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building a new Hobby King 550 flybarless

#1
Dear friends, I am a beginner in rc but I am so enthusiast. I already have a blade 450 but nowadays I want to build my own.
I am fascinated about the 550 hk flybarless.
Could I please ask you to suggest to me how to choose the components?
Would you be so kind to tell me which servos should I get, which asc, which pieces so to complete the unit?
I would love to make it as much "turnigy branded" as possible, and also I could do with a suggestion built with the cheaper items of the turnigy range, and another one with the most expensive one, so to learn about the technical differences.
thank you for your support!
S
 
#2
If any of the viewers has just 5 minutes, i would love to hear all kind of suggestions.
Including: yo kid go buy a glider first! Hahahahaha :)
Help me out, let me have a steep learning curve, i am sure there are many quality teachers in here.
Thanks!
 

colorex

Rotor Riot!
Mentor
#3
If any of the viewers has just 5 minutes, i would love to hear all kind of suggestions.
Including: yo kid go buy a glider first! Hahahahaha :)
Help me out, let me have a steep learning curve, i am sure there are many quality teachers in here.
Thanks!
Tip: Don't limit yourself to just Turnigy brand - I admit I use Turnigy LiPos, Turnigy neckstraps, a Turnigy charger, Turnigy ESC's, a Turnigy motor, Turnigy programming card, Turnigy LED strips... etc

but I also have other brands that do work really well... I have a RedBrick 25amp ESC, I use Hextronix DT750's on my tricopters, I use a DX6i for a transmitter, GWS props, etc...

Almost all Turnigy stuff is good, but don't think all other stuff is crap. Read all the reviews to see if it's worth it!
 
#4
Hi there, how have you been doing! :) yes thanks, I promise that I will treasure my dx6i.
How do I choose servos, esc and motors? How do I interpret the specs?
For servos I dont know how to pick their size and then their strength.
For esc I dont know what to take into account when considering its max current.
For motors I dont know what to consider for kilo voltage...
Most of the reviews are interresting but I still fail the techincal basics so to make up my own opinion...

You would not be a big fan of the 9xr then? I just wish it will have sliders so to control flaps in a bixler 2 for example...
Thanks, take care! :)
 

Ak Flyer

Fly the wings off
Mentor
#5
I posted in your other thread but I forgot to add that I would consider the belt drive version. Check out the Josh and Josh reviews of the 550's. They had nothing but problems with the torque tube gears and it was a factory problem not something they could tune out. They had two failures in two flights. They had to convert to a belt drive to make a full flight for the review.
 
#7
Wow, this forum is amazing, I am so grateful for your availability! Yes, let's stick to this thread, I will divert the other one into this from now on.
I will check the details with more patience tomorrow. As for the torque tube, I followed up on that and at least from a commercial standpoint, HK and later the Joshes claimed that an updated version of it (the current one I would like to buy) solved the issue effectively.
Your contribution is excellent, I already wanted to get the zyx unit.
As for the asc and motor, can you please tell me what specs are important? What do the kv represent in motors, and what should I aim for max amps in an asc. If I can choose, could I have all the electronics running at 6V or are there drawbacks?
On the 550 can I also choose how many s cells and how many mAh to supply it, freely?
Thanks, I'd love to pay you back...
S
 

Ak Flyer

Fly the wings off
Mentor
#8
Well, the KV is crucial with all motor setups. KV is a speed rating. ie. 1000 kv x 22.2 volts (6S battery) = motor turns 22,200 rpm at full throttle. The recommended 1400 kv motor x 22.2 volts = 31,080 rpm. This x gear ratio gives you your head speed. Since head speed is a critical number in helicopters I don't stray far from recommendations. Higher head speed gives you more stability from wind etc. but makes your inputs react much much faster giving it a twitchy feel compared to a lower head speed. You can change your throttle settings of course to slow it down, but you don't want to be working half throttle all the time. You should be setup and geared to have a max throttle that will not cause the blade tips to go supersonic or over run the recommended speed of any components.

You can run a 5S or 6S setup but you will be limited with 5S and end up pulling more amps to do the same job. You are better off with a 6S setup. The mah is up to you but to get any sort of run time you will need the recommended 4000-5000 mah. The cell count (5S or 6S) is the voltage. That determines how the system will operate. The mah is how long you can run at that voltage. You also need to account for the discharge rating (C-rating) of the batteries. If you require a constant 50 amps but your batteries can only provide 30 then you are doomed to failure. Helicopters require lots of amps so you can't just get the cheapest batteries all the time.

