|May 28, 2012, 01:10 PM|
Another E-Sky HBK build
I will start this build with the radio gear, simply because I have to center the servos before they go in the frame.
First some soldering, my ESC needs a Deans plug. I'm using Exceed-RC proton 30A (looks to be one of many HobbyWing clones) and it comes with some variation of banana plugs (Pic #1). Last time I ordered a similar ESC it came with 12awg battery wires, for some reason this time I'm seeing a 16awg wires on this one, hopefully they will not melt when I fly. It has been a while since I soldered wires that thin to a ESC, this time I have the pleasure of keeping my fingerprints intact. This is also a good time to solder the BEC wires if you plan to use a BEC.
After soldering is done, I keep my fingers crossed and plug in the ESC to a Turnigy programming card, hopefully I'm right about this ESC being a HobbyWing clone and the card will not burn. Without any further suspense I can say that the card worked perfectly. Set the brake to off, very soft start, and a high LiPo cutoff voltage. Be aware that this ESC gets quite hot, so that external BEC might be a good idea after all.
For this Heli I use a DX6i, but everything I do applies to any other radio that is compatible with helis, of course the menus will not be the same, but you have a user's manual for that.
Now I can plug the receiver and center the servos. Firstly I create a new model in my radio, then change model type to heli, bind to the receiver, then plug all of the servos into the rudder channel, since I know it's centered (as long as I don't touch the stick). Then I mix and match servo horns to find which ones will be closest to 90 degrees.
Now I can move on to the frame, with lots of pictures to come. The helis I received this time came broken down for shipping convenience, so this is a good opportunity to check everything while putting it back together.
Very important, when handling the belt, make sure it never gets bent beyond what is absolutely necessary. It's a very unpleasant experience to have a belt snap mid flight, also inspect it frequently and keep it lubed with 100% silicone spray. I have noticed that the teeth on these belts get ground down after a few dozen flights and the tail starts to slip. You will hear a cracking noise when doing hard flips and other tail demanding maneuvers, Either the belt tension is not enough or it's worn, If it is worn then this is when you should replace the belt, don't try to get "one more flight" that might be your last flight for that heli. Another high maintenance thing are the head dampeners, when those get worn, a tail strike is possible, you will see the heli nod it's nose when inverted, land immediately and replace head dampeners, the stock ones get worn every twenty or so "hard" flights.
Now the important stuff. This heli needs a belt roller mod, otherwise the roillers will eat the belt in no time. The problem is that the rollers do not align with front pulley and need to be lowered (Pic #2). I use a tiny washer above each roller and find some longer screws to keep everything in place. I am unable to take the roller apart after doing this mod, so I can't take any pictures of how this all looks, but it's trivial enough. The measurements of the washers I used are 0.37mm thick, 2.78mm outside and 1.53 inside diameters. While I'm on the washer topic, tail box needs some too, since the screws can wedge in and break the tail box, this I can take the pictures of, so Pic #3.
Before closing the frame halves, pull the belt through the tail boom (make sure it's not twisted inside), assemble the main shaft with the pulley and the bearings, then lube one way bearing and put the main gear on. Slip the main shaft through the belt (Pic #4). Now the frame halves can be closed. First clamp the lower bearing while pushing it up to prevent any up-down play in the main shaft, then push the upper main shaft bearing down with the collar while tightening. If there's any vertical play in the main shaft, move the collar down.
Next comes the tail. I have taken mine apart just to check if everything is the way it should be, but I don't recommend doing this. E-Sky uses far too much thread locker at the factory and the risk of stripping or snapping bolts is really high. Also there's no real need to take the tails apart from balancing tail blades.
Now I separate the swashplate from the rest of the head and slide it over the main shaft. This is required because next step is placing servos and they keep the anti-rotation bracket from coming out, which keeps the swash from being removed or put on the main shaft. (there's a way to unscrew the anti-rotation pin from the swash, but it's such a small part that I can't aim a screw driver good enough to get it in.)
Next step is placing servos in the frame. I screw the ball links in the servo arms first. I use the furthest hole on the horn, since I'm obsessed about getting as much throws as I can, of course I later check if nothing in the head binds, if it does, use a hole closer to the center.
Now I set up the swash mixing in the radio. This is for DX6i, but these steps work on any radio with 120 degree CCPM mixing. Some radios, like RDS8000 are tolerant of both, rear and front elevator 120CCPM, make sure you choose the correct option first, DX6i has no such setting, but there's a built in workaround. The elevator servo (front in this heli) goes to elevator channel, aileron and pitch servos are chosen by deduction, first I plug in the rear left servo in the aileron channel and rear right in aux. Then move collective up and down. The swash should move up and down, but my rear left servo is reversed, so I go to servo reversing menu and reverse the aileron channel. Now all my servos move correctly as far as collective is concerned, luckily enough, aileron and elevator work too, but if they did not, here's what I would do. If the ailerons were reversed, I would un-reverse the aileron servo, reverse the aux and switch the aileron and aux channels (or go to swash mix on DX6i and set "aile" to -100 instead of 100, 60 is default) For reversed elevator servo only reversing the "elev" in the DX6i works, other radios have a different swash mix. If collective was reversed I would reverse the elevator servo and then switch aileron and aux channels.
