Dune and Demon.

[Boris the Blade]

Hi guys,


I am just starting with Dune and seek for your advise.
I have few helis to compare here: TSA600 and stretched to 600 TRex550. All have BD3SX.

My questions are:

1) What head and tail gains do you run? Mine seem to be very low compared to my other setups: 62 on head and 48 on tail. Usually they are 70/55-60 respectively.

2) Does the end of your fin vibrate? None of my other helis does. Hand on tail boom does not feel too bad but the look is alarming.

3) If I will turn tail blades under servo load I will feel a sort of "loose construction" Especially plastic triangle arm feels loose at the point of ball link.

Hope you can help, thanks!

[thefrog]

I'm sure you'll get better answers but my few cents below.

1) I installed a 3SX on my Faifa and tested this weekend. Gains are 65/54 but the tail is still too high. So your numbers seem fine. On my Diabolo the 3SX numbers are higher (70/70).

2) The tail fin should not vibrate at all. You most probably have a meshing issue - either in the tail gearbox or the crown gear setup. Check the manual and follow the instructions closely. Also ask for help here.

3) Not quite understanding what you mean but there should be no slop or play. The tail should be perfect. If there is an issue it could be partially responsible for the vibes you mentioned in 2).

Originally Posted by Boris the Blade

Hi guys,


I am just starting with Dune and seek for your advise.
I have few helis to compare here: TSA600 and stretched to 600 TRex550. All have BD3SX.

My questions are:

1) What head and tail gains do you run? Mine seem to be very low compared to my other setups: 62 on head and 48 on tail. Usually they are 70/55-60 respectively.

2) Does the end of your fin vibrate? None of my other helis does. Hand on tail boom does not feel too bad but the look is alarming.

3) If I will turn tail blades under servo load I will feel a sort of "loose construction" Especially plastic triangle arm feels loose at the point of ball link.

Hope you can help, thanks!

[Boris the Blade]

Thanks Thefrog,

That's what you get when you buy used machine. No regrets though...

1) All in line then, no worries.

2) Found loose bronze slider insert. There was no trace of thread lock... Now tail moves much better. Still some gap on the tail rotor shaft (up/down, in/out). Minimal. Bench tested - still vibrates, just the end of tail fin, hand on the boom feels just regular.

Should there be ANY movement on the pitch links and tail control arm? Mine live a bit in and out.

Would be great to know more about the "meshing issue" you mentioned. I have an assembly instruction, but there are just blow up pictures.

3) It is clearly loose plastic tail control arm and tail pitch links.

Now I have to do something with this torque vibes.

[Sage]

Hi,


2) Make sure that tail assembly is mechanically built properly. No bent shafts, proper backlash, etc.

KSM tails are known to be very sensitive to tail rotors being out of balance.
In worst case the grips may came loose from the hub during hover/flight if tail rotor is not dynamically balanced.

Make sure that grips have a little bit play on the hub and are spaced evenly from the centre of the hub.

Remove main blades and spool up tail rotor.

If there are some visible vibes on the tail fin apply a 1 cm piece of electric tape to one of the tail blades and spool it up again.
If it does not reduce vibes remove it and apply it to the opposite blade.
If vibes are reduced but still there keep shortening that piece of tape until tail fin vibes are gone.

Once tail rotor is properly balanced you will have one of the most smoothest helicopters in your fleet.

Hope it will help.

[Boris the Blade]

Thank you Piotr,


Sounds a bit weird that balancing of the tail blades. None of my previous helis was that sensitive... I'll give it a try. I tried balancing tools I have since 450 size heli time. Blades are too light to be balanced on that tool (I have Rail blades).

Assembly seems to be OK, the sound is smooth, no clicks no tight points.

[Smoggie]

I just put a Dune together. I've only flown it four times but I also noticed a vibration on the tail fin. It seems to be only at low headspeed and disappears at higher RPM.