As far as radios go, I fly Spektrum and I love it. I am a big fan of Futaba radios and Spektrum radios, I don't have any experience with the Turnigy radios but I hear about just as many problems from them as anyone else. I really wouldn't worry about the telemetry with your heli. I would just fly with your DX6i from your 450 and call it good. I have the telemetry on my DX8 and I don't use it much. With my planes I have time to check the telemetry but I really don't have time to look at the little screen when I'm flying my heli's. As long as you have your setup correct and you have a soft cut off on your esc then you can land safely. If you have a hard cut off then you can always autorotate, if you have that in your bag of tricks. The nice thing is 550's have so much more rotor mass than 450's that auto's are much much easier. The big thing is to have a timer set and listen to it. Start with 4 minutes and see how much battery you have left. Then try 5 minutes or 5.5, working your way up to a time that you a comfortable with. Never exceed your timer.

Now, for electronics. You can run 6.0 volts with no problems as long as your servos have a 6.0 volt rating. Almost all Rx's will handle 9 volts with no problems. If you don't see a 6.0 volt rating then don't push it. You will fry a servo and crash. You'll need to get a BEC that's rated for 6.0 volts and enough amps to power all your servos without causing the voltage to drop too far. Some esc's have a built in BEC. The recommended ESC has a 2S-6S rating, 5.5 volt BEC with 3A BEC rating. This is adequate unless you run some really high torque high draw servos. I think their recommended package is a pretty good one.
 

colorex

Rotor Riot!
Mentor
#9
Hi there, how have you been doing! :) yes thanks, I promise that I will treasure my dx6i.
How do I choose servos, esc and motors? How do I interpret the specs?
For servos I dont know how to pick their size and then their strength.
For esc I dont know what to take into account when considering its max current.
For motors I dont know what to consider for kilo voltage...
Most of the reviews are interresting but I still fail the techincal basics so to make up my own opinion...

You would not be a big fan of the 9xr then? I just wish it will have sliders so to control flaps in a bixler 2 for example...
Thanks, take care! :)
I've been doing fine, thanks! Just a cold which makes me stay inside...

I'd also love to have pots/sliders on my DX6i... a friend has a 9X, but I'll wait for the 9XR and get it if my pcket allows... As for specs - it's something that will come with time. But here is a brief explanation:

Motor - Very slow motors (300kv - 1000kv) are usually made for multirotors. Slow motors (1000kv - 1500kv) are used for 3D planes, slowfliers, or stuff like that. Faster motors (1500kv - 2500kv) are mostly for faster planes, racers, and that kind of planes. Very fast motors (2500kv - 5000kv) might be micro motors, if not, they are usually for EDF's (electric jets).

ESC - The motor should have a max amp rating in the description - then you should get an ESC about 15% - 25% bigger than needed - to keep them cool.

Servos - shouldn't be too hard, recommended are HXT900 9grams for almost anything you make out of foam less than 4 feet wingspan. If you strip them too often or need a bit more strength then you might consider metal gear, MG-90's are a good name.

If you want to scratchbuild planes - let me give you a list of stuff you could use:

for 300-500 grams final weight: HXT 24gram 1300kv - 8x3.8 SF prop - 10 amp Turnigy Plush - HXT900 or HXT500 servos - 500 to 800 mAh 3S lipo

for 500-1200 grams final weight: DT750 outrunner - 10x4.7 SF prop - 25 amp Turnigy Plush - HXT900 - 1300mAh to 2200mAh 3S LiPo
 

Ak Flyer

Fly the wings off
Mentor
#10
Motor - Very slow motors (300kv - 1000kv) are usually made for multirotors. Slow motors (1000kv - 1500kv) are used for 3D planes, slowfliers, or stuff like that. Faster motors (1500kv - 2500kv) are mostly for faster planes, racers, and that kind of planes. Very fast motors (2500kv - 5000kv) might be micro motors, if not, they are usually for EDF's (electric jets).
That's not necessarily wrong but it only holds true if you are using the same voltage battery for all applications. For a general use 11.1 vdc 3S battery then that's a good rule of thumb. But, since this is a larger heli question we're talking higher voltages.

Lipo cells are all 3.7 nominal voltage. Therefore your voltage is 3.7 x number of cells. 1S = 3.7, 2S = 7.4, 3S = 11.1, 4S = 14.4, 5S = 18.5 and 6S = 22.2

The KV rating has to be matched to your supply voltage and gearing to result in optimal prop or rotor RPM. Say that you are trying to get a prop speed of 10,000 rpm at full throttle.

