Two versions of the frame : one compact single deck for analog only, and one split-deck with a longer tail for HD systems.
This frame is designed for a tilt between 0° and 30°, as there isn't much room on the top plate, and to keep the center of gravity balanced.
Because the nose is short, you will have some props in view in the GoPro Session footage below 30°.
I do not recommend you the Pragma frame if you have no basic knowledge on how to design prints, as I don't intend to design for every standoffs, cameras, antennas, VTXs, etc…
Many tutorials are available on Youtube on how to modify and create models; learning is cool.
If you wanna fly an open source frame made for HD with a lot of premade prints for a wide variety of accessories, I recommend you the Jeno 5.1" frame.
Nobody stops you to modify the frame, or even doing your own : )
The armlocking system is taken from the famous Apex frame : pressnuts are inserted in the arms, so you don't have to worry about them sticking out under the ESC, risking shorts and damage when the frame flexes.
Arms are locked into place with a small gear-shaped key. This particular design allows carbon cutters to easily check if tolerances are well respected by inserting the key in one arm : it should't have any play.
Pressnuts needed are specific but pretty common, they can be foundHERE.
The central stack has 20x20mm and 30.5x30.5mm M3 patterns ( Sorry TBS, no gorilla mount )
You cannot access the stack screws after the frame is assembled : make sure it's tightly screwed.
Straps slots are a must; they are designed to be weaved as follow. If there is rubber sewn into the straps, it will grip the battery, acting a bit like a lipo pad.
I highly recommend you filing those edges ( shown in red ) under the top plate if you are using thin straps, otherwise they will get slowly cut by the sharp carbon. Also do it around the XT60 hole for good measure.
Only two screws are flush with the top plate where the battery sits. The two screws holes in the back are not chamfered because of durability concerns : one unlucky bad hit on the back could fragilize and break the corner, and you will have to change the whole top plate. Use button head screws to keep the surface as smooth as possible to prevent damaging the battery if it slides back harshly.
Arms end are crown-shaped to protect motors bell uniformely from front and side impacts. They protect well enough with a must have TPU print, but still stay light to keep an overall agile feeling.
There is a big hole in the top plate to let the XT60 pass through. Use it or not, it's up to you ; )
When you are screwing the GoPro mount in the two front screws of the top plate, it usually squishes the TPU and can obstruct a bit the vision in the FPV feed. That is why you can insert two optional pressnuts under the front of the top plate, allowing you to screw the TPU mount a bit further back.
If you wanna go with this mounting pattern, make sure to let some room in your GoPro mount design to fit the screw with a washer , and naturally adding a hole on top for the screwdriver tip to go through. Note that you will also have to make an opening for the XT60 to pass through if you're routing it here.
The frame is able to fit up to 5.1" propellers. It has enough clearance between the props and lipo to fly without having to worry about cutting a strap. Although, if you decide to slam the frame, 4.9" propellers are recommended.
The analog version is very compact in the back, it can fit the TBS Unify Pro HV ( with a thick double sided tape, easy peasy ), Rush Tank Mini, T-Motor FT800, and other compact analog VTXs.
The following example has Ø5mm standoffs, and doesn't include TPU prints, please make sure to verify if you gear fits in.
The HD version has a longer tail, and is in split-deck style. It should fit most HD VTXs with 20x20mm M2 and 25.5x25.5 M1.6 patterns.
The following example has Ø5mm standoffs and doesn't include TPU prints, please make sure to verify if you gear fits in.
The analog version of the Pragma with a single deck allows you great flexibility for standoffs size.
28mm 7075 aluminium standoffs for the base frame is recommended, but you can go as low as 20mm with a nano camera and a small FC in the back ( like the Kiss Ultra Mini for example ). You will have to drill out the 20x20 holes up to Ø3mm, or directly modify it in the CAD software.
If you decide to slam it, make sure you are using a compact HD camera like the GoPro Session, otherwise you will risk chopping off your camera when props are bent upward - plan ahead wisely.
The HD version of the Pragma is a split-deck frame, with a longer tail. It needs two different sets of standoffs ( 28mm in the front/20mm in the back recommended ). If you prefer, you can go with this version for analog gear too.
SIDE NOTE ON TPU DESIGN
The bottom plate TPU protection is separated from the FPV cam mount and Backpack because it is something you will have to replace, and it takes less time to print and easier to replace than the whole thing.
Tip : Heat the TPU with a heatgun to stretch it and facilitate the implementation if needed.
Print the bottom plate protection sideway to prevent having to get rid of the annoying support generated in the process and it's a bit more robust .
You could also file every sharp carbon corners in contact with TPU to mitigate the tearing a little bit, but bear in mind that it is an element you'll have to change from time to time if you crash, like the arm bumpers.
THIS FRAME LOOKS SO SIMPLE, WHAT'S SO SPECIAL ABOUT IT ?
Nothing, that's the point.
After many iterations, weird and original designs, experimenting with various arm locking systems, I realized that keeping it simple is the best approach for something you will bash and crash. A good frame is a frame your forget about : )
FRAME SPECIFICATIONS
Ø221mm motor to motor
Support up to 5.1" propellers
Naked weight of approximatively 130g ( depending on the hardware )
2mm thick top plate
2.5mm thick middle & bottom plate
5.5mm thick arms
16x16mm motor pattern
Center stack : 20x20mm M3 / 30.5x30.5mm M3
Back & Front : 20x20mm M2 ( HD Version : 20x20mm M2 + 25.5x25.5mm M1.6 in the back)
Maximum square size of VTX with Ø5mm standoffs : 29x29mm ( HD version : 35x35mm )
Central stack height of 20mm with 28mm standoffs ( 28/20mm standoffs for the HD version )
Maximum recommended battery size : 40x40x80mm
HARDWARE
To keep it simple, some screws are longer than needed, but you can use M3x6mm for screws holding standoffs in place.
“Buttons heads screws” is just what I use, and using Torx screws is a plus !
Motors screws are usually included with the motors, be careful and double check that they don't touch motor wires / windings. M3x8mm is ok if you use all 4 screws per motors, but I suggest you filing longer screws down to 9mm. The more thread in motor holes = stronger, 1mm does matter ( that's what she said )
For the analog version :
( x16 ) M3x8mm Button Head Screws ( +2 if you are using the top plate pressnuts )
I've been cutting all my prototypes with Pierre-Louis from https://fpvcncdrone.com/ and you can find the Pragma frame on the website. I trust him to respect tolerances and good quality standards.
