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T-REX 450 › T-Rex 450S Spins out of Control
09-15-2007 03:16 PM  10 years agoPost 1
Joe64D

rrNovice

Taji, Iraq

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I'm new to the T-rex So if anyone out there can help me I would be great if your reply was in plain engilsh, and many of the terms concerning transmitter and gyro settings sound like an ancient alien laguage. So here's my Problem

When I first got the Helicopter put together It hovered fine, and the the heading control was great until I transitioned into forward flight and made any kind of turn. When I did this I lost complete control of my tail rotor and the helicopter spun. Now, every time I try to pick my Helicopter up of the ground, regardless of my tail rotor imput from the transmitter it developes a rapid counter clockwise spin that cannot be stopped. I live in a pretty remote part of TX (military) and have restricted access to Hobby shop support. I read the manual on my transmitter front to back and tried adjusting the gain on the gyro, the only progress being a slight reduction in the rate of the spin. So my question is, What is causing this spin and how do I get this spin to stop?

My system on a Futaba 6EX, with a Futaba GY-401 Gyro, and a Hitec HS-56HB as my Tail rotor pitch servo.

Any insight into this would be very helpful

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09-15-2007 03:19 PM  10 years agoPost 2
z11355

rrMaster

New England

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did you crash it?

what is the current ATV (TRVL ADJ) values for the RUDDER channel?

one of several things is happening.....

you either have the gyro and/or servo direction setup wrong which is
unlikely since if that was the case, it never would hover OK.

My hunch is that you set the TRVL ADJ wrong, got the machine to spin
too fast when you gave it rudder and in the process, stripped the tiny
gear inside the servo so it now doesn't really correct like it should
(which leads to the 'it spins all the time'.

You should disconnect the long pushrod from th tail servo and see if
the plastic servo arm 'slips' when you hold the arm and give some rudder input.

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09-15-2007 04:02 PM  10 years agoPost 3
Joe64D

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Taji, Iraq

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I had a Hard landing resulting from the LTE experience that broke an bent a few things. But thats all been repaired. The Servo is brand new,I bought it yesterday thinking it was just a servo issue. How do I make Travel adjustments?( I'm assuming thats what TRVL ADJ means). Is that the same as EPA(End Point Adjustment)? if it is my EPA is set at 100% I checked my servo and it didn't slip any, as I would hope it being brand new.

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09-15-2007 04:10 PM  10 years agoPost 4
arffy

rrApprentice

Ny

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If you put on a new tail boom make sure you put the servo on the same way .Meaing maybe you faced it the opposite way as in arm travel.You might have to reverse the setting on the gyro itself.I did that a few times.

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09-15-2007 04:13 PM  10 years agoPost 5
TomRex

rrElite Veteran

West Palm Beach ​Join Date:​12-28-2005

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450 "S" not sure whats in there

Does yours have a plastic belt gear on the tail drive gear assembly? Some of them have been known to slip after a few flights. If you have the reduction type gears and you find your shaft/gear is slipping try one of these http://www.readyheli.com/HS1216_84_...p/hs1216-84.htm

or these
http://modefosheli.com/inc/sdetail/20400

Ignorance is the absence of facts.Stupid is lacking the intellectual capacity to comprehend the fact

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09-15-2007 04:23 PM  10 years agoPost 6
Joe64D

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Taji, Iraq

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I did have to replace my tail boom, but I'm sure I have the servo set up the same way, I put it back together using pictures of my own helicopter that I took right after I finished buiding it. And I had the belt slip issue early on as well, but that was fixed when I went to the Metal belt gear. Now the belt stays put. Are there any other Ideas? I'd really like to get this thing flying again soon

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09-15-2007 06:32 PM  10 years agoPost 7
docjoe

rrElite Veteran

Stockton, CA United​States

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Double check both the gyro servo direction and the rudder servo direction. This is a common cause, as has been said earlier for the gyro to be reversed. Even if you didn't change it, sometimes weird transmitter things happens and the settings get reversed. Believe me, sometimes stuff like that happens!

Joe
We haven't seen Colonel Angus around these parts for years!

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09-15-2007 09:09 PM  10 years agoPost 8
Joe64D

rrNovice

Taji, Iraq

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How do I check the gyro servo direction,I'm assuming that has its own channel, but wich one is it? I've tried reversing channels 4 and 5 and still have the same rapid counter clock wise spin, I'm begining to think I have a Bad 401, Or maybe my Rotor RPM is too low to provide adaquate anti torque thrust from the tail rotor. Thoughts? comments?

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09-15-2007 10:25 PM  10 years agoPost 9
arffy

rrApprentice

Ny

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It's on the gryo .It's a little switch.

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09-15-2007 10:30 PM  10 years agoPost 10
RICHW

rrVeteran

Cupertino, CA

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Is the belt turning the tail rotor in the right direction? Forward tail blade should move up toward main rotor.

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09-15-2007 10:37 PM  10 years agoPost 11
docjoe

rrElite Veteran

Stockton, CA United​States

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For the Tail blades, make sure that the tips of the tail blades move in the same direction that you move the rudder stick.

As for the gyro, I think the tail slider moves the same direction as the direction you move the whole tail. To check make sure that the tail blade tips move in the opposite direction of the spin direction. (Guys can you just verify this. I'm just think this off the top of my head and usually need to see it).

