HK 450 MT build Thread.

[anwar]

The whole Ball Link assembly is 100% metal. If the screws are tite ill leave it as it is or loctite it with blue loctite.

Better to put blue loctite yourself, just to be sure.  Be sure to clean the screws before putting them back with loctite.

[vinay]

Anwar, I have a problem. All these days I have flown the Highly responsive 3D models on the sim. Which usually have a pitch curve of something like

Pitch = 0 25 50 75 100
Throttle = 100 90 100(From align manual. No personal experience here.)

Now If I have to Configure the Heli with Curves for the beginners hover like the below, Iam scared I will crash.:

Pitch = 45(Negative by -1 degree) 60 75  90 100
Throttle = 0 25 50 75 100

Because for me, pulling the stick down means PUSHING the Heli Down.

Also if I want to set the Heli in 3D mode like throttle 100 90 100, what is the head speed I need to configure? 2650 at 100 % for a beginner?

I wont be doing an inverted flights or anything. Just hovering only. But I want the pitch stick to behave like the 3D models as I am used to It.

Also to see the Helis stability and initial maiden flight should I use the 0 25 50 75 100 Throttle curve? with a appropriate pitch curve as I mentioned above?

[anwar]

There are two schools of thought on this.

1) Separate pitch curve for normal flight and 3D flight (-4, +4, +9 low-mid-high for normal and -10,0,+10 for 3D for these types of helis).

2) Same curve for both normal and 3D flight (-10,0,+10).

I started with [1], but experience has taught me to change to [2].  Instead of adjusting pitch curve for normal, adjust your throttle curve so that you can have stable hover at around 60% (or 65%) stick position.  But this also means that you should be careful when you come down to land.  

This gets a bit more interesting when you add the "throttle hold curve" into the mix. Having a single curve for normal, sport, 3D and hold modes avoids issues like the heli jumping or dropping suddenly when you change modes. Also when you start practicing autorotations (on bigger helis), you will be familiar territory as far as pitch is concerned.

[vinay]

ok, I will try to understand what you told later

For now, I have removed the ball link assemble and the total head from the main shaft to put the Swash plate leveler in there. Nice little tool really a must have for 9 USD.

Since RDS does not allow me to program EPA on the cyclics, I need to do all the adjustments manually by loosening/tightening the ball links a little/ and trim a little.
I will try to level the swash plate as much as possible safely manually, then use the sub trims to trim them. No other options for me on the RDS

But when it comes to flying many people prefer RDS for the crisp controls over the DX7.

[anwar]

Since RDS does not allow me to program EPA on the cyclics, I need to do all the adjustments manually by loosening/tightening the ball links a little/ and trim a little.
I will try to level the swash plate as much as possible safely manually, then use the sub trims to trim them. No other options for me on the RDS

I don't use EPA for normal setup of helis.  All you need to get as close as possible to zero pitch (that also means the various head pieces are as level as possible) *at mid-stick*, with a 0-50-100 pitch curve.  If the mechanical setup alone does not allow you to get there, use sub-trim (as little as possible). 

If the RDS does not support reversing of an entire control (aileron/elevator/pitch), that would cause some extra work.

EPA is used for removing aileron-pitch and elevator-pitch interactions, which is not a real concern (until you start doing tic-tocs in one place etc).

Regarding throttle curve for normal, assuming you leave the pitch at full range (-10,0,+10) or so, you will need something like 0, 35, 50, 65, 100.  The idea is to have enough RPM for hovering around 60% (or 65%) throttle, and have enough rpm around the 30% to 40% position to land without bleeding off too much.

[vinay]

Beware anabond blue users, use as little as possible even in high vibration areas.!!!! A Small amount of anabond got on the shaft and the whole ball link assemble got jammed. Phew. I had to put the shaft on the whise and hammer it with a cutting and a nose plier carefully.

Learning a lot of lessons . Its testing my patience to the maAAAAAAAAAAAXXXXXXXXXXXXXXxIIIIIIIIIIIIMMMUUUMMM. I am not giving up.

I need to finish it today at any cost.

[gauravag]

Take it easy. You tend to make mistakes when you try to hurry things up.

[vinay]

Gaurav, Iam in fact assembling it carefully and slowly. But there are some mistakes no matter how carefull you are, you learn only after committing those mistakes 

I wanna finish this at any cost. Too bad I cant maiden it till saturday.

