Heli doing 90deg left on power punch, need your help please

[Blinky]

Hi all,

I have my heli back up and running after a long cold winter (and a small crash before stopping). But I have a problem that is driving me up the wall.

Setup:

3DX 450 B frame
CopterX head/tail - Align 325mm glass fibre/ K&B 450 tail blades
Trex main gear, copterx autorotation gear and tail gear
13t align motor pinion
G401B gyro with Align DS520 digi servo
Scorpion 55a esc with -8 motor
Loong Max 2250mah 25c lipo
Dx6i

Throttle curves
normal - 0 35 70 85 100
idle - 100 90 80 90 100

Pitch curves
normal - 40 50 65 80 100
idle - 0 25 50 75 100

Pitch range is 10 10 I think.

Right, the problem. When I punch the power from a hover to go into a fast climb out the heli will turn 90deg left before starting to hold. I have tightened the belt so there is no slipping, flattened part of the motor shaft and the tail gear shaft (the one connected to the auto gear) so that the grub screws dont slip on the shaft.

It doesn't turn as much when in idle up but still turns a little. The gyro is holding the tail in heading hold but I am having problems with the tail wagging. Before the re-build I was able to have the gain on the Rx at 100% without any wagging and the delay on the gyro is at 0%.

Could the motor just be to powerful for my setup?? I have seen video's of this motor running on similar heli's without problems though.

Have I missed something or is something just dead/dieing??

Please help if you ahve any idea's as I am getting really p**sed off with this, I just want to fly again.

Sorry for the long post and cheers in advance for any help/info.

Blinky

[brin]

check out the tail when in rate mode .if you try and hover preferably in calm conditions the tail should hold if not then you need to center the tail.

[Blinky]

check out the tail when in rate mode .if you try and hover preferably in calm conditions the tail should hold if not then you need to center the tail.

By that do you mean setting the tail up to hold in rate mode, not centering the slider on the shaft??

[machasm]

This might sound stupid but check that the belt is properly seated at both ends of the drive train and not twisted so that the teeth are on the outside!
Also check that the pulleys have all their teeth, partcularly the tail shaft drive pulley.
Does the tail have enough travel? No binding and moves smoothly from one end to the other with the corresponding rudder input?
You should be fine with this motor and pinion combo.
Have you been able to measure your headspeed? If so what is it?
Adrian.

[David Drew]

Is the G401B the cheap copy of the Futaba GY401 ??

I still have probs on my Trex 450 with the GY 401. Similar issues, not 90 deg but def a lag before it grips. Also a slight wag on hover which stops in FF.

David

[brin]

By that do you mean setting the tail up to hold in rate mode, not centering the slider on the shaft??

yes the tail should hold in hover with no wind. if you setup in rate on the bench the tail blades should dead straight with equal amounts of travel on the slider, you will have to set up the end points on the tail servo .this is just one thing to try ,it sorted out the same problem i had with my 450 .

[brin]

ps the other thing you could check there is a small grub screw that holds the tail grip assembly onto the tail shaft this may be slipping .

[Blinky]

machasm - The belt is seated correctly and the correct way round. I am unable to read the head speed, but I am not sure about the travel on the servo, I have the control rob on the inner most hole on the servo arm and the travel on the gyro is at 100%

David Drew - Yeah it's a cheap clone that is holding it's own, very good gyro for the price.

Brin - Sorry to sound stupid, if I set the tail baldes to zero pitch and run in rate mode then the heli will spin, I have got the blades set to zero pitch but only use heading hold. The blade holders were slipping before, but I have since removed them and filed a flat spot on the shaft to prevent slipping.

What is the ratio for the head and tail on a trex 450, I currently have one complete rotation of the main blades to 4 rotations of the tail blades, is that correct or is there a different gearing setup that I can use to increase the tail blade speed??

Cheers for the help.

Blinky

[ivor-bigen]

Hi
to set the gyro up.
all trims to middel includeing subtrim
switch the gyro to rate mode and on the bench makes sure servo horn is at 90 degrees.
Also Set the pitch slider up at 90 degrees.

now you need to (on a calm day)
fly it
with the gyro still i rate mode, lift the heli up into a hover, try not move the pitch stick to much as this will cause the tail to drift.
now when it settles into a stable hover take a note of what way the heli is turning.
if for eg it turns to the right.
make an adjustment on the tail pushrod and re test the hover again keep doing this untill its sits with minimal to no drifting.
once its sitting nice like this its ready for heading hold mode.
once you switch to heading hold you should only need to set your gain level, no more adjustment should be needed.
Ivor

[brin]

Hi
to set the gyro up.
all trims to middel includeing subtrim
switch the gyro to rate mode and on the bench makes sure servo horn is at 90 degrees.
Also Set the pitch slider up at 90 degrees.

now you need to (on a calm day)
fly it
with the gyro still i rate mode, lift the heli up into a hover, try not move the pitch stick to much as this will cause the tail to drift.
now when it settles into a stable hover take a note of what way the heli is turning.
if for eg it turns to the right.
make an adjustment on the tail pushrod and re test the hover again keep doing this untill its sits with minimal to no drifting.
once its sitting nice like this its ready for heading hold mode.
once you switch to heading hold you should only need to set your gain level, no more adjustment should be needed.
Ivor

thanks ivor thats what i have been trying to explain

[andylinney]

Hi
to set the gyro up.
all trims to middel includeing subtrim
switch the gyro to rate mode and on the bench makes sure servo horn is at 90 degrees.
Also Set the pitch slider up at 90 degrees.

now you need to (on a calm day)
fly it
with the gyro still i rate mode, lift the heli up into a hover, try not move the pitch stick to much as this will cause the tail to drift.
now when it settles into a stable hover take a note of what way the heli is turning.
if for eg it turns to the right.
make an adjustment on the tail pushrod and re test the hover again keep doing this untill its sits with minimal to no drifting.
once its sitting nice like this its ready for heading hold mode.
once you switch to heading hold you should only need to set your gain level, no more adjustment should be needed.
Ivor

Just the reason why I love my v-bar and spartan gyro - the most basic mechanical setup on the tail and they just work...

[brin]

I have the control rob on the inner most hole on the servo arm and the travel on the gyro is at 100% [quote]

i have the 9257 tail servo but my ball link is in the outer most hole ,if you have it on the inner most hole it may not give you enought travel on the tail slider.

[Blinky]

Cheers guys, I am about to have a go at it now, I will let you know how I get on