Flybarless unit position ?

[Bungy15]

Is there a best position for locating a flybarless unit? I’vesearched the internet and forums and don’t seem to be able find any informationabout this. On Goblins the unit is normally positioned behind the main spindleand on the Trex Dominators forward of the main spindle but height wise they arevery similar.
I’m in the process of designing and manufacturing my own 550size heli and the perfect place for the flybarless unit (Brain) would be justunderneath and central to the main spindle.
Any thoughts on this would be greatly appreciated.

[waveydavey]

I don't think it really matters. There was a thought that a tail gyros best position was as close to the mainshaft as possible but I don't there was any real evidence one way or the other. I would consider electronic placement and making it viable without extending servo, sensor cables etc. better than a scientific approach.

[Grumpy]

I dont think it makes any difference at all. If there was any advantage in putting it directly below the main shaft manufacturers would be doing it. More practical considerations usually drive, like a place that allows convenient routing for the wiring and for access to programming ports/ buttons /gain pots or whatever.

[ChrisB]

Mikado say it does not matter where it is on the heli as long as its square to the frames of course,front,back,bottom,top off centre makes no difference as the whole model rolls and flips at the same rate regardless.

[tomatwalden]

Somewhere not overly exposed to vibrations I'd guess.

[Pj1969]

On the MSH brain it gives over 10 different positions you can fit the unit, just click on the one you have chosen and the software works out all the geometry for you and don't forget if you have a USB connector, that you can easily get to it.

[Bungy15]

Managed to get a picture to upload at last so hope it views ok in post. This is a work iin progress picture of the PJS 550. Thanks for all the info, greatly appreciated

[waveydavey]

Love it, I'd love to have the know how and time to do something like that.

[Mike Sanders]

Wow, that looks great. Did you do that machining or are the alloy parts from a standard heli (or helis)?

[Bungy15]

Yes did all the machining, even the servo arms including the splines, just for info the servo arms are adjustable every 1.2 degrees so can be set bang on without using any sub trims. the main shaft has radial and thrust bearings and during the build I keep an eye on the COG so with the 120 ESC and battery positioned where they are I can use the longer 600 length boom and the battery etc all still fit nicely under a standard Trex 550L Dominator canopy. Its also much lighter than the standard 550 dominator so fingers crossed should fly well

Thanks all

[myxiplx]

Ok, I like the solid mount for the battery plug (EC3/EC5??), is that something you've made yourself?

[Guest]

Impressive.....looks like a very nice piece of solid engineering.....liking the Goblin-Trex theme......are those Torx bolts I see in the frame.....very Thunder Tiger e700.....!!!

Would love to have the equipment to make something like that myself......don't think I'd be allowed a lathe/CNC milling machine in the spare bedroom....!!

[Peteski]

FBL unit just needs to be square to and horizontally inline with the mainshaft. Height doesn't matter and it can be in front or behind the mainshaft. The obvious place on your photo is on top of the machined boom support.

[Rachel]

if you want perfection directly under the mainshaft so the fbl unit only see's yaw, and on the COG so that it only see's pitch and roll, without any interaction.... but this is not possible so I always go for a low vibration point , usually provided by the heli manufacturer.
Edit I see the location of your unit and its good to go :-)

[Peteski]

if you want perfection directly under the mainshaft so the fbl unit only see's yaw, and on the COG so that it only see's pitch and roll, without any interaction....

There is no interaction between the axes anyway because the heli frame is rigid, so yaw pitch and roll angles will be the same at any point on the frame. It's only the orientation of the axes relative to the mainshaft that is really important (i.e. the unit needs to be square to the mainshaft) so that the control directions are all correct. Most FBL units can be programmed in the software to be located upside down, forward or rearward facing etc, but they always have to be square to the mainshaft so that the FBL axes line up perfectly with the helicopter axes.

That's a very good point about low vibration too. That would be far more important than placing it directly under the mainshaft.