I like taking risks with my flying (to my quad, not people) and as such value ease of repair over big-brand, expensive setups. So, I came up with this design, and it's already been subject to a heap of abuse and been back in the air within minutes of a crash. All you have to do is take some cable ties when you head out! :-)
The following will show the steps I went through with this particular build, but this Instructable is mostly intended to illustrate the general design, and it's up to you to adapt it to whatever are the critical components it needs to conform to, eg. motor size, prop size, etc. The essence is the durability and easy serviceability.
Step 1: Frame Geometry and Design
The nylon spacers also serve as 'stops' for the arms, when pushing them back in after a repair, so that they sit at the correct depth into the frame.
But, the real ease-of-repair comes from using the cable ties to secure the arms in place. NO GLUE. For the front arms especially, they typically will be impacted towards the rear of the quad, and in these cases when the arm is free to slide inside the frame sandwich, all that typically happens is one of the cable ties just breaks.
As long as the arms don't twist then the quad will fly perfectly fine. Also, in my build, the arms can even shift forwards/back slightly, but even that doesn't affect the flight characteristics. Just as long as the arms don't twist!
For this build I used 10mm square tubing. Here's a link to product page:
Step 2: Planning the Frame
The drawing below is what I used for the Micro FPV Quad (also here in Instructables), if you want to use that as a reference guide. This build used the exact same proportions, but scaled up by 50% (compared to the micro). I think the diagonal of motor to motor is 440mm in this build.
Step 3: The Upper and Lower Plates
The holes only save a very negligible amount of weight, but I find the holes incredibly useful later, for doing the wiring! You have much more sneaky routes to get things hooked up :-)
Also, the drawing on the MDF has three small circles where I planned to put three nylon spacers. These are the ones that act as stoppers for the arms. I added a further two, in the middle of the frame later on.
Step 4: The Motor Mounts
This is a very fiddly step, and it pays to do it carefully! But, essentially, you're just making something that you can put two bolts through to secure the motor, and two places at which cable ties can go around it to secure it to the square tubing arms.
Also below is a photo showing the end result of one of the mounts, but this is jumping ahead slightly.
Step 5: Getting the Mounts Level
NOTE: be sure to place the mount plates fairly accurately into position before allowing the epoxy to dry!
Then end result should be like in the next photo. (although, I haven't yet attached the cable ties in that photo)
I was also checking the weight before the electrics were installed, and in this case came in at about 170 grams.
Step 6: Wiring It Up
Also, a week or so later, I actually snipped the main cable ties holding the arms to the frame, and unscrewed the nylon spacer screws, and took apart the frame, and laid out a lot of the wiring, and then screwed the frame back together.
but, for the first test, I just did an ad-hoc wiring like in photo below.
Step 7: The Final Build
The final touch was to carve out a custom foam canopy, which is held in place at four points on the frame with strips of velcro (ie. hook-n-loop tape). This gives much need protection to all the electrics, but with the velcro makes for easy serviceability of all the components.
Step 8: The 'Crash' Files
The second photo was two cable ties. It looks pretty bad, but was quite a simple on-field repair!
Anyway, I hope you get some good take-aways from this IN-deSTRUCTABLE :-)