Next step is swash leveling. I set throttle hold pitch curve to 50% flat for that. Then I use a swash leveling tool and ball link pliers to make sure that the swash is perfectly level. When leveling swash, make sure to not adjust it's height too much. For every two turns in one direction for one servo, I put one turn in opposite direction for the other two. If you do change the height of the swashplate while leveling it, don't worry too much, it will get fixed when setting main blades for zero pitch. (Pic #5)
Now that the swashplate is level, I can set my throttle hold pitch curve back to where it was and turn off the radio. Now I decided that it is a good time to set correct belt tension. When pulling the tail boom out the belt rollers will spread, this is not good at all, so I use a thin long cable tie (Pic #6) to keep the frame from spreading. How do you know how tight should the belt be? I don't know, I like my belts loose to minimize friction, but not too loose to start skipping or touching the sides of the tail boom. I also spool the heli up and move the tail servo from one side to the next listening and watching the belt jump, then I add tension as required.
Now I install the motor and solder the 3.5mm banana plugs. I set the gear mesh by feel, this gives me a more accurate mesh than the paper method. I play around with the gear trying to feel just a tiny bit of play, then turn the main gear around a few times and find the high spot, then loosen the screws and again get that tiny amount of play between the teeth, then thread lock and leave it. E-Sky's brass gear eventually wears out after a few hundred flights, so bees wax of 100% silicone lube is quite important to keep the wear down.
Next I installed the rudder servo. I set up my helis to fly in rate mode as well as heading hold, but only heading hold is necessary for most people, so I won't describe the setup in detail. The gyro goes to rudder channel and gain goes to gear (with DX6i).
One thing a lot of people complain about when it comes to E-Sky Honey Bee King 3 and 4 is that these helis are tail heavy. I have anticipated this problem too and decided to make a battery tray allowing me to mount the battery far forward. I dont't know what kind of plastic it is that I'm using, but it can be cut like glass (scratch and bend to break). I use 3M outdoor double sided mounting tape to hold the tray down and use Velcro type material on the battery and the tray. (Pic #6, #7 & #8)
Now the only thing that's left is the head setup. I will take apart the head for this and rebuild it just to make sure everything is the way I want it. I will not write on how to take it apart or how to put it back together, only how to set it up correctly.
Step one is centering the flybar This is to make sure that both paddles are exactly the same distance from the center. I take the paddles off (counting the turns so I can later put them back on the same way) and then I use a digital caliper to measure the distance from both ends to the control arms. Once the flybar is centered, the paddles go back on. I then use the pitch gauge combined with paddle leveler tool to set the paddles to zero pitch. Then I use the caliper again to double check the paddle distance from the center of flybar. Afterwards I spool it up without main blades and make sure that the paddles track perfectly. And lastly I use thread locker on the paddle screws.
Next I make sure that the washout bracket and flybar mixing arms are perfectly level at 50% collective. If the washout bracket and mixing arms are not level, adjust the servo to swashplate arms (equal amount for each servo) to center the washout bracket. At this point it is possible that you will see binding between the head pieces if your throws and swash mixes are at 100% under full collective and full cyclic, do not worry too much about that yet, later I will lower the mixes to a more reasonable amount. If this binding still bothers you, get a center hub (with the necessary links) from a Belt CPX. I believe that head hub eliminates some of the binding between grips and flybar links.
Next make sure that the short links between Bell-Hiller mixers and the blade grips are exactly the same length. At this point I also repack the main blade grips, I don't trust the factory to do this right. Next I balance the blades and mount them, this time I was pleasantly surprised by a perfectly balanced set of blades right out of the package (I won't match CG this time). Now it is very important to set the main blade angles with a pitch gauge I can definitely see I need a few turns on both blades this time. Set your collective to 50% and adjust the longest links on the head (swash to Bell-Hiller) to set the pitch to zero. I advise to lock the flybar with some adhesive tape or just keep it level while measuring the pitch. The collective range I ended up with is +10 and -12, I will fix that with my pitch curves to get even +- 10 degrees in stunt mode and throttle hold.
Now I track the blades, lube every bearing I can find and go test fly this baby.
To convert this heli to a King 4 I need canopy mounting posts. After removing tail braces and fins, the King 4 fuselage converts this thing to a King 4.
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