Tubular 7inch frame - superlight and superstiff - no CNC needed

Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5365636.

Update 03.05.22: I beefed up the clamps a bit, so they are more rigid (parts 01-04). Rest has not changed.

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Note: This frame is work-in-progress. While the basic principle has proven to work perfectly, the "official" 7" version i'm still tinkering with - most of all with the right length/thickness of the 3d-printed parts to connect the rods together. I just finished my build and will do flight testing next. If you want to build one now, please also consider the 6" version. I've been flying that one for months, and it's just amazing: https://www.thingiverse.com/thing:5368370

Also if you plan on building one or would like to get more info, there is a Discord server dedicated to this type of frame. You'll get all the support you need there. I'll do what i can to help.

https://discord.gg/Fy6fkBGWNm

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Hi there,

what about a frame that is super light yet crazily stiff, extremely modular? A frame that you can build at home without the need of a CNC workshop? And that costs just around 20$? Well, something along these lines would probably be written on a product listing if this would actually be a product ^^

I have been designing tube-based frames around 10 years ago already, and i always felt a shame that this kind of fframe was nowhere to be seen nowadays.

I am currently working on making a video about how to build the frame - stay tuned!

While this frame is super stiff and light, it probably isn't really suited for a freestyle frame. I haven't crash-testet it too much, but i'm pretty sure it's easier to kill than your typical freestyle frame with 5mm+ arms. I'm mainly cruising and doing long range.

Note: live picture taken from the 6" version.

Now lets check the claims:

<h1>1) super light yet crazily stiff</h1> This 7" frame does weight around 60-85g in total (depending on the rod strength and used mounts). This inclused the GoPro as well as the GPS mount. It uses 6mm and 8mm carbon tubes that can purchased in many places. Make sure they are "twilled", not "pulled". Twilling handles torsion better.

You can use the classic 8x6mm and 6x4mm rods (2mm material thickness), or 8x7mm + 6x5mm for less weight. The weight difference is about 20g (about half of the tube weight). For your first frame and heavier builds i suggest using the thicker ones.

The carbon rods are glued to the plastic parts using CA-glue (superglue). This creates a crazy strong connection. You can use PLA and it will work, however it'll break easier in case of a crash. Better use Nylon or ideally carbon-infused Nylon (this also prints easier than pure Nylon).

<h1>2) extremely modular</h1> There are many tubes all around that you can easily attach different mounts to. Want a vertically mounted ELRS antenna? Well, there is a mount for that. Basically anything is possible. I will gladly help with a certain mount if you provide me with details. I plan on adding a parameterized Fusion360 files of different mounts, then you can easily adjust the mount to your needs (e.g. GPS). I uploaded the files for a "classic" build, with the electronics in the front and battery on the back. There is about 30mm distance in between, which should be enough for a Caddx Vista Air Unit + FC & ESC stack. I currently am building my a bit different, with the electronics on a lower level, and the battery on top (as i want to use a 4s2p / 6s2p battery). I'll add the files for that soon.

Also i added files for my setup, which is a naked GoPro on a BetaFPV housing, as well as a Caddx Vista DJI camera + CrossFire Immortal-T antenna. I also added a universal camera mount, on with an Immortal-T mount, on without.

ELRS antenna mount (horizontal & vertical) coming soon.

<h1>3) build at home without the need of a CNC workshop</h1> Well, you only need to buy the carbon tubes, a saw and a 3d printer. <h1>4) costs just around 15-20 bucks</h1> In the last 2 months prices have gone up quite a bit. A year ago i purchased rods for 5-7$ per meter. Now these are almost 10$, so for 2 of them thats 20$. You won't need all of them, but the filament also costs a few cents. So lets say 20$. <h1>Important information:</h1>

Length of the carbon tubes:

8mm diameter (you need 970mm in total): 1 x 320mm (front motors) 1 x 290mm (back motors) 2 x 180mm (front to back) 6mm diameter (you need 584mm in total): 2 x 133mm (front stiffeners) 2 x 153mm (back stiffeners) Cutting them roughly is good enough, a milimeter more or less is not too much of a problem.

Possible sources for all sizes except 6x5mm: https://aliexpress.com/item/1005002332108832.html https://aliexpress.com/item/32856519256.html

<h1>Further tipps:</h1>

• as carbon rods have a rather low tolerance, they can easily actually be 0,1 - 0,3mm more thick or thin than they should be. Therefore you'll most likely need to file up the difference. file as long as needed until the PLA parts can be pushed on the rods with medium resistance. They shouldn't flow freely, but also it shouldn't be too hard to move them. Otherwise the PLA will break

• If the PLA should break, just superglue it back together. Use activator spray to save time

• i added the print material (and amount) in the stl files

• for print orientation see the attached image

• I suggest printing the mounts vertically. They will break super easily when removing the support material though. Just superglue it back together. When putting them on the frame and off they will be fine.

<h1>Before putting on the glue:</h1>

• make sure that all parts are in the right place. To do so, measure and mark the correct positions of the PLA parts (an picture with measurements will follow soon)
• in order to easily mount everything together, put in the stiffeners last
• place the frame on a flat surface. All motor mounts should touch the ground. If they don't, twist the frame around until they do

Thats it for now, i'll update the instructions over time. I also have created a 5" and 6" version, which will follow soon.