- September 18, 2017 at 2:13 pm #44163
Not sure what to call this one. My working title was “fakeowl” since I had in mind something like the FlexRC owl but wanted to size it for 5″ props. I had seen something like that before but couldn’t remember where or what it was called. After I started drawing it and talking about it on the flitetest.com forums the guy who had the owl that inspired me reminded me that it was his shen drones Danaus I was thinking of. And that in turn was based off a QAV210 with prop guards added.
For reference my Onshape project for this is here: https://cad.onshape.com/documents/a023e2b86f7f9d2ca94cf0a7/w/8954d4f2255b144f9064ef10/e/3d3ae8cebc5730c002d79eb8
I started last Monday just sketching out some ideas to get a feel for what I was hoping to make and get a feel for how big it would be:
Seems viable. Last week my wife had to work late all week so I wasn’t able to get out to my shop and actually cut anything until Thursday. Instead I continued to revise my design in CAD:
And side view to gauge how tall the standoffs need to be:
Starting to come together! That motor in CAD was one I found in onshape search that was close but not quite the same as what I’d be using. But good enough for a mockup. And by Thursday I had some time to sneak out to the shop and run some gcode. I had planned on using 1/8″ ply but was only able to find 5mm ply in sizes large enough at my local stores. So gotta go with what you can find sometimes:
Hey, this is looking pretty viable! Let’s put some gear on it. This is the “guts” from my “ultra budget mini quad” 3D printed angled arm edition (I’m not good at naming things) that also featured parts made on my MPCNC (The top and bottom plates) but they were simpler and could almost have been cut by hand quicker and easier. This is finally something I wouldn’t want to cut by hand and a good chance to really put the MPCNC to use!
I could try to fly it like this…but…one of the design aspects on this is that it’s kind of “inverted” with the motors on top and the props below them. The idea is with less obstruction under the motors you get slightly more efficiency – but I’ve also heard that this style of setup just “flies better” this way. So this is just mockup at this point.
Next I ran off a bunch of standoffs on my printer:
And now it’s time for other other plate. Should be easy, it’s simpler with no motor mounts, no flight controller mount, and no battery strap holes! Plus the outside is simpler since only 3 sides have “Dents” leaving a shelf in the front for my FPV camera.
But the forum gets upset if I post too many photos and things got…complex…on that simple cut so…next post please!
Attachments:September 18, 2017 at 2:29 pm #44171
Ok, the easy part! Let’s cut the bottom plate! Um…no, not so easy. I’ve been using painters tape and super glue to hold my work down. On smaller things this has been wonderful. But on 13″ square stock with a warp to it even with kicker super glue just didn’t hold well enough. The work had lifted slightly cutting the top plate but it was still usable. The lower plate…didn’t come out as nice – some parts were substantially damaged:
But it was good enough to get a feel for how it would assemble and see if my spacers were tall enough:
And get a feel for how stiff it would be fully assembled:
Overall it wasn’t bad…but I wasn’t super happy either. I decided it needed 4 more supports around the prop guard sections, and one more in the center which I had left out to leave room for FPV gear but now decided I wouldn’t need that room. So top and bottom would have to be recut anyway as I expected.
So let’s try cutting a new base plate again! I’m only cutting 1.5mm per pass right now, I know I can go deeper on this ply but wanted to take things easy. All looked great up until the last pass of the final cut (the outer perimeter) when my glue failed again 🙁
Nuts. Ok, let’s try carpet tape. I don’t like it because of how much it gums up the bit if I cut into it. But it sticks better so with this warped ply maybe it will work better.
Good news – the work stayed fixed! Bad news – once again the cut failed on the last pass of the last operation – this time my machine appeared to skip a step 🙁 But it did show me I could be doing full depth passes.
Next two tries I went with deeper cuts…and switched from carpet tape back to masking tape with glue – but used some 3M “90” aerosol contact cement “Industrial Strength”. Layer of tape on my spoilboard, layer on my work, 2 quick coats of glue and let it set a few minutes – boom that workpiece isn’t going anywhere but is easy to remove when done with no sticky residue! But again I had things fail on the last pass (only 2 this time so at least I failed quicker!) of the last operation 🙁
Starting to get frustrated here. Went back to shallower cuts and positioned the work in a different part of the table to see if it made a difference (Seriously, the more complex top plate cut easy 1st try – why is this simpler bottom plate fighting me!) This time it missed steps and messed up on the first pass of the first operation 🙁
Grrr. Well, that workpiece is ruined let’s just try it again for giggles. Yep, even in this other position on my bed it failed in the same place. What the hell.
Ok…let’s think this through. Try running the gcode with the spindle off and raised up just to see how it does. I can hear what’s happening and pay attention to the machine and not the bit this way. Hmmm, that’s interesting. Turns out my left Y Roller is making an odd rattling noise right where things fail. That roller was printed out of different filament than my others and did seem a little looser when I assembled the machine. The Y is also slightly out of square, I have to pull the left side in a bit against some stops to square it before powering up at which point the steppers hold it square.
