Wren 44 Trex 700

[Drummer_andydrummer]

Hi everyone,

which is it best to run as far as stunt curves are concerned a flat line for throttle or v curve ?...

cheers

[Kiba]

While not a Trex 44, my Magnum 44 with a Wren 44 needed V shaped collective to throttle curves and also required cyclic to throttle mixes to maintain reasonable headspeed doing aerobatics & 3D. If you're just flying easy circuits and the like a shallow "V" collective to throttle curve will probably be sufficient.

The 44 doesn't need a lot of throttle at 0 pitch and hover pitch to maintain headspeed but beyond that you need to feed in a bunch more throttle to maintain headspeed especially if you plan on flying the heli hard.

Here's how I approached it...

1. Spool the heli up on the ground and while at zero pitch adjust the throttle curve to your target headspeed.

2. Bring the heli up into a hover and note the collective stick position. Move the next points on your throttle curve left & right to line up with the collective stick position at a hover, this makes it easy to adjust hover RPM since you'll have a point on the throttle curve directly at the hover collective point. Now adjust those throttle points up and down to the desired headspeed at a hover.

3. For the points beyond hover, I did several sustained climb outs at different amounts of collective and with the help of a datalogger logging the headspeed I adjusted the throttle curve points left/right and up/down as needed to maintain headspeed. I ended up with a 9 point throttle curve.

4. Now that the collective to throttle curve was done, I tried flying the heli through my usual routine. While it did OK for most things I found that the headspeed decayed rapidly in moves that used a lot of cyclic but very little collective (such as tight funnels.) For this I had to create cyclic to throttle mixes. These mixes don't add any additional throttle if there is less than 15% cyclic input but starts feeding in more throttle beyond that. The mix curve is also somewhat like a parabolic curve that doesn't feed in any throttle from 0-15% cyclic input, feeds in a little extra throttle from 15-40% cyclic input, then ramps up quickly beyond 40% cylic input. I can't recall exactly without my TX in front of me but I think the overall mix is capped at about +15% throttle at full cyclic input, this is what was needed to maintain headspeed in tight funnels. Remember to set up a mix on both the elevator and aileron inputs.

[Skiddz]

I didn't have benefit of a data logger, but I did have a friend with a tach.

Flat pitch, flight rpm on the ground.
IGE hover, tweak throttle curve to maintain RPM.
OGE hover, tweak throttle curve to maintain RPM (This was *slightly* different so I split the difference between the two readings.
Slow cruise flight, tweak the curve.
Medium cruise flight, tweak the curve.
Fast cruise flight, tweak the curve.
"Patented" Chris Bergen "rocket-launch" takeoffs and pull pitch climbouts for about 5-6 seconds. Tweak, launch, repeat.

I did this for normal mode at 1450 RPM, IU 1 at 1550 and IU 2 at 1650.

IU curves are sort of a V, but the "legs" are not straight...

I don't 3D, but I fly big and fast with this thing and I had my buddy tach once through the entire flight. There were a few headspeed changes that exhibited themselves as (his words) "Slow blade rotation" as he tached