If the tail blades move opposite the rudder, then you need to reverse the rudder servo (make sure you know what channel it is plugged into.

If the Gyro is reversed, then use the switch on the gyro itself to reverse it.

That should help if the problem is either the gyro direction or the rudder direction.

I think all of us at one time or another have had this problem.

Oh yeah, make sure that the tail belt is turned in the right direction, meaning that the blades move in a counterclockwise direction when facing the tail rotor.

Joe
We haven't seen Colonel Angus around these parts for years!

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09-15-2007 10:45 PM  10 years agoPost 12
Dave_E

rrApprentice

Stanwood, WA

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You went to a metal tail drive gear? How about the front nylon gear? That's what broke on me after a bench mishap. Hold the tail rotor blades and turn the main by hand. If the main turns... you've got a broken gear up front. Replace it also with a metal gear upgrade.
Let us know what you found when it's fixed (group learning you know). Dave

CHECK 6

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09-16-2007 12:28 AM  10 years agoPost 13
Joe64D

rrNovice

Taji, Iraq

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Ah HA!!

A it would seem my Tail rotor is spinning clockwise. Such a simple thing to over look. now comes the next obvious question, How do I get it to spin the other direction?

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09-16-2007 12:44 AM  10 years agoPost 14
docjoe

rrElite Veteran

Stockton, CA United​States

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You loosen the boom block, push the boom in and you should get some slack. Now you really should pull the boom out, look down the boom to make sure that you don't have a full turn of the belt but just a half turn, and make sure that when you turn the belt one way or the other, that it matches the direction of the tail drive gear movement. I think it is a 90 degree turn clockwise (but check it just in case).

Joe
We haven't seen Colonel Angus around these parts for years!

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09-16-2007 12:47 AM  10 years agoPost 15
Dave_E

rrApprentice

Stanwood, WA

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When you replaced the tail boom, you "rotated" the belt the wrong way. 90 degrees CCW from horizontal at the tail. OR... 90 degrees CW from vetical at the forward drive gear.

CHECK 6

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09-16-2007 01:00 AM  10 years agoPost 16
Joe64D

rrNovice

Taji, Iraq

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WTF!!!

Either I'm completely stupid or god hates me, or both. I fixed the tail rotor direction, checked and made sure the tail blades are feathering in the right direction, and the SOB still spins, actually I think its spining faster. Could it be my Gyro has gone bad or is there something else that I'm missing?

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09-16-2007 09:27 AM  10 years agoPost 17
Tolla

rrApprentice

Cape Town, South​Africa

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I agree with some here. Those plastic tail drive gears are prone to slip on the shafts. Replace both front and rear with the metal upgrade.Learnt the hard way.

Also, I have had the original Align front metal tail drive GEAR teeth wear, so that the belt would slip over the teeth. Slipping was, however. only a problem when the gyro was compensating hard and fast. During not-so-vigorous flying it would be fine and as such took me a while to figure out.

Check setup:
1. main rotor turns clockwise as viewed from above
2. tail rotor turns anti-clockwise as viewed from the right.(The bottom of the blades throw dirt into the main blades)
3. The tail slider moves right on right rudder and left on left rudder.
4. Make sure you do not twist the belt too much when turning it otherwise it will bind. Turn it only throgh 90-degrees.
5. check the gyro direction:
a. check which way YOUR servo horn rotates when you give RIGHT rudder.(mine rotates rearwards)
b. now, pick up the heli and,very quickly,jab the NOSE to the LEFT.
c. watch the rotation of your tail servo horn.It must rotate in the same direction as when you give right rudder.
Because you are forcing a nose left attitude, the gyro will compensate by giving right rudder. you are checking whether the gyros right is the same as your control stick right.

Here's is sonmething else I would like t share.I cannot explain it but it's true.
I wanted to change my 9650 tail servo for a s-75 to fit into a 500E fuselage I was fitting.
That's all I did. change the servo an switch the gyro switch from digital to standard servo.
Well, on starting up the heli would spin around like crazy.
Stopped, checked tail rotor direction etc, tried again, Same thing.
Figured the gyro was operating the wrong way so I reversed the direction swithch and all was okay.
I cannot explain it but I have learnt to ckeck my setup after any changes are made.I thought I may have swithched a wrong switch but i have a little sheet on which i keep my settings written down...

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09-16-2007 12:20 PM  10 years agoPost 18
TomRex

rrElite Veteran

West Palm Beach ​Join Date:​12-28-2005

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Does yours have a plastic belt gear on the tail drive gear assembly? Some of them have been known to slip after a few flights

Ignorance is the absence of facts.Stupid is lacking the intellectual capacity to comprehend the fact

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09-16-2007 03:49 PM  10 years agoPost 19
Joe64D

rrNovice

Taji, Iraq

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I think we got it guys!

What a great way to start the morning! I just took a look at my Tail rotor gear box to find that I can rotate my tail rotor without the belt, or anything else moving. So I think I've got a bad gear. So I think that may be the final solution. with any luck I'll be able to pick up a replacement, or better yet a metal upgrade this after noon and have some good news later on, Thanks Guys! and Gals if applicable.

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T-REX 450 › T-Rex 450S Spins out of Control
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