Baby Tricopter build

Baby Tricopter

Time to build a Baby Tricopter. This is a 170mm motor to motor crazy 7:1 thrust to weight ratio beast of a tricopter. It’s small and durable and a real blast to fly. So lets get started.


I’m going to built this baby tricopter (with F3FC + BabyPDB) together with the baby tricopter electronics pack.


Before we start mounting stuff, I highly recommend finishing off the carbon fiber in the kit. There is a crescent shaped diamond file included in the kit for this purpose. File the edges lightly. Wear breathing protection and be outside when doing this. Carbon fiber dust in pretty nasty stuff.

Be sure to get the holes as well.BabyTriBuild12

The reason why you should do this is mainly that the edges become smoother (duh), this keeps zip ties from snapping prematurely, tape wrapped around things last longer, battery/camera straps lasting much longer and recedes the chance of you cutting yourself when handling the copter.

Now we can mount the BabyPDB using the 10mm long nylon screws, fiber washers and standoffs.

The fiber washers are there to keep the BabyPDB from touching the frame. There is no exposed pads or anything on the bottom so it should be fine touching the carbon, but better be safe than sorry.BabyTriBuild4

Mount the board with the large pads towards the tail.

You’ll be needing a pigtail with the battery connector you plan on using. I’m using the 5cm XT60 pigtail, which I stripped back a bit to get more surface contact on the pads.

Soldered in place.

To get a bit more speed and torque from the BMS210 feedback servo, I bridged the 6V pads on the BabyPDB to get it to output 6V instead of 5V.

Screw the nylon standoffs down to hold the board in place.


Mounted in place. BabyTriBuild13

The wire on the BMS210 feedback servo is quite a bit too long, so we’re going to steal a piece to use to connect the PDB to the flight controller.BabyTriBuild14

That length looks about right.BabyTriBuild15

Strip and tin.

I connected the red wire to the BEC+ output, the brown to GND, the orange to ISENSE (current sensor) and the yellow to VBAT (raw battery voltage)

Picture of the bottom of the PDB for reference.BabyTriBuild17

Solder the wires to the correct pads on the flight controller. The pads are quite clearly marked.


If you plan on powering anything power hungry through the flight controller I recommend moving this resistor over to the “BEC” position. This will bypass the built in 5V regulator on the flight controller. Instead the BEC voltage will power the board and all pads marked “5V” will output the BEC voltage.

So for instance if you plan on powering RGB LED’s through the board, I highly recommend doing this.

Now we’re going to do the tilt mechanism.BabyTriBuild19

If there is any hint of the tilt having any friction, lightly sand the pieces until it’s buttery smooth. BabyTriBuild20

If the screw is causing friction, try screwing it a ton of turns. The threads should wear down the plastic some and reduce the friction.

Strap down the tilt using two zip ties.BabyTriBuild22

Mount the zip ties so that the “knots” face the opposite direction.

Looks pretty good.

Mount the servo block in the grooves. If the block doesn’t sit all the way down flush, use the included file to remove a small amount of plastic. You want it to lay flat against the bottom.

Strap down the servo. You’ll be needing 2 zip-ties connected together to reach all the way around the servo. This also gives better strap down force as you have 2 places to apply force. Again alternate the “knots” not to get all force on one side. The groves for the tilt block extend backwards which will let you slide the servo back later when doing the servo alignment.

Time for the motors and speed controllers. BabyTriBuild28

The front two motors you can strip the wire really short for a clean and light setup. If you don’t like doing that you can always keep the long wires and fold them back over the ESC.BabyTriBuild29

Pretty clean.

Baby tricopter electronics kit include thick black heat shrink lined with a kind of hot glue. When shrunk the hot glue melts and if you squeeze the edges properly when the heat shrink is still hot, the ESC’s will be water resistant and very durable.

The back motor and ESC assembled a bit differently than the front 2.