But…when I set the current on my steppers I did so very conservatively, and with the machine where it sits naturally not squared up. Once squared there are a few small spots that seem to take a bit more effort to get past. Ok…let’s turn up the steppers. They’re still lower than the smaller steppers on my 3D printer and still stay cold to the touch.
Finally got the bottom to cut with no issues! Alright! But, let’s have another post break so the forum doesn’t complain about me linking too many photos before we finish this story.
Attachments:September 18, 2017 at 2:41 pm #44177
In my excitement of finally getting the lower plate to cut cleanly I didn’t remember to get any photos. I just ripped it off the bed, sanded it down a bit and sprayed on some varnish.
Then recut the top plate with the design changes. I made a small mistake here – can you spot it? Entirely my fault. My daughter found the problem quicker than my wife when I showed it to them:
If you can’t spot it here’s a closeup:
Doh, totally forgot to define operations for those four holes 🙁 And the rest of the ply I have on hand is looking pretty ratty. So…bolted the original plate to this one (all the holes lined up perfectly but it really showed off how the outside cut of the original plate was damaged when the work lifted off the spoil board) and used it as a guide to drill the missing holes. So…re-assemble:
That varnish really makes the bottom pop 🙂 This looks “right side up” to me – but I know it’s actually upside down. So let’s see the top:
Was getting late so I skipped varnish…I’ll do that tonight. But maybe I have enough time to get it in the air before I crash for the night.
I’m running dRonin on this like I do all my multi’s but it had an older version – so plug it into the newest release and let it do it’s magic update. Then run though a configuration…figuring out which way the motors should go and which way the props should mount was a bit tricky with everything “upsidedown” but I managed to figure it out. Had to swap a few motor positions in software and the accelerometer calibration seems to have detected the upside down controller…so let’s try and fly an autotune flight.
Nope, I’ve got the instaflips 🙁 Ok…double check everything…all looks good. Except…hmm…that artificial horizon is responding backwards. Let’s do a yaw calibration. Ahh, there we go. Needed roll set to -180 and yaw set to -180 to compensate for the upside down controller.
Ran my autotune – got good looking numbers….and gave it a quick test flight at lunch. Very happy! Even flew it into a tree on purpose and it didn’t even crash due to the prop guards!
I’m still a bit worried about it’s long term strength. The PLA standoffs seem weak and the ply isn’t all that strong either – though once assembled the whole is definitely greater than the sum of it’s parts for stiffness and strength. I’ll probably redo the standoffs in PETG or Nylon. And would like to get some 1.6mm carbon to cut the plates out of – but that’s not in the budget right now. Heck even G10 or delrin aren’t in the budget since 12″ square sheets are just barely big enough to fit this and 24″ sheets are expensive to ship and I have no local suppliers 🙁
Tonight I’ll have to varnish the top plate and work on mounting up my FPV gear. Looks like a little all in one camera/vtx will fit inside the frame nice and protected so that should be easy:
Attachments:September 18, 2017 at 3:13 pm #44186
I like that. All the parts are so good now the little extra weight from having guarded props surely is better than munching props all the time. Down facing motors another plus!
It is cooling down here so maybe I can go find a nice spot to learn to fly, sims get boring pretty quick. When I bust my frame This is next for sure.September 19, 2017 at 8:16 am #44209
Well, I would suggest something better than cheap 5mm luan for the material:
To be fair I was wrong about doubting the PLA standoffs – they held up just fine. Also this is after purposefully flying it into several trees to see how it would react (bounces off) and bouncing it off the ground a few times (Like a hard landing only faster). But a 45 degree nearly full throttle slam into the ground was more than it could handle (I just can’t resist doing lots of fast flips and rolls even though I really don’t have room for them in the front yard!)
I’ll rebuild…but may or may not use ply again. G10, Delrin and CF are just too expensive to have sheets shipped though. So thinking about milling it from a HDPE cutting board…or maybe lexan, or maybe making my own composite from denim (old jeans) just to be totally different.
Attachments:September 19, 2017 at 8:34 am #44213
Dang, that took a beating. Maybe do the outer edges replaceable?September 19, 2017 at 8:50 am #44215Dang, that took a beating. Maybe do the outer edges replaceable?
