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Goblin 700 › BK 7001 servos not right on goblin 700
08-23-2014 03:33 PM  3 years agoPost 1
raspeitia

rrApprentice

US - WI

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Hi,

I'm reposting from a different forum in hopes someone else has any ideas.

Here are some pics and YT videos of the problem

------------------
Hi,

Just got my goblin 700 competition at IRCHA, but I'm having issues with my setup of the cyclic throws mechanically.

I got the BK 7001HV cyclic servos, but the throws and positioning don't seem mechanically right.

If I mount them without the rubber grommets like other folks are doing, I can push the servos higher against the mounting bolts and can get the servo arms closer to manual specs 42mm (manual says 40mm) and the black pitch arms accordingly to have the mixing arms horizontal.

The problem is then the servo arms are too far in and not 90deg vertically, so I get a torquing of the rear servo at full pitch and cyclic. I can see the servo arm bend! not good.

If I put in the dampeners, then they are dead in line with the links and no torquing, but I lose height and I have to make the servo links longer to get he swash mixer arms straight. This means less threads into the threaded rod. I already only had 5mm into each ball before with an 8mm gap.

Then it seems that the geometry is off, because the servo links have to be longer, that I get a non-even/centered ride in the anti-rotation brace (sitting higher because the loss in height for the servos).

I cannot make this right any way that I can see.

Were these servos a bad choice?

Any help is appreciated. I am posting a video and some pics.

Thanks.

Ray A.
------------------

I put in some spacers and the servo links and lower swash arms do line up, but I still get that binding up top in the anti rotation bracket when at full pitch and full forward cyclic.

If you can see from the video. At center stick, with the mixing arms level, the swash is NOT in the center of the anti rotation bracket. The bottom has 3cm and the top has only 1.5cm.

Is this correct? I feel like this bracket is too low and should be higher.

You can see how the servo binds at top pitch and pulls the bracket back. When it does this it torques on the servo arm too.

If you can see the swash itself does not bind on the main shaft, its not even close to doing that. Its mainly the AR bracket that seems to be causing things. The servo arms, lower and upper swash links look good geometry wise.

Am I missing something?

Ray A.

Watch at YouTube

Watch at YouTube

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08-23-2014 04:38 PM  3 years agoPost 2
Craigdieslemac

rrKey Veteran

Valdosta, Ga USA

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Have you gone through the entire setup on your FBL controller? Just curious if you have the swash settings correct and are running around 12 degrees of pitch and 8 degrees of cyclic/aileron? you may be putting the swash into a position that it will never get to in any actual flight condition.

Achieving actual center for your swash is just a matter of adjusting your swash input and output equally and opposite. if you want the swash to be lower, shorten your input rods and lengthen your PC rods. This will not change your pitch in the blades, just where your mechanical center is. I would still check after you make this adjustment and ensure you have your 12 degrees positive and negative and 8 degrees of cyclic, and that you are at zero with the collective in mid position.

As far as your input rod length is concerned, you should have plenty to make whatever adjustments you need to. I would make sure with the collective in center position that you have them lined up as closely as possible to being center with the ball ends on the swash, on full up or full down, they will never be centered. I have a few heli's that aren't even straight in line at center stick.. but thats how I have them adjusted on purpose to to suit the intended use of the aircraft.

Aut viam inveniam aut faciam

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08-23-2014 05:57 PM  3 years agoPost 3
raspeitia

rrApprentice

US - WI

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Craigdieslemac,

Thanks for the info.

I think I have everything as mechanically as close as I can get it. I was trying to keep the mixing arms horizontal if possible.

If not really needed on this heli, I can lower the swash as you mentioned. I was just not sure if that would affect any of the inflight mixes that would cause weird flight characteristics.

I'll have my friend walk me through the vbar setup again and verify the 12 and 8 of cyclic.

Thanks.

Ray A.

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08-23-2014 07:10 PM  3 years agoPost 4
Craigdieslemac

rrKey Veteran

Valdosta, Ga USA

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If you used vbar, you can get it right for sure, it's all I use. If you are getting 12 degrees of pitch on either side, I wouldn't be concerned. Make sure you check your gyro directions before you fly. Tilt the heli left and right and make sure the swash moves in the opposite direction. Then tip it fore and aft, again making sure it moves opposite to your moves. Check the tail as well.

If all is well, take a short test flight and see if it is behaving as you want it to.

Aut viam inveniam aut faciam

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08-23-2014 07:16 PM  3 years agoPost 5
eddiscus

rrElite Veteran

Dumont, NJ-USA

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Would adjust the swash ring value to eliminate mechanical binding when max pitch and cyclic are applied at the same time.

Logo Xxtreme 800
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08-24-2014 04:11 AM  3 years agoPost 6
RPM 1.5

rrKey Veteran

Cape May New Jersey

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Servo's horns are they set correctly at center, seems that something binding?????????????
That's the 1ST thing I do before set up !!!!!!!!!!!

Ray

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08-24-2014 04:45 AM  3 years agoPost 7
nickmcdonald

rrNovice

new lenox, il

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raspeitia, definitely use the grommets and don't . You want everything as mechanically perfect as your physical setup will allow. If I understand from your pictures, you're running the DFC head. It looks like your only option is to find some longer threaded rod for the servo to swash links.

The links on my 770 were more than long enough to get the entire threaded portion into the link. If you feel like yours are to short, just get some new ones. Don't compromise.

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08-25-2014 03:43 AM  3 years agoPost 8
raspeitia

rrApprentice

US - WI

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So my friend looked over my setup in the vbar and we also started from scratch and resetup everything on the wizard, and it still does it.

Checked that the max pitch and cyclic setup degrees were right in the vbar setup wizard.

Still binds!

My friend said we could try the vbar cyclic ring setting and just just bit the bullet and input 68%, just before bind.

Not sure if that will affect the flight characteristics, but I'll find out on the first maiden this week.

Yeah, I also figured that the only way to get the swash in the middle of the anti-rotation bar would be to have the mixing arms not horizontal. I guess I've always been taught to have everything as square as possible. Plus the manual also shows the mixing arms level and does not mention that.

My friend just went and checked his goblin 700 and it also does this!

So not sure at this point. I guess i'll fly with the cyclic ring and then try lowering the swash later to compare.

Ray A.

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08-25-2014 04:44 AM  3 years agoPost 9
nickmcdonald

rrNovice

new lenox, il

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Could swap to the HPS head, it's bracket is much taller and won't bind.

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08-25-2014 08:57 PM  3 years agoPost 10
raspeitia

rrApprentice

US - WI

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Just to tidy the thread up...

So there it is.

If a Mikado pilot and Bert Kammerer tell me that the servo balls should be backed off to approx 15-16mm and not worry about the geometry there, to get the cyclic right, you cannot get more definite than that!

Going to re-setup the servo arms and try it.

Thanks guys for the help and thanks to Bert K. and Mikado team pilot Laughingstill for clearing things up. Awesome support for the hobby!

Ray A.

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Goblin 700 › BK 7001 servos not right on goblin 700
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