HK 450 MT build Thread.

[anwar]

Helipross sometimes takes a few days (I have had up to 4).

[vinay]

Guys and Gals,

Had been to jakkur yesterday and flew the heli, and all the problems had solved. The head speed last time was a bit slow, this time upped it to 2850 and the tail started slightly wagging. Have to reduce the gain slightly. But the Gyro was holding up with no drift at all. I hovered it for like 40 seconds and then my fingers started shaking. Gave the TX back to Rajesh to land it.

Also finally I put the TX in 3D mode -10 +10 with V power curve to test fly it w/o the training gear. Rajesh flew and concluded that its good for hovering and circuits but there was some problem when the heli was inverted, said that the Gyro may not be holding properly or something. Only he can comment on what was happening  as I was only a spectator.

Well to be frank it is no way even 25% as stable as the Mini Titan that Gaurav was hovering in the Video. But I believe that If I can master this Heli, I can fly any Heli in the future as bigger the Heli gets, the more stable they will be.

I also downloaded the TREX 450 V2 addon for the RF G4.5 here
http://knifeedge.com/forums/downloads.php?do=file&id=8136

The Heli is still giving me only 4 to 5 mins of hovering instead of 9 mins. I will try some other settings on this sat and see where the problem is. It should either be
1) Tail belt is tight (Adarsh said the belt tightness was perfect)
2)Pinion gear too near the main gear
3)Motor has an issue.
Any other suggestions? Though If I rotate the head manually, then it will turn 3 to 4 rev before coming to a halt. Doubting the motor.

I think that with a lower head speed(2800) my Heli is a lot stable that the one on the sim(3100). Since I dont have a choice of flying until next sunday, I will practice hovering on the sim on that 450 addon, that should make hovering my Heli a little easier. Since I was free today and no work on the Heli finally  , I thought I will work on my Tea Racer  .

http://www.rcindia.org/electric-planes/tea-racer-build-thread/

[anwar]

Great !

About the flying time, have you tried multiple batteries (or someone else's batteries) ? Another suspect is bad connections/soldering.

Good to see the tail issues are resolved. I guess you went directly to HH mode, and it worked fine. I was hoping that the gyro would hold well in 3D mode also, hoping to see Rajesh/Rotorzone pitching in with what was wrong in 3D mode. 

I am pretty sure the tail issues that Gaurav is seeing are also something simple/similar.  Just going through the radio and ensuring no mixes are enabled inadvertently is a good idea.

[vinay]

It was my batteries only and people using the same motor/ESC/11T pinion are getting 9 mins hovering time at 15 amps current draw on the same 2200 3S flight max battery. I have to solder connectors to watt meter yet and then check. The solder is all perfect anwar, Iam an electronics engineer infact .

Yup, we went directly in HH mode, where is the time to test in rate mode . Also I dont want to steal much of Rajesh's time. He is already doing more help than I expect from anybody at the field. So when I learn hovering stably, I will do the rate mode trimming as you suggested.

Yup, even I was expecting some good performance from the Gyro when doing flip/loops etc. Don't know what the problem is. 

AFAIK Gaurav has switched off revolution mixing. Hope to hover well next time. 

[RotorZone]

Check the motor timing. Wrong timing can result in higher current consumption and motor and esc heating up. But still the effect can't be as much as 50% as you are seeing.

Regarding the 3D mode, I didn't pursue it fully to find out the cause. It is working good enough for Vinay's need to hover and do circuits for now. Didn't want to risk a crash with a misbehaving heli. It was all over the place on flips. Once the gyro gave away too. Could be a setup issue or may be just bad blades, it is still not tracking properly. Also I had to take it high since it was misbehaving and that didn't aid the visibility.

There is a little play in the swash and the links are a little too loose on the balls too. All these might be adding up to the problem.

[vinay]

Timing was in low mode only.

The swash play is slightly more than the new piece that I inspected at ujjwals house on his new heli. The ball links are loose because I had removed them over a 10 times during assembling as I was learning to assemble. I plan to replace all the ball links after my next crash (Hope not to crash again though  ).

However my next Heli will be as perfect as I can possible get it too.

I cant help with the blade tracking as the blades them self are warped or the blade holders are slightly bent, which are not visible to the naked eye so near to the center. They only become apparent at the far edge of the blade.

[anwar]

The HK450TT PRO is da house   Will build and test fly in the next couple of days.

