.. here comes the hype train. all aboard! Pod in the form of fairings for quads have been around for a while (Anakin, Robocat etc). However courtesy of the innovative design from Shendrones with the Orca and Mako (See Calums Mako Build Log here), integrated pods which double up as part of the frame are becoming popular.
Pods are becoming less about only providing an aerodynamic / aesthetic fairing and becoming a clever way to act as part of the frame as well. they can house the camera, vtx, rx and antennas. Taking it to the extreme they could even be plug and play allowing you to quickly swap the brains of the quad over should you need.
3D printer technology gives us the chance to easily manufacture a complex pod geometry at home and coupled with the use of flexible filaments (bioflex, TPU etc) we can make them robust enough that it makes sense for a race drone. Flexible pods could even improve the crash resistence of the quad as they will absorb the energy from the impact by deforming, protecting the stuff inside (hopefully!)
With all the hype PropNuts thought it would jump onboard and I designed my very own. With various spare unibody frames laying around we thought it would be a great idea to convert one of these to a pod racer. The QAV X (Clone, see the build log here) is currently my favorite and was the perfect candidate.
Where to start?
My day job as a mechanical engineer definitely helped here, CAD packages for 3D modelling are relatively simple to use these days, however designing 3D surfaces and shapes required for a pod and making it fit requires a bit of skill. First thing was first, I downloaded ready made models such as the QAV X frame, Naze 32, Motors etc from GrabCad.com and built up a digital mock up of the quad. This allowed me to visualise the build and use the models for space allocation.
Using 2D sketches and lofts I then created the rough outline of the pod in 3D, using a shell command to turn it into a thin shell. The trick here is to correctly constrain the 2D sketches such that I could drive the dimensions of the pod as desired.
Measure, Update, Repeat..
The pre-made 3D models are only good for a first start. The next step was to measure accurately my own frame using calipers and update / create the parts I needed in the 3D model for further refinement. Parts such as the Matek PDB I was using and the RX were not available online so I had to model these up as simple plates and boxes to mark out the space I needed on the mode. I quickly found things shaping up and coming together more and more.
Now all major components were in and the shape was roughly there I needed to model up how the camera and vtx were going to be held in the pod (all other components are attached to the carbon frame). The method here is to roughly locate the items where you want them and then adjust the 3D model of the pod in context to add the features needed for integration of the components (i.e. mount points and screw holes for the HS1177 camera, VTX antenna hole).
There’s only so much messing around that can be done with a 3D model. When I reached the point that the pod looked reasonable with all required components housed snugly, I saved the pod as an STL file and put it through a 3D printer slicer program to prepare to first printing. The slicer converts the 3D geometry into layer by layer commands that the printer can follow to produce the part.
To save time and effort, I printed the initial test in PLA plastic (this is quicker and cheaper than the flexible plastic I have planned for the pod) after all I don’t expect that the first print will be perfect.
I was pretty pleased with the results, the overall shape was printable with no supports required. The parts fitted snugly into the planned positions including the camera.
The Tramp VTX fits nicely strapped to the top of the pod using a zip tie, with the hole for the antenna pig tail adjacent. The pigtail however extrudes a but too much and would clash with the carbon plate so this will need adjusted in the 3D model before the final print to get it to fit. The camera mounting has about 0.5mm clearance at the moment which means that even when the screws are in there is not much friction stopping it swivelling.
For refinement, I will adjust the model such that the fit has a slight interference with the sides of the camera, providing a little friction to help stop it rotating too easily and changing angle during flight.
To fit to the frame the pod needed a little trimming as it clashed with the ESCs. Ideally the ESCs would be further out and then only a small cutout would be required to clear the wires. However this would mean trimming my motor wires extremely short which I am trying to avoid.
A few small adjustments are still required (RX antenna holes, clearance for ESCs, frame mounting hole positions, insert/nut to hold the pod to the frame, VTX positioning) prior to it working fully but it is halfway there.
I will post Part 2 to this tech blog shortly where I will reveal the changes and final design / print for the QAV X Pod where we may also share the STL file exclusively to PropNuts readers for their own print!
Watch this space!