Roban 700 AS350 FBL Gains and Head Speed

[StripedGear]

Hey... back in December I got 700 Roban As350. I have had to do several mods and rotor head work to get this thing flying using what came with the kit. I did mod the main shaft and now using a Goblin 700 main shaft. And went with a matched set of 690mm blades instead of one that came with it.

I'm testing now and have had a lot of issues getting the FBL controller dialed in. I went from having short fast pitch pumps to slow, big wave oscillations...
I'm using the Naza controller. I have a couple of them and have setup several for friends. I am very familiar with the Naza but I seem to be getting into high percentage values for the FBL gains in order to get it flyable. I'm not sure if that is the right thing to do.

This is a big 3 blade heli with a rigid head [no dampers]. I started at 1300 rpm and then 1350 for most of the testing.. On the last flight the other day I went to 1400 and it flew better. But I'm not sure of the right HS for this head and blades.

Here's stats

Roban 3 blade head
Zeal 690mm blades
Scorpion 4035 530 kv
Ice HV80
Align DS615 x 3 Futaba 9254
Naza H controller
Ratio of 13.83 to 1
Motor pulley is 22t
Main gear 78t
Sper gear 20t

1400 = 91% 1450 = 94% so I'm good if I use these HS.
Reaching an rpm is not an issue.. Knowing what HS I need is...

Any help with this would be appreciated. Thanks.

[StripedGear]

pics

[Andy01]

I know nothing about Naza, but I would have thought that something closer to 1250-1300rpm would be an appropriate starting headspeed. I run my helis as follows;

Long Ranger - 2x 710mm 1350rpm
Seahawk - 4x 600mm 1350rpm
EC-145 - 4x 820mm 1050rpm

So, since yours is a 3 blade 700, I would have thought that a bit slower than 1350rpm would be a good starting point. But hey, if you like the way it flies at 1450rpm, go for it, it just cuts flight time a bit. There is no point in trying to fly a low headspeed just because others do - you should fly a headspeed that works for you.

I assume you have seen the threads on RR about vibes in the Roban mechanics etc causing issues ? Some FBL units don't like vibes and can misbehave badly.

Colin

[StripedGear]

I know I have a thread there on vibs but it was the mechs only. Sanding and polishing the metal gears because they were so rough they caused vibs. But I don't think I've seen one the FBL unit with the Roban.
I wasn't looking to fly at 1450. The bird just got more ridged at that rpm, but I have to admit that I haven't tried 1300 after raising the fbl gains to 170. I think I'll check it out.

But that was one of my questions.... Is it normal with a multi blade head to have such high fbl gains?
Thanks.

[Andy01]

Can't answer your question because it is specific to Naza I think. The Skookum gains don't go that high in my experience.

I can't say that I have seen any real difference in the gains between a 2 blade and 4 blade on a SK720, but I can't speak for Naza. High gains are normally more associated with smaller models.

Colin

[StripedGear]

Ok, thanks.