Cheap $14 camera from eBay (Hobbyking has it too now), attached with velcro and zip tie on the horizontal stabilizer of my CopterX 450:
Watch out: there are 4 versions of this camera for sale on eBay, but only the one with a microSDHC slot is the good version. There is a video comparison here: http://www.youtube.com/watch?v=LT8rqod3Gj0.
IMPORTANT SAFETY NOTICE: This heli is not supposed to be flown in such a confined space. It can hurt you badly if it hits you. I’ve taken a few safety steps since the first flight given the risks I was taking: always wearing safety glasses, never hovering with the tail pointed at me in case the tail blades come off and also not flying at eye level for the same reason. The throttle hold switch is always ready to be flicked (very important) — if you listen carefully, you’ll notice the RPMs going down before it crashed. My living room is “L” shaped so I was standing at the “foot” of it, kinda sideways to the heli. Safety first, but I really wanted to fly that thing Now I fly in a school gym.
This is one of the few steps remaining before my first test flight. I’ve used a swashplate leveling tool instead of trying to eyeball it or using a bubble level. I bought it from ReadyHeli and it is was pretty simple to use (Hobbyking has it now for only 3 bucks). Everything now is level, from the servo arms all the way up to the blade holders.
I didn’t have to readjust any linkage lengths; it was just a matter of adjusting the servo subtrims and travel adjustments (AKA ATV or End Points) on my transmitter. I think that’s because I had my linkage lengths already measured according to my previous post.
When using the leveling tool, I found it easier to use a flashlight to check whether the tool is touching all three points in the swashplate. Have the flashlight some 15cm from the swashplate and hold a piece of paper on the other side of the arm. Then check the shadow on the paper: if there is any gap between the swashplate arm and the tool, you’ll see a thin horizontal bright line in the shadow projected on the paper. A few subtrim clicks up or down will eliminate that gap. Maybe this is overkill, but at least I can tell that my swashplate is perfectly level
As suggested in forums, setup the rotor head symmetrically: at midstick, with 50 on the pitch curve, everything should be centered/level/at 90 degrees angles. That includes cyclic servos, seesaw holder, flybar cage, blade holders, etc. The videos from MikeysRC were very helpful for this step.
Simply fold the blades back over the boom, hold the flybar and look at the heli from the side. If the two blades overlap exactly, it’s 0 degrees. I don’t know how accurate you can get “by-ear”, but this method is much more reliable than a pitch gauge. I also set the maximum positive and negative pitch this way, fine tuning in the field by comparing upright / inverted climb out.
There are many options on how to mount the electronics on this heli. I liked the idea of installing motor-related stuff in the front, near the motor (ESC and battery) and radio-related stuff in the back (receiver, remote receiver and gyro):
Servo wires: the wires of all my cyclic servos go through only one side of the frame. I didn’t like the idea of having a servo wire too close to the main shaft, like I’ve seen in other builds.
Receiver and ESC: I’ve used adhesive backed Velcro to mount the receiver (Spektrum AR6200) and the ESC (Turnigy 40A Sentry). The AR6200 was positioned in a way so that the antenna wires are sticking out from the frame. Before applying any velcro or sticky foam, I cleaned the surfaces with rubbing alcohol.
AR6200 remote receiver: it was mounted with the standard sticky foam included in the CopterX 450 kit. I had to cut two small squares in the left top and bottom corners of the foam to make room for the two tail boom block screws. I also made sure to mount the remote receiver slightly lower than the tail boom block to protect it during a crash. In a crash, the flybar paddles might (or probably will?) hit that part and destroy your expensive receiver.
G401B Gyro: the gyro was mounted on the bottom of the boom block to protect it from a tail boom strike. This is very important, especially if you’re using a $100+ gyro (not me ). Some people say it is best to mount the G401B with a metal plate in between (boom block + foam + metal plate + foam + gyro) to avoid tail drift. The only metal place I had lying around was a PC slot cover, but it worked well after some cutting (25mm long). I used Futaba gyro foam pads (FUTQ1000) instead of the original ones from CopterX.
Foam and metal plate
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G401B Gyro mounted with foam + metal plate + foam
Tail control rod: the CopterX one is too long, making the servo arm hit the gyro. I had to cut the rod by 3.8mm to be able to move the servo away from the gyro. Instead of cutting 3.8mm from only one side, I cut 1.9mm from both sides so there is still thread left. Now the servo arm can move freely in either direction without binding.
Check and if required re-screw the tail rotor control arm (it’s the plastic “L”-shaped arm). Mine wasn’t fully screwed on.
