Johng

My Feedback: (4)

I bought a used T-rex 450x , at a pretty good deal a few weeks ago. It's got the heavy plastic blades, all plastic moving parts, HS-55 on everything. Alighn HH gyro. Spektrum Radio. Got things more or less how I wanted them and gave it a hover last night.

My experience: I used to fly an LMH quite a bit, forward flight, etc. But it's been a few years. Anyway, I know a little about heli's.

I've got it on training gear, with the freely spinning ping-pong balls. The first thing I found strange is the fact that it would spin 180 when the power first hits the main rotor. I guess on cement there isn't enough friction to stop this. Seems like it's just a newtonian reaction of the accelerating rotor disk, while the tail rotor does not have the power to counter the motion. Is this common? I would expect it to be reduced quite a bit when I change to lighter blades.

Also, I'm getting a good bit of tail-wag. I've reduced the gyro gain to almost nil, in HH mode. It holds a solid general heading, but wags constantly. I've researched and seen that any binding can cause this. Plus, the HS-55 is a rather weak and slow servo for the job. I'll be ordering -56's at least for the whole heli. I'll also be checking the tail rotor mech for any play, as well as the belt. Any other suggestions to even this out?

Third, not a TR issue. The main head seems free & smooth. Right cyclic = right slide, forward = forward, back = back. However, it seems that left cyclic results in left AND forward motion. I was very carefull that I was giving pure left stick on the Tx when I was looking at this. The rotor disk looks like it is tilting towards the left front when I do this in the air. On the ground, the rotor looks like it pitches forward, and I have looked and there is no odd "mixing" being done where I'm getting some sort of cross command on the ele channel. Only the ail channel is moving. What could be causing this?

JPKII

Assuming you are using an Align 25 A ESC, listen to the tones on start-up to make sure you are in helicopter mode (which enables soft start). The other option is airplane mode which starts the motor with full force and will cause the heli to quickly rotate (snap) around.

As far as the cyclic servos I bought 65MGs for my XL (HDE) and have been very happy. Transit times are the same between the 56HB and 65HB the 65s just offers greater torque. If your X is CCPM I think you may need a little extra oomph. For the tail rotor I use the Airtronics 94761Z with my 401 gyro. This has proven to be a really good, stable set up for me.

Joe

Johng

My Feedback: (4)

Thanks man, good point on the ESC.

VinceHerman

Hi John,
Joe is spot on about the ESC kick.

The tail servo is a pretty demanding application. I am not a fan of using the HS55 there. HS56, HS65 or better, a digital servo (with a gyro that supports it). Binding can lead to all kinds of poor tail performance, but I would not think that wag is one of them. Wag is a problem in the feeback loop. Gyro gain (which you are already adjusting), slop in the linkage, slop and poor centering in the servo (loose the hs55 on the tail), or even a very high head speed. These are all things that I associate with wag.

As for the interactions on cyclic control, is this behavior seen when you are on the ground? Or in ground effect? Then this is normal. You will get some errant cyclic control when the heli is bound by the ground, and in a low hover, there are all kinds of disturbances.
Let us know if things improve at a 3 or 4 foot high hover.
Vince

RcFlyer06

My Feedback: (4)

John,
I've noticed on my rex that too low of a gyro gain setting can cause something of a lazy tail wag, you gotta find that point where it's not so fast you have the fast tail wagging and not so slow that you get the lazy left & right bounce. I'd blame the servo though. Vince is right, an upgraded tail servo would most likely clear things up the best. I'm using an inexpensive hs-81 and it works great

Ken448

if you are getting wag on the tail and the gain is -0- on the gyro itself, go into radio settings and drop the GER setting (in Trav Adjust menu) a little at a time. I fly a Spektrum as well but use the Futaba 9650 servo and my GER is set at about 40%

Johng

My Feedback: (4)

Just a bit of followup:

I've been reworking this thing how I like, but haven't flown it since I found the wag. I did find a few more things wrong with the tail:

The belt is loose
The tail pitch slider has a lot of play in it. The collar that connects to the bellcrank and drives the pitch is quite loose on the body. at least 1/32 free play
The tail pushrod was flexed to go thru the mid-boom guide. I've reinstalled a HS-56 on the tail, with the horn positioned for a very straight drive.

I have the day off for the hurricane/ tropical storm/ thundershowers/ threatening clouds/vicious drizzle so I'm gonna call the hobby shop an go down there and get a couple long booms and a new belt and rework the whole deal.

VinceHerman

TOO funny!!!

don_87

If you can swing the cash, and if they stock it, you might want to spring for the aluminum cnc tail assembly. Might want to watch the finless videos too. A lot of Free valuable info there.
Good Luck, Don

Johng

My Feedback: (4)

Well, we all know the isn't such thing as "A" helicopter. They are just parts that are assembled into something that flies. Between flights, parts are changed, replaced, tweaked, etc. So, as I get into the thing, I'll probably change over to more aluminum parts. But It'll probably be the head that gets upgraded first. I'll fly with the cheap parts while I'm still in the risk zone of getting back to forward and nose-in flight.

Anyway, that's what I did. And the pitch slider has no slop compared to the old one. Still haven't flown. Maybe tonite.

Johng

My Feedback: (4)

Well, the thing is flying pretty well now, with a slight glitch. The tail pitch slider is well off-center when trimmed for straight flight. It is about halfway towards the boom. I'm not sure why.

My theory is that it's from the fact that I have the 335 blades on here for training. perhaps they generate more torque than the smaller blades....

Wag is gone. Helps to read the gyro directions for one thing. They call for 50% on ATV for both RUD and GER. Did that and I'm turning my gain back up now. The tail bobbles just a bit with pitch changes, so it needs a bit more gain. Still glad I have a tail slider without play.

Blade tracking seems to change every few flights. I don't think I'm abusing the head but who knows...

The great thing about this is to be able to fly a pack off at lunch.