Breaking Things

As I started getting more comfortable with flying, I started trying more stupid exciting maneuvers. Inevitably this resulted in more crashes. Most of which are fairly harmless only resulting in a few broken props. But eventually I ran out of luck and hit the ground a bit harder and more upside-down than usual. The resulting impact pushed the camera through the fiberglass top plate and ruined it. At this point I decided it was time to make a decision. They don’t sell individual parts for my frame design, so I would either have to buy an entirely new frame (40 whole dollars) or figure out a way to make my own new top plate. Being the cheap person that I am, I decided to go with the latter option.

Learning Inventor

After a bit of overthinking and under-planning, I decided to buy a sheet of carbon fiber off eBay and have it laser cut into frame pieces that I would design while I waited for the CF to ship. This seemed like a good project to use as an excuse to teach myself Inventor especially considering time wasn’t really an issue. This is the model of the top plate that resulted from my musings with Inventor. I made the part a little wider than the original to add some strength around the slits at the edges. I also made the cutouts running through the center thinner and removed a couple cutouts that I deemed unnecessary. Overall, I’m pretty happy with the result and loving Inventor so far.

3d Printing

I grew a bit impatient waiting for the CF to arrive now that I had my new top plate designed and decided to 3d print a PLA prototype to make sure everything fit. Surprisingly, everything fit pretty much exactly as designed. This plate was printed at 2mm thick and 100% infill. It only weighed about 2 grams more than the original 1.5mm thick fiberglass piece, but definitely didn’t feel anywhere near as strong. None of that mattered to me though because it meant that I was finally able to fly again.

Breaking Things pt2

I took the frame out flying and was surprised at how good it felt in the air. Flight characteristics were indistinguishable from the original fg top plate. However, it only took a few batteries before a tree jumped in front of my quad and it once again landed upside down directly on the camera. This broke the top plate. As a plus side, I’m really impressed with how tough the Xaiomi Yi that I’m using is. It’s a little scratched up, but has taken one heck of a beating without giving in. Unfortunately, I didn’t take any pictures of the carnage that was once my top plate, but I did continue flying. This probably wasn’t the best idea, but I’m more of a “fly it till it can’t fly any more” type of person. Surprisingly, it still handled pretty well considering the top plate was cracked in half. That is, until I decided to try flying through a playground and managed to snap the lower plate as well (see video below).

Back to the Drawing Board

The sheet of CF came in the mail around the same time that I broke the bottom plate, so I decided it was time to finish modeling the rest of the fame and have it cut. I really like Inventor after this whole process, there were a lot of handy features that are just plain missing from Autocad. I’m sorry if the exploded view is terrible, I’m still figuring things out.

Here’s the part that I really should have researched before beginning this venture. Carbon fiber is really hard to laser cut, and I don’t own a laser cutter… After calling a couple places specializing in laser cutting, I decided that CNCing the pieces would be a much more feasible idea. Unfortunately, I don’t know anywhere around me with open access to a CNC mill. I wasn’t going to let that discourage me from flying again though. I had all the files I needed, so I set up the 3d printer and whipped up a new top and bottom plate. This time I printed them 3mm thick and they felt much stronger.

Breaking things pt3

This time I was pretty surprised at how tough the frame was. It took a couple pretty hard hits before eventually snapping entirely in half.



Materials Testing

The last crash killed the frame. I’m honestly surprised that it didn’t break from the first crash as that’s easily the hardest crash I’ve had with this quad. I have some nylon filament that I would like to try printing plates out of. It’s a bit flexible, but I haven’t been able to break anything that I’ve printed with it yet, so I’m excited to try making a frame out of it.

PLA was my first choice for a replacement fame because of it’s rigidity and low warping while printing. However, I had come nylon filaments lying around that I wanted to give a shot as well. Here are some different bend tests for the different materials.

PLA



The PLA had a little bit of give before eventually snapping in half. It wasn’t as strong as the original GF plate despite being twice as thick. I’m sure it’s nowhere near as strong as a CF piece would have been.

Bridge Nylon



This nylon ended up being a little bit more flexible than I expected when printing at 3mm thick. Needless to say, I don’t think this material will make a very good frame.

Nylon 910



This nylon was still very flexible, but I think it is just rigid enough to be used as a frame especially when teamed up with a printed bottom plate and the GF PDB.

Full Nylon Frame



Well, I don’t think there’s too much to say about this. It’s gross looking, nowhere near as rigid as it should be, and bendier than a winding river, but you bet I’m going to try and fly it.



Everything is a bit more rigid with the rest of the fame and components attached, but it’s still really bendy. I’m looking forward to seeing how/if it flies.

If you look closely at the top photo, you can see that the arms are tilted inwards a little bit. I forgot to take the shrinkage of the plastic into account when printing the fame, so it’s about 1.5mm shorter than it should be pulling the top part of the screws inwards and tilting the arms.

Flight Test

Frankly, it flew better than I expected. That being said, it constantly felt like I was fighting the thing. The best way I can think of describing it was like trying to hold on to a slippery fish. Whenever the quad was undergoing a constant force, like a constant turn or just flying straight, the performance was almost identical to the original frame. However, quick maneuvers were a different story. It usually continued turning for a bit after I let go of the stick, but the tricky part was that it was a different amount of time for each turn. It wasn’t like momentum carried through the turn where you could predict how much it was going to overshoot, it just kind of had a mind of it’s own.

Here’s a link to a raw video (LOUD) of one of the flights with the nylon frame. You can see the awkward flight characteristics pretty clearly.

https://drive.google.com/a/emerson.edu/file/d/0B_F5aGhMCdYPUkZrd0tHYmNJYXc/preview

I didn’t have any serious crashes with the frame yet, so I can’t speak for durability, but I’ll make sure to keep this place updated with everything that I find out.