[vinay]

Swash plate leveling at low medium and high pitch. Pitch curve = -15 50 125% Radio used RDS8000



Test after 80% assembly without main rotor.

Pitch curve =   -15 50 125%
Throttle curve = 18 8 18



Pending work:
1)Install main rotor blades and adjust pitch.

2)Maiden it.  

Some more Pics:

[anwar]

Throttle curve = 18 8 18

   

That means your motor will always be running, as you are never at zero throttle !  Or did I miss something obvious ?

[anwar]

Plus, it looks like you may have built the head wrong, just can't say for sure from the pictures posted so far.  Can you post some close-up shots of the head ?

You should also route your servo wires away from the sharp edges of the frame, if possible (cable-ties help!).

[rckatty]

Vinay are you trying to level the swash plate using the RDS8000, then the below link will help you do it.

http://www.helifreak.com/showpost.php?p=766655&postcount=5

Hope this helps.

[vinay]

Anwar, The throttle curve of 18 8 18 was used inside the house to test the Heli, If I had used Higher and the Gyros gain was higher then the tail would have started moving, Its just an experimental value. I have not yet decided on the final values.

Well just wondering, For all the 3D Helis, the motor will always be on right, atleast for 3d flying?

I will post some close up pics once I get some time.

Also I have used zip ties in 3 places apart from tying the ESC, I have trimmed them so you are not able to see them, and 2 are on the other side. None of the metal frame edges are sharp, they are very smooth finish, and as it lools in the photo, the wire are comfortably sitting, not loose or not very tight. Just a proper fit. , I spent 2.5 Hrs to finish the wiring mess.

Karthik, Thanks for the link, thats what I have been looking for, the manual is a useless piece of crap. I have leveled out the swash plate already physically itself as much as possible and using the Servo centering option. Let me go through the site and see what else the radios allows me to do.

Some questions:

1)I have fixed the flybar paddles in such a way that, they are perfectly parallel, when I tested it at 25 % throttle and no input from the sticks its not blowing any air, up or down? Is this the right way to do? Or should they have some angle of attack?

2)Any tips/links on what all I need to take care before maidening, like how much gain/delay on the gyro, head speed to tail speed ratios etc?

3) How to check CG?

Thanks.

[anwar]

Anwar, The throttle curve of 18 8 18 was used inside the house to test the Heli, If I had used Higher and the Gyros gain was higher then the tail would have started moving, Its just an experimental value. I have not yet decided on the final values.

Well just wondering, For all the 3D Helis, the motor will always be on right, atleast for 3d flying?

I understand that these are not final values.  But a throttle curve for normal flying should always have "0" as the value for the low stick position.  Only for 3D flight would you go for a non-zero value for the low stick position (and yes, the motor will always be on), but even then you will need to switch back to a non-3D mode for landing and shutdown (where the low stick position value is again zero). 

Overall, just wanted to stress that a "V" shaped throttle curve is only for 3D / sport flying, otherwise you could get hurt. It would have made more sense if the values were "0 8 18"

[anwar]

Also I have used zip ties in 3 places apart from tying the ESC, I have trimmed them so you are not able to see them, and 2 are on the other side. None of the metal frame edges are sharp, they are very smooth finish, and as it lools in the photo, the wire are comfortably sitting, not loose or not very tight. Just a proper fit. , I spent 2.5 Hrs to finish the wiring mess.

If you are confident about the shard edges not cutting into the wire insulation, then we are fine 

We do usually route some of the wires from the servos on the front side of the heli to the back "inside" the frame though.  There are usually small slits for the cable-ties to go through in the main shaft area of the frame.  This also makes the heli look neater with less wires exposed.

Some questions:

1)I have fixed the flybar paddles in such a way that, they are perfectly parallel, when I tested it at 25 % throttle and no input from the sticks its not blowing any air, up or down? Is this the right way to do? Or should they have some angle of attack?

2)Any tips/links on what all I need to take care before maidening, like how much gain/delay on the gyro, head speed to tail speed ratios etc?

3) How to check CG?

1. Just make the paddles parallel to the "flybar cage". (http://video.helifreak.com/?subpath=/finless/trex450pro&filename=headp2.wmv , you may need to register).

2. Gain is something you set by experimentation, start with around 40. The important thing is to slowly spool up, and see if the heli goes into a spin, in which case, you have to reverse the small dip switch thingy on the gyro.  Delay should not matter in this case, as you seem to be using a fast enough digital servo.  There is no headspeed to tailspeed ratio you can manually adjust. It is a belt-connected drive, which means that part is decided for you already. Just spool up slowly, and see if the tail is responding to the right inputs.

