help - multi blade rotor head setup

[Andy Mc]

Need some advice please - i am busy trying to setup a 3 blade rotor head on my 450 for my Augusta 109.
I think i understand the phasing side, as in locate one of the swash ball links behind the AR, the proceed to move the head around so that the trailing blade grip/blade is at 90 degrees to the tail,when i have it at that point, is the blade supposed to be at 0 degrees pitch? does it matter? or do you just have to have the blade set at 90 degrees to the tail boom? all servos are centered whlist i am doing this.
I have watched loads of vids & done reading up about it, but just seem to be stuck at this stage.

any help welcome

[Andy Mc]

Ok sorta past this stage now - i just did the 90 degrees phasing and made all my linkage rods identical lengths etc.. got it into a hover at about 55% throttle, nice and easy, the heli seems extremely agile atm, very very twitchy on cyclics, and any more throttle seemed to create a bit of slow tail wag.
Any ideas on what to change?
I have linear throttle curves, ended up with pitch curves of = 20-35-50-70-90
There is a stock align 450 pro motor 3400kv with 13t pinion, i have bought a 11t pinion today, should i install it to slow head speed down? anything else i can do to tame it down a bit?

I have also in v-stabi set scale settings. might try lower the tail gain to maybe assist with wag?

once again, any advice appreciated.

[myxiplx]

For a 3 bladed head using the same blades as you were running on 2 blade I would start at around 30% lower headspeed, so dropping from a 13t to 11t pinion is a good start, but even that may not be enough.

You will usually find your cyclic gain needs reducing. The slow tail wag sounds like too low a tail gain, which would be expected if you've reduced your headspeed as you've reduced the mechanical gain on the tail. If you saw a fast tail wag I would say lower the tail gain, but in this case I suspect it's the opposite.

You may also find you need to run bigger tail blades now, or somehow increase the tail authority. Depending on your model there could be a few options here, three bladed tails, larger blades, increasing tail ratios, etc... The lower headspeed needed by the three main blades will slow the tail down considerably, but while you've added another blade on the head, it doesn't sound like you've also done that on the tail.

[electricsceadu]

on the swash lower the amount of travel on the cyclics
to tame the head down
eg go from 8 deg of cyclic pitch to 5 or 6 deg
and add expo to help also

on the tail this is not uncommon with multi blade heads using a std tail designed for a 2 blade head
increase the tail blade size length and width
and alter the gyro gain as needed

[tomatwalden]

...
I have linear throttle curves, ended up with pitch curves of = 20-35-50-70-90
...

Do you really mean this? Are you saying you have a throttle curve of something like 0,25,50,75,100 or do you mean a flat throttle curve like 70,70,70,70,70 ?

If the latter, fine. If you really are using a linear throttle curve though, you should change that!

[Andy Mc]

Hi Tom
Yea i have linear on idle 0, so use it up to 50% throttle then switch to idle 1 which has a flat curve ie 90 85 80 85 90. I this still wrong? All my helis are like this.

[tomatwalden]

Hi Tom
Yea i have linear on idle 0, so use it up to 50% throttle then switch to idle 1 which has a flat curve ie 90 85 80 85 90. I this still wrong? All my helis are like this.

That's less worrying as you're just using a linear throttle curve to mimic "soft start" in the ESC. TBH, it's not really needed with most ESCs as they all (for the most part) have soft-start so that any sudden jump in requested power from 0% to say 80% results in a slow, gradual spool-up.

The shallow curve you've given for idle-1 is OK for a non-governed ESC. If you use a governor, you should have completely flat (eg. 80,80,80,80,80).

Anyway, as already mentioned I think ... slow tail wag = gain too low. fast tail oscillations = gain too high.

[Grumpy]

EDIT... sorry i just noticed that you are using Vstabi, so I'm guessing your FBL is a Vbar?

To stop the slow wag you might try reducing 'Acceleration' in the advanced tail settings and/or reduce 'I gain'.