|May 02, 2007, 02:47 AM|
Axe CP Full Brushless Conversion w/Pics
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 ESCíS
Gyro: Futaba GY240
From Tower Hobbies: HPI cone washers (LXN050), Hitec 24 ďextension wire (LXHZW3), GWS tail housing (LXHHE4), Custom Works cone spacers (LXNUA4)
From Radio Shack: Radio Shack's Normally-Closed momentary micro switch (275-1548).
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 Iíve found to do this is to pop off the flybar links at the swashplate and remove the head bolt (see pic). Itís 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 didnít 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 motorís 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.
Iíve 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 donít 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. Hereís 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). Itís 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 thatís it.
OK, now onto the tail motor. Using the OE tail housing itís a simple bolt in procedure.
I didnít go that route. I used a GWS tail housing because itís beefier (see pics). It doesnít 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 thatís 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 donít 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 itíd 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 didnít protrude into the hole, but it did so I ground it down till it was flush. Notice the pattern yet. Iím paranoid about electrical shorts. At this point itís 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 24Ē servo extension for the wiring on the tail motor itís a snug fit through the tail shaft, but itíll go (see pic). I fed just enough wire through the tail shaft from the ďboom sideĒ to make the connection to the motor. I did it this way so I wouldnít 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. Itís 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 ESCís. This is pretty straight forward as you can see from the pics. First I soldered the motor connectors on to both ESCís. Then I soldered the battery wires from both ESCís onto a common connector. I used a Deanís Ultra Plug. For mounting I used 4Ē zip ties for the main ESC and double-stick foam tape for the tail ESC. After that itís a matter of hooking up the motor wires and Rx connectors. Donít forget to disable the tail ESCís 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 didnít seem to work right. It seemed like a pole on the motor was burnt out. It turns out the ďSuper-SoftĒ start option on the ESC doesnít have the power to start the Axeís heavy (compared to a propeller) rotor. Took me a while to figure it out, but resetting the ESC to ďSoftĒ start solved the problem.
Problem number two. The tail ESC wouldnít arm. Turns out the GY240 and ESC donít like each other. As close as I can figure these particular ESCís 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 ďno Rx signalĒ 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 thatís my Axe CP full BL conversion. I hope you found it helpful.
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|May 02, 2007, 02:57 AM|
Wal-Mart Tail boom
... and now the Wal-Mart knitting needle-to-tail boom mod. At three or four bucks for two of them itís a great mod. Itís also fairly straight-forward. Just pop off the buttons and cut to size. I did this with a Dremel and cut-off wheel. The hole from the tail shaft screw is 5mm from the edge. The hard part is grinding or sanding down the tail shaft evenly. I did it with a Dremel and used a screw as an arbor, but putting the tail shaft in a drill would probably work better. You could also have a machine shop lathe it down. Going that route Iíd bring a couple tail shafts.
Aside from that I changed out some of the Axeís hardware too. I changed the head button screw to a Dubro 3mm x 6 flat head screws (Tower Hobbies-(LXFRJ8). I thought it looked better . I also did the popular cap-screw mod on the blade grips, but they hit the blades when they folded forward so I went with Heli-Max 2mm x 5 button head screws (LXLBR0) and Heli-Max 2 x 4 x 0.3mm washers. The washerís slightly smaller outer diameter allows it to only contact the inner race of the bearing. This helps alleviate that ďsticky collectiveĒ problem the Axe sometimes exhibits after a changing a broken blade grip. The lower profile bolt no longer hits the blade. The Button head does require a smaller size 1.27mm Allen though as you can see. Though this size is rare itís SAE counterpart isnít, usually listed as .05Ē or .050Ē itís the same exact size. I use Integy 0.05Ē drivers (LXKTH7) and they work great.
Well thatís all Iíve got so far so good luck and happy flying.
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|May 02, 2007, 02:58 AM|
My flight report on the BL set-up
The tail has a lot of power. In fact I recommend the AMMO 12-30-3850 if youíre going to a BL tail motor and maybe even a DD tail if youíre not worried about bending the motorís shaft in a crash. The 3850 is actually the one I meant to get. I have to pay closer attention when ordering .
