700 Comp' 'toilet bowling'!

[George J]

I'm sure this has been said before but anyway....just built a 700 comp' carbon with HPS head and from the first flight it's had the 'toilet bowl' effect thing going on at lower head speeds. It has now had maybe 30 flights on it so is properly run in now, have added shims twice now to remove the axial play on the head and does this exactly the same as when new.
Once up to speed it's fine and not noticeable, I fly it at 2000 plus but where it's now becoming really annoying is during autos when the head speed bleeds off and the whole heli starts wobbling.
I was wondering if anyone has a cure for this as its starting to get annoying!

[rb30cory]

What FBL unit? If you have everything setup right mechanically I'd start reviewing your gain values and adjusting them. Only head wobble I get is perhaps around 1000rpm when I'm finishing a baby auto and letting it hover with no power.

[George J]

Vbar Neo but its nothing to do with the gains or vbar set up. It's something to do with the head/ dampers/ shimming etc but just trying to find a solution.
Autos is where it's worst and once spooled up and I'm throwing the heli around it's completely gone and it flys great as expected.

[alexmit]

Originally Posted by jonesheli

Vbar Neo but its nothing to do with the gains or vbar set up. It's something to do with the head/ dampers/ shimming etc but just trying to find a solution.
Autos is where it's worst and once spooled up and I'm throwing the heli around it's completely gone and it flys great as expected.

Is this the HPS2 or HPS 3 head? What head speed are you running when it wobbles? Please share more information about your setup. Blades, Servos, Motor, ESC, Etc. The more info you can provide the better.

[George J]

Originally Posted by alexmit

Is this the HPS2 or HPS 3 head? What head speed are you running when it wobbles? Please share more information about your setup. Blades, Servos, Motor, ESC, Etc. The more info you can provide the better.

HPS2 head, Xera 4530-500 motor, Vbar Neo, Futaba/Kingmax HV servos, Kosmik 160 and Align 700mm mains. I've re shimmed the head twice now but was just comparing my 700's head to a friends 630 also with HPS2 head at the field just now and mine is most likely a bit heavy on the preloading as its very rigid in comparison and the 630 autos great and has no such wobble tendencies so I've just come indoors after removing a couple of shims on the head so will see if that improves it, I'm sure it's just down to getting the right balance of shims/dampers etc.
It's worse during autos at the moment though and once spooled up it completely disappears so will report back when I've flown it again.

[Vas10]

When you have a heavy preload there is a certain RPM range at which you have that wobble. So if you want to run it like that you need to adjust the RPM to avoid that sector(usually the sector is about 100rpm wide and some times there are 2 sectors 50rpm each at different places). Also if nothing works try loosening up the main blades but then you have to be careful with the 3D. So keep testing and good luck!

[rb30cory]

I experienced a small wobble today - saw it when coming in to land. After further inspection I found my main gear jesus bolt needed a little snugging up. I could barely wiggle my main gear side to side (bolt is the fulcrum.) I snugged it down and guess what? Next flight wobble was gone. (took about 80 flights to get a little loose)

Give it a fine tooth comb it could be as simple as my example above

[George J]

In-between rain showers I managed a garden flight and its massively improved by removing a shim from each side, not perfect yet but has made a big difference so am getting close to sorting it.

Anyone know if there is a slightly softer damper I can stick in it? I notice in the damper pack there is 3x different sets of dampers, type A, B & C, are these different hardness?

[alexmit]

Originally Posted by jonesheli

In-between rain showers I managed a garden flight and its massively improved by removing a shim from each side, not perfect yet but has made a big difference so am getting close to sorting it.

Anyone know if there is a slightly softer damper I can stick in it? I notice in the damper pack there is 3x different sets of dampers, type A, B & C, are these different hardness?

From the HPS 2 Manual:

The new HPS 2 head offers an independent dampening system for each blade grip, there are three dampening settings:
A = Soft for smooth response.
B = Medium.
C = Firm for direct and precise response.
We recommend starting with the medium setting.
For safety reasons we suggest to not exceed 2300 rpm.

Download here:
http://www.goblin-helicopter.com/sho...ay/H0428-K.pdf

[George J]

Originally Posted by alexmit

From the HPS 2 Manual:

The new HPS 2 head offers an independent dampening system for each blade grip, there are three dampening settings:
A = Soft for smooth response.
B = Medium.
C = Firm for direct and precise response.
We recommend starting with the medium setting.
For safety reasons we suggest to not exceed 2300 rpm.

Download here:
http://www.goblin-helicopter.com/sho...ay/H0428-K.pdf

Thanks for that, didn't see that. Do you know which ones would've been supplied with the kit by any chance?

[alexmit]

Originally Posted by jonesheli

Thanks for that, didn't see that. Do you know which ones would've been supplied with the kit by any chance?

Off the top of my head, no. I thought you said you were looking at all 3 dampeners, (A,B,C) which I 'think' it ships with all 3.

[George J]

Originally Posted by alexmit

Off the top of my head, no. I thought you said you were looking at all 3 dampeners, (A,B,C) which I 'think' it ships with all 3.

Sorry I meant I was looking on Fast-Lad site in the spares, my kit only came with the one set but not sure which ones they are but guessing they would all ship with a 'stock' damper wether A B or most likely C maybe?

[Grittner]

For what i know, the HPS 3 come with "A, B, C" option HPS2 does not.

[George J]

Just ordered the damper pack which has all 3 in so will remove the ones in the head and fit the next softest one when I get them.

Thanks for the help.

[George J]

All seems to be ok now that I've removed a couple of shims so it seems that too much preload was the issue here. Autos were fine and could get the headspeed way lower than I'd ever fly it so all good.

[TT]

Glad you got it sorted! I haven't had this problem with my Goblin 700 / HPS head but I did have the same problem (perhaps more severe) with an Align 700E due to overly stiff dampeners. It is painful to watch a heli eat itself on the ground when all you did was land it. Aggravating to say the least.

[George J]

Put some flights through the Goblin yesterday and it was the first session with it where it didn't feel a bit loose and a bit horrible and tbh it is now flying as I want it to.

However, I have to say that this Goblin is the first heli I've had for a long time which has needed so much effort to get flying properly, it was nearly up for sale last week! Even a Trex 700 now will fly spot on straight out the box so was a bit disappointed as was really expecting the HPS head to just work but on mine it is a very fine balance between damping and preload if you want the heli to be more than just a 2300 rpm smack heli!

All good now anyway, thanks for any input

[alexmit]

Originally Posted by jonesheli

Put some flights through the Goblin yesterday and it was the first session with it where it didn't feel a bit loose and a bit horrible and tbh it is now flying as I want it to.

However, I have to say that this Goblin is the first heli I've had for a long time which has needed so much effort to get flying properly, it was nearly up for sale last week! Even a Trex 700 now will fly spot on straight out the box so was a bit disappointed as was really expecting the HPS head to just work but on mine it is a very fine balance between damping and preload if you want the heli to be more than just a 2300 rpm smack heli!

All good now anyway, thanks for any input

Glad you got it worked out. I don't believe your experience is typical. I think a 3 bladed head is a bit more work than a 2 blade setup if you experience setup bugs.
Please close this thread since your issue is resolved. :-)

[K2Freak]

Funny. My 770 and 570 carbons both maidened flawlessly, but 6 weeks later I'm still struggling to get my 380 to be even sorta flyable. Major tail issues. Go figure...