Trex 450XL Pitch curve help

[dunke...@gmail.com]

I have joined the wonderful world of RC.
After much deliberation I chose to go the heli route as I have a big
garden
and a park cross the road where I can practice.

I bought a TREX 450XL CCPM kit complete with Align 450L motor and
BL25T ESC.
The radio is a Spektrum DX7.
Batteries are flight power EVO Lite V2 2500mA.
Gyro is the Futaba GY401.
Charger is the Swallow Advanced and I have the flight power V Balance.
I built up the kit and had it set up by one of the experts from the
shop.
I have training gear attached.
Pinion was a 15T but I replaced it with a 13T.
I have been through about 10 battery's so far and I am managing to
hover at
about waist height for a few minutes at a time.

The problem I am finding is I am not getting good battery life.
After 6 or 7 minutes the Trex starts pulsing which I am told is the
sign
that the battery is going flat.
If I let the Trex rest for a few minutes (I assume the battery is
recovering
during this period), I can then take off and hover for a few more
minutes.
After the batteries cool down, the 2 of the 4 leds on the V Balance
fuel
gauge light up for each of the 3 cells in the pack.
It could be my beginner way of flying, it could be not enough pitch ,
new
batteries, training gear weight,
not enough pinion main gear slack etc. etc.

What I would like to do first is change the pitch curve.
It's in the normal position now with values of

L=20.5 (is this too much negative pitch and should I change it to say
50%?)
1=55.5
2=77.0
3=92.5
H=100

Throttle curve

L=0
1=20.5
2=43.0
3=69.5
H=100

Am I on the right track?

What do you suggest as a first step?

[Kevin]

buy a pitch gauge ??

--
Kevin R
Reply address works

[Mike @ zen]

<dunke...@gmail.com> wrote in message
news:aaa829d5-a419-47ef...@t63g2000hsf.googlegroups.com...

When the Trex starts pulsing STOP flying and charge the battries or you will
fook them up.
For longer flight times use a 11T Pinion, it will do you for just hovering.
Next get a pitch gauge
Then........

pitch ....

Norm.
40 45 50 75 100

Idle 1...
0 25 50 75 100

Idle 2...
0 25 50 75 100

Throttle you will have to play around with depending on what pinion you are
using

My t-rex 450 is set up like this on 13T Pinion

Pitch

norm
40 45 50 75 100

idle up 1
0 25 50 75 100

idle up 2
0 25 50 75 100

Throttle

norm
0 50 70 70 80

Idle 1
90 85 80 85 90

Idle 2
100 95 90 95 100

I use the same Pitch curves on my T-rex 600e and two t-rex 600n's

Have a look at a video called .....Pitch and throttle curves 101

http://www.helifreak.com/showthread.php?t=11373

[Kevin]

without a pitch gauge any curve numbers are meaningless as you have no
idea what the pitch actually is

[phi...@samsat.co.za]

Thanks for your responses.
I will get a pitch gauge.
However I am looking for a rule of thumb.
For the current battery problem I am facing should I leave the
throttle curve as is and
just increase the low value pitch to say 50 to give me more lift for
the less throttle?

[Robert Roland]

On Mon, 28 Apr 2008 00:50:14 -0700 (PDT), phi...@samsat.co.za wrote:

>However I am looking for a rule of thumb.

The rule of thumb is that the current load goes up as the head speed
goes up.

>For the current battery problem I am facing should I leave the
>throttle curve as is and
>just increase the low value pitch to say 50 to give me more lift for
>the less throttle?

Changing low pitch won't make any difference. You must look at the
hovering pitch. To reduce head speed, you must increase hovering pitch
and correspondingly reduce hovering throttle.

Note that the T-rex 450 does not like a low head speed. It will start
wobbling if the head speed gets too low. There was a thread here a few
days ago about recommended head speeds.
--
RoRo

[Kevin]

these are my setting

mine for what its worth are
throttle (not so much a curve as a dog leg)
mine 0 75 86.5 96 100
yours 0 20.5 43.0 69.5 100

pitch
mine 29.6 44 57.5 70.5 82
yours 20.5 55.5 77.0 92.5 100

I think you need to ramp the throttle up a lot quicker and get the head
speed up to 2000rpm+, and reduce the pitch, your 1/2 throttle pitch is
nearly what mine is at full ,but I only hover and do gentle circuits

I seem to remember reading that brushless motors are lot more efficient
at higher RPM's

[phi...@samsat.co.za]

Thanks.
I re-adjusted belt and pinion tensions, this along with the change
from a 15T to 13T pinion has made a huge difference.

I have also increased the throttle pitch but not sure it has done much
though.

I had a bit of a hard landing yesterday and since then the tail seems
to wander quite a lot, almost
as if the gyro is not working properly. Not sure if it's due to the
hard landing or due to any of the adjustments I have made above
requiring re-adjustment to the gyro?

[Kevin]

your tail does it gyrate back and forward or keep drifting?

[phi...@samsat.co.za]

It keeps drifting. I think I may need to reset the Gyro neutral point?

[phi...@samsat.co.za]

Thanks very much for the input.
Will give all the suggestions a try.