This is the last iteration of the C series that I will post. The C6 has already been built/flown to prove out a new motor/body configuration for the VX1 project.
- Frame Features
- Bill of Materials
- Frame Assembly
- ESC Configuration and Installation
- Vtx Configuration and Installation
- Installation of Remaining Electronics
Only section left to do… may take awhile
2. Frame Features
After extensive thought, calculations, and testing, I can finally say that I am happy with the end result. Features of the frame:
- Z frame (see advantages of a Z frame)
- Roughly 230mm size frame (depends on motor angle)
- Aerodynamically optimized
- Symmetrical design with center of gravity, center of thrust, and aerodynamic center all in alignment – very important for full motor utilization
- Battery (up to a 5s) is positioned inside the body to keep the center of gravity balanced
- Round motor arms instead of flat “thrust blockers”
- Aluminum body which also acts as a heat sink for the ESC’s and video tx
- Potential to be waterproof (pending temperature results)
- Motor pylons:
- Motors can be adjusted to any angle
- Increases the radius of rotation of the motors. As the motors are rotated on a more aggressive angle, the increased rotation radius prevents the propellers from “overlapping” (as viewed in the direction of movement). This in turn prevents the back propellers from getting dirty (or turbulent) air.
Although the design is simple, it does take some patience/craftsmanship to build.
3. Bill of Materials
NOTE: When buying carbon fiber, make sure it is the woven pattern, otherwise trsional stiffness suffers
- (1) 2 inch O.D. (outer diameter) x 1.93 inch I.D. (inner diameter) x 106mm long aluminum tubing from McMaster Carr
- (2) 8mm O.D. x 6mm I.D. x 178mm long carbon fiber tube from Amazon
- (4) 10mm O.D. x 8mm I.D. x 5mm long carbon fiber tube from Amazon
- (4) 10mm O.D. x 8mm I.D. x 2mm long carbon fiber tube from Amazon (use leftover from above item)
- (4) 5mm x 10mm strips of 400 grit sandpaper
- (1-2) plastic Easter eggs OR (2) Estes NC-80B nose cones from Amazon (a bit more sturdy than the eggs… a lot of wasted material though)
- (4) 10mm tube mounts from Ali Express
Electronics: (some things can obviously be substituted as long as they fit)
- (4) Brotherhobby 2206 T2 2300kv motors from Fly RC Now
- (4) Spedix HV 30a ESC’s from Piroflip
- Betaflight F3 flight controller from Piroflip
- Ublox M8N GPS from Banggood or Ready to Fly Quads
- Micro Minimosd from Amazon (also an FTDI adapter for programming it from Amazon)
- AKK X1 Video transmitter from Amazon
- Anbee Circular polarized cloverleaf antenna w/ RP-SMA plug from Amazon
- Crazepony mini FPV cam from Amazon
- Any standard sized 1300-1400mah 4s lipo or 5s 1300mah lipo (5s Tattu fits)
- Small satellit Rx such as the Lemon Rx DSMX from Amazon
- Thermal paste from Amazon
- 400mm x 205mm x 0.5mm silicone thermal pad from Amazon
- 5 minute epoxy from Amazon
- Clear silicone sealant from Amazon
- 6 inch x 6 inch x 0.016 inch copper plate from McMaster Carr
- (2) antenna tubes with caps from Prop Shop
- Threadlock (Loctite 242) from Amazon
- Monokote trim from Prop Shop
- GoPro type lens (I had one in my electronics junk pile)
- 3mm nylon wire mesh guard from Prop Shop
- Anodized low profile prop nuts from Piroflip
4. Frame Assembly
- Drill 8mm holes through each end of the aluminum tube. They should be drilled so the center of the hole is 5mm from the end of the tube. Take the time be sure the arms are parallel and in line with each other. If not, use a file on the aluminum to correct the alignment. Epoxy will take care of any structural integrity that is lost. Also – it’s kind of close to the end and the aluminum may even distort and rip at the edge, but its not a big deal since again the epoxy will save the day.
