Friday, June 19, 2015

ZMR frame Mini tricopter

Im sure many people have a ZMR frame or 2, maybe even some broken arms, or they have just moved on to a better full carbon frame. I have found the ZMR frames great and easy to change the layout for custom builds like I did in these builds.

I found myself in both camps, I moved a ZMR build over to a EMAX full carbon frame for my learner FPV rig. This left me with a spare ZMR frame, so I got to thinking ... which is always dangerous.

I love tricopters and after unsuccessfully reducing the size of my Titan tricopter I decided to try and make a tricopter out of a ZMR frame. This is the process I went through.

The finished version:1

Heres a quick video of the finished version:1 flying

The first thoughts was to use a 10x10 carbon arm that was left over from the Titan trim, But after some mockups I decided against it.

First mockup with the 10x10 carbon boom, rejected.

Testing the layout options. Trying to fit the servo in and spacing.

Design re-think, Doh, why not just use a ZMR arm. So after a little fiddling I found that the camera plate slots on the ZMR frame are almost identical to the ZMR arm holes. All I had to do was use a 3mm drill to widen the gap to allow a 3mm bolt through. 

I also used some washers to provide some extra strength so the bolt wouldn't pull through the plate in a hard crash.

I used 10mm standoffs like I did for my other ZMR builds to secure to the bottom plate. It was surprising strong.  I used the outer arm holes to provide some more rigidity.  This did make the distance to the tail motor mount a little longer, 20mm compared to the front motor distance. But I think it may help in-fact, I hope it will give the tail more leverage and drive.

Ok, on to the big challenge the tilt mechanism. 

Firstly a huge shout out to David Windestal, Captain Tricopter !!. He designed and made public under CC Licensing an awesome 3D printable tilt mechanism

I started with the v1 of these and started play around with it on a ZMR arm. 

After a little playing, trimming it become clear that it was going to be really easy to zip tie it to the arm, even with the larger servo it fitted nicely between the tilt and top plate. The spacing also provided the tilt a lot of protection. 

I designed a 3D fully integrated plate that had the alignment all done, I had a 3D file of a ZMR arm, I then just joined Davids bottom tilt design at the required height and alignment so that the zip tie groves lined up. I also spent some time making it so that the server would just slot in. I had spare servo that I could test with, it was not ideal. But it was free and on hand. ( I late changed it for a smaller one) 

First design printed out.

First design Tilt and servo all buttoned up. 

Test fitted to the mocked up frame.

Design re-visit
So after the first design you always find issues and better ways of doing things. So I found that if I used a DYS 1806 that with the prop was very close to the large servo, there wasn't enough clearance. 

I plan to start with the DYS1806 2400kv, 5045 props, then move up to the EMAX2204 , 6045 props. I needed this to be strong. To help both of these issues I decided to increase the thickness of the motor mount plate area. I expect to crash, so I NEED strength / durability.

The other issue I ran into was that my 3D prints were not producing good strong splines in the motor tilt portion. I also wanted  the option to try and use different servos so didn't want to be limited to the spline that was part of Davids design. 

Thicker top plate compared to the earlier version.

So to allow the use of servo horns I just altered the design to have a recess. This allowed for servo horns of various sizes from different servo's to be easily installed.  

The other change was to split the bottom plate so that I could swap out servos / servo types without having to remove the main tilt assembly. 

Servo horn screwed in, it only requires one screw.

All zip tied on to the ZMR frame

The design allows for 3 zip ties to hold it on. 2 using the ZMR arm holes and one extra at the arm base.

I also swapped to a smaller servo, its on the best. I had these left over from a HobbyKing Trifeca tricopter build. Its a Turnigy TGY-9018MG. Its smaller than the one I started with, time will tell if is a durable servo for this sized model. I had to then design a new servo mount plate. It has a cut out slot that orientates the servo and stops and movement backward. 

Now I can easily swap servos out if required. Just design a aft bottom plate.

