PROBLEM WITH TREX 500

jplot · Posted: Thu Feb 05, 2009 5:24 am Post subject: PROBLEM WITH TREX 500

I have a unique problem with my newly built Trex 500, and am searching for someone who can tell me where I have gone wrong.
Since my six months of learning has taught me that it is difficult to learn anything with the heli bouncing all over on the ground, and then when it does get airborne for a short hop, the heli heading is soooo difficult to control, and especially so with the transmitter in the hands of a newbi.
My recent solution was the building of a test work stand with which I can test many different sized helicopters with the chance of a parts breaking crash very limited. The unit allows full 360 degree rotation in azimuth and allows the heli to lift off a foot or so, and that is out of ground affect.
In my repeated testing with the T500 mounted in the stand, the unit at first will turn to the right with the further advancement of throttle, then just as it reaches close to the point of lifting off the turning of the head ceases, even with full right rudder input, and as it lifts up the rotation of the head to the left, increases even more. Needless to say, an unflyable condition.
I have accepted a lot of solid advice from veterans on how to keep this from happening and here are some of those things that I have carefully double checked and found OK.

Make sure the tail servo moves toward front of heli when turned by hand to the left.
Make sure the tail servo moves toward the front of the Heli when the rudder tx is moved to the right.
Make sure the belt is working well and no slipping of any kind is taking place.
If you have a Heading Hold gyro, make sure the red light is staying on.

I have implemented with all kinds of changes in the tx setup, and adjustment controls, and carefully moved the tail servo all over the place looking for the perfect position, and think I do have it there now. Still, after going through some four batteries over the last couple of days I get the exact same results every time I fire it up.

Any idea would be appreciated. I am hoping there is one last rock that I just have not as yet overturned.

jer
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Dumb Thumbs · Posted: Thu Feb 05, 2009 6:30 am Post subject:

Your problem may be caused by vibration acting on the gyro.
(I'd bet that test stand thing of yours adds vibration to the heli, I'd ditch that idea & go for regular type training gear).
Even if it doesn't, if you have the gyro mounted on the gyro tray move it to the top of the tail boom block. It's a much more stable point to mount the gyro. The gyro tray is a good idea from Align, but it just don't work. Many have found mounting it there causes vibration issues acting on the gyro.
Adding more foam tape when mounted to the gyro tray doesn't help, so don't waste time with it.
Good luck & let us know how you make out.

jplot · Posted: Thu Feb 05, 2009 11:26 pm Post subject: TAIL ROTATION PROBLEM

That was a good tip and I thank you but I took the heli off the stand and it tested the same. This 500 is the smoothest running heli I have yet to encounter and at present is not causing any vibrations of any kind.

When I am running these tests I know the heli in both HH and normal, is sending the tail rotor to full pitch and that is where it is at when I am getting the rotation to the left at high throttle and liftoff. Wierd and mystifying and I guess I will have to keep searching for the answer.

The gyro is rock solid and already mounted on top.

Thanks

jer

cgage · Posted: Fri Feb 06, 2009 10:13 pm Post subject:

I'm just a beginner a this and you know a lot more about 400's and bigger. However, there is a website a someone offers some material on resetting the tx to a training level as oppsed to sport. Since i dont have a 400 yet, I havnt purchased it ($12) but I will when I get a 400.
http://www.rchelicopterfun.com/blade-400.html

Crashagain · Posted: Tue Feb 10, 2009 12:50 pm Post subject:

If the heli is spinning while trying to lift off, and you have the rudder servo moving the right way by the transmitter input, then I would venture a guess that you have the servo reversed on the gyro. There is a
(norm-rev) switch on the gyro. Switch it and see what happens. God knows I have done this and changed the switch and everything is fine.

Dumb Thumbs · Posted: Tue Feb 10, 2009 9:05 pm Post subject:

Very strange indeed. I guess you have already checked for any binding issues in the servo to tail. The real "acid" test is to remove the main blades, disconnect the pushrod from the rudder servo, have someone hold down the heli (REAL TIGHT) and spool it up to about half stick. Then move the pushrod by hand from stop to stop. You'll feel if something is not right.
Have you double checked the tail rotor to make sure it's assembled correctly & is greased?
What gyro & rudded servo are you using & at what gain setting BTW.
When you first set up the heli did you adjust the rudder pushrod in RATE MODE first to get the mechanical center for hover?
Could be a bad gyro. Know anybody you can borrow a gyro from to see if that clears up the problem?
Is the REVO MIXING turned off on the Tx (should be)?

RRG · Charging Joined: 03 May 2010 Posts: 1