1s 3.7v x 2700 kv motor = 9,990 rpm

2s 7.4 x 1350 kv motor = 9,990 rpm

3s 11.1 x 900 kv motor = 9,990 rpm

4s 14.4 x 700 kv motor = 10,080 rpm

5s 18.5 x 550 kv motor = 10,175 rpm

6s 22.2 x 450 kv motor = 9,990 rpm.

The difference is that the lower KV motors are usually larger motors meant for larger heavier planes. They are doing much more work so they need the higher voltage to operate correctly but they spin slower per volt so that you don't overspeed your props. You will find that the rules are pretty much the same for all airplane props.

Now with helicopters you are talking much lower head speed, usually less than 3000 rpm for a small heli and closer to 2000 for a mid performace 550. So with a blade 450X your setup is as follows.

11.1 kv battery x 4200 kv motor = 46,620 motor rpm.

10 tooth pinion and 142 tooth main gear = 14.2:1 ratio. So, 46,620/14.2 = 3,283 max rotor speed on a Blade 450X.

The standard 450 has a 3800 kv motor. Same calculations. 11.1 volts x 3800 = 42,180 motor rpm / 14.2:1 gear ratio = 2970 max head speed on standard blade 450.

Apply this to the recommended setup for the 550.

6s 22.2 volts x 1400 kv motor = 31,080 motor speed.

16 tooth pinion and 170 tooth main gear = 10.625:1 gear ratio.

31,080 motor speed / 10.625 gear ratio = 2925 max rotor speed. Very acceptable.

If you used the same motor but only 5s batteries it would go as follows.

18.5 1400 = 25,900 motor speed / 10.625 gear ratio = 2,437 max rotor speed. You would notice a severe lack of performance compared to a 6s setup. You would need a 1680 kv motor to get the same rotor speed. That changes your amp draw though because you are using less voltage. Less voltage means more amps to get the same amount of work done.

So, you can see that general recommendations don't really hold true for helicopters because we are using such deep gear reductions and most brushless planes are direct drive.
 
#11
You guys are taking me for a big ride! Thanks, I am learning plenty, really interesting and useful. Tomorrow with more time I will follow up and get other details out to discuss.
As long as I am interested in more realistic flight dynamics, would it be ok to fix the rotor at an absolute low rpm? What is the ideal figure generally? I know that blade lengths have to be taken into account for subsonic speeds, especially when travelling at top speed in forward direction...
 

Ak Flyer

Fly the wings off
Mentor
#12
No because these helicopters aren't designed for low rpm use. They will not function properly and you won't be able to pull out of something if needed. You are much better off setting it up properly and then learning to fly it in a scale fashion which in my opinion is much harder. Doing a scale landing approach is much more difficult than simply coming to a hover twenty feet up and dropping straight down. Same with taking off. Scale flight is harder to pull off.

The speed of the rotors is highly dependent on the size and setup of the heli. I would start like this. With the recommended 3D setup, have a linear throttle curve. Then find out where you start lifting off the ground. Check your throttle and pitch settings to get an idea of the power and pitch it takes just to hover. Then set yourself an idle up speed somewhere a bit over that. Real helicopters fly with a fixed rotor speed. They have to because they can't quickly accelerate and decelerate that much mass. Any throttle adjustments are simply to maintain that speed regardless of torque. Governor systems can do that for you and some ESC's have that built in. Idle up is not the same as a governor because idle up simply selects a throttle position but doesn't account for load.

Back to rotor speed, if you don't have enough speed then you don't have enough lift to pull out of trouble. I find that setting a v-curve throttle of say 80,75,70,75,80 would be better and just tune your pitch curve down a bit. Keep the head speed up but not maxed out though. This also depends on the blades you are using. If you are using some nice carbon Rotortechs or something like that then you can run a higher head speed. You also need to make sure the blades are properly balanced. Balanced blades will also take less power to turn and give you longer run times.

If you can already fly a blade 450 then try experimenting with some throttle setups and pitch setups and see what the results are. Try a linear throttle curve, a v-curve, a lower v-curve, try limiting your pitch throws, see what happens. But write down all your inital settings just in case and be prepared to crash if you push it too much.

You have a flight mode switch on the left side by the trainer switch. It's labeled gear in white and F Mode in red. Have a stock setting that you are comfortable flying with on settting 0 and try your new stuff out on setting 1. This is a MUST for ANY TIME you are trying out new settings. Always have a backup program you can go back to instantly if things go south. I have a three position flight mode switch on my DX8 so I have two modes that I fly in normally and keep the third for experimenting. At any time if things get out of shape I flip back to setting 0 which gives me full throttle and pitch to get me out of trouble.