[vinay]

What electronics are u planning to use?

[anwar]

Transferring from my Trex 450 SE v2, which has a broken frame.

http://www.rcindia.org/rc-people/anwar-from-kerala/msg640/#msg640

[vinay]

Looks Yummy  but those things are way too expensive for me But since you fly 3D, you have to use those only I suppose.

[ujjwaana]

<Posting on Vinay's behalf, as he is far in his native town fields and flying 20 sorties a day!!>

Some doubts form Vinay:

1. Should the ESC Break setting ON/OFF ?
2. After 4-5 min of flight some metallic "Kir...Kir" sound is coming  out .. any idea what could be the culprit ?

[gauravag]

Great going !! Looks like Vinay is having some fun. Cant wait to see some pictures/videos.

From what i know, no need to set up ESC braking. No-brake mode should be OK. Because even if the motor is braked, the rotor would spin due to the autorotation gear. So no reason to use energy and brake the motor.

Now the Kir-kir sound could be coming from the motor, or from one of the bearings. Since it comes after 4-5 mins could be related to motor temperature.
But need more info to help further. Does it come at a specific throttle/speed ? Is it a high pitched metallic squeal ?

Others, more experienced here, can guide you better here.

[sunk?]

hi guys,
yes 'brake' should be set at 'off' this is only for 'planes' not heli.
regards
don

[vinay]

AFAIK the brake settings should be set to ON.

Here is what happens.

When the brake is off and you pull the throttle down, I noted that the Turnigh PLUSH ESC slowly and steadily reduces the motor speed to zero (takes bloody 3 to 4 seconds). This will eat away the gears in case of a crash.

If brake set to ON, then when you pull the Hold switch or pull down the throttle then the ESC will immideatly stop the main gear from spinning and getting eaten away. I experimented this morning and I strongly feel Like BRAKE SHOULD BE ON! 

[gauravag]

Welcome back Vinay. We all missed your presence here.

I think When you have the brake to OFF, and you pull down the throttle, the ESC simply cuts power, and the motor rotates with its inertia.

When the motor rotates with its inertia, and with no input voltage, current is induced in the coil. When the brake mode is ON, the ESC shorts the circuit, and hence the motor comes to an instant halt.

Thats what i deduced.

[vinay]

Ya, may be you are right, But the brakes ON actually does the the right job to the heli right? in saving the gears from being eaten. Also I do not think its the inertia. What I noted was that even though I tried slowing down the motor with my finger with brakes off, the motor hesitated to slow down and took its own time. 

[anwar]

Right.  Brake ON leaves power in the coil to forcefully stop the blades. On some ESCs, there is "OFF, Soft Brake and Hard Brake" settings, the last two differing on how abrupt the stopping is.

When it comes to helis with auto-rotations ability (one way bearing), it does not really matter whether brake is on or off, either way the blades will freewheel. One helis without auto capability, brake is critical, that it should be turned off.

The preferred setting for brake is OFF for all helis in general.

[vinay]

Anwar think of the scenario in NGChannel aircraft accidents investigation style

With brakes OFF:
1)Saturday @ 6: 15 AM 30 seconds  : The Heli is about to hit a wall in 2 seconds
2)Saturday @ 6: 15 AM 31 seconds  : You suddenly pull down the Hold switch realizing a crash in advance.
3)Saturday @ 6: 15 AM 32 seconds  : The Heli hits the wall and the head is stopped instantaneous. Forget free wheeling here. The head is stopped in microseconds.
4)Saturday @ 6: 15 AM 32.2 seconds: The ESC is braked OFF and is still spinning the wheel.
5)Saturday @ 6: 15 AM 32.4 seconds: The motor had main gear and some other parts for break fast!  

With brakes ON:
1)Sunday @ 6: 15 AM 30 seconds  : The Heli is about to hit a wall in 2 seconds
2)Sunday @ 6: 15 AM 31 seconds  : You suddenly pull down the Hold switch realizing a crash in advance.
3)Sunday @ 6: 15 AM 31.8 seconds: The ESC is braked ON and Gear is stopped. (But motor can still rotate if rotated by hands)
4)Sunday @ 6: 15 AM 32 seconds  : The Heli hits the wall and the head is stopped instantaneous. Forget free wheeling here. The head is stopped in microseconds.
5)Sunday @ 6: 15 AM 32.4 seconds: The Main gear and other parts are saved!  