I checked mesh on the torque tube gears, front is perfect, rear was a bit loose, so I added a 0.2mm shim to remove the slop. I don't imagine that was the cause of the vibration to be honest, but will find out shortly when I go out and fly again.

Tail blades are CY, I've not tried balancing them as it's not something I've ever had to do before.

[Boris the Blade]

Originally Posted by Grumpy_Old_Man

I just put a Dune together. I've only flown it four times but I also noticed a vibration on the tail fin. It seems to be only at low headspeed and disappears at higher RPM.

I checked mesh on the torque tube gears, front is perfect, rear was a bit loose, so I added a 0.2mm shim to remove the slop. I don't imagine that was the cause of the vibration to be honest, but will find out shortly when I go out and fly again.

My vibes exist at any hs.Only the bottom part (longer) of the tail fin shivers. Top part is stable.
Is it correct that TT has a free move between directions?

[TheKingPhisher]

I've found from my own experimentation that in general thinner tail fins will have more visible vibrations than thicker tail fins so I don't think seeing vibrations means something is wrong per se. That said I haven' built mine yet so I don't know if it's normal or not in the case of the Dune.

[trillian]

Originally Posted by Grumpy_Old_Man

I just put a Dune together. I've only flown it four times but I also noticed a vibration on the tail fin. It seems to be only at low headspeed and disappears at higher RPM.

I checked mesh on the torque tube gears, front is perfect, rear was a bit loose, so I added a 0.2mm shim to remove the slop. I don't imagine that was the cause of the vibration to be honest, but will find out shortly when I go out and fly again.

Tail blades are CY, I've not tried balancing them as it's not something I've ever had to do before.

I only just started noticing a vibration in the tail fin on mine and think this is because I now have a bright orange fusuno fin so it's very easy to see if it's moving. But it only does it spooling up and then it's fine so maybe that's normal. I'm also using CY 95s. I have other tail blades I could try and see if the vibes go away.

I think mine also has a bit too loose mesh in the tail gearbox so I'll have a look at that as well.

[Smoggie]

Four more flights today and although everything went fine (she flies great) the vibes on the fin are still there. On closer inspection the vibes are there at all headspeeds, but at higher headspeed the amplitude is a bit less. The vibes aren't extreme, the fin maybe moves 1/8" but at a very high frequency making it a blur.

I'll try checking the tail blades for balance and if that doesn't show anything then the 'adding tape' suggestion mentioned above.

[trillian]

Well now I'm slightly puzzelled because I can spin up the tail blades here with no main blades and there's no vibrations at all, not even a little bit.

The slop I was seeing seems within spec because it's only the front tail gear and crown gear, there's no slop in the tail case. (And the mesh in front seems fine, not too loose or too tight).

So the vibes appear to not have anything to do with the tail blades or TT. I'll just have to watch it closely next time out.

[wadders248]

The Kasama helis are all sensitive to any imbalance in the tail. It's always worth a read through this sticky

[thefrog]

To the OP, a second hand airframe may not have been built properly by the previous owner. Check the backlash in the tail gearbox (should be a very small amount), use the 0.1mm and 0.2mm shims if needed) and lube the gearbox every 20 - 25 flights.

[Boris the Blade]

Originally Posted by thefrog

To the OP, a second hand airframe may not have been built properly by the previous owner. Check the backlash in the tail gearbox (should be a very small amount), use the 0.1mm and 0.2mm shims if needed) and lube the gearbox every 20 - 25 flights.

What kind of lubricant should I use? And how much?

[thefrog]

Originally Posted by Boris the Blade

What kind of lubricant should I use? And how much?

The kit comes with a bronze coloured grease - no idea what it is, I've never used it. I use a white Lithium grease and have a syringe with which I dab a bit of grease on. Whatever you decide to use, stick to the same base. I suggest that before you mess around balancing tail blades first check and lube the tail gearbox. I looked at the Dune manual online and it seems you can't adjust the crown gear mesh like the Srimoks. Perhaps Dune owners can confirm?

[TheKