Von Ohain

Hi!

This is my first build thread, so bear with me.
Sorry for the picture quality. I got my camera ruined by a careless friend some weeks ago, so all pictures were taken with a replacement cheapie.
The HK 500 GT arrives as a kit, but with major components pre assembled.
From building the HK 450, I learned that taking apart these components and going over with locktite is a good idea.
On my 500 however, they had done a good job, and all screws that in my opinion would need locktite, was already locktited in place.
That didnt stop me from checking, anyway.
The rotor head, the tail, and the frames is pretty much complete out of the box, so building it is a matter of sticking these together, and hooking it up with its electrics.
This is how it went:




I started with mounting the cyclic servos, as they can be a bit cumbersome to reach their mounting screws after the rotor and tail is in place.
I choose the Turnigy TGY 930, because they are cheap, got good critics, and are one of the few servos that will fit this copter, as it uses a odd servo dimension.
Something in between a standard servo, and a regular mini servo.






Then I mounted the rotor head, after doing the locktite routine on every single ball link ball, screw and nut.
They were already threadlocked, but I had to check.
Link lenths were already well adjusted, and I didnt have to alter any of them to make pitch go to zero with cyclic servos in neutral.
Only adjustment I did to the head links was to make blade tracking right.





Remember to hook in the tail the tail rotor belt, when you already got the frame split up for locktiting.
Otherwise you have to split the frame again in order to hook up the belt.
You can trick the belt in place without splitting the entire frame, but it envolves a bit of bending and nasty business that can go horribly wrong, if you bend too much, and the frame wont go back to be straight.





Also remember to put in the tail boom when you hook up the belt. Otherwise you need to split either the frame again, or deassemble the preassembled tail rotor unit.
The lenght of the tail boom could possibly be an issue in some kits. Im my kit, the boom was as long as it possibly can be. The boom is set as short as possible on my heli, and that gives a good tightness on the belt. Had it been just a milimeter longer, the belt would been too tight.





Tail rotor control link hooked up. No trickery here, just straight forward. Remember locktite on the screw fastening the ball, and dont let it get into the link itself!





Vertical fin in place. No trickery here either. The fin is fastened in the same screws as is holding the tail rotor assembly together. Wich is preassembled, so this means I had to undo these two screws, put the fin in place, and screw them back on.





Screw loops CAed on to the tail boom supports.
Some people think they should not be glued in place, but just left loose. So the supports can just pup out in case of a crash, and no damage is done.
I disagree with that, since this is a 3D helicopter, you can pull just as hard negative Gs, as positive. In negative G, the tail boom supports are under stretch, and if they arent glued in place, they provide no support at all.
The twist of the tail belt also causes one of the supports to be under stretch, the other under compression. And if they areny glued, the one under stretch wont be doing anything for support.





Dont think I know anything about modellers! Oh no, I got ground crew, setting it up for me =)
Kitty has screwed the tail boom supports in place here =)





"Meow! This tail rotor got me really interested. Oh yes, I dont like fighting my boring siblings. None of that nonsense for me, only helicopters!"





Motor mounted. It was a bit tricky to reach the mounting screws, with the cyclic servos already in place.
In retrospect, i should probably put the rotor head, and gears, in place first without fastening them down.
Then put in the motor as the very first thing I did, then removed the rotor and gears, and then put down the servos.
That would been easier. But mounting the motor afterwards works too. Kind of.





Gyro glued into place with silicon. I dont like using double sided foam tape, since its too stiff in my opinion, and it looses its grip over time.
Putting the gyro on a generous, thick splash of soft silicone dampens much more vibrations, and it will not loose its grip.





Note the silicon slob under the gyro. Quite thick, and excellent damper for vibrations =)






Servo wires stripsed into place.
I tried to keep as many signal wires as possible on one side, and to the rear.
And every wire related to the power system on the the other side, to the front.
To minimize interference from the ESC switch noise, into the reciever.





Reciever hooked up...





... and stuck into place.




Soldering 4.5mm bullet connectors to the motor.






"Oh yes, me really likes these boxes they ship copters with nowadays. RRRRRRR"





"Rawrrrr, oh yes!"






ESC stripsed down and hooked up.





Paddles centered, angled up and fastened down.





And the thing is done =)



First test flight was a bit of a scare.
After a few minutes of hovering, I walked to pick up my post, flying my copter along with me.
As I landed it, rotor spinning, to pick up the post, the tail servo failed.
I didnt notice this before I were about to take off, and noticed I had no tail control.
Shortly after, all cyclic control was lost aswell, and I powered down the thing instantly, and disconnected the battery.
Back home, I noticed that the tail servo was very warm.
So I assume what happened is that the tail servo shorted, drawing so much amps that the BEC couldnt keep voltage up. Hence the cyclic servos stopped working aswell.
But I did have throttle control all time, so that must mean the reciever can work with much less operating voltage than the servos. Reassuring, I really dont want the reciever to be the first one to black out....
Luckily, I ordered one servo extra, so I just swapped the tail servo, and the thing is flying again =)
Close call, taught me to run the cheap servos in a servo driver for some minutes to test them, before I actually fly them.

