Tricopter Build Manual

Last Updated: 3/9/2012 for kit version 1.1

The Pro Tricopter Delrin Kit will provide you a precise tricopter assembly.  To achieve the best results, take your time and follow this manual closely, especially when assembling the ZeroYawSlop Yaw assembly. Some of the steps are unique and require your attention to get right. We assume reasonable RC model building experience, know how to solder, have wired ESCs and motors, and have wired RC RXs before.

To do the assembly, you will need the following tools:

  • Exacto Knife
  • 1/8″ drill bit and drill
  • .050″ allen wrench for axle collars (included in kit v1.1)
  • Allen wrench for frame screws
  • Hot Glue
  • Thread Locker such as Loctite
  • Small phillips screwdriver

Also see RCExplorer’s Build Manual of the Pro Tricopter Delrin Kit for more pictures and information. Just realize that information will change as the kit is updated and certain pictures and instructions may be outdated at other sites. Always come here for the most up-to-date version of the build manual.

Click pictures in this manual to zoom in.

General assembly instructions

  • Secure all stell nuts with Loctite so that they won’t come loose from vibrations. A nut/screw coming loose at the wrong moment can cause an easily avoided crash.
  • This kit is made from precision laser cut Delrin and other materials. Unlike plywood or balsa RC kits that often require sanding and cutting to make interlocking parts fit, the interlocking parts in this kit fit perfectly. If you’re asked to make modifications to the parts (adding “chamfers”), you have to follow the instructions carefully as we will only ask you to make tiny adjustments that are almost not visible. Take your time…
  • The kit includes many small parts that are easy to loose. We suggest you use a cloth on your work surface and place the contents of the small parts bag into a small bowl so that screws, nuts, etc. can’t easily roll and bounce off your work surface.
  • The kit includes many nylon screws and nuts. Nylon screws are extremely light adding almost no weight to the kit. The same screws in steel would weigh over 30 grams, which was the reason we’re using Nylon instead. Keep in mind that Nylon screws strip extremely easily. Do not use any force. If you feel resistance to your turning of the screw, stop turning! I recommend you only use your fingers to tighten the nuts onto the Nylon screws as you will have much more feel for when to stop turning. If you use tools like a screw driver and needle-nose pliers, you will likely not feel when you should stop tightening. Do not over-tighten the Nylon screws/nuts. Once they strip, they are not going to work well, if at all.
  • Minimize prop and motor vibrations by carefully and precisely balancing your props. If you don’t have a good prop balancer, I suggest you get one. You will go through a lot of props and you will always want to use balanced props for the best flight performance.
  • Click all pictures to see larger versions.

Parts list

Updated parts list for kit version 1.1

2Main Delrin Plates
1Orange Flight Controller Cover
3Clear Acrylic Feet/Legs
1Bamboo Camera Mount
4Regular Motor Mount Plates
2Yaw Motor Mount Plates
1Yaw side plate
1Yaw side "L" shape plateServo Holder
1Yaw top plate
1Yaw bottom plate (with 3 slots)
1Servo bracket
2Axle holders
1Yaw motor mount vertical plate
1Yaw motor mount vertical plate with servo horn
1Jig (Delrin)Helps you to mark the exact location of the pivot hole for the front arms. Also helps with the markings you need on the booms.
830mm M3 Nylon ScrewsCamera Mount
1120mm M3 Nylon ScrewsMotor Mount to Boom Connections and Yaw to Boom Connection
46mm M3 Nylon ScrewsFlight Controller Cover
23M3 Nylon Nuts
1420mm M2 Steel ScrewsMotors using M2 Screws (out-runners or other motors will require different hardware)
1020mm M3 Steel ScrewsArm pivot, arm stop, optional arm fold-back stop. Frame to back arm connections
14M2 Steel Nuts
10M3 Steel Nuts
425mm Nylon StandoffFlight Controller Cover
610mm Nylon Standoff2 for the connection between front of frame plates. 4 Flight Controller Cover stand-off extensions (if needed).
1Yaw AxleYaw assembly
21/8" Axle Collars with set screwYaw assembly
1Allen KeyFor axle collar set screws
2Ball-bearingsYaw assembly
820mm Nylon Spacers (black)Camera Mount
1410mm Nylon Spacers (black)Motor Mounts
11/4" OD, 1/8" ID Nylon SpacerYaw Axle spacer
16" of NeopreneFlight Controller Mounting
2Black ball linksPush-rod assembly
2Black 2-56 socket cap screwsPush-rod assembly
2Silver washers flat on one side, curved on the otherPush-rod assembly
22-56 nutsPush-rod assembly
11" 2-56 threaded rodPush-rod assembly


A great build log by Gallaway with lots of pictures — many more than are in this manual. This build uses fiberglass booms, but most of the pictures are relevant no matter what boom material you choose.

