These are the fully 3D printed T4 (quadcopter), Mini T4 (quadcopter), and T6 (coaxial hexacopter) designs I've posted on Thingiverse.com (aside: "T" is for Tubular). The comments section on Thingiverse doesn't provide a great place for discussing designs so I've created this topic here instead.
These designs are based on a tubular arm with a vertical "I" beam running down the centre. This design seems to be very strong and rigid and all of these designs are very stable in flight.
Other common features include:
- motor wiring is routed through the arms and down into an enclosed (ventilated) power and ESC tray.
- batteries are located in the centre of rotation (T6 is designed for dual batteries).
- bevelled cable "tunnels" provide a way to route cables between the power tray and top plate.
- Top plate is designed for Pixhawk or APM flight controllers with elevated GPS.
- Bottom tray has mounting points for a Tarot Gimbal.
- Optional long and short legs include "springy" feet. The legs are designed so the 3D printed threads "wrap around" the arms which makes them quite strong for their length.
- Sketchup files are included so folks can modify both designs to suit their needs.
I figure I've put hundreds of hours into these designs with prototypes and drawing time. I'd love to get feedback from anyone who makes one. Together we can improve these designs for everyone's benefit.
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Thanks for you comments, they are appreciated.
Regarding 2, the mast is not so much for GPS reception as to keep the external compass away from the power components.
I have to admit I haven't done any CompassMot testing but just added the mast as it seemed like a good idea :-). If you ever feel like doing some tests comparing compass locations (and post the results) that would be awesome.
Hi,
I just finished building my T4 quadcopter. I used DJI motors (920KV). I think they are the ones that are also used in the DJI Phantom. The copter flies awesomely stable and I'm very pleased with the first result. It even lasts 15 minutes on a 5000mAh battery.
However I discovered from the logs that hovering requires 85% throttle (take off weight is about 1400g in the current setup). I'm now hoping that switching to 4S will fix that power issue.
Do you have any hints on how I can increase performance? I'm rather new to drones so I'm thankful for even basic hints.
Cheers,
Frank
Nice looking build, well done!
I'm surprised about your throttle %. Is that what you are seeing on your stick too - when flying manually?
I just did a quick test of my T4 for reference:
- 850kv 3DR motors
- 10x4.7 APC props
- 3S 6000mah nano-tech battery
- all up weight 1420 grams
- hover throttle 45%
What size/pitch are your props?
For more lift you either need bigger or higher pitch props (limited by what the motor can swing) or spin them faster (using by using a higher voltage ie 4S battery) OR reduce the weight (ie by using a smaller battery).
Historically I've been rubbish at choosing motor/prop combinations which is why I now play it safe and stick to combinations proven in commercial vehicles of similar all-up-weight. For the T4 I use the combination from the 3DR Iris.
The props are 9.4x4.3. The % is the value I got from the flight logs (CTUN>ThrOut).
Also I can see that the copter is very slow at stopping descending:
A quick search indicated that the DJI 2212 (920kv) motors should be able to handle 10x4.5" props. I'd recommend giving that a try.
A 4S battery is another option but 4S is a bit less convenient if you want to start adding any camera gear as most of that can't handle the higher voltage so you need to add some kind of regulator.
I just ordered a bunch of 10x4.5 on amazon and a set of nuts that fit the CW/CCW threads on the DJI motors. 4S 3Ah battery was already ordered. I'll report back when I had the chance to test them.
My plan is to add more weight (speaking: a camera incl. FPV/OSD) to the drone but in the current config it's not an option. There is no power margin at all.
When I add the props and the 4S battery will the power boosting effect add up?
BTW: I made a short video: https://www.youtube.com/watch?v=WHYxyBsLIII
And I also ordered some shorter patch cables for linking the RC receiver to the APM. Looks like a real mess at the moment. :-( I wonder where you put the RC receiver in your T4. I can't see any in your photos.
I don't think you'd want to do both props AND 4S battery. A quick search showed that those 2212 motors may melt if you try to spin 10" props with them at 4S voltage. The first discussion I found in search is here.
For RC on the T4 I'm using a Spektrum satellite receiver (cable tied to the GPS mast) which has a single small cable directly into the Pixhawk flight controller. Most flight controllers now support at least one kind of "single cable" RC connection rather than having to have a cable for each channel. Search for PPM/CPPM (not PWM), SBUS, DSM etc. It's a case of getting a receiver / flight controller combo that works together (but worth it to get rid of all the cables).
I just tested the 10x5.4 blades with 3S and the motors are getting so hot the plastic in the motor mounts is melting. With the 9.4x4.3 original DJI blades (the ones used in the Phantom 2) there is no heat issue.
Anyways I decided to go a step further and print the X8 arms to upgrade my copter to an X8 which then has plenty of power and better motor cooling as well as carbon fibre crosses which will not bend when the motors are getting hot (despite the better cooling).
I have to figure out how to print a higher bottom tray as I will have to fit two 4in1 ESCs in there then.
For the time being you can enjoy a video I made using the current setup which is actually working just fine (60%thr to hover): https://www.youtube.com/watch?v=x8Zc-Bx2PKg
Thanks for posting the video Frank - nice!
I guess that confirms that the 10" props are too big for those DJI motors.
Have you considered building a T6? The only reason I ask is because it supports dual batteries. It think the flight time with a T4 in X8 mode would be pretty limited. ...I'd still love to see it though.
How much (vertical) clearance would you need inside the bottom tray. My guess would be at least 25mm?
Doing some basic calculations:
Formula: <Weight> * 100 / <Thrust at 100%> = <Hover Thrust>
Current X4:
1800g * 100 / 2600g = 69%
(vs. 65% taken from logs)
Planned X8 (best case / worst case):
2600g * 100 / 5200g = 50%
2600g * 100 / 4600g = 57%
(vs. 5200g projected / 4600-4900g expected with coax loss taken into account)
This would make 3000g hover at 65% (worst case) which means I can pack additional 300-400g payload onto the copter. And that is without taking into account the possibility that I can switch to the bigger props.
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