The full length of the wires should be used, and they should be soldered on at an angle.

Shrink some heatsink over it and squeeze the edges.BabyTriBuild35

To screw down the motors use the included 6mm long screws. If you use longer screws you might damage the motor windings and smoke your motor and ESC. Always use blue locktite when screwing anything metal into metal.


I mount my motors using 2 screws instead of 4. This reduces the weight a bit. If the threads were to strip in a crash I can always mount the motors using the 2 holes that were unused before.BabyTriBuild36 BabyTriBuild38

One thing you really don’t want on any multi rotor is components moving around during flight, as this can create unwanted input to the gyro, making your copter fly bad.BabyTriBuild39

Double sided foam tape is a great thing to put underneath your ESC’s before strapping them down. It helps keep them in place as well as gives some dampening, which protects the ESC in a crash.

Strapped the ESC down with a zip tie. You can also use electrical tape or similar.BabyTriBuild41

Now mount the back motor.BabyTriBuild42

Screw it in place, but remember to mount it so that the wires comes out this way.BabyTriBuild43

For clarity, this is the way you want the wires to come out.

This is so that there is plenty of slack in the wire to allow for smooth, unhindered moment throughout the whole servo range. You can also see in the picture why we soldered the wire at an angle. Things get tight otherwise.BabyTriBuild45

Looks like a rats nest at the moment. We’ll start cleaning that up now.BabyTriBuild46

The back ESC should be soldered to the back ESC pads. Do not solder the ESC wires to the battery connector pads as this will bypass the current sensor and your current draw and mAh draw will be off by around 33%.BabyTriBuild47

The left ESC needs to have the red wire shortened and soldered to the + side of the PDB.

The right ESC is the opposite. The black wire needs to be shortened.

I’ll be using a X4R-SB receiver from FRSKY. I’ve removed the pins and directly soldered some servo wires to the SBUS output and kept the SPORT wire.

To protect the receiver I’m going to use some liquid electrical tape. It’s fantastic stuff which makes stuff water resistant and creates a rubbery kind of coating. If you plan on using it I highly recommend testing that the receiver works properly before putting the stuff on. It’s a real pain to get off. It’s also a good idea to take a picture of the top and bottom side of the board just in case something doesn’t work, you can go back and inspect your work.BabyTriBuild51

The reason why I’m using the X4R is that I had one laying around. If I would built another copter I would use the XSR receiver, which is smaller and lighter and fits in the stack without modification.BabyTriBuild52

Once dry I added some thin heat shrink.BabyTriBuild53

Will solder the receiver to the flight controller in a bit.

While we have good access to the power pins we might as well solder in the FPV system. I’m using a HS1177 camera and a Eachine TS5840 with a 90° antenna connector mounted on this build. Not super happy with this video transmitter though. Will probably switch it for a TBS Unify pro HV, which is a much better quality.

Soldered the signal wire between the camera and video transmitter.

I’ll be powering the camera via the 6V BEC on the BabyPDB. This will take load of the built in 5V regulator on the video transmitter, which will keep the video transmitter a lot cooler. The BabyPDB BEC also has a cleaner output as well as it protects the camera from voltage spikes. The video transmitter I’ll be powering straight from the flight battery.

I soldered the video TX + to the VBAT pad. The – to GND, the camera + to the BEC+ pad and the camera – to GND.

Schematic Video TX, cam, pub

Schematic. The reason why I don’t power the video transmitter from the built in BEC on the BabyPDB is that the minimum operating voltage on the videoTX is 7V. If you have a VTX that can handle 6V I recommend powering it from the BEC as it will significantly reduce the heat generated in the VTX.