Prepare All Parts

The laser cut parts come with a protective film covering. Remove it from all the parts by peeling off a small corner and then pull the hole piece off slowly. Also make sure you push out any pieces that did not yet fall out. The Delrin motor mounts, for example, may have the cut out hole pieces still stuck inside the cut-out. Push these pieces out with a small screw driver.

The Yaw Assembly

Prepare the Axle Holders

The axle will need to be fitted with the two square axle holders (see picture).  The axle holders will hold the axle very tightly and without any play.  This will require you to push the axle into the Delrin with some force to squeeze the axle into the hole, which by design is smaller then the diameter of the axle.  To help the axle squeeze into the Delrin hole and achieve a tight fit, use an exacto knife and shave a tiny bit of the edge of the hole to create a “chamfer”. Here is what a chamfer looks like.

A chamfer helps the axle enter the Delrin holder. Do NOT increase the overall size of the hole! The picture does not show an actual kit part, but simply illustrates what a "chamfer" looks like

It is critical that you do NOT increase the overall size of the hole. It will seem as if the axle’s diameter is too large to fit into the Delrin — that’s intended.

The axle holder with Chamfer. The hole's maximum diameter is still the original, tight diameter.

Once you have added the Chamfer, lay the Delrin piece flat on your table/workbench and place the axle perpendicular into the chamfered hole.

Now, tap the axle into the hole gently like you would hammering a nail into a wall. Just do it gently and keep the axle perpendicular on the Delrin as you do it. Tap once or twice and then look at the Delrin part from the bottom to see if the axle has come all the way to the other side. Do not try to press the axle into the Delrin with your bare hands! The axle ends are very sharp to cut through the Delrin. Once the axle made it through the hole, twist the Delrin piece further onto the axle:

Note that the Delrin should now be at a perfect 90 degrees to the axle. Repeat the same with the second holder.  You should end with the following:

Add one of the 1 / 8″ axle collars onto the short end of the axle. Make sure that the axle only sticks out about 0.5mm from the collar and that the Delrin piece is butted up right against the collar. Use Loctite to secure the collar’s set screw in place. Now seat the two Delrin holders into the Delrin piece shown in the picture below.  Make sure you are using the Delrin piece that has a slot in-between the two axle holders.  This slot will later hold the servo mount and it is important to know that you are working with the bottom of the Yaw assembly (as opposed to the top, which does not have this slot).

Now add the top part to the other side of the axle holders.

Add the L shaped plate which will be your servo mount. Take the servo bracket and push it into the two slots in the L-shape (see picture). Once the servo bracket is pushed through the L-shape, you will push it up all the way so that the servo bracket enters the slot in the bottom of the Yaw assembly. DO THIS WITH CARE as the servo bracket is thin. If you push each side un-evenly, it may snap due to the uneven pressure. Make sure the servo bracket is all the way up and completely seated in the bottom of the Yaw assembly.

Yaw assembly with bottom, top, and L-shaped Servo holder.

Now, close the Yaw assembly with the remaining side wall and slide the 1 / 4 ” nylon spacer onto the axle.

This picture is incorrectly not showing the servo bracket, which we added in the step above.

The axle should now be fitted in the Yaw assembly without any play and without being able to move it or twist it.

Now, we are going to fit the ball-bearings into the motor mount for the Yaw assembly.  To prepare the two Delrin pieces that will hold the ball-bearings, add a Chamfer like we did to the Axle holders.  Again, do NOT increase the overall diameter of the hole.  The ball-bearings will be pressed into the holes with force and they will fit tightly without needing glue.

Add a tiny Chamfer to help the ball-bearings find their way into the Delrin.

Now, do the same to the second Delrin piece that has the servo horn on it.  Lay both Delrin pieces flat on your table/workbench and position the ball-bearings right over the holes.  The ball-bearings have a flange that face up.  The Chamfer should help you position the ball-bearings so that they are lying right above the hole.

Now, take a hard flat object and lay it on top of the ball-bearing. Push with your hand onto the hard flat object — lean onto the object with all your weight until the ball-bearing squeezes into the Delrin. You should clearly feel as the Delrin gives way to the hard ball-bearing.  The flange on the ball-bearing will stop the ball-bearing from going too far into the Delrin.

Now that the ball-bearings are tightly fitted into the motor mount pieces, take the top and bottom motor mount plates and finish the assembly.  The flange of the ball bearings should face outward (the two flanges should not face each other).  This will prevent the ball-bearings from ever sliding out of the Delrin.

Finish the motor mount by adding the top plate of the mount, then slide the motor mount assembly onto the axle.  Use the 2nd 1/8″ collar to fix the motor mount in place.  You do not want any play between the motor mount and the Yaw assembly.  Secure the collar’s set-screw with Loctite.

