Embla tail vibration issue, heeeeilp!

[maddog7]

Hi all,
I'm having a mare with an Embla 450 I bought new in November last year, rather than explain it all again I'll just paste a copy of the email I've just sent to the (good) people I bought it from.

As well as the things I've looked at I took it to the field at the weekend and had two very knowledgeable forum members (Stuart and made2fade) take a look at it. They made some good observations and suggestions but my issue still remains.

I wonder if anyone has any suggestions?
Cheers in advance

D


"Hi Folks,
I bought a Hirobo Embla 450 from you in November last year. I had a problem with the kit motor vibrating very badly which you kindly swapped for me. The replacement was much better but still out of balance. I balanced it but the heli still behaved like the beastx was affected by vibration so I put it in the naughty corner and forgot about for a bit. I recently aquired another motor from a friend which is smooth as silk and fitted it thinking it might give me the Embla I'd hoped for. Unfortunately it behaved exactly the same way.


I thought I'd better look into it and it would appear that there is quite some vibration coming from the tail.
Without the hub attached the vibration level seems fine, with the hub but no blades, it seems acceptable too, as soon as blades are attached it's significant. Bizzarely, I even tried an Align 450 hub/grips/blades assembly and the vibration is still there?



I've tried all sorts to see if I can remove/reduce it but it still persists and I'm certain it is what is causing the thing to fly so badly. I've weighed the tail blades on a .01g scale and checked their balance on a glass balance (they even balance upside down) and as far as I can tell they are perfect. I disassembled the tail hub, measured all of its dimensions as best I could using a calpier, weighed the grips and measured them too. Tail shaft is straight, bearings seem free, I've tried different belt tension etc and I can't find anything.


I'm not really sure what to do from here, I wonder if you have any suggestions? It's a shame because it's such a nice heli and has only had a total of about 4 or 5 flights.


Thanks in advance
D"

[maddog7]

anyone?

[electricsceadu]

i would check that you have assembled the thrust bearings correctly
built the head up correctly
check all the shafts with a dti gauge whilst still fitted to the model
re-balance the head, blades and tail assemble etc

make sure you haven't got a bent yoke on the head etc
you never know mr delivery driver could have dropped your kit or played football with it

make sure the blades are in track and the motor is ok


if you think you can try flying the model without the beastx, you only need to hover it
if all is well the problem is in the beastx or its mounting

if not then its in the model or the servo's etc



and also make sure the blades are not too tight

[maddog7]

electricsceadu
Thanks for taking the time to reply.
I'll check the main rotor assembly order just to be sure, though the vibes happen without any main blades attached.
The tail grips don't have any thrust bearing in them, only radials.
Good call on the DTI, I'll give that a shot. The tail shaft looks spot on though by eye. I've not looked at the main yet, will do though.

I might try balancing the entire head/tail assembly on the balancer to see if that shows anything.

I've tried the tail blades from free swinging to bar tight and everything in between (remember no mains attached) and still loads of vibes.
For flight testing I've tried 2 sets of main blades with varying tightness with no difference.

I've not flown a FBL heli without a unit before, might be an interesting or possibly expensive experience! hehe!

Thanks again, you've given me some ideas to try!

D

[franky975]

I would try to balance the tail hub with the blades fitted on a magnetic balancer if you have one.

[Made2Fade]

TBH my moneys on it not having anything to do with the tail hub at all. I think that putting the hub/grips on is just amplifying the vibes through its weight. It will be very interesting to see what it turns out to be.

[Downdraft]

Is it a belt or shaft driven tail?
If its a shaft have you checked that a small amount of Epo hasn't wicked its way into the bearing in the tail boom. Or perhaps a bad bearing from new, it does happen.

[Made2Fade]

Its a belt driven tail Sean

[maddog7]

I would try to balance the tail hub with the blades fitted on a magnetic balancer if you have one.

Thats one pf the things I was gonna try Ferenc. Cheers for the suggestion though.
How was your Sunday?
D

[maddog7]

TBH my moneys on it not having anything to do with the tail hub at all. I think that putting the hub/grips on is just amplifying the vibes through its weight. It will be very interesting to see what it turns out to be.

I think I'm gonna remove the main head completely and see how it behaves, I might see if I can drive the tail directly without the maingear and see what happens. It's really puzzling.
Cheers for the suggestion Lee.
D