pitch curves

[wizzel1]

Hello, I have a 450 size scale heli with a 500E fuselage. I put on a five blade head and when it lifts off it is real floaty. The head speed is lees than 1000RPM. With a five blade head what kind of PITCH CURVES should I be using to get the head speed up and have more control. I'm assuming the head speed should be @ 1500RPM ? Thanks

[Keyrigger]

There's a couple of ways to do it. One is to keep it like 3D where mid stick is zero degrees pitch, and the other is to mechanically set the swash so that you have around 3 to 5 degrees pitch at mid stick with the arms and swash at 90 degrees to the main shaft. Normally, a mechanical setup like that will give you -4 degrees or so of pitch at low stick and in the neighborhood of +12 degrees or so of pitch at full stick.

With today's modern radio systems, you can digitally set your hover pitch, negative pitch, and full pitch from a standard 3D setup and although there is merit to keeping the servo travel identical from hover to the extremities, I have found that with today's modern high power servos, it doesn't really matter. Also, you can alter the exponential to suit how quickly you need the servo to respond as you approach travel limits. Options galore.

Don

[getsuyoubi]

5-blade heads on a 450 are really tricky. A friend of mine has the same setup, and the same problem you describe. His solution was to install symmetrical blades to reduce the lift, which allowed him to run higher headspeeds. With the asymmetric blades the heli was extremely sensitive to the slightest breeze unless he lowered the eheadspeed so much that the tail wouldn't hold.

[Andy01]

Are you sure the headspeed is that low ? To get 1000rpm on an old Trex 450 SE V2 with original 150T main gear and even an 11T pinion, you would have to have either a slow motor (maybe 2000kV) or be running 2s, or be throttling dramatically with ESC.

With a fairly stock setup;

RPM = 3500kV x 11.1V x 0.9 x 11T / 150T = 2565rpm at 100% towards the end of a flight. So either;

Running at 1000 / 2565 = 39% throttle, or

Motor = 1000 / 2565 x 3500kV =± 1365kV motor, or

At 2s, rpm = 2565 x 0.67 = 1710rpm, and then throttled back.

I would think that a decent headspeed for a 5 blade 450 would be around 1900-2000rpm. I would be surprised if it flew well at 1500rpm, and a little surprised if it even got much off the ground at 1000rpm, and I would guess that the tail authority would be close to non-existant.

Colin