It’s a great idea to have a beeper hooked up to your flight controller. This will greatly help when doing the tail tune and it will also help you find your copter when you crash it in tall grass and such.BabyTriBuild58

To keep things simple I decided to solder it straight to the board. You don’t have to do it this way. You can just as easily use some wire to get it away from the board.BabyTriBuild59

I bent the – pin of the beeper to 90° at the base and then 90° again further down to be able to reach the pads.BabyTriBuild60

Now we can start soldering signal wires to the board. The red and brown servo wires are connected to the pins on the edge labeled BEC + and GND. This will power the servo with the 6V from the babyPDB.BabyTriBuild61

The orange servo wire is soldered to the pad labeled number 2 and the yellow to the “FB” pad. If you’re using a servo that doesn’t have a servo feedback wire you only need to solder the servo signal wire to the “2” pad.BabyTriBuild62

Closeup of the soldering for extra clarity.BabyTriBuild63

Now the ESC wires. This is the way the signal wires should be connected:
Pad number 1 = Tail motor
Pad number 2 = Servo
Pad number 3 = Front Right motor
Pad number 4 = Front Left motor

F3FC Racing

F3FC Racing

All the black wires should be soldered to pads marked “-” This is important as the ESC’s might act weird otherwise.BabyTriBuild65

All hooked up.BabyTriBuild66

Time to connect the receiver. I connected my receiver in the following way; – to -, + to +, SBUS output to R3 (RX pin on UART3) and SPORT to T2 (TX pin on UART2). Also mount the nylon standoffs at this point.BabyTriBuild67

Some double sided foam tape to mount the receiver with. It’s also going to get squished down by the transmitter plate, holding it firmly in place.BabyTriBuild68


Use a zip tie to mount the video transmitter to the transmitter plate.BabyTriBuild70

Mount the transmitter top plate using the M3 nylon nuts.BabyTriBuild71

Mounting the camera is really simple. The bracket that is included with cameras such as the HS1177 and the Runcam Swift fit into the milled down grove. This grove prevents the mount from turning and holds it firmly in place.BabyTriBuild72

Use a 6mm screw to mount it. If you’re using a Runcam swift use the 2mm screws that comes with it to mount it. You might need to file slightly on the HS1177 bracket as the manufacturing tolerances on those brackets are far from perfect.BabyTriBuild73

Use a m3 lock nut on the bottom.BabyTriBuild74

Look at that fanciness.BabyTriBuild75

The camera angle can easily be changed. If you think the angle is changed too easily you can always add some thin double sided tape on the inside of the bracket, but I’ve never needed it.BabyTriBuild76

The bracket really is super light and pretty a pretty clean solution.BabyTriBuild77

Now we’re going to mount the bottom and top plate.BabyTriBuild78

The kit includes some nylon standoffs. Place these over the 4 holes that are still unused.BabyTriBuild79

Place the bottom plate on top of them.BabyTriBuild80

Use the 14mm long screws and shove them through the spacers and the unibody frame.BabyTriBuild81

Screw on the 30mm aluminium spacers.BabyTriBuild82

Mount the top plate using 4 6mm long m3 screws.BabyTriBuild83

The top plate has slots in it to fit both GoPro and Runcam 2 form factor cameras. If you’re not running a camera on the top plate you can mount the battery there instead of on the bottom if you wish.BabyTriBuild84

Time to mount the antennas. To do this we’re going to use some good old zip ties.BabyTriBuild85

The top plate has slots for mounting these zip ties. Just slip them through and tighten them down.BabyTriBuild86

Closeup of the zip tie mounting.BabyTriBuild87

Slide over some heat shrink over both the zip tie and the antenna wire.

The heat shrink shouldn’t be too big. It should be able to shrink nice and snug around the zip tie and antenna.BabyTriBuild89

Shrunk down.BabyTriBuild90

Congratulations! The build is now done! Don’t forget to load the firmware onto the board and do all the setup. This process is the exact same as on the Tricopter V4 and Mini Tricopter, so you can look on the setup videos for either and set this thing up without any problem.