Trim the two tail control ball links (plastic arms) with fine sand paper to make sure they move freely. Mine were clearly moving with too much friction. These are the surfaces I had to sand:
I’ve followed Mikey’s RC video guides and things went smoothly. The only annoying part is getting the two front servos in place, as you have to bend the frame a little bit to insert them.
Like Mikey explained, do not connect the servo arms to the servos yet!
I’ve updated my post about assembling the frame, as there is no need to apply thread lock to certain screws until you reach this step and install the servos. At least for the HXT900 servos, there is no other way besides bending the frame… So these are the frame screws to remove (only from one side):
Motor installed! I actually did this last weekend but got a chance to blog it only now…
I’ve soldered the bullet connectors of the ESC and motor and got the pinion gear installed at the correct height on the motor shaft. Then it was just a matter of screwing the motor to the motor mount and making sure the gap between the pinion and main gear is OK.
Items required:
Motor pinion gear (I’m using a 11T pinion on the Typhoon 2215H motor)
Two button head screws to attach the motor (the screw size depends on your motor — both the the 2215H and 2836-3700 use M3 screws, and 5mm is enough)
Steady hands to screw the motor in a hard-to-reach location
Before you screw the motor into the frame, decide where in the frame you’ll want to have your battery, ESC and receiver installed. Depending on the ESC location, you’ll want your motor wires pointing towards the front or back of the helicopter. Check this Finless Bob video on electronics placement options. I’ve decided to have my wires pointing towards the front as my ESC will stay at the horizontal mount in the front.
Make sure to buy a pinion gear for the correct motor shaft size (they’re usually 3.17mm). Both Turnigy 2215H and 2836-3700 motors use 3.17mm.
The 2836-3700 motor has (in theory) a 3.17mm shaft, but it is actually a bit larger than 3.17mm. My pinion gear wouldn’t fit so I had to sand the shaft a little. Anyway, I decided to use the 2215H for now.
When attaching shrink wrap to the motor and ESC connectors, don’t make them too long otherwise it’s harder to bend the wires. In my motor I used 20mm long shrink wrap but 12mm would have been enough. Not a big deal, though:
The Mystery gyro G401B (sold by DealExtreme, HobbyKing, xmseller, etc) requires some modifications before using it. It’s a $20 gyro$14 gyro, so don’t expect it to have the same build quality of a $150 Futaba GY401
Two major problems were reported in the G401B forum threads:
The gyro circuit board is not firmly attached to the plastic case, causing problems to the gyro operation.
The solder joints of the tiny switch for digital/analog/normal/reverse mode can break off the board when flipping the switches.
Items required:
Hot glue gun (I used a small 10W dual temp gun)
Small piece of soft foam – 2.5cm x 2.5cm, about 0.8cm thick (1″ x 1″, 1/3″ thick)
How to fix:
It seems like a lot of work but this is actually a 5-minute job:
Unscrew the gyro case lid and carefully remove the circuit board from the plastic case.
Add hot glue to the solder joints of the switch block (both sides) so it is secure on the board. If you add too much glue, it will be harder to put it back (I had to carefully trim the excess glue with an x-acto knife).
Apply hot glue to the servo solders on the board, so the wires are held not only by the solders. Don’t let the hot glue gun touch the wires as they will melt.
While you’re there, apply hot glue to the solder joints of the two vertical circuit boards.
Apply hot glue to each corner of the case and insert the board again. Use something long and thin (like a small screw driver) to press the board against the glue so it gets fixed on the plastic case.
Insert the square piece of foam when screwing the case lid back. It will help keep the board in a tight, fixed position.
NOTE: Steps 3 and 4 are optional and might be considered overkill by some. I did them anyway as I didn’t see any disadvantages.
Gyro circuit board, before applying hot glue:
Board glued and gyro ready to be closed:
Soft foam:
UPDATE 02/Dec/2010:Trainboy64 has posted a nice video on YouTube showing basically the same thing:
I prefer to use cheap but reasonably reliable parts than crashing expensive ones. At $4 each servo, I don’t mind stripping the plastic gears whenever I crash. The replacement gear set is only $0.90 and I’ve got a few of those stocked already. It’s quite a difference between spending $12 (3x $4) vs. $90 (3x $30) for a brand-name servo. Anyway, I might upgrade my cyclic servos to digital and/or faster ones later.
). Some people say it is best to mount the G401B with a metal plate in between (boom block + foam + metal plate + foam + gyro) to avoid tail drift. The only metal place I had lying around was a PC slot cover, but it worked well after some cutting (25mm long). I used Futaba gyro foam pads (FUTQ1000) instead of the original ones from CopterX.
# tail -f /blog/comments