Wednesday, August 30, 2006

Tach Take Two (P61 & P 62)

I recently adjusted my pitch and throttle curves to try to get more headspeed. My Tx is a Hitec Optic 6 which has 5-point curves.

Normal: 25-25-50-100
Idle Up: 0-XX-50-xx-100

Normal: 0-40-90-100
Idle Up: 100-xx-90-xx-100

Having adjusted the pitch throttle curves, I decided to tach the Trex again. Here's a shot of my set up. Nothing fancy, just a board over the skids with a couple of 24 ounce blue ice packs as weights. The tachometer is taped to a piece of cardboard and pushed under the blades. (Yes, I'm wearing safety glasses)

You should be able to make out the speed: 2880 at 50% stick which equates to about 90% throttle.

2790 here was done at about 90% stick in idle up. There is some pitch load here.

Here's a cool shot during spool down. The flash was able to "freeze" the blades.

Sunday, August 27, 2006

Packs 57 to 60

Here are some battery run times and temperatures:

  • Battery 1, 9:47, Pack Temp 132F, Motor Temp 142F
  • Battery 2, 8:25, Pack Temp 121F, Motor Temp 150F
  • Battery 3, 8:43, Pack Temp 117F, Motor Temp 152F
  • Battery 3, 9:47, Pack Temp 130F, Motor Temp 157F

Thursday, August 17, 2006

P47 -P 56 Idle-up and pitch curves

Packs 47 through 56 were spent hovering high and practicing side in hovering at various heights.  I'm flying in the church parking lot almost exclusively now as I really need the space to "fly out" of trouble.  I had a couple of really close calls (back and forth pendulum swings close to the ground) and had to punch out full throttle to get out of trouble.

I also played with flicking to idle-up mode today.  I've been wanting to try it ever since I tached the headspeed.  However, I just didn't feel confident to do so. 

So, I spooled up slowly and got a nice stable however at 1/2 stick, reached up and flicked into Idle-up mode.... Nothing...... no change.... which is what I expected as I matched my pitch and throttle curves between normal and Idle-up.

Flew around fine, it was nice having more "downward authority" to get the heli down (today was about 10 mph gusting winds).  I then tried to do a full-collective climb out.  Pushed the throttle stickup up hard, the Trex shot up but I could hear the motor really bog, and the tail swung all the way around and headed for the nearest tree.   Fortunately, I was able to recover and get the Trex under control.

After another pack, I called it quits and set upon examining the swash movement and actual blade pitch.  As you know, this heli was built for me by someone else as I did not feel comfortable building the SE from kit.  Now, after countless hours of reading forum postings and watching Finless's videos, I'm pretty confident I can manage any Trex build/tuning issue.

OK, put the Trex on the bench and unplugged two motor wires (to prevent accidental spoolup) and set to measure the actual blade pitch in idle-up.   Using the Align pitch gauge, my full up-stick pitch was +15!   Way too high (in-fact off the gauge)  No wonder my motor bogged on the climb-out.    I set about adjusting the pitch using the swash menu, reducing Ch6 (pitch) from 70 to 35.  That brought the pitch down from 15 to around 9 (positive and negative).   Changing the pitch swash also gave the swash clearance at full negative pitch.  Before, the swash actually hit the top of the frame.  I also adjusted the EPA of the CH1 (aileron) to prevent the servo from over-driving the swash left and right.

So the take-home lesson for today... if you get a RTF helicopter, don't assume that it was built correctly.  Educate yourself and check it.

Tuesday, August 08, 2006

P43 - P46

Installed the LiGlow Alarm from Thanh Tran over at RCgroups.

Here is the "large led"
Here is the "small LED" and the control board on the frame.

And here is the 93 dB alarm. The LEDs flash consecutively during normal flight. When the voltage from the pack drops below 9.4 volts, then the LEDs glow solid and the buzzer beeps.

After running 3 packs to the alarm, I've noted that the batteries run about 9:26 minutes and I put back around 1923 mAh back into the pack. This is a little too much for me so I'm going to keep using my 8:00 minute timer for now. I think what's going on is that since all I'm doing is hovering, the voltage drop doesn't really occur until far later in the pack. I suspect that once I do more "serious" flying, the packs will be taxed more and the alarm will come on sooner.

Friday, August 04, 2006

Taching the heli (P41 and P42)

Tached the heli yesterday using a Hobbico tachometer

I put a board accross the landing skids and put some weights on the board to keep the heli from moving. I then attached the tach to a stick and pushed it under the spinning blades.


Normal at mid stick (65% Throttle): 2760
Idle up at mid stick (65% throttle): 2860

At full stick in idle up, the rpm is about 2760 as the pitch has increased to 100% in addtion to the throttle. Clearly, I need to adjust my pitch curves and throttle curves so that the transition to idle up from Normal to Idle Up is smoother.