FPV350 Build Log

[HerkyBird]

As a few people have commented in another thread, it's a little quiet on here at the moment due to the weather and time of the year so I though I would have a go at doing my first ever Build Log.

I've already got a fully loaded 450 size quad but was finding that for proximity flying, quick flights on the way to/from work or if out travelling with the family, having to pull out a bird that I need to mount props on and worry about charging up GoPro's, tweaking gimbals etc. was reducing the amount of flying time and hence enjoyment I was getting. I have a good sized hard case and a rucksack and my main constraints were to be able to get it in the case with props on and in the rucksack with props off, neither of which I can do with the 450. I tried a home brew micro-quad last year but it was a bit too small so ended up with a DJI F330 kit. This was just about the right size but I couldn't easily mount my HD19 (fpv/recording camera of choice for this smaller quad) in such a way to get the props out of view. Also, no matter what I tried in the way of mounting tape, rubber grommets, earplugs, motor or prop balancing, I still could not get rid of the vibration/jello issues with the HD19 so I decided a dirty/clean frame frame was worth a shot.

Now the QAV400 looks like it should fit the bill perfectly but unfortunately is just a little to large and a lot too expensive! I tried to find something else suitable in the market but couldn't so I've decided to have a go at designing my own frame in very much the same style as the QAV400 but 350 size which I'm going to dub the FPV350. I've never used a CAD package before but am OK with normal drawing packages so I downloaded the free LibreCAD tool a few weeks ago and set about designing my own frame and have thoroughly enjoyed it. Initially I wondered about basing it around genuine QAV400 arms as I feared the arms would be the trickiest bit but even they were much too expensive. Typically, the F330 arms are a perfect size but the frame end is much too tall for a dirty frame element but I have an idea that a simple modification to them may turn them into the ideal candidates for the build ... and they are cheap too.

For completeness, here is my full component list:

• Frame - 1.6mm G10 sheet courtesy of our fellow forum member Globulas
• 4x Modified genuine DJI F330 arms
• Hardware


• Primarily from the F330 plus misc nuts&bolts
• 6x 30mm Aluminium Stand-offs
• 4x GoodLuckBuy Anti-Vibration Rubber Posts
• 4x DJI 18A Opto Esc
• 4x DJI 2212 Brushless Motor
• 4x DJI 8" Props
• Naza v1 with GPS
• EZuhf 4ch lite Rx
• FatShark 250mw vtx
• Immersion RC Spironet Antenna
• HobbyKing  E-OSD (very interested in the MinimOSD thread as that would be ideal for this build)
• Lost Model Alarm
• Boscam HD19 camera
• 2200mah 3s Lipo

It should be noted this is meant to be a 'fun to fly' bird not an AP platform hence only allowing for the HD19 as the sole onboard camera to save weight.

Over the past couple of weeks I've been ordering up all the odd bits of hardware I need and have been stripping down the F330 so I've moved from this (pre EZuhf/Naza install)...

...to this...

..and now to build it according to this...


My plan is to do as much as the build as I can this weekend given how rotten the weather is but as I don't have laser cutting or CNC capability, all the frame work will have to be done with basic power tools so may well take longer than I expect and I have to be reasonably sociable to my wife and 8 year old too :).

[Coyote]

We all love a build thread :) Nice detailing :)

[CurryKitten]

Looking very interesting Grant.  Looking forward to hearing your feedback about cutting with normal power tools.  The forum has gone crazy for 250's and we've all got 450's already, so cool to have an inbetweener :)

[HerkyBird]

I've done a couple of frames with normal tools before and they came out OK, slow going and not as accurate and tidy as cnc stuff though. They aren't your every day household power tools but some very cheap woodworking tools I picked up for modelling, I have the following 3 plus a dremel of course which is what I use for the final shaping with sanding drums. The G10 is very hard on saw blades though, I get through a couple per frame but again they are only cheap ones, if I got some better quality ones designed for fibreglass I'm sure they would be better.

[HerkyBird]

Frame prep and a few words on the frame plate design

It's up early (for a Saturday anyway) for me today as I want to crack on with the build before I get dragged out shopping later, so having printed out the frame patterns last night I've now finished trimming them out properly and stuck them to the G10 with a good old Pritstick. For those of you who haven't worked with sheet G10 before, you may not know that when it comes it has a thin layer of protective plastic film on each side for protection which is great as you can draw on it or in my case stick paper to it and it just peels off the G10 itself cleanly when you are finished.

As the frame is designed around 4 plates, 2 for the dirty side and 2 for the clean side, much of the work only needs to be done twice as opposed to 4 times as I intend to stack the 2 clean and 2 dirty plates together while shaping them. I've purposely designed them so the lightening holes line up wherever possible for each set to aid this. Also, this means I only need to fully trim out 2 sets of patterns not 4 as you can see below because when they are stacked each bottom set will be hidden. The final concession I've made for ease of fabrication is to just shape the edges of the frames where the arms attach as straight edges. As any of you who have used DJI frames know, they shape the attachment recess and on the F330 in particular there is a rectangular lug protruding from a curved edge, a very hard shape to manually reproduce accurately or quickly without CNC so as I don't believe it is structurally required, I am skipping that element (we'll see if that comes back to bite me later!).

Here is the extent of this mornings work so far, just finishing my coffee then it's off out into the workshop to start cutting.