Also don’t forget to do the tail tune setup.
BabyTriBuild92 BabyTriBuild93 BabyTriBuild94 BabyTriBuild95

BabyTriBuild101 BabyTriBuild96 BabyTriBuild98 BabyTriBuild99 BabyTriBuild100

This is one crazy fast and super agile tricopter. I really look forward to seeing your builds and FPV videos! Please post them in this section of the forums. Good luck with your build!

36 thoughts on “Baby Tricopter build

  1. Looks pretty clean! I spent hours last night, trial and error, getting the motor numbering correct. Mine was difficult because I used a 4-n-1 ESC and it was not numbered the way the motors are laid out and does not match cleanflight. I should have just waited the 6 hours left before you returned lol


  2. To me the directly soldered wires seem like a big failure point, especially on a racing multicopter that will be crashing into stuff at high speeds. Perhaps it would make more sense to use pin headers instead; I think most will agree that the added durability would make up for the few added grams of weight. It would also be nice if the PDB and the F3FC were stackable; this would make for a cleaner and more rugged connection.

    Anyone else feels the same?

    The rest of the build seems pretty easy, and the Baby looks absolutely lovely! Regarding the vTx, a RMRC Cricket or a Lumenier TX5G2R would probably fit nicely.


    • I garee… partly.
      I agree, Baby Tri design is nice but it have some untapped potential. Stackable PDB & F3FC like TBS’s Cube can be fantastic.
      Ad directly soldered wires: I had / have lot of 250sized racer quads. In begins i have all trought connectors. After lot of flights and crashes i removed almost all conectors…

    • You can use pinheaders if you wish. The board is designed to be able to use 9×2 pinheaders soldered on the side, just like the KISS FC. I personally find that directly soldered wire hold up better than connectors. Just a personal opinion though. Do as you wish.
      Thought about making them stackable but I mistrust connections using hard mounted connectors between 2 boards. Most connectors are not rated for the vibrations generated in our application. Soldered on wires felt a lot more robust to me at least. Also saved space on the board and reduced cost.

      • I guess it comes down to personal preference. I think if I use epoxy or hot glue the solder joints will hold up even better 🙂

    • I eye-balled my servo and it works. It’s the same setup as my mini and my v4, so I just made it close using the frame and top plate as a guide. That tool didn’t really fit my baby so I just got it close, but it seems just fine with the feedback servo


    • The ESC pads and wires come pre-tinned with lead-free solder. David re-tins the wires with 60/40 lead-based solder, which is superior because it melts at a lower temperature and thus doesn’t one to apply as much heat (which can be harmful) to the PCB. When the two types are mixed, the solder joint looks dull; it’s not a cold joint 🙂

      • I didn’t say it’s a cold joint 😉 I know the cause, I just like my joints shiny, so I apply my 63/37 or 60/40 solder until the joint is nice and shiny, possibly removing excess with iron’s tip. Maybe I’m too obsessed with that 🙂

        • I used a all-in-one ESC on mine, so all the motor wires were de-soldered and new, longer wires were added. It’s pretty easy to do and makes it a really clean setup. Don’t be scared to cut your wires, it is easy to do and just requires some 20ga silicone wire if you cut to short. Good luck!

  3. hi david,
    as always, nice build! im also interested in this copter, but i have a question:
    is it possible to make the frame (tail arm) maybe 10 – 15mm longer? just to make a little more space between the
    servo, ESC and PDB.
    by the way, making all arms 15mm longer would make it possible to install 6″ props.
    how does it sounds like?


    • The trend in the hobby is to go smaller now. I’d actually like a smaller tricopter, one that could compete with all the 130mm quads that are coming out. My baby tricopter has the exact front width dimensions as my ZMR210 quad. I love it!