So I was just reading the heli freak forums about a guy's Predator 90 that he does pretty hard 3D with and his rotor speed is only 2100. I don't have a tach so I don't know what the head speed is on my Hawk Pro but I think it's currently a bit higher than that. I am using wood blades so I don't push the head speed very much, plus the stock head on the Hawk isn't set up for high rpm anyway. I'm told that without upgrading to a full metal head I shouldn't try to go near 3000, probably no more than 2700-2800. I'm guessing around 2600 would probably be the lowest I would want to run but I think you should just experiment with it. I don't really 3D this one so I haven't upgraded it. I'm going to build up a Radikal, either an N640 or a G30 for 3D.

I found a lengthy thread including pics and a build blog for a HK-550. Check it out.

http://www.helifreak.com/showthread.php?t=425381&highlight=HK550
 
#13
Wow, this thread became a thesis on helicopter basics. I am so impressed. Thanks!
I am somehow imagining on dealing with the beginning of a dedicated F3C attempt, and that's why I wanted to dimention it with some limits.
Today I was very busy at the office, I will catch up with all you wrote and then ask you again for more.
You are what I needed :)
 

Ak Flyer

Fly the wings off
Mentor
#14
Well I would have to do some research but from my understanding F3C is all about precision. If I remember right there are a lot of hovering sections with high speed precision aerobatics mixed in. Large round loops, holding a line while inverted etc. and in between hover rock solid. There's a lot of different setups for that. I was reading a bit about this and it seems that some people will have their flight modes set up for each so the head speed is different for the hovering section than the fast stuff. F3C competition models have to have a fuselage as well not just a canopy. staysee.jpg
Seems like a cool competition, probably a lot harder to master than basic 3D where it can look chaotic.

Happy to help with whatever I know.
 
#15
Bottom line: you guys ROCK! I am amazed, already loaded with informations, it will take me some time but I am learning wonders :)
I will be back, can't wait to prepare my purchase list now.
Who wants to bet on the total price with me? I want to get close to the absolute lower end, yet with proper quality of units (quite impressed about HK as of now, myself).
Thanks!
 
#16
Oh my oh my oh my... I have checked things here and there, and realised that the budget for a 550 is a bit edgy, since batteries and servos tend to be premium and expensive.
So! Plan B is:
switch towards the HK 500 model (completely, completely different costs);
save some more so to add a 600 to the line later... (I think that a 700 will never be storable in my small convertible car).
Thanks, I think I will switch again to a new topic title soon :)
Great website this flitetest!
 

Ak Flyer

Fly the wings off
Mentor
#17
They definitely aren't cheap. Helicopters in general are more expensive, I think that's one main reason they aren't as popular. Plus the costs of learning and crashing and the complex setups. There are less expensive alternatives but I can't attest to their quality. I personally run plastic gear cheapo servos on my 550 nitro but I know I'm going to have to upgrade eventually. I have some cheap metal gear servos that I'm probably going to swap them out with. I'll see if I can find them for you. There's also some places to find cheaper blades, I'm loving a set of carbon blades I got from ebay for my 400. They are cheaper and better than the stock wood ones I was getting from Blade. The flybarless setup is going to be the same price either way and you're looking at 55 bucks for the one we were talking about before. The flybar setup is cheaper but more complex, I would definitely spend the extra and go flybarless.
 
#19
Ah well, great contributors, I updated myself and besides the electronics, what is hitting me is the battery costs.
A good 550 will need an ample 6s, while a 500 will manage with smaller 6s, and even reutilising my 3s connected in series (as a backup).
This means that I can handle the "fuel" a bit more easily, and also the servos will cost much less, since I will need 4 units (also taking care of the fast speed for the tail).
The 500 offer is slightly cheaper (that was not my main variable) and is delivered with blades already, so I will focus on that.
At least it is definitely bigger and more whole, more complete than my current blade 450. I have to say that the 450 really feels a bit below the limit, I will settle with a 500 first (especially because I want to match it with the 9xr, too).
Is anyone here a big fan of the HeliCommand unit? Is there something similar that you would recommend? Otherwise I fell in love with the ZYX and I will focus on that to start with.
Thanks!
 

Ak Flyer

Fly the wings off
Mentor
#20
The 500 is quite a bit bigger than a 450 so you'll enjoy the added size and stability. I think that the blade heli's are pretty high quality (not like JR or Sab) and you may find a cheap 500 lacking. That said, my second hand Hawk flies beautifully and the quality of parts is quite good.