Correct me If I am wrong.

Also free wheeling is a concept that helps in case of power failure or motor failure to land the heli. The one way bearing does nothing in case of a crash to save the gear. Its just a mechanism to glide down.

[vinay]

Now I want a scenario why brakes should be OFF.

[vinay]

Welcome back Vinay. We all missed your presence here.

RCI Missed me? I thought every body had some peace of mind for a few days here at RCI! 

[anwar]

I have seen various reasons for this being discussed.

1. On helis without the one-way autorotation setup, you lose any remaining possibility for landing with some rpm in the blades.

2. Sudden brake in some cases cause the teeth of the main gear to grind off, due to inertia from the head.

3. Sudden stops cause the heli to swerve on the tail un-commanded, as if an unknown amount of rudder is applied.

4. In your example, if the blades hit something in a crash during the time the ESC is applying the brakes, that does more damage than it would have otherwise.

5. And finally, if you are like me, there will be one day in your life when you forget to turn on 3D mode yet go inverted  Brake is that last thing you want in that scenario !

[vinay]

Well ANwar here is what I feel. Dont consider this as an argument but rather as an active discussion. I have least experience in RC and my doubts are high.

I have seen various reasons for this being discussed.

1. On helis without the one-way autorotation setup, you lose any remaining possibility for landing with some rpm in the blades.
Will leave this alone as we are discussing TREX/ autorotation.

2. Sudden brake in some cases cause the teeth of the main gear to grind off, due to inertia from the head.
Will leave this alone as we are discussing TREX/ autorotation. This will not affect in the case of HK450/Trexes as there is autorotation. In our case, the inertia is just of that of the main gear alone and nothing else. I tried it today morning and it works like a charm on a cheap quality EBAY gear.

3. Sudden stops cause the heli to swerve on the tail un-commanded, as if an unknown amount of rudder is applied.
I totally agree, I recently had a battery connector failure for 1/2 a second and I experienced this. But we pull the hold only when we know we are anyway gonna crash right!

4. In your example, if the blades hit something in a crash during the time the ESC is applying the brakes, that does more damage than it would have otherwise.
Not really. It is better that the main gear is stopped by the ESC rather than the motor still continue to spin against the accident's force(of course slowing down slowly) causing more damage.


5. And finally, if you are like me, there will be one day in your life when you forget to turn on 3D mode yet go inverted  Brake is that last thing you want in that scenario !
Brake stops the main gear, but autorotation goes on. By the way it reminds me that Rajesh did the same thing with his atom 500  

[vinay]

For a change.  HK plastik and MT.

The MT crashed into a tall grass when hovering nose in.

Main gear shredded, both jesus bolts broken, HXT gears shredded so changed them the MG 14s, no problems with MG 14 this time. Main shaft slighty slightly slightly bent, I may replace it as it is causing a lil vibrations.

[anwar]

Will leave this alone as we are discussing TREX/ autorotation.

If the discussion is about auto-rotation enabled models, then your example of hitting the wall is completely superfluous, as there is no real difference at the blade level in either case. 

The only thing that matters is the possibility of main gear teeth getting ripped of due to the inertia between the main gear and the motor pinion itself. And that is why the general advice is always to let the main gear the motor freewheel, by turning off brakes.

And even though I mentioned that the presence of the autorotation gear pretty much nullifies the effect of brake (and such helis are the norm these days), I kept on mixing examples of ones with and without that capability.  In summary, brake has become less of an issue now, except for the main gear teeth.

[vinay]

Flew 6 batteries today. Temp was around 38 degree celcius (100 degree F).

I did not take my cap and I literally killed myself in the sun for 4 hrs.  

Here is what I noted.

1)The new HK401 gyro is still not holding (with the DS480). Its slightly drifting. On my first pack it held well then started to drift after some time. Temperature is the problem?  :confused: If yes next time I will tie a white piece of cloth around the gyro or place it below the Heli.

2)I heard some metallic rubbing noise. That kind a 'kirr kirr' noise that comes when a knife is sharpened against a rotating surface. At first I thought it was the motor, now I am doubting the main shaft bearings as they were slightly notchy after 2 crashes. Any idea from where else it may come. It comes at above 60% throttle.

3)Didnt like the slow head speed. I tried 0 75 75 75 80 and it was crappy on 2215 11t. Put it back to 0 75 90 90 100 and it was fine.