T-Rex 500 headspeed too low?

[Autotechnica]

Hey guys,

I have my T-rex 500 setup with an idle up throttle curve of 70 flat. I'm running a 12T pinion on all original align stuff (motor, ESC, servo, etc). It's a flybarless DFC w/ 3G gyro.

I've lost control and almost crashed several times now due to odd behavior in the air. I'm training myself to fly scale since I have an MD500 and AH-1 Cobra. I'm learning on pod and boom before I move on to my scales. I mainly hover and fly figure 8's. I have my rudder/cyclic set to respond pretty sluggish with about 80% D/R and 15-20% Expo. Anyways, when I bank either left or right and I try to pull out of a corner, sometimes it seems as though the heli is trying to fall over on it's side. It seems to be falling over on it's own weight. I'm curious if maybe I'm just banking with the heli turned to the side too much or maybe my head speed isn't high enough to stabilize it. When I do try to pull the heli back upright, it seems to really struggle to do so. I feel like I have to slam the stick hard in the opposite direction to get the weight to shift. Once it does correct, it's not smooth and feels like almost a total loss of control. It hovers great and moves side to side just fine. I'm very comfortable with this lower head speed but could this be causing the problem? I also stopped using carbon blades as I find it's very unstable, especially in the wind. It'll balloon up very quickly when I have +ve collective pitch as well. I really liked flying with plastic scale blades, but I'm afraid of how they will handle heavy wind. I've compromised and I run FRP blades. Although, I still want to run plastic on my scales.

Keep in mind I plan to only fly scale. I have no interest in 3D or Acrobatics. I don't need responsiveness. My main goal is realism and stability.

This video below pretty much shows the extent of my current flying abilities on my HK500TT... (I cannot fly nose in)

HK500TT / T-Rex 500 / Tarot 500 light flying. (2 min 22 sec)

thanks guys,

Bry

[Russell Harding]

Some of what you describe sounds like low headspeed (ballooning, and DFC is known to wobble due to the stiff/no dampening in the head).

Others could be control behavior as programmed in the FBL unit (cyclic gain to high -> unstable feel). Also keep in mind the transmitter DR and Expo can be effected by the FBL settings too.

Do you have a PRO (tail servo in the frame) or not? Then I can do a quick headspeed calc for you.

You may also not have the headspeed you think you do if your ESC endpoints are not set.

[Autotechnica]

It's a normal frame (non-pro). Basically I changed parts to FBL from a flybarred ESP version. I also upgraded the tail rotor to the pro version. However, all gearing should be non-pro. I setup the 3G using the basic setup through the gyro controller. I haven't accessed or change any settings via USB link. As for the ESC endpoints I thought all align ESC's are just set from 0-100 and configured with lowest and highest stick positions? I know on my Phoenix ICE ESC I had to change the endpoints a bit according to the beeps. BTW, if I run a flat throttle curve, do the endpoints really matter (just curious)? So with the carbon blades and the ballooning affect it could be that I'm not getting sufficent lift with my current headspeed so wind causes it to balloon as well as instability? I was afraid more headspeed would make the heli even twitchier causing even more instability and making collective more sensitive. That's really the last thing I want.

thanks for your help! I'd really like to try some new settings this weekend.

Bry

[Russell Harding]

You are probably at 2200 rpm which is the low side but not crazy low. It is pretty easy to bump up the throttle though to see if it helps. You don't want to go over 2700 on the ESP tail ratio, but you don't have to worry about that with your gearing.

Yes. Endpoints matter regardless. Imagine your esc is expecting 0-100 and you are sending -20 to 80. Then your 70% would be more like 50%

[Autotechnica]

Now I'm a bit paranoid. I will check that I setup endpoints properly tonight. Thanks for the help.

Should I be worried about esc heat at 70% throttle?

Thanks

[Russell Harding]

Heat is probably not an issue if you're flying relatively easy.

[gaurdian101]

I just did the same thing changed my 500 esp to fbl also and I also was running low head speed with my fb setup and when I changed to fbl I had to up my throttle allot more speed you said your running a 12t pinion I'm running a 13t and I had to put my th curve setting to at least 75% or better to get that wobble to go away....I bet you might have to run 80% with that 12t to run right....after I up'd my speed that thing fly's better than ever fell in love with it all over again....my to cents is all hope it help......

[Gladius]

The "falling over on its side" behavior you described sounds like inexperience to me, since you mentioned that you cannot fly nose in yet. I had a crash due to that same behavior a little over a year ago, and it was simply due to me leaning the heli too far into a banked turn. Once the heli has some bank to it, you've lost a lot of your vertical lift, and the heli will fall like a rock.

My recommendation is that you focus on all your hovering orientations. Get comfortable flying nose in, or every time you try to do a circuit or figure 8, you will have a hard time completing it once the heli gets to nose in. That practice will also help you tell how much bank is enough in the different orientations.

[Autotechnica]

Hey guys,

I upped the throttle curve to 75 flat on idle up and it does help make banking a lot smoother. It also speed up the cyclic which I didn't like. Even after adding more expo I still found it too responsive.

Gladius, you're definitely right about having to learn orientations. My figure 8's are not quite figure 8's, more like S's. The heli seems to get farther and father away each time I complete a bank. Up in the air, I can barely tell if it's 10 degrees towards me or 45 degrees. That makes it really hard for me to fly the figure 8 properly. Last week when I flew I took into consideration the orientation of the heli when coming out of a banked turn. Flying a bit slower and keeping it upright helped a lot in stabilizing the heli. I no longer got the feeling it was tipping over.

Thanks,

Bry

[WildBird22]

If you want to learn to fly scale, then you need to back up a little. Can you hover with the tail facing you 10 feet away, at 10 feet in altitude within a 6 foot radius..and hold it there?

Can you hover as the above, but with the helicopter 90 degrees to the left....and to the right by 90 degrees?

Have you flown the helicopter in the video with the flybar? There are alot of questions, but that's not the point. The point is that scale flying is not about figure 8's or S's. Orientation is one of the basics in Helicopter Control. Learning to hold a steady hover will teach you basic orientation in all positions...including nose-in, and stick control by "thinking ahead". In your video, your flying too fast, too high, and too far....slow down! Its not hard....it just takes time.

Also a basic setup for "scale" on a 500 size helicopter is a 1600Kv motor (2-blade), 10 to 12T pinion, and a head speed somewhere from 2100 - 2300.