I had a Turnigy Integrated Micro Quad which once broke and then it was unfixable as the broken parts continued to break again as soon as the quad touched something. No amount of glue or CF rods helped.
So I wanted to have a new one, which is about the same size (maybe a bit larger).
Here the as-complete-as-possible shopping list for my small quad (which turns out to be larger than expected):
- 750mm 6mm CF rods from HobbyKing
- Balsa wood, 3mm thick, about 200x75mm from LHS
- Glue (epoxy usually)
- 4 Motor mounts from Chris Moon
- 16 M3x6 screws (better: M3x8) from LHS
- Plenty M3 spring washer from LHS
- Plenty M3 plastic standoffs of various size
- 4 Park300 motor 1380KV from HobbyKing (incl. Prop adapter)
- GemFan 7035 7x3x3 from GotHeliRC (black and orange, both CW and CCW)
- Multicopter power distribution board from GoodLuckBuy
- 4 SimonK Brushless 12A ESC from AbuseMarK
- Naze32 from AbuseMarK
- 3S 2200mAh from HobbyKing
How to build the frame
Cut the 6mm CF tube into half and cut one into half again. Ideally split it into 3 pieces so that the 2 short pieces are the same length and together they are 6mm (the diameter of the tube) shorter than the long tube. What works well to cut them is a Dremel.
Cut balsa wood into squares: 75x75mm (for top and bottom) and 70x70mm. Cut the smaller ones diagonally and glue 2 identical triangles together. Check that the wood fibres are alternating left-right and forward-back like plywood does.
Put the carbon tubes in diagonally and glue them all with epoxy. What you should have now is a square piece of wood with 6 carbon tubes sticking out its diagonals. It’s right and rigid enough for a small quad.
I have everything in this order from bottom to top:
- Below main base frame: battery straps attached with screws, and rubber foam. Simple battery holder.
- On main base frame in the corners: ESCs attached with zip ties (drilled holes left and right the ESCs and pulled zip ties through them)
- Drilled a hole along the sides of the base frame M3 screws inserted from the bottom. Fix with washer (large as balsa is soft) and spring washers, and on the top side washer, spring washer and nut. Then some space left (as I used long M3 screws), hex nut, spring washer, power distribution board. Then nylon threaded M3 spacers.
- A GF plate with 45x45mm holes. I could have used anything, but I had this handy.
- On this GF plate I put one of those sticky things. It’s very sticky, and supposed to absorb vibrations (usually earthquake like vibrations though). I figured it’s worth a try to solve 2 problems: attach the Naze32 FC to the frame and isolate it as much as possible from motor/prob vibrations.
- In a corner of the CF plate I put some sticky velcro. The counterpart on the receiver.
- The some nylon spacers, and a GF protection ring
After setting up the Naze32 flight controller with the latest baseflight software (r202), everything worked out of the box. Later I changed looptime to 2000uS for for general interest than anything else.
The result is a quad which works very well in acro mode, and well in level mode. The baro works too. Mag not tested.
Needs about 70% throttle to float, which is a bit more than I expected. It also makes 2S batteries difficult or even impossible to use.
Important things to note
- I used balsa wood because it’s soft and light. But next time plywood will be used. Or GF or CF for the bottom/top face of the main frame board.
- I’ll make the base board larger so nothing has to stick out (like the receiver does now)
- Need a Naze32-to-KK-size (45mm square) adapter, preferably with vibration absorption
- My guess is that if the battery is with the FC on a board and that board is isolated from vibrations, it’ll be less vibrations for the FC. It might inadvertently lead to something like this as you cannot stack boards as I do now, so you need to work along the other axis.
- 1 motor was clearly more out of balance than the other ones. A zip tie fixed that to a manageable level.
- All props need balancing. 3 blades props are a bit more troublesome to balance, but look at this and for smaller props this. Until I balances them, hovering in level was not working well. It worked, but just barely.
- I need a proper prop balancer. The one I have is of cheap quality and the rods and screws are out of balance, which makes prop balancing more dependent on those instead of the propeller.
Update: I got a better prop balancer and it helps a lot to keep vibrations out.