The head speed is way up. Itís too high actually. Itís 2880 rpm in a hover and 3000 rpm at full throttle. The thing is a rocket. Iím still using the stock Tx so I donít have the luxury of Throttle/Pitch curves therefore I canít optimize my set up. Even if I could optimize the curves Iím nowhere near the skill level to take advantage of 3000 rpm.
Iím also stuck with the OE 14T pinion. Iíve heard itís a weird pitch. Regardless I havenít found any other pinions that will work. The run time is down about 3 minutes or so from the brushed motor set-up and Iím not happy about that either. With my pinion problem Iím now looking to go to a 2900Kv motor. I look at it this way since there doesnít seem to be a direct correlation going from brushed to brushless I look at this first motor as a point of reference plus it was only $15. Anyway Iíll let you know how it goes when I get the new one.
|May 02, 2007, 03:10 AM|
Long Beach, CA
Joined Sep 2006
Really good thread. Funny thing is that I just recently modded my axe to brushless & HH gyro, and I picked up the 8mm needles at walmart. Got em in blue and gold. 4 for half the price of the heli-max piece is a bargain, and the walls are a bit thicker so they should hold up a little stronger than the stock noodle, i mean boom.
|May 07, 2007, 12:42 PM|
Well I've put a few flights on the BL set-up and it's working well save for one problem. During quick or sharp rudder inputs the tail jumps around and wind seems to make it worse. This caused a nice crash the other day which luckily only resulted in a broken strut. I'm told this may be gyro resonance since the motor isn't acting fast enough the 240 is over compensating. I'm going to try a few things to rectify or at least lesson this effect such as a DD tail and tweeking the gain, but until I do I can't recommend a BL tail.
I also found out from a fellow poster that Freestyle Hobby has a belt driven tail in the works for the Axe so that's another option.
|May 07, 2007, 11:56 PM|
Very nice Heliko !
It looks a lot at what I would like to do but, what I have is only on paper
Very informative on the pinion and other problems you've got.
Do you think that choosing a different tail ESC like the Electrifly would resolve the arming problem ?
In fact your very informative "build" is a revelation I think I would stick with a main motor BL mod only
|May 08, 2007, 01:00 AM|
Hey DaySpeed thanks.
Dayspeed did you mean the Great Planes ESC's? I have one, but after I ordered it I found that their "automatic voltage cut-off feature" cut's power too soon and you end up loosing the tail before the main motor. That's no good so it's going back.
As far as I know the Castle Creations Thunderbird 9 and Phoenix 10 are pretty good and don't seem to have arming issues, but you need the PC link in addition to the ESC to program them so it could get costly. About $50 for the T-bird/link combo and $70 for the Phoenix/link combo. There's also the Hextronic 10A ESC from United Hobbies, but I'm not positive it would work.
Your idea to only upgrade the main motor is a sound one. If you bought the stuff from United Hobbies it also would be fairly inexpensive. At least till I get the my tail issues ironed out.
As for the GWS housing the OE bearings work perfect.
|May 08, 2007, 07:20 AM|
Joined Jan 2007
Wait, was this while using the stock 3-1 or after your brushless conversion? Btw, I ordered that 3100kv motor, I'll let you know how it works out.
|May 08, 2007, 11:55 AM|
Yes, I meant the Great planes ESC. Oups, so if I also use that for the main motor it's going down at 67%? Not for helis !!
I'll check the other ESCs.
I guess I will let you spent the money for now
|May 08, 2007, 03:35 PM|
I may actually go with a Pixie 7 and the OE tail motor (since it's already a N60) with a maybe a DD T/R until I can get some more info on how to make this work better or get better at flying so I can recover when the tail twitches.
To illustrate further the helis fine inside, but outside the wind and my more aggressive flying style and the twitchyness of the 240/BL tail combo have resulted in 5 broken grips, 2 broken tail rotors as well as a broken skid support and a bent mainshaft. All in the past couple days.
After reading numerous posts on BL tails I don't thnk I can get the performance I want yet. I say yet because I believe someone out there is working on some kind of gizmo to smooth out the communication between the gyro, ESC and BL tail motor.
|May 08, 2007, 04:40 PM|
Listening ? Me ? Of course I'm listening !!
what do you mean I 'm not listening ??
what did you say?
I red the spec for the Electrifly, Great Planes ESC but did not realized that it would simply cut at 67% of voltage red and that you can't change it.
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