- NOTE: read ahead to see where to rough up the inside surfaces (with sandpaper) of the 10mm O.D. rings and the outer surface of the arms where the rings will be placed.
- Slide 2 of the 10mm O.D. x 2mm long fiber rings onto each arm (the rings should be on the inside of the body). Once the arms are centered, slide the rings so they are butted up against the body and use super glue to hold them in place.
- Place the 10mm x 5mm long rings on the ends of the arms and super glue them in place.
- NOTE: don’t try to epoxy all areas at once – only mix up enough epoxy to do a few places at a time and be sure to rotate the frame to avoid drips until the epoxy sets.
- Use some 5 minute epoxy to secure the arms in place making sure to use enough for a nice fillet. Do the same for the rings on the ends of the arms.
- Using super glue, glue a strip of sandpaper on each of the rings on the ends of the arms (this gives a better bite for the arm clamps to grab on to).
- Using a 1/8 inch drill, drill holes into the pylon arms as shown below. Make 2 of each pylon arm to make sure the motor wires are oriented correctly. NOTE: The diameters on the holes should be 3.2mm, not 3.29mm…
- Using threadlock, loosely attach the pylon arms to the arm clamps and clamp them onto the body arms.
- Using a dremel tool, cut out an opening for the battery in the bottom of the aluminum frame Using the pattern below.
- Using a dremel tool, cut a slot in the arms wide enough to run wire down them for the motors.
- Cut ands sand down either the Easter eggs or nose cones until they match up with the aluminum body diameter.
- Carefully drill a hole through the front nose cone for the FPV camera lens.
- Don’t attach the front/back cones on yet. The frame is done for now.
5. ESC Configuration and Installation
Installing the ESCs to use the body as a heat sink is a bit of a challenge. The main thing to remember is that you need to leave as much space as possible for the battery, so keep all the wiring/soldering as flat as possible.
I found that the best way to configure the ESCs was to solder them back to back as shown in the picture below.
Shrink tube was used to protect the components from shorting out on the aluminum. Thermal pads were cut and placed to allow heat to transfer to the frame. Make sure the thermal pad makes contact with the body BEFORE the shrink tube does. Pressure will have to be applied for the shrink tube to make contact with the body. While still applying pressure, super glue the ESCs in place.
Alternative and recommended method: This is the method I will be using from this point onward. Basically the thermal pads are no longer used and windows are cut out of the body for cooling. Super glue is used to secure the ESCs in place and then silicone sealant is used to prevent electrical shorts.
6. Vtx Configuration and Installation
7. Installation of Remaining Electronics
Rx: The case was taken off the Lemon Rx and covered in electrical tape to protect it. It was then glued to the inside top of the frame inbetween the antenna tubes.
GPS: The gps was mounted inside the top rear cone using silicone sealant.
Minim OSD: Unfortunately, the Betaflight OSD would not show up for me, just a black screen. I tried every wiring configuration possible so I ended up having to use a Minim OSD. This was mounted in the front cone using silicone sealant.
Flight Controller: After mounting all the electronics, I soldered all the wires up the the FC which is placed in the front cone in front of the arm like the one shown below:
Although the one in the picture is already secured with epoxy, do not epoxy the FC until all of the wiring is soldered.
After all the components are in place, use some silicone sealant on the soldered ends of the wires and/or connectors to keep them secure in a crash. The cones can then be put in place using super glue. I also ended up using Monokote trim to secure the nose cones even further. I’m not completely satisfied with the cone attachment – not very secure feeling.
April 5, 2017: Not for this project, but I am making production one of the primary objectives for the next generation of frames. After solving one of my biggest design issues, the next gen frame will be a dramatic improvement over the C series of projects. I will post another project page by the end of the weekend that will outline a few highlights, etc. It is still just a consideration, but it would be fun to be able to see the benefits of all the R&D.