Quad copter chassis build

Fox Mulder

I have just recently finished building a quad copter and thought I would share some images of it being made. Previous to this I haven't had any experience with quad copters so what I have ended up with is a bit heavy but it seems to fly alright albeit the battery doesn't last very long.

Finished quadcopter

Its made of an upper and lower carbon fibre plate, sandwiched in between is an aluminium structure that the battery sits within and it also supports the ends of the booms that the motors mount to. The motors sit inside an aluminium housing and the wires feed through the inside of the booms. Lastly there is an aluminium helicopter style landing skid.



Motor mounts

Most of the parts are made on a small milling machine which I converted to CNC. The motor mounts have windows on the sides to allow air to flow through the motor. The end fits inside a carbon fibre tube.

Part is roughed out

A base section is left on untill the last machining operation to allow the piece to be clamped and to measure off.

A set of jaws are then made that fit around the part to allow the bottom to be machined off.


Centre structure








As before the bottom is machined off last


Clamps

These are small clamps that the hold the carbon fibre booms in place again they are aluminium. They use a small M3 fastener to clamp the boom.


Part is reamed to get a good fit with the boom



Carbon fibre plates

The carbon fibre panel was stuck down with double sided carpet tape onto a fixture plate. My mill doesn't have enough x-axis travel to do the entire part so its fixtured in place with pins. When one half has been cut the part is then flipped 180 degrees and the other half is cut.




Booms

The booms are made from 18mm OD carbon fibre tube. A slot is cut at one end to allow the motor wires to enter.

Fox Mulder

Landing skids

The quad copter had skids similar to a helicopters.




The landing skids are machined on a fixture and then flipped to do the opposite side.


I made a small tube bender as I originally wanted to make the skids from all bent aluminium tube that was brazed together but I found it hard to get a neat brazed joint between two tubes. In the end I only got to use the tube bender on the front upturned edge for the landing skid.





Other bits

Lower bracket for the GPS

The remaining stock was taken off with a mini lathe



Upper bracket for the GPS

I made aluminium washers to suit the counter sunk stainless bolts I bought


Pre anodising

The below image shows the chassis put together before the parts were anodised.



I originally wanted to anodise the aluminium parts orange as you can see in the below image but I was having trouble getting the colour to match between the parts so I unfortunately had to strip half the parts and change to black.

Fox Mulder

Anodising

The parts are first etched in caustic soda. This gives them a finish which almost looks like a sand blasted finish.


Finish pre etching, shiny with machining marks

Finish after etching, matt finish. The etching will remove most machining marks.


Parts are then placed in the anodising bath



After anodising the part can be dyed, the gloss look is just because of the wet dye on the part. The final finish is matte black



The finish is then sealed in boiling water


Assembly

This is the finished quadcopter




Motors are screwed on from below

The booms are held in place with the clamps and fit into the ends of the central structure. No glue is used so you can replace them easily.



The speed controllers are cable tied onto the carbon fibre plates. The battery is held in place with a velcro strap

The power distribution board is fitted underneath the quadcopter and all the wires run up through slots in the carbon fibre plates



I haven't flown any other quadcopters before so I cant compare it to anything but it seems to fly well although the flight time is unfortunately quite short. I only seem to get about 5 minutes before the low voltage warning starts flashing.

If I was to build another I wouldn't use any aluminium in the construction as it is unnecessary and only adds weight. Using simple flat carbon fibre panels seems a better option and if you need to have 3d parts making them from magnesium would give you a minor mass improvement for a similar cost.

Spec:

Motors: EMAX 2213-935kv
Props: 10 inch
Speed Controller: EMAX 25A
Battery: 2450mAh
Controller: Naza Multi Rotor lite with GPS/Compass
Reciever: Spektrum AR400
Quadcopter mass with battery: 1308g

civdef

Fantastic fabrication - enjoyed reading that!

Weight is the enemy of flight, sometimes you end up having to sacrifice strength / durability to get endurance.

The other way you'll stretch endurance is to use bigger props turning more slowly on higher voltage batteries. You probably have room to go out to 13" props or more?

The Doktor

Thats really fantastic... the nicest home made build (and nicer than lots of commercial) ive seen. Fair play to you!!