Now with this design I can center the motor tilt and slide the servo onto the servo horn and zip tie it down. The ZMR arm angle really helps hold it place. Since the arm narrow outward once you zip tie the servo on any force applied to pull the servo back actually tightens the zip ties.  

Full complete frame mock up. Very happy with how the tail worked out.


First build
DYS1806 2400kv Motors
Rotorgeeks 12 amp ESC
Naze32 Acro / Baseflight
5045 Props
D4RII / Telemetry

I wanted to try and keep the design to only use the ZMR bottom plates, that meant I had to try and fit everything between the plates. This meant that I had to do a full soldered wire harness and not use a PDB. 

I used rotorgeek 12amp ESC that I got second hand. The front ESCs are forward in the frame to allow room for the NAZE in the center.

The front arms are only held in with 2 bolts / stand offs not the usual 4. Time will tell if that impacts durability. I gave me the required room to fit the ESCs in.

Tight fit in the nose. I also used one of my ZMR 3D printed LED bars. Got to have some bling.

ESCs held in with zipties using the free arm holes

The routing of the motor wires.

The rear motor ESC is mounted off to one side. This will allow room for the D4RII to be mounted on the other side.

Top plate on, making sure everything fits in the 13mm gap.

Doh, I forgot the batt lead. Had to de-solder and add. ( It was late and cold in the garage)

Onto the NAZE and D4R. Its a tight fit but very doable. The NAZE uses the ZMR FC mount points and I used nylon bolts/nuts.  The D4RII was held with a little 3M double sided tape and a zip tie.

Everything was powered on and double checked.

Top plate added for the final time. I am really happy with the over outcome from a re-purposing and looks point of view. 

I added as many standoff as I could to try and help with rigidity. Any stand off that was close to wiring was cover in heat-shrink.  The Standoff that were on on the arms required 3mm spacers. 8045 prop spacers are perfect for this.

Time to load the firmware and tune.


Planning ahead I have ordered a tilt mechanism from Davids site and also one of the recommended digital servos.  But so far after one flight the current setup is holding up well. 

I will just need to design a server plate for the new servo.  This will also allow me to run the custom Cleanflight firmware that adds much better performance for tricopters.

3D Files all on 

For a TGY-9018MG servo setup 

ZMR250 Arm protectors

Tuesday, June 9, 2015

Raven 234 FreebirdRC plus Update

While in America I got one of these frames sent out to me. A Raven 234 Acro full carbon frame. I wanted to improve my acro flying and I felt the only way I could do that is with a nice small really strong frame. As I crash a lot and usually hard. As evidence from some of my videos. I tried the Hoverthings frame and it flew great and was fun, but was a little big.

So after a lot of research I decided on the Raven, Brain from FreebirdRc has been great with communications and answering my questions. It was delivered very fast while I was in the US staying at a friends place, Brian shipped it out fast to make sure it arrived before I left.

Once I got back to New Zealand I found some time to start the build up of the frame. I had some parts that I wanted to reuse, and some key requirements that are particular to me.

  • I didn't want the ESCs on the arms
  • Easily swap motors (I tend to damage these)

The plan was to use DYS1806 2400kv spinning 5040 on 3s to start with and feel my way up to 2204 spinning 6045s on 3s once my skills improved.

So on with the build, Once thing to note, this thing is small, really small with very little room to place anything, even a Naze32 board seems big on it. 

The biggest challenge was to try and get everything on the frame and mounted. I spent a few hours trying different options and layouts. The below one is what I settled on. It wasn't going to be the tidiest, But I knew that I would change soon, either due to crashes or new parts to try on it.

The ESCs are ZTE opto 12amps these are small, but look big on the frame, and were harder to mount than I thought they would be. 

I used a PDB to make the wiring "less" messy. Once I mocked it up and got positions sorted it was time to solder.

