Starting a new thread to show what I'm working on. I'm building a new Octocopter of my own design. The goal is to use it for Aerial Photography, lifting a mid-weight camera such as a Sony Nex5. It will of course be using Arducopter for control. ;)
I started off researching the various kits on the market, and starting getting analysis paralysis. I looked at all the options such as Droidworx AD8, Cinestar, CarbonCore, and SteadiDrone. But I just wasn't happy with the design on them, particularly for the price they ask. Combined with the fact that I can be pretty frugal, and have a strong DIY ethic, I decided to just design my own.
The basis of the design relies on many of the Hobby King quadcopter parts. I liked the design of the motor mounts, they are very professional looking, even compared to some of the high end machines. And I liked that the boom mounts are blocks of aluminum instead of plastic. Very rigid. I also liked the look of the dome on their H.A.L. quad, but since they don't sell it seperately, I bought the whole kit, it's only $34, amazing! I might end up using the rest of it someday, who knows? So, I basically emptied out their stock of Talon parts, so if you need to fix your Talon quad and the parts are backordered... sorry!
Once that was settled, I set about designing the center frame. My design required a few things, namely I want all the wiring hidden. I don't want any spaghetti showing. Particularly with the ESC's, while still allowing cooling airflow. This required the center hub to be larger than is typical. I then needed a smaller subframe to house the avionics.
You can see these plates below. The larger one houses the HAL dome. You will notice the 3 blue anti-vibration grommets in the middle. This is the APM1 pattern. I did that just because. Maybe I'll use an APM1 as a stand along gimbal controller. The second plate had grommet mounting for an APM2. The final plate is the top plate, and has bolt patterns for the Ublox GPS and the magnetometer.
This next photos shows the avionics frame built up with an APM2 mounted. 25mm aluminum standoffs are used. I don't like the plastic standoffs typically used. They get loose, and lead to vibration. They also break easily. This structure ends up being quite rigid.
Here is the avionics frame mounted on top of the main frame. Yes, the main frame is HUGE. I actually don't see the point in having a tiny center frame, and then long arms. This seems like it just leads to flex, and doesn't leave you with any real estate to mount your avionics.
This photo shows one of my design features. I put some cutouts on the bottom frame for weight savings, and then made matching cutouts on the top frames. This creates some nice conduits to run wires neatly.
Here it is with the HAL dome mounted and one of the Talon arm mounts bolted in. I'm really happy with how stiff the assembly is already.
Here it is with one of the arms mounted. These are the short 220mm arms, I also got some of the 320mm arms. One may wonder how I'm going to get away with such short arms and 13" props.... Astute readers will know what I'm planning already. ;)
This last photo shows one of the ESC's in position. This is a Hobby King F-40A, it's somewhat larger than typical 20A units which is partially why the frame is so big.
That's it for now. I had the plates cut out of aluminum to start with because it's cost effective. If it all works out, I'll probably have it redone in carbon fiber plate for the weight savings. I was a little uncertain about the weight, but it looks like the frame will come in at 1070g all in aluminum. That's about 300g heavier than a Droidworx AD8, but not too bad. It will drop about 1-200g if redone in CF.
Yup, I used the APC 12x3.8". It's pretty much the only prop I'll bother using. I have heard from several people that the CF props are not nearly as efficient.
OK that's what I will get. You order them from apcprop.com or did you find a better source? Their store still isn't working but they do take phone orders.
IMAX set to 5.0.
That's the problem. Way too low. Slowly move it up to 25. In 5.0 steps. I'd tell you to go to 25 right away, but just in case...
I think the only risk here is it might causing flipping on take-off if you stick around on the ground with the props running. So just move it up slowly. This will help the motor-out flight.
I would have to check, but I'm pretty sure I had it at 25. And I didn't have any flipping on takeoff problems.
Thanks. I've never actually tuned IMAX before. Just left it at default. Need to read up on what it does but will take it up like you said. I had another ESC die on my (my fault) because it wasn't strapped on and the heat sink vibrated lose. So I stuck on a RedBrick 70A. In the beginning of this thread we had a discussion about whether it would fit. Well it fits nice. Just slides right in after remove the arm. The problem is I couldn't seem to reflash it and it didn't seem to like being with the other 7 F40s. So I gave up and am waiting for new ESCs to arrive Monday. Not sure why it wouldn't flash. I even have the flashing tool that goes right on the atmel that I used on the F40s but no luck. Shouldn't you be able to mix ESCs?
Also to make replacing ESCs easier, I'm going to solder on 13 XT60 connectors in a circle on another copper disk I picked up. It will be like yours with washer on top of washer but with them sitting in that groove on the terminals of the XT60s. You know the part that has the half circle cut. They will sit there nice and be real easy to solder and unplug if I need to replace. The way I replaced these last three was the cut and snip method on the wires and then soldered the new one in place but it was not fun or fast :)
have you cut /build any octo main plates to interested parties thus far? and if so how much and would you have more available to sell? I rather have alu main plates over HK's CF plates.
Hi Mike, I actually have a number of aluminum plates cut and ready to go already.
Working on tuning IMAX and had an apropos moment. Got it up to about 15 and one of these crap motor mounts broke. Probably it was another one of the ones in a hard landing. Rob did you ever find any more durable ones that fit those booms? It was cool to see it cut the prop in half, drop the motor and the octo was just smiling at me like nothing happened :) Luckily it was the only motor I used bullet connectors on so it just unplugged itself and fell to the ground.
The only thing I can think that would happen if it was further away and I had to RTL it is the ESC would burn up like before when I intentionally unplugged a stuttering motor because of a faulty solder on one of the three motor wires. When I did that test and tried to take off, it just smoked the ESC. Do you know if that is normal if you throttle up an ESC without motor connected?
No, I haven't found any other motor mounts that would fit, but I didn't really look. On my new design, I'm going to make my own from 6061 aluminum.
I don't recommend straightening bent mounts for this reason. Just throw them out and get new ones. At least they're cheap.
Yes I'm sure it was one I straightened out. They were so slightly bent that I didn't think it mattered. This is the second one that broke like this. I don't think an unbent one would break so I'm just going to keep some on hand. I bought 8 extra so I'm good for now.
BTW, the APC props are much better than those CF. Also I realized 5 of them I forgot to put their little reducers in so they might have been out of balance because of that. Now it doesn't make that growling sound when I punch it or do a quick yaw.
How are you finding the performance of this octo? I'm torn between this and a coaxial octo. Also, are you in a + or x configuration?
I think Rob had a crash and didn't rebuild yet but I can say mine is more than a rocket and super steady for filming. I think the power is going to come in handy for lifting heavier cameras. I don't plan to use it for speed. I will start with a sony nex5. I'm not flying with the weight of the camera or gimbal yet so it feels more than overpowered. I've never even tried to push throttle to 100%. I think in a second I wouldn't see it again! I'm in a + config and with 320mm arms. Rob dwarfed his to 160mm if I'm not mistaken. With no so new 4||3300mAh 4S batteries I get 13 minutes. Probably will get down to around 10 with the camera added. I can send you my tuning parameters if you need.