      • Hi Michael,
        You can make your baby copter even smaller, running with 4″ props.
        But, tricopters dosnt have a weight/lift ratio like a Quad. Using smaller props means less lift capacity, you must use smaller batteries. Means less flight time…
        Maybe im wrong. Who knows…


        • I think the baby’s a great size. 4min flight time is +- similar with the quadcopters of the same size, though not sure about the thrust difference (i don’t have it 😉

          Now then again I also like a slightly bigger tricopter.. because im not flipping it around non-stop or racing it mainly. I like having a bit more flight time (and thus be a little slower) while still retaining some characteristics of the smaller copter:
          – light
          – transportable easily
          – small enough props and body that it doesn’t care for the wind and stuff

          with that in mind I got myself the mini-tricopter integrated frame (im actually going to get a new one because the new f3 board is neat). I used to use the old yellow-pcb from David + a flite test plate.
          Anyway, on that frame I use mini-tricopter sized arms:

          – 1400-1600kv motors (i have 1400kv atm – these: – it’s hard to find decent motors of this size these days, everyone has 2000kv+s or 800-900kv’s that are suitable .. these are fine 😉
          – 7×4 props
          – 1400mah 4S battery
          – same equipment as everyone else otherwise (aikon bl heli_s esc’s, hs1777 cam, …)

          and the whole thing flies about 13min and I often put a sony action cam (az1) for hd recording directly on top of the board. Another advantage is that the camera is well centered and has digital stabilization built-in, which makes the video look like there’s some kind of gimbal 🙂 (if the camera is not well centered these things don’t work as well for some reason)

          The other cool is that is that it fits in a turnigy half-soft-case for radios (this: WITH the radio (I use a deviation devo 7e that i modified, it’s great for its size)

          Anyhow, its like a sporty version of the big tricopter, without going all the way like the baby (or the mini – though honestly I think the baby is a better design than the mini for it’s application, sturdier smaller punchier! maybe i should also get one…)

          • I have all 3 and I love them all. The v4 is the endurance flier and stays in the air about 20 minutes, give or take. i used DJI 920kv motors and 9″ thrust boosted props. My baby is still being worked on, mostly waiting on the PIDs to be released, but it has emax 2300kv motors but uses a all-in-one ESC. The pride of my fleet is my mini, which i have re-named the Scout ship. I extended the arms 1″ and run 8″ HQ props and emax 1500kv motors for about 10-13 minute flight times. Its portable, fast, and looks like a terminator HK in the air! All have their place, and i would highly recommend getting one of each. The battery tray on the v4 will house a gimbal soon. Long endurance, gimbal stabilized in the big. Medium range and nimbleness in the Scout ship. And full on madness in the baby!!!


            • very cool thanks for sharing your fleet! I quite agree with you regarding how the baby, modified mini, and regular tri all have a place. I just think the stock mini doesn’t anymore, the baby’s much nicer for full madness, and a slightly bigger mini (at least with slower motors and bigger props) is more all-around fun (nimble & decent range like you said)

              note: i kept 7″ props because they clear the “default” arm size. I like that size mainly for transport and a little better wind resistance, but 8″+1500kv is really close and quite similar (i had that setup before in fact, both with 1500kv and 960kv.. the later flies a good big longer but not so nimble)

              Have you posted pics on RCG?

              • I have not, but I will soon. Been busy lately and also repairing my regular heli fleet and building foam airplanes with my daughter. It’s hard to keep everything up and picture worthy lol

  4. The F3FC controller recommended for a baby – can I use it on a quad? I realize it’s heresy to mention this in here, feel free to send me straight to Hel for this.

  5. Hey guys,
    I’ve a spare TBS Unify pro 800 mW 5v laying around here somewhere.. Since I’m a huge fan of the pnp core pro may it be possible to fit it into the frame? I can really use the current sensor thing because I use a futaba radio. Maybe it can sit on the back arm with the ESC on top?

  6. This has to be one of my favorite Tri’s, I have a few. However one thing that I am finding is that to change the channels on the VTX at the race field it is a real PITA. I think this could have been looked at a bit better in design when it comes to access in the top plate for push buttons or dip switches.

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