Xcompact project. Portable and flexible DIY frame.

Hello everyone,

I would like to share with you my latest project. Currently I am at the crossroads and would appreciate any feedback.

The main goal was to design a truly portable drone that fits into a backpack. I was unhappy with the foldable frames on the market, as they were all too large. The ones which fold in horizontal plane still have a problem with landing gear, and in umbrella-type frames you need to sacrifice the space for electronics. I ended up with such requirements:

  • Compactly folding core

  • Arms fixed with a screw (no plastic clips)

  • Detachable legs  

I've decided to use two 16 mm tubes as a frame core in order to make it strong and flexible. I've made two modules for front and rear arms. PMMA plastic is used to reduce the prototype costs (however, 3mm plates are surprisingly strong), later I am planning to switch to carbon fiber. The most compact folding is achieved when arms are above each other.

Firstly I was attaching legs to the core tubes (PVC plastic). But then I realized that they can be fixed with the same screw as arms.  And this shortens the assembly time. Legs can have different length, mine are short just because I ran out of tubes.

Following the modern trend I added a vibration isolated plate. The number of damping balls can vary depending on the load. Some balls have flexible position in order to fit to different core sizes.

My current frame size is 710mm and it folds into ~ 370x170x120 mm, which is less than 8L volume.

While the weather was not good for flying I decided to collect my thoughts. The frame is portable and also turned out to be quite flexible. Several holes can be drilled for the arm-fixing screw -> several square frames can be build from the same parts.

I started to dream about "Lego" for drones. The main point about "Lego" is that from the same parts one can build various things. There are some plastic analogues like RotorBits, however I was considering only carbon fiber and aluminum parts. Currently with my friends we are working on such set of universal parts for multirotors. Here are the characteristics we implemented in the kit:

  • Frame size D: 400 - 800 mm (8 - 18 inch props)
  • Folded size: L x 160 x 120 mm (L ~ D/2 + 60)
  • Variable arm angle, > 10 different square frames
  • Detachable legs
  • Arms and legs are fixed with an M4/M5 screw 
  • Quad or X8 configurations
  • Vibration isolated center plate
  • Different camera layouts
  • Optional: Retractable landing gear, vibration damping motor mounts, prop guards, integrated PCB

Personally I am really happy with the result.

Even my large 710 mm drone fits into a backpack. The frame is easily customizable: in order to change the size one simply slides the arm-modules, also variable parts can be attached to core tubes or to the center plate.

At this point I would like to hear your opinion. Did you also think about a truly portable DIY drone? Which characteristics would be the most important?

 

Views: 4028

Comment by Tony K on December 4, 2015 at 8:24am

Hi Denis,

First of all i'd like to say this is a great idea and good work. Personally i am interested on the vibration isolation part. Have you measured the results before/after ? what is the end result. ? 

Also how do you like those motors ? are they 380 or 580 ? 

Comment by eUGENE on December 4, 2015 at 8:50am

Hi Denis,

Its cool in my opinion. What about the weight?

Comment by Denis Krylov on December 4, 2015 at 10:25am
Tony, I haven't done vibration tests yet. Honestly, I think that with plastic plates you won't see any reasonable damping.
They are too soft. And with CFK I will definitely do some tests.
Comment by Denis Krylov on December 4, 2015 at 10:31am
Motors are 380KV. 7 are good, one is slightly unbalanced (not sure if it was from the beginning or after a hard crash). Unfortunately, I can't compare
Comment by Denis Krylov on December 4, 2015 at 10:51am
Alp, the prototype weights around 700-800 g. depending on the configuration.
CFK version will be around 500-600.
Comment by Gary McCray on December 4, 2015 at 12:20pm

Great design, very innovative.

I would suggest that the deployed inner frame plate outer arm retention screw holes may not have enough material at the outside of them for best resistance to less than perfect landings.

easily solved by adding another quarter inch at the outside of the frame plates.

Possibly the frame plates would be better made from CF plate or G10 or FR4 fiberglass.

I have found CF plate, G10 or FR fiberglass can be reasonably routed with proper tooling (polycrystaline diamond coating) and is easily straight cut with a wet circular diamond saw (tile saw).

Best Regards,

Gary

Comment by Denis Krylov on December 4, 2015 at 2:59pm
Gary, yes, I was greedy with material on the edges. Still the frame survived after a couple of crashes.
I consider CF plates to be my next step. I was thinking about CNC milling both for CF and alu parts.
Comment by Gary McCray on December 4, 2015 at 3:16pm

Hi Denis, 

CNC milling aluminum is easy these days with proper carbide coated bits wet or dry.

But CF plate really does require specialized micro crystalline diamond coated bits, carbide, just doesn't cut it and leaves a ragged edge.

You might also look into G10/FR4 phenolic fiberglass plate, it is very strong and doesn't shatter or break as easily as CF plate (it is slightly easier to machine than CF plate).

I use it in my CF tube H copters.

Best,

Gary

Comment by Denis Krylov on December 4, 2015 at 3:46pm
Gary, thank you, I will check those materials. And what do you think about ordering custom CNC parts?
I believe, it's quite expensive for small orders.
Comment by Gary McCray on December 4, 2015 at 6:51pm

Hi Denis,

Generally CNC is seriously expensive for small orders, because the setup and programming charge is the same.

There are some important things to keep in mind.

Getting a panel simply 2D routed is less expensive because set up and programming is easier and less expensive equipment is involved.

I would suggest that if you are actually contemplating seriously making these in small production that you consider getting a small 2  1/2 or 3D router yourself.

Since you would be working with aluminum, CF and fiberglass, something with a rigid frame and tight tolerances would be preferable.

Suitable CNC routers would start at about $8000.00 for a ShopBot Buddy or similar.

You might be able to find something down in the $4000.0 to $6000.00 range, but beware of un-supported Chinese routers with inadequate or non-available critical parts and questionable software compatibility.

Mach 3 or 4 software compatibility is the minimum and I don't like Mach 3 because it is based on an old Windows DOS system that has less and less available support.

Although initially at least a Bosch or Dewalt router head with an improved CNC collet is usable you would want to eventually upgrade to a true CNC spindle for an additional $2500.00 or so.

I have a solid DIY CNC machine, but they are so much work and cost to do right, unless you want to make DIY CNC your primary hobby I strongly recommend going with a low end but competent commercial unit.

And no, at this time I am not interested in doing any CNC work for other than my own projects.

At my current setup and expertise level it is way too much work.

In fact, looking at your design, I would consider using a wet diamond circular saw to cut the rectangular frame plates to size and a simple drill jig plate using drill jig bushings to use on a drill press to drill the holes, much simpler (and cheaper) in low production.

As for the arm and motor mounts, I would try real hard to come up with some designs that did not require CNC machining. (Doing this personally too by the way form my plate and tube H copter designs.)

Unless you really want to CNC your own, you are much better off avoiding it, because short run programming costs will kill you, especially with lots of changes and different models (which are inevitable).

Best Regards,

Gary

Comment

You need to be a member of DIY Drones to add comments!

Join DIY Drones

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service