[HerkyBird]

Been busy in the workshop this morning and have the frame plates virtually done, The cutting out and drilling was fine but the lightening holes were a pain. I drilled them first, opened them up with a jigsaw and then finished them with a 1/4" dremel sanding drum. Unfortunately the cheap sanding drum I got off ebay for £1.77 wasn't up to the job and disintegrated after a few minutes so I had to cobble together an alternative with a grinding bit with the sandpaper over the top. Not ideal and the edges aren't as good as I would like so I may have to set-to with a file later. So, casualty list so far, 1 dremel sanding drum, 1 scrollsaw blade and one jigsaw blade (both worn smooth!) this G10 really is tough stuff!

So far, weight wise I've added a bit as the original F330 frame was 47g and the new one is 86g. Unfortunately I don't see much opportunity to save weight anywhere so I think I am going to have to take the hit, the F330 weighed in at 927g so I guess this isn't too bad.

Off out for lunch now so I'll have a go at the arms later.

[friesianflyer]

Looking good!  :D

[HerkyBird]

I've had a go at the arms now to modify them for use on a much lower profile plate spacing that will form the dirty frame and I'm really pleased as it has worked well. As you can see, I've removed all the mounting structure below the arm level to give a flat mounting point which means the legs themselves under the motors will still be perfectly good, in my mind a bit better than the original which never gave very good ground clearance. As a bonus, doing this has removed 6g per leg so that's over half of the extra weight I've added so far balanced out already but I still have the extra weight of the additional hardware for the rest of the frame to worry about. I'll also have to get creative about how to mount the bottom board to these arms as the threaded brass inserts in the arms are only about 5mm deep so I think I will probably need one long bolt to go all up though the dirty frame to hold it all together.

[Gundummy]

Nice build - keep it coming.   :D

[HerkyBird]

Houston, we have a problem...

Nothing too major but as you can see in this photo, in their wisdom DJI don't mount their brass threaded components in the arms vertically meaning my bottom plate holes don't line up  >:(. I'm not sure why they do this as I would have though this put unnecessary stresses on the bolts? Anyway, it's been easily 'resolved' by opening the lower holes out into ovals (what would a custom build be without at least a couple of 'adjustable' holes  ;D).



I've opened out all the relevant holes now and done an initial fit and mounted the anti-vibration posts. Please excuse the ugly silver Phillips bolts, they will be replaced by black button head hex bolts when I know exactly what I need to get. The long bolts though the arms will have lock-nuts on but the anti-vibration posts will need to have standard nuts threadlocked as tightening locknuts may tear the threaded sections out of the rubber. Finally for this section I added a couple of plastic hex pillars halfway down the frame to stiffen the center section up as it was a bit too flexible. I had to cut these down to the required 9mm as I only had 12mm ones in my 'bit box'.



Now to a quick assembly of the clean frame to make sure that all fits how it should before I get the soldering iron out and work though the electronics.

[HerkyBird]

..and finally the whole frame has come together and it even fits in my rucksack!



Now to start fitting it out with all the gear, Esc's first I think and some form of simple home made power distribution, for the battery to Esc side anyway.

[HerkyBird]

Have been busy today working on the electronics, I've fitted most of the components onto the clean frame to make sure they all fit OK in the real world as opposed to just on the CAD tool and to check exactly where the Esc cables need to get to, it's looking good so far. I still need to connect all the components up but that's a job got later in the week.

Most of the time today has been spent on getting the components for the dirty frame prepared. I wanted to keep the wiring as neat and tight as possible so I decided to optimize the DJI Esc's by removing the bullet connectors (safer and saves weight) as well as shortening the battery and servo leads.
Out of interest I weighed up a motor and Esc before I started and after
 
...and as you can see I've saved 7g per set by removing the connectors, I've now also shortened the battery leads but have had to extend the motor leads so no saving there.
 
Finally, I've wired the lot up to a central 'power bar' which is just the cable going to the battery connector. This has proved very troublesome as I don't think my soldering iron is really powerful enough so please don't look too closely at the soldering as I'm rather embarrassed by it! It seems strong enough but I have plans to borrow a more powerful iron soon so will tidy things up a bit more then.
 
I've powered up all the Esc's and motors and they all run up OK and I even managed to get them all going in the correct direction first time too, I was very relieved when it all went OK though as having done so much tinkering around I was sure something wasn't going to work! All I have left to do on this section now is add in a tap off the main power rail to power the flight and video gear, tidy up the wiring with some tie wraps and then wait for my black hex bolts to arrive to finish off the assembly. This may take a few days so probably noting more to report until later in the week now so here's a quick posed mock-up shot of what it's looking like so far...

[HerkyBird]

Finally completed the build today. I wired up a very tidy harness for the E-OSD, Camera and vtx as you can see here and got it all nicely installed only to find that the image wouldn't sync, unfortunately it turns out I had been a bit heavy handed feeding a wire in under the heatshrink and I've knocked off a surface mount component  >:(. I've stripped it out and wired it all straight up now and it works just no voltage or timer readout now. On the plus side, as I mentioned earlier, I've been debating getting a Minim OSD and hacking into the Naza GPS so it looks like I have an excuse now...

Finally, I've wired up the EzUHF to the Naza and the lost model alarm with a very much shortened lead and it's ready to go. Weight has come in at a reasonable 949g ready to fly with Li-Po vs. 927g for the original F330 which I am happy with (helped by the lack of OSD of course). I have a very short test flight in the garden this afternoon in poor light and high winds and all flies fine with no apparent vibration on the quick video I took. The model did seem to be lacking in power to climb vertically which is odd, I'm thinking gains may need tuning as I made the mistake of saying 'yes' to the 'new firmware version available' prompt from the DJI software when I ran it up.
With this weather who knows when I will get to try a proper test flight but I hope to post some videos and a flight report eventually. It's been a fun build and I'm pleased with the result, lets hope it flies well!
Here are a couple of final pics of the finished model.