VTX Case Preliminary Report

Requirements: 

• Secure Fastening: Prevents VTX from coming loose mid-flight

• Full enclosure: Prevents the device from shorting on other loose metal/wires that may introduce themselves during rough flight

• Airflow: Allows airflow over both the top and bottom of the device to cool case down

• Case Requirements: Has proper exit holes and support for the data cables as well as antennas

• Durable: Case must survive potential crash while fastened to cabin roof.

• Mounting: Must be able to be mounted on the top of the avionics bay cabin

• Fan: Must incorporate cooling fan

Constraints:

• Case must be complete by April 1st

• Case must not exceed height of 35.5mm

Criteria:

• Case minimizes area

• Case minimizes weight

• Case Maximizes strength/durability

• Case Maximizes shock absorption/dissipation

What is the VTX’s purpose?

• A VTX (Video Transmitter) is responsible for transmitting live video feed from the drone's camera to the pilot's video receiver on the ground. The purpose of the VTX is to provide a clear and reliable video signal to the pilot in real-time so that they can navigate and control the drone effectively.

Design Solution 1: VTX inside RFD case

• In order to incorporate the VTX inside the RFD case it would need to be physically separated by some sort of barrier between the two to protect against potential shorts. 

• The VTX needs a different mounting solution than the RFD uses as there are no mounting holes or anywhere to grab the VTX case.

(Current Top/Bottom half of RFD mounting case for reference)

Open

Design Solution 1 Case:

Open

Design Solution 1 Pro’s:

• Only requires one fan to cool both the VTX and RFD

• Uses less power, weighs less, and takes up less space then separate case design

Design Solution 1 Con’s:

• Complicated Cad work

• Increased potential for interference in between signals and shorting between VTX and RFD

• Increased assembly/disassembly timey

• Will be a tighter fit inside cabin

Design Solution 2: Make Custom VTX Case

• Because the VTX case has no mounting holes or clear surfaces which could be fastened, a unique mounting solution is necessary.

• Some fastening methods which I will analyze include using tape, zip ties, and velcro. Methods such as mechanically fastening the VTX with clamps or collar shafts have been considered but were deemed to be infeasible due to the VTX’s sensitive components and aversion to any conductive materials including metal. 

1. Velcro:

Pro’s:

• Easy to install and remove: Simple and quick way to mount electronic components without the need for screws or adhesives.

• Non permanent: Easily removed and repositioned.

• Vibration Reduction: Cushioning effect helps to reduce vibration and shocks

Cons:

• May leave residue: Over time, the velcro's adhesive may leave a residue on the component or surface it is attached to

• Weak adhesive: May not adhere to component properly or may peel off.

2. Zip Tie:

Pro’s

• Secure: Provides tight and secure hold on electronic components which prevents them from moving or vibrating.

• Easy to install

• Versatility: can be used in a variety of locations and orientations. Con’s

• Risk of damage: Can exert significant pressure on electronic components

• Difficult to remove: Need to cut Zip Tie to remove it

3. Tacky Tape

Pro’s

• Easy to install: Quick mount and removable

• Non-permanent: Ease of removal and repositioning

• Shock Absorption Cushioning helps absorb shocks and vibrations Con’s

• Weak adhesive: May not adhere to component or case properly

• Possible interference: Due to tacky tapes malleability it may interfere with electrical components on the VTX’s surface.

Possible Design Solution 2 Cases:

(These are Front View drawings. Due to the drawings being a little confusing I implemented a colour code)

1. Using Velcro and Zip Tie                              

1. Using Velcro and Tacky Tape

Possible Design Solution 2 Cases Decision:

It was decided to use model 1., which integrates both velcro and zip ties in order to achieve an uncomplicated set up which properly secures and cushions vtx.

Design Solution 2 Pro’s:

• Relatively easy CADing compared to solution 1.

• Uncomplicated setup for both cases

• Increased redundancy in case a failure occurs to one of the cases.

Design Solution 2 Con’s:

• Required two fans to individually cool VTX and RFD case

• Uses more power, weighs more, and takes up more space then integrated case design

Design Solution Decision:

VTX Case CAD:

• Full Assembly (Without Top):

• Full Assembly (With Top)

Run Down of How It Works:

• The case comes in two parts, a top and bottom, which are both fastened together via four M3 bolts located in the corner of the case.

• The case is fastened to the top of the fuselage bay using another four M3 bolts which are fastened into the circular mounting protrusions on the side.

• The fan is bolted into the case via four M2 bolts.

• The VTX is fastened to the case using Velcro on its bottom and zip ties which tie around and under the bottom half of the case.

• The case is fabricated out of 3D-printed carbon fibre filament.

Testing:

After a prototype version of the VTX case was printed, it was tested by mounting both the VTX, fan, and assorted cables to the case. When testing, many observations were made regarding potential issues with the case. After trying out an assortment of different header configurations, it was noticed that no matter what header was used, the attaching cables would always either block airflow to the fan, or be forced to run backwards towards the fan which caused fan to cable clearance issues.

After referring to the electrical leads, (Ethan and Daniel), and checking the RFD on Cornflakes, it was noticed that the RFD case also had the air-flow problem.

Due to there being no header configuration which exists which would not interfere with the airflow on the VTX and RFD in their current configurations, it was decided that the only solution would be to reposition the VTX 90 degrees on the yaw axis so it is perpendicular to the fan, while keeping the RFD parallel with the fan so airflow could travel in the proper direction over its heat sink.

It was also noted that lowering or elevating the VTX or RFD in their cases would increase the airflow from the fan over both. Also, due to it being extremely difficult to bolt in the top of the fan when the case is closed, that only bolting the bottom two bolts of the fan is sufficient in keeping the fan firmly in place (as confirmed by Daniel). Also, it was noted that yellow tacky tape alone works better than both Velcro and zip tie combo which was planned to be used to fasten the VTX case. Using yellow tacky tape would also mean that two slots at the bottom of the case should be made so the VTX can be taped over and around the bottom of the case for extra reinforcements and redundance.

It was also noted that both due to lack of space inside the electronics cabin and because now the VTX and RFD cases could be mounted side by side, that the best course of action would be to integrate both inside a single case. This was not done before due to there not being enough space, height wise, to mount the cases on top of each other and because they could not be mounted one after the other due to interferences with their antennas.

Testing:

Isometric View of Case:

Isometric View of Bottom Half of Case:

Isometric View of Top Half of Case:

After printing a test case out of PLA filament, it was observed that the case preformed its required functions but some minor improvements were noted to be made in SolidWorks before the final case was printed. These include: Removing the counter bores on the top of the case, deepening the counter bore on the bottom, widening the RFD wire slot on the top, making a slot for the fan wire, adjusting the back mount so as to not interfere with the fan, and making a slot in the bottom of the case for tape to go around the VTX.

Final VTX/RFD Case

After making the aforementioned changes to the VTX/RFD, the case was printed out of PETG and tested.

Conclusion:

Where To Find: