!!!WARNING!!!
This is a very, very long post.


Parts list: (see pic)

Main motor: KB20-40-17L 3400k from United Hobbies

Tail motor: AMMO 12-30-4110 from Tower Hobbies

Main ESC: H-Wing Pentium 18amp (HW P18A) from U.H.

Tail ESC: H-Wing Pentium 6A /.8bec/6g Speed Controller (HW-6A) from U.H.

Programming Card: OEMRC P-Card for H-Wing ESC’S

Gyro: Futaba GY240


Misc. Parts:

From Tower Hobbies: HPI cone washers (LXN050), Hitec 24 “extension wire (LXHZW3), GWS tail housing (LXHHE4), Custom Works cone spacers (LXNUA4)

From Radio Shack: Radio Shack's Normally-Closed momentary micro switch (275-1548).


The Build
OK here we go! As you know taking the blades off helps a lot. Or you can take off the whole rotorhead. The easiest method I’ve found to do this is to pop off the flybar links at the swashplate and remove the head bolt (see pic). It’s only 3 points and the head will then pull off in one piece. Now that access is easier I moved on to removing the main motor, 3-in-1, and tail motor. Taking the tail boom off makes this easier too.


With the motors out I then removed the pinions. I used a GWS micro-heli pinion remover (see pic). It worked well on the main motor, but I had previously pushed the tail motor pinion on further to increase clearance between it and the tail rotor so it didn’t work there. I used some small diagonal cutters and pried it off carefully. It came off pretty easy so no big deal. Putting the pinions on the BL motor was easy enough too. On the tail motor I did cut about 1-1.5mm off the end of the shaft with a Dremel again to maintain clearance between the pinion and tail rotor.


I took a measurement from between the OE motor’s can to the bottom of the pinion so when I re-installed the pinion on the BL motor it would be centered vertically with the main gear. My pinion was a bit off so I adjusted my measurements to center it. To install the pinion I used a piece of hard wood. Since the shaft protrudes past the gear I also drilled a hole in the board for shaft relief. With that I was able to press the gear on. The tail can be done the same way.
I’ve also heard C-clamps work very well too.


When installing the main motor I had to file the slots in the frame to get the screws straight going into the threaded holes in the motor. I used the original 2.5mm x 5mm cap screws with the HPI cone washers (see pic). They worked great. The washers don’t bend or cone. They come pre-coned. On some motors the side of the washer may have to be filed to clear the bearing housing on the motor (see pic). It depends on your motor. Here’s a word of caution on threading in the screws. Do not use a ball type hex driver here. I used a 2mm Integy driver from Tower (LXKTJ2). It’s just too easy to cross thread into the aluminum housing of the motor. I also made sure the wires were toward the rear of the heli. Once you set your mesh tighten her up and that’s it.

OK, now onto the tail motor. Using the OE tail housing it’s a simple bolt in procedure.


I didn’t go that route. I used a GWS tail housing because it’s beefier (see pics). It doesn’t have long slots for the motor screws like the OE housing so the motor fits very securely. In fact with the pinion installed it took some work to get it in. The GWS housing also has a different offset from the OE housing so it requires a spacer (see pic). A Custom Works cone washer worked perfect (see pic). With the smaller part of the cone against the bearing it only contacts the part of the bearing that’s spinning which is good.


My tail motor came with 4 screws. I thought they were a little long so I cut off a millimeter or so just to make sure they don’t contact the windings.


OK, so now the tail motor is mounted in the housing. At this point you need to salvage the old tail shaft or get a new one. When putting the tail shaft into the tail housing make sure the threaded hole for the boom screw lines up with the bottom of the tail housing like on the OE housing. I dabbed a little CA on the tail shaft to keep it secure in the housing. I added a step here using a modified Wal- Mart knitting needle (more on this later) I had to reduce the diameter of the tail shaft so it’d fit inside the needle (see pic). The needle has thicker walls.


Then I test fitted the shaft in the boom (see pic). I also wanted to make sure the tail shaft/boom screw didn’t protrude into the hole, but it did so I ground it down till it was flush. Notice the pattern yet. I’m paranoid about electrical shorts. At this point it’s nearly ready to go into the tail boom, but before that the motor still has to be wired.


For the tail motor wires I used the Hitec 24” servo extension for the wiring on the tail motor it’s a snug fit through the tail shaft, but it’ll go (see pic). I fed just enough wire through the tail shaft from the “boom side” to make the connection to the motor. I did it this way so I wouldn’t have to pull the whole length of wire through the tail shaft. I then desoldered the connectors and soldered the Hitec servo wire directly to the motor. After determining proper length I resoldered the connectors on the Hitec servo extension wire (see pic). I then pulled it through the boom using fishing line. It’s tight to get the connectors and wire down through the hole between the main gear and boom without taking out either the servos or main-gear (see pic). You may want remove to either or both of them out to make it easier. You could also solder the connectors on after the wires are through the boom and around the bend.


Now we move on to the ESC’s. This is pretty straight forward as you can see from the pics. First I soldered the motor connectors on to both ESC’s. Then I soldered the battery wires from both ESC’s onto a common connector. I used a Dean’s Ultra Plug. For mounting I used 4” zip ties for the main ESC and double-stick foam tape for the tail ESC. After that it’s a matter of hooking up the motor wires and Rx connectors. Don’t forget to disable the tail ESC’s BEC (see pics). I cut the negative and positive wires out completely. The only down-side is now I need to use the BEC from the main ESC to use the program card with my tail esc. To rectify this problem I took a Y-servo harness and cut out the white signal wire on one side (see pic).


Now I have had some little problems pop-up.

First the main motor didn’t seem to work right. It seemed like a pole on the motor was burnt out. It turns out the “Super-Soft” start option on the ESC doesn’t have the power to start the Axe’s heavy (compared to a propeller) rotor. Took me a while to figure it out, but resetting the ESC to “Soft” start solved the problem.


Problem number two. The tail ESC wouldn’t arm. Turns out the GY240 and ESC don’t like each other. As close as I can figure these particular ESC’s need to power up and receive a signal from the Rx at the same time. The gyro initialization caused a problem. After some experimenting I found that if I interrupted the Rx signal between the gyro and ESC after the gyro armed the ESC would beep a “no Rx signal” code. I discovered that if I unplugged the ESC from the gyro then plugged it back in it would arm. Cool! However instead of pulling it apart every time I installed a normally closed momentary switch to temporarily interrupt the signal (see pic). It worked out well. Now I wait to arm the tail till the body is on and the heli is ready to fly.


The only catch is that the throttle must be at zero which means the gyro has to give a 0% throttle signal. If the heli has been turned counter-clockwise then it will not have 0% throttle.
So I just to turn it clockwise till the servo armed. The other thing I did with the tail ESC is set 0% throttle at mid-stick instead of far left. Not bad considering that none of this stuff was designed to work together.


Anyway that’s my Axe CP full BL conversion. I hope you found it helpful.