Finished PCB and ESCs

Next I needed power. I 3D printed a XT60 holder that would fit between the frame plates and make a very secure connector. Once in place I planned to hot glue it.

I had to mount the PDB and feed the battery wires up through the frame and solder inplace. I didnt really like this solution, but for this build it worked out really well.

Next it was time to secure the ESCs, I used 3M double sided tape and small zip ties.

All secured down.

Next was to tidy up the ESC cables. Since the are opto ESC I removed the power cable, leaving signal and ground. I then shortened to fit the frame. I also added a 5v regulator to power the Naze32 and D4RII receiver. This was zip tied  over one of the ESCs.

Next was the soldering up of the Naze board

Test fitted to get the lengths of the ESC wires, Once the length was decided it was time to solder the connectors back on. 

All wired up bar the receiver.

The Naze32 is isolated with small rubber o-rings to help reduce vibrations from the frame.

The vBat cable from the PDB 

The mess that hides under the Naze,.

I also added a small white LED strip to help with orientation. It was just hot glued to the frame.

I used a FrSky D4RII receiver using PPM, I just soldered a short servo cable to the Naze long enough to just fold around to the D4R.

The last two wiring parts were that telemetry cable for the D4R and a buzzer.

The D4R was doubled sided to the top cover plate and the antennas were shrink wrapped to some zip ties off the top plate.  

Over all the build is not the tidiest, But is fully functional and was ready for me to go flying. I loaded up baseflight and configured the board.

All up weight I was really happy with coming in about 260grams (by the time you add props and nuts) about 380 with 1500 zippy compact.


Well this little frame rocks, unfortunately I do not, After putting on a base tune and doing some test flights I crashed a lot. I was use to heavier less agile combos that my timing was completely out and I was either over rotating and powering out at the wrong points. I ended up chipping a few edged on the arms, but over all the frame showed complete disregard for my incompetence. 

However I then went to a larger park and started increasing speed and multiple flips, that's when it really went all wrong. I was practicing the power up flips, the one where you power into the flip and then reduce power a lot and it causes the quad to do multiple fast flips under no power. Well I got my timing wrong and it hit the ground hard. The frame was completely fine, However the DYS1806s were not. I managed to bend 3 shafts and snap another completely, yip 4 for 4 damage. The shafts in the DYS1806s are very thin, about 2.5mm and do bend easily. Not ideal for acro crashes.

Of course this happened on my first battery and that was my day done. 

Decision time. I had just sold my fatshark goggles and has some cash so I decided that I needed rebuild this quad, and put stronger motors on it. I decided on EMAX 2204, since I already had 2 spare from one of my other orders, I have crashed them hard and they seem to have survived well. Plus 2204 will easily spin props from 5040 - 6045 so easier to find my preferred combo.

I was also not happy with how it looked, I know that has no impact on flight or my ability to fly it, but I like tidy builds. So since I was flush with some cash I also ordered these from : ReadyToFlyQuads

These will allow me to make a very clean install, very much looking forward to getting these part to redo the frame in a tidy build that the frame deserves. 

So what to do with the current parts. We I had a cheap hobbyking 260 frame that I had planned to build up and a learner frame for my daughter. So there is no time like the present and since I had done all the hard work it was easy to transfer over to the other frame.

First step was to strip the Raven.

The HK 260 has a larger center space, I marked up where the holes for a 35x35 board needed to be and drilled holes through the frame.

Then it was just a matter of mounting the already complete PDB. The ESC easily and tidily slotted around the PCB in the center cavity.

Add a old Naze and its nearly done.

All done, currently with a old naze32 and orange receiver 

But is made for a nice tidy quick build.  I used he repaired DYS1806s as this will just be a hack flier.

It will be a great learner quad. I just hope that it will be durable enough,

Now its a waiting game for my new parts so I can make a super awesome build of the Raven. Look for that build coming soon.


Will this confirms how strong the raven is, This is what happened to the above build after a small crash.

Cant wait for the new bits to arrive.