8 grams

  Wazowski was my first attempt at building ultra light weight quadcopter for racing purposes. This was built on summer 2017 and since then, it has been going though constant upgrades to achieve better flight experience.

Goals for this upgrade was to:

• reduce weight even further
• strengthen the tower structure
• have onboard DVR
• have clover leaf antenna instead of dipole antenna (allows racing with multiple pilots at the same time)

Parts used for this upgrade:

On board DVR	HMDVR-S
Top plate	QAV-ULX carbon fiber top plate
Standoffs	Anti-vibration damper with fixed screws
VTX antenna	UXII Stubby LHCP UFL 5.8GHz 1.6dBi
Propeller	HQ 5*4.3*3

Personal rate settings from Betaflight (enlarge image size to see details)

  I have been using the default rates setting so far so I wanted to try other rates setting that is more optimized for FPV racing. Big thanks to Seth from Georgia Tech Unmanned Flying Club who shared his racing quad's rate setups, I found a new setting that is more precise at the center joystick control and more maneuverable at the end control.

Left: traditional rotation,  Right: reversed rotation

  Picture above depicts quadcopters in forward flight. Blue arrows mean the quadcopters are moving forward, white arrows show the rotation of the propellers, and red dots show the center of thrust of each propeller.
  I swapped all 4 motors and propellers to have propellers spinning in opposite direction compared to the traditional rotation. There are aerodynamic benefits to this setup for racing and this video explains the theory in detail. As the quadcoter moves forward, the spinning propeller's advancing blade produces more thrust than the retrieving blade. This shifts the center of thrust towards the advancing blade. Regardless of the prop rotation direction, rear propellers work less efficiently than the front propellers in forward flight because they have to deal with turbulent air created by the propellers spinning at front. Center of thrust at the outer position compensates this inefficiency due to principle of moment. It is also said that in reversed prop rotation setup, rear motors can work more efficiently under fast yaw movements.
  Other advantages are since the propellers are now spinning outward from the camera lens, I don't have to clean the lens as often since it is free from debris coming from propellers. Also, since the propellers are now pushing "away" whatever objects coming towards at the center of the quad when forward flying, it is less likely to get tangled up on things like tree branches.

  Also, new propellers (HQ 5*4.3*3) are installed. I found them durable and efficient, I can see why many fpv racing pilots say this is one of the best props in the market.

Bottom view

What have I done...

  This is a sketchy way of making traditional motor to be naked bottom. (No, I'm not being dirty. That is what people call motors with minimalistic mount design.) Just dremel off the unused aluminum excess material at the bottom and this saves approximately 2~3 grams per motor. There are 4 motors in a quad so total of about 10 grams were saved by doing this mod. It's always good to have motors as light as possible because with less weight at the outer edge of the quadcopter, motors have to work less to overcome the inertia in order to change drone's orientation.

Close up views of rear(left) and front (right) motors

  The stators were exposed since the motor is now naked bottom. So to protect the copper wires, I surrounded them with thermally conductive, but electrically insulating epoxy. Notice for the frontal motors, I left the aluminum material remaining at the outermost corners of the drone. This will protect the magnets from getting hit when crash happens.

HMDVR-S onboard DVR and LHCP antenna installed

  I've been using dipole antenna for the vtx before. It is light and works well when flying alone but it tends to cause interference when flying with many other pilots. Thanks to rapidly advancing drone technology, I found a left hand circular polarized (LHCP) antenna that is small and light (only 1.6 grams with UFL connector!). It's still 1 gram heavier than the dipole antenna I was using before but I can live with that number. The antenna is mounted tilted backwards to optimize signal radiation coverage when the drones is tilted forward during forward flight(which is majority of the case when drone racing).

  Onboard DVR is added on the back of the quad. This only weighs approx 4 grams total with the micro sd card and heat shrink cover. Advantage of having an onboard DVR is that it can record video footage without capturing all the signal glitches seen on the goggle.

  Also, RFX185 frame's top plate is replaced with QAV-ULX's top plate which has more material around the M3 holes to hold onto the screws.

Flight controller is happy with rubber rings + 2 floors of vibration dampers 

  I am still using LUX 32bit flight controller which is known for having overly sensitive gyro. Soft mounting all four motors weren't enough to stop the quad from twitching at the mid throttle and throttle punches so I added rubber rings under the FC and 2 floors of vibration dampers below to filter out unwanted vibrations. This significantly improved the flight controller's performance as no more random twitches were detected during flight. Also, using vibration dampers as standoffs make tower designed frame structure stronger as it uses metal screws compared to using nylon standoffs (these shear easily in crash).

All up weight is 404.6 grams with 4cell 1500mah LiPo battery

Rear view

  I'm a broke college student so I try to upgrade as much as possible before moving on to building another completely new setup. Most of the upgrades are therefore hardware related modifications while I try not to replace all the expensive electronics. Some tinkering with the betaflight software are usually part of the upgrade as well. Wazowski has been going through upgrades for almost a year now and I think it is now reaching it's limit in terms of flight performance unless its flight controller and all 4 motors are replaced with better components. That would be a huge investment as those are usually some of the most expensive parts in a quadcopter. Anyways, I say Wazowski is still a solid race quad as all the upgrades and improvements done to it compensates for the old components it is using.

Upgrade summary:

• reversed propeller rotation
• replaced dipole antenna with clover leaf antenna
• remove excess weight from the motors
• replace top plate with beefier plate
• HQ 5*4.3*3 propellers
• replaced nylon standoffs with vibration damping standoffs
• added onboard DVR (HMDVR-S)
• newest Betaflight filmware at the moment (Betaflight 3.3.0)
• optimized transmitter joystick movement
• permanently turned on airmode, anti gravity, and dynamic filter features
• disabled arming angle
• adjusted rates for more race compatible setup
• added prearm feature for extra safety
• etc... (miscellaneous small improvements)

Improvements for future iterations:

• top mounted battery placement
• better flight controller
• better motors
• 6cell LiPo
• I might as well just build another drone

Heart gears

Heart Gears (Screwless)

"Got a whole lotta love!" - SC2 Marauder

  I've always wanted to build heart gears. I think it is just way too cool. Thanks to emmett from thingiverse (link to CAD source), I only needed to customize the print setup before printing to have the parts in my hands.

Goal of this build was to:

• kill time (might have been a better idea to study more system dynamics exams :p)
• prove that I have a heart

Parts I used for this build:

Filament	PLA plastic (black)
Paint	Enamel spray paint+primer (red)
Coat	Enamel clear coat spray

First few layers

  3D printing was done in Invention Studio at Georgia Tech using Ultimaker 2.

Finished print

  The parts are printed with 1.2 mm wall thickness (a bit of an overkill) but that was to compensate for the dreadful amount of sanding required to minimize unevenness of the surface due to print layers. 

Parts polished with dremel and sand papers

It was dark outside so it's not my fault that the parts look like freshly extracted organs

  Parts are spray painted with color in multiple repeated process of slightly spraying overall and then drying. This is to evenly distribute paints and prevent them from concentrating in one place. After the color is set, clear coat was sprayed in similar process to protect the painted surface.

This thing rotates pretty well

  The 3D printed pins that connects the gears to the center piece were widened at the middle with pliers so that the gears are less likely to get disassembled from parts rotating. After that, the gears were assembled and rotated for personal gratification.

Improvements for future iterations would be:

• apply on the surface with putty or anything that can fill up the uneven texture
• maybe use a red filament in the first place
• use SLA print for finer resolution instead of FDM print