3. I usually check it by hanging the heli on the main blades (around the middle part).  CG is usually not a big issues on these helis.

[vinay]

Got your point anwar, I will ask a 100 questions when it comes to programming later, And I will not maiden it unless i get a green signal from you guys that 'all iiz well' after complete setup.

Some pics you asked for, The head is rotating w/o problems and with different inputs from the TX and that is how it arrived from HK, Something wrong you noticed ? Please look at the photos, that you asked for.

I think its time for you to buy additional disk space on the server

[vinay]

Anwar, I am sorry, I meant to ask Head speed to tail Pitch ratio, Once I am ready to fly the heli, to counter act the head speed rotation, there should be an initial pitch on the tail right? Or should I just leave that to the gyro. I may be wrong here.

Also the gyro goes to Headlock mode only on gain above 50. Other wise its a rate gyro. Also I can set the gain through the RDS8000 remotely.

[anwar]

Headlock mode is more "forgiving" to improper setup.  One quick way to setup the tail is to put it in rate mode (non head-lock), make sure the slider is around middle, then put it back in heading-hold mode, and go fly. 

The right/perfect way to do it is to place it around centre in rate mode, and fly it in rate mode itself and compensate for any drift by mechanically adjusting the tail control linkage length.  To be absolutely perfect, you have to put it in 3D mode (after the above mechanical correction in rate mode), take the heli up high (all in rate mode), bring it down fast using lots of negative collective, and stop it quickly with a quick pump of high collective pitch. If the tail still holds (ie, does not swing in any direction), then you are good to go in terms of mechanical setup.  After this, go back to heading hold mode, and fly like that until you need to rebuild any part of the tail.

[anwar]

Some pics you asked for, The head is rotating w/o problems and with different inputs from the TX and that is how it arrived from HK, Something wrong you noticed ? Please look at the photos, that you asked for.

I think its time for you to buy additional disk space on the server

Seems fine   Just looked weird in one of the earlier pictures.

[RotorZone]

The right/perfect way to do it is to place it around centre in rate mode, and fly it and compensate for any drift by mechanically adjusting the tail control linkage length. 

Reminds me, I'm yet to do this on my Atom. Have been putting off doing this during the initial flights and then forgot since I fly only on HH mode.

To be absolutely perfect, you have to put it in 3D mode, take the heli up high (all in rate mode), bring it down fast using lots of negative collective, and stop it quickly with a quick pump of high collective pitch. If the tail still holds (ie, does not swing in any direction), then you are good to go in terms of mechanical setup. 

What does this indicate about the mechanical setup ? Thought this test was for gain/delay.

[anwar]

What does this indicate about the mechanical setup ? Thought this test was for gain/delay.

It ensures perfectness of the whole setup (the last turn that is possibly required even after trimming in rate mode using plain hovering, and delay). 

Gain itself is another matter in my experience, where a tail-out inverted 3D flight seems to be the best criteria/test.  Increase the gain until the tail wags (frequent wags where movement to each side is small) in tail-out inverted flight, then dial down the gain until it subsides.  Nothing tests gyro performance like tail-out inverted flight (like when you are doing a "hurricane" pattern maneuver).

[RotorZone]

It ensures perfectness of the whole setup (the last turn that is possibly required even after trimming in rate mode using plain hovering, and delay). 

Ok will see if it shows up during my trimming. I doubt I'll encounter this situation as the gyro holds nicely through all maneuvers already. The Align GP750 is working far better than a Futaba GY401.

[anwar]

Ok will see if it shows up during my trimming. I doubt I'll encounter this situation as the gyro holds nicely through all maneuvers already.

And I have been waiting for a video of yours forever

The Align GP750 is working far better than a Futaba GY401.

Yep, it is a good gyro. Holds very well on the Trex 500.

[RotorZone]

And I have been waiting for a video of yours forever

I still  haven't taken any videos. For now, here is a pic from the maiden.

[sk010962]

hey vinay this is the video of 250 HK build by nuttcaze. Probably it might give some more additional info needed for the build

Part 1:
http://www.youtube.com/watch?v=IiV-BW2ttuI&feature=sdig&et=1264607903.73

Part 2:
http://www.youtube.com/watch?v=r5vuaGRbN58&feature=related