The gear I fly with is:
Transmitter: Futaba T 9C AP, with Corona CT8F 8 channel, 2,4 GHz module for this particular model.
Reciever: Corona CR8D
Gyro: HK 401
Servos: Turnigy TGY 930 (all of them)
ESC: Turnigy Plush 80A BEC
Motor: Turnigy Typhoon 500, 1800Kv
Battery: 3s2p Turnigy 1800mah 40c - 50c


Conclusion:

The gyro is fine for hovering and flying around. Its definetly NOT a acrobatics or 3D capable gyro.
And this is the best China gyro I tried so far, so if you want a gyro for acrobatics, you got to pay. China isnt up for it (yet).
Same applies to the TGY 930 servo. Not fast enough for being a tail gyro on a 3D pilots copter.
As cyclic, the TGY 930 does fine. Its precise, strong and tight. It has metal gear, so it will stay tight with wear and tear aswell.
The Corona radio gear performs amazingly well, not just for being cheap, but amazingly well compared to anything.
I flew the belt cp with Corona for nearly 60 hours now, and has yet not had any glitch.
I also used it in the Surge Crusher, a RC boat. Where its wet, hot and nasty. Performs well there aswell.
Futabas stock 35MHz does not handle electronic models, as the switch noise from the ESC severely impacts the reciever. Even with PCM.
Futabas stock 2.4 GHz is downright dangerous, it blacks out with heat, and batches have been made where 2 recievers or more got the same ID.
Meaning that if 2 of these is to fly togehter, it will get as interesting as flying on the same frequency with 35MHz.
So Im very impressed with the Corona 2.4 Ghz. Better than any Futaba stock recievers I tried so far.
The batteries is a bit small, giving me only 10 mins of flying time.
I read about people putting on 2500 to 3000 mah, 6s packs in this heli.
But where do you find place for that? With canopy on, my 3s2p 1800mah packs is pushing the limit of space.
Really bad battery space on this copter. And hence, also on the original T-rex.

Thanks for reading Input and suggestions is appreciated =)


http://hobbyking.com/hobbyking/store...idProduct=9975

gi1mo2

I use the Turnigy 3000mah 6S battery in the HK500GT, and it fits, but very tight. First thing you should do is get rid of the plastic tail. Mine failed after 5 batteries (problem reported by others as well). A bolt holding the tail grip sheered from the tail shaft. Get the metail tail grips or simply the complete metal tail. I also had problems with the main gear not being round causing me to replace 2 stripped tail gears.

Von Ohain

I read about that tail problem (maybe in an earlier post of yours? ), of course too late for putting it in the same order as the copter itself.
And now my VISA is blocked, because I discovered someone had bought GM parts on it. And since i dont own any GM vehicle, the person placing that order was definetly not me!
So long story short, I wont be able to order a new tail before I get a new VISA.
I just have to hope it holds until i can get the metal one.
Im flying on just 3S in series, so I hope my low rpm can keep the plastics alive for this period.
What motor are you using, and how many Kv? I read people use 6s on this copter, but if they use 6S with a 1800 Kv motor, as mine is, the head speed will be insane?
I know the T-Rex likes head speed, but still....
With 3S, it flies fine for my basic piloting skills. Its definetly no thriller, and 3S wont get and fancy aerobatics going.

gi1mo2

I use an [link=http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9258]1800 Kv motor[/link], and had to get an 11T pinion to reduce the head speed. I also reduced the throttle max on my transmitter. Still...

Von Ohain

That explains a bit.... Its the same motor I got.
I tried fitting 4S1P 4000mah batteries, but there were no chance.
They just got into the battery bay, but were too long for the canopy to go on.
I also tried fitting 6S1P 3000mah batteries, but they really were too big. Couldnt fit in widht, length nor height.

gi1mo2

The [link=http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9262]6S1P 3000 mah[/link] battery does fit with the connectors to the front. I don't move it all the way up so the canopy fits.

Von Ohain

Thanks for the input =) I will place a metal tail, and maybe a 6s 3000mah battery on my next china order =)

gi1mo2

I find that any time I order batteries from HK, my shipment goes through Swiss Post rather than Hong Kong post office. Twice (if not three times) slower from Swiss Post than HK Post. I separate my battery order from my parts order when I can (and if economically feasible).

flyingfisherman

My Feedback: (1)

hey there i have a exi 500 2 mods that helped me . i cut the main frame from just in front of the servos down along the hole for the battery strap. the hole for the battery strat is the perficte angel andif you can make the cut land just right . you can use the hole as part of the cut this helps ceep the line strate. then move the battery tray down and re drill new holes. this will give all the room for any battery. also with the boom all you need to do is cut the boom on the part that goose in to the boom block about 5mm then make the slit that keeps the boom rotating a little longer for this i used a rat tail file of the right size. this also helps because if you leave the boomthe way it is the belt will ride the part of the boom that sticks out. this is because the tail drive gear opens up the belt to wide for the part of the boom that sticks out inside the boom block hence cutting it off. hope this helps your belt will be much happier and more free for autos. if i had better enternet i could just show a picture but i am shure there lots on the net