Could be done that way…but it’s heavy enough already so I don’t really want to add more parts. I’ll probably try lexan since it’s fairly cheap and I can actually get it locally. But…it’s also heavier and I know from past experience it doesn’t hold up very well to my abuse either. It should look cool at least 😀September 24, 2017 at 5:57 pm #44645
So…haven’t had much time to work on this this week. Brakes on my truck failed on my way home on Tuesday – thankfully they held enough pressure for me to make it home without hitting anything…but we were down to one vehicle on week with lots of after school things for my daughter and meetings for me and my wife. So I wound up having to ride my bicycle to and from work the rest of the week. Finally got time to repair the truck Thursday evening…and didn’t tighten the drum adjuster enough so on my test drive they failed again…I hate drum brakes. Rode the bike again Friday…and finally got them repaired Saturday without trying to rush in the dark so things went much better. Truck is stopping better than it has in years now.
But…all that meant I wasn’t able to get to the store to look for any material to cut a replacement frame from. Finally today I got a chance. Went up looking for some lexan…but all they had was 0.093″ and it was quite pricey in a piece big enough to cut the frame from. But I went for it. Then I saw some 0.125″ PVC sheet that was only $8. Hmmm…PVC is pretty tough…not very stiff but this frame stiffens up when assembled so at that price worth a try.
The PVC cuts like butter with my 1/8″ single flute endmill. One pass nice and easy. Could have done two passes for a cleaner cut but right now I’m more interested in quick and dirty than finish quality. Just want to get it together and see how it does.
One more plate and 40 screws later:
Well, it looks pretty good. But…that PVC is just too flexy. It did stiffen up but not enough for me to trust it to fly. It can twist very easily and I could easily see a motor giving enough thrust to deform the frame and cause all kinds of problems.
But I did pick up that sheet of lexan as well. Unfortunately I rushed too quick and tried to use the same gcode…but I didn’t notice the lexan was thinner. So I was taking a bite out of my waste board as well and the lexan was a lot tougher to cut, and my work holddown was failing on the lexan….so it did NOT go very well.
It’s also kind of hard to get a photo of this stuff once the protective film is removed.
You can see just how bad the cut was due to a combination of too fast of feed rate, too deep of cut, and the work moving:
But it was enough to see how stiff it would be:
Man, this thing would look so cool all out of lexan. But…I’d have to find thicker lexan – it’s still too flexy 🙁
Guess I may have to follow through on my threads to make some “denim micarta” from old jeans and give that a try….
On a happier note…cut this out of foam with the MPCNC this weekend:
I had a few minor mistakes in my CAM, places where I did a through cut but should have done a score cut, or score cut that should have been through cut, or score cut that should have been marking cut. And made a few mistakes in assembly. So this one won’t be getting RC gear. Instead I turned it into a chuck glider for my daughter since she liked it so much:
Going to revise my gcode and cut another for myself, got an EDF on order for it and can’t wait!
Attachments:September 25, 2017 at 8:12 am #44691
You had a crazy week!
I know the testing/experimenting sucks when it doesn’t work out but when you find the right material it will be awesome. Clear would be so freaking cool. I had my tubular build fold itself literally in half so you are right to worry about flex. Some is needed though for durability.September 25, 2017 at 9:00 am #44699You had a crazy week! I know the testing/experimenting sucks when it doesn’t work out but when you find the right material it will be awesome. Clear would be so freaking cool. I had my tubular build fold itself literally in half so you are right to worry about flex. Some is needed though for durability.
Yeah, weeks like this…I can do without 🙂
I enjoy the testing/experimenting. I’ve been building quads for almost 4 years now and am fairly involved in the dRonin firmware project. I’m constantly looking for new/different ways to build them.
I’ve used wood, aluminum, various plastics, CF, G10, CF/G10 composite, CF/Birch composite…and in one ill fated attempt…bread. (I really wanted an edible copter!)
CF is great…but expensive. And I’m just not a fan of using flat plates of composite – I’d rather do a custom layup with some form to it and make something stiffer/lighter than bolting plate together.
So this is just a bit of fun. I could go with one sheet of ply and one of Lexan or PVC and that would probably be fine. But the whole thing out of clear would sure look neat. (even neater if I engraved something into it and edge lit it with some LED’s….) so I’m probably going to check another local store to see if they have any thicker lexan. I know I’ve found it locally before but it may be too expensive in a large enough sheet to cut this from.September 25, 2017 at 9:04 am #44700
Get super crazy and 3D mill some HD foam and give it a fiberglass skin?September 25, 2017 at 9:08 am #44702
I have been thinking about trying something like that…but I’d probably just use the foam as a form and then dissolve it out leaving just the fiberglass skin.
Now that the weather is getting nicer and I can work outside that kind of thing is becoming possible again. In the summer I didn’t want to be cramped up in my little shop with the fumes from resin 😉
I still want to try using old jeans and epoxy to make my own composite…it’s just something I’ve been kind of fixated on for a few years but haven’t quiet got to actually putting into action.September 25, 2017 at 9:12 am #44707
I did see a Denim knife handle made that way, it was from his great grandfathers jeans or something. It did end up looking amazing.
You must be logged in to reply to this topic.