Now, make sure that the servo “L” and bracket assembly is straight and that the L that holds the servo mount is not bent.  Next, secure the servo bracket with some Hot Glue.  You do not need a lot of hot glue. Just fill the holes so that the servo bracket can’t slide back down.

Prepare Your Booms

Take 10mm square wood (or other material) and cut your desired booms length. The two front arms are the same length. The back arm with the Yaw assembly is 3 inches shorter. So, as an example, if you were building a slow-flyer FPV set-up, you may choose 20″ long booms. You would cut 2 booms to 20″ and the back boom to 17″.

Preparing the front arms

Your kit comes with a jig that you’ll use to make a mark (use a needle) so you know where to drill the pivot holes for the front arms. Mark both pivot holes by lining the jig’s end up with the arm’s end. Now drill the holes using a 1/8″ drill bit.

Use the jig to find pivot hole location and where to cut 'notches'

Next, use the jig on the other end of the front arms to mark where you will add notches. To add notches use an exacto knife and cut out a little “V” shape. You will use the two notches that are closer to each other. The notches will hold the nylon screws that secure the motor mounts onto the arms. This prevents the motor mounts sliding off the arms. Do not make the notches deeper than they need to be. They just need to be deep enough so that the nylon screws can pass through the holes in the motor mount plates.

Next, secure two motor mount plates onto the boom with M3 / 20mm nylon screws and nuts. Never use force with the Nylon screws. They strip very easily, but are strong enough to hold the motor mounts in place. User your fingers to tighten the nut onto the screw.

Prepare the back arm

The back arm is secured to the frame plates with the same technique as the motor mounts are to the front arms, but is using 4 M3 20mm steel screws and nuts. Use the jig to mark your notch locations, but note that you’ll use the two notches in the jig that are furthest apart.

Slide the yaw assembly onto the end of the back arm as far as it’ll go. Use a needle to mark the two holes you will need to drill to secure the yaw assembly onto the back arm. Drill the holes with a 1/8″ (or M3) drill bit. Secure the yaw with 2 20mm nylon screws and nuts. Add a 3rd nylon screw through the yaw assembly to press the two yaw sidewalls together so they can’t came apart.

Assemble the frame

The main body is assembled with the orange flight controller cover, the body ‘top’ plate (which has 2 large holes), the body ‘middle’ plate (which has 3 large holes), and the bamboo camera mount.

First, attach the 4 25mm nylon male/female standoffs to the top plate. The 2 in the back are secured via a nylon nut and the 2 in the front are secured with the short 10mm male/female standoffs (which will be sandwiched in-between the top and middle plates). You will later add the orange flight controller cover to the top with 6mm nylon screws. Attach the short 10mm standoffs with nuts. The top and middle plates are now connected.

Take your front arms and place them into position. Use M3 steel screws and nuts to secure the two front arms via the pivot holes. Use 4 M3 20mm steel screws to attach the back arm. Add M3 steel screws to the front of the main frame plates which will stop the front arms from bending out too far. Attach the bamboo camera mount to the middle plate of the frame with 8 30mm nylon screws/nuts and black 20mm nylon spacers.

Attach the motors

To attach the motors, use the 20mm M2 steel screws and nuts. Use black 10mm round spacers in-between the motor mount plates.

Yaw Servo & Push-Rod

UPDATE: Since March 2012 the kit ships with black DuBro ball-links and no longer with the white ball-links. The DuBro ball links come with a black ball-link that includes a steel ball, a black socket cap M2 screw, a silver steel spacer that has a flat surface on one side and a rounded surface on the other, and an M2 steel nut. The  screw is first inserted into the stell ball of the ball link, then through the spacer with the rounded surface facing the ball, then through the Yaw control horn (or Servo horn), and then the M2 nut (the included M2 nuts are a bit larger than the rest of the M2 nuts in the kit).

Slide the yaw servo into the servo bracket with the servo arm facing down (away from the arm). Build a push-rod with the included ball links and the included 2-56 threaded rod. The threaded rod may be too long for your servo depending on how you mount it. You can easily shorten it with a bolt cutter. The black plastic ball links may also need to be shortened a little bit depending on how you mount your servo. Make sure the threaded rod is not twisted too far into the ball links.


Finish Up

Finish up your assembly with wiring of the ESCs and battery harness. Affix some velcro to the bottom of the camera mount (velcro is not included in the kit) where your battery will be located. Attach your flight controller to the top of the frame with your preferred selection of foams such as neoprene and double sided foam tape. Attach the feet with zip ties or with the included 16mm M3 steel screws and nuts.

Reference Pictures