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
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
full of potential, but hampered by faulty drive system
Dynastinai is my first attempt of building a battlebot with modular weapon system. It was greatly inspired by leading 3lb battlebots Silent Spring (link to Jamison's blog) and Margin of Safety (link to Aaron's blog). The name Dynastinai comes from dynastinae, which is a scientific name for rhinoceros beetle. I changed the letter "e" to "i" to respect the naming tradition of Robojackets Battlebot (all battlebot names end with letter "i"). Also, I thank Robojackets and its members for providing me the tools I needed and doing a design review for this project.
The modular weapon combat robot can be very effective in the competition because the driver can strategically choose which weapon to use against specific type of opponents. Depending of the types, battlebots are usually like rock, paper, scissors; one type of weapon is strong against certain weapon type, but is weak against another weapon type. For example, horizontal weapon is useful against many drum spinners with exposed vertical walls but is quite ineffective against wedges or vertical spinners with wedges at front since those deflect the horizontal hits. However, vertical spinner with two sharp prongs like the one designed above in the picture are effective against wedges or vertical spinners with wedges at front as those prongs put large pressure on to smaller area on the floor and this tend to dig under the wider wedges. This type of vertical spinner is at the same time, weak against horizontal spinners like the one designed above since those prongs are exposed to shear hits.
The goal of this project is to:
build interchangeable weapon (one horizontal, one vertical)
all basic structures made out of 3D printed materials
This is the bottom view. The top plate does not have to be removed at all unless it gets damaged. Only one bottom plate can be removed to access batteries and the other bottom plate can be also removed to access drive motors. The dove tail design of the module interface and the aluminum posts makes difficult to rip apart the module from the chassis in all directions.
CAD - 3D printed chassis, electronics removed
Aluminum standoffs are inserted into the 3D printed pieces. Top and bottom plates are then secured onto those standoffs with screws. This allows the top and bottom plates to clamp on the 3D printed parts and gives them compressive preload and prevents delamination. Screws and nuts hovering in the photo above are used to secure wheel guards on to the 3D printed chassis.
Half section view of horizontal module
No screws go through the 3D printed horizontal module. The aluminum pieces are clamped from top and bottom to give 3D printed part compressive preload: prevent delamination.
Half section view of vertical module
There are two bearings on each end of the vertical weapon. The motor is fully enclosed and is well protected inside.
Prototypes first before using expensive carbon fiber & kevlar
3D printing in action (horizontal module)
completed part
that's a lot of support structure to remove
Vertical module is printed with its one side facing towards the bottom. This way, I could clamp the print layers sideways to prevent delamination.
CNC milling horizontal hub mount
Horizontal hub motor mount straight out of CNC mill
Sadly, I didn't account for the tool deflection and the inner diameter where the bearing would sit was 0.002 inch smaller. The bearing would have still went in if I made a press fit but I didn't want that for the sake of easy maintenance. I used a dremel to carefully sand off the inner diameter little by little until the bearing could slide in with minimal interference.
chassis assembly almost complete
On the vertical module, you can notice there are some nylon material extruded out and surrounding the vertical wedges. Without these, vertical wedges would be vulnerable to hits as it is just held by few M3 screws and it doesn't take a lot of force to shear those.
Where else would you find S7 tool steel laying around up for grabs?? :)
I was fortunate enough to find the S7 tool steel in the scrap pile in Robojackets shop. They weren't gonna be used by anyone and apparently, they have been laying around there for a while. So I cut a small piece off from one of them, made a request to the machining mall to have it lathed, wire EDMed, and then heat treated to make a vertical weapon.
Assembly almost complete. Stator on the vertical module is also machined and epoxy glued.
Fabricated, with horizontal attachment
Horizontal weapon was made out of 3/16 inch thick AR500 steel - waterjetted.
Bottom side
Bottom cover is composed of two plates to easily access the internal components that are just needed. Also, too many screws on the horizontal weapon. I think I can reduce number of screws here for the next iteration.
With vertical attachment
Internal view
Inside is full of spaghetti. I couldn't optimize the wire length because I had to borrow drive motors and drive ESCs from other robojacket team members since I didn't have those.
I can take off this cover and access the drive motors
The drive motors are composed of gearbox and brushless outrunner. Because of this, rooms for the outrunners to safely spin had to be designed. Here I clamped the gearbox (not spinning part of the drive motor) in an elevated position so that the outrunners have enough vertical space to spin. Also, a thin wall was made to prevent any wires from making contact with the outrunners.
Stator inside the motor mount (top), assembled motor hub (bottom)
The stator is is machined to fit into the hub motor. Also, it is covered with thermally conductive but electrically insulating epoxy glue to be more resistant to heat and take impacts better when it makes contact with the magnets around it. The aluminum hub is first waterjetted for the holes and general dimension and then tuned on lathe for precise cuts. Magnet ring from the original motor is cut and press fitted into the hub and is covered with same epoxy glue to keep magnets in their place.
horizontal module disassembled
vertical module disassembled
damage taken on the horizontal module during the rumble
Even though the 3D printed part was clamped, delamination occured on the 3D printed part, and aluminum chunk was taken off from the hub motor mount. I will be strengthening this part in the future iteration.
damage on the right wheel guard
damage on the left wheel guard
HDPE wheel guards held pretty well. It covered majority portion of the 3D printed parts and the wheels and took almost all the hits. The damages to the wheel guards don't concern me since they are designed to be consumable and are cheap and easy to make (it takes 20 seconds to waterjet one).
Dynastinai testing its horizontal weapon
I see a lot of potential to this robot. There were many good aspect like the interchangeable weapons, efficient hub motor weapon, 3D printed chassis, 6 cell lipo battery. However, it was ultimately hampered by faulty drive system. Whenever I made sudden left to right movement or vise versa, the ESCs went into a reset mode and the robot was immobile until I put the control joystick at the center and wait for a second. In a fast paced, agility requiring combat arena, Dynastinai was immobile for significant period of time due to this mishap.
Not having my own drive system was a problem too. I had to borrow other Robojacket member's drive ESCs and motors so I had to spend significant amount of time taking the drive in and out instead of test driving or checking out if there are any other problems.
Also, I didn't put soft pads around the electronics inside so after hard hit from a vertical spinner, the weapon ESC got damaged and wouldn't spin up the motor anymore.
Dynastinai never won and its win loss ratio is 0:2 from Motorama 2018. However, now I know what to fix so hopefully I can build a more formidable combat robot (Dynastinai V2) in the future.
For future iteration of this robot, improvements would likely be:
have my own, reliable drive system (brushless -> brushed motors?)
less free space for soft mounting drive motor, use double sided foam tape or polyurethane rubber
more space for the wheels to rotate
6 cell -> 4 cell lipo ? (this way I don't have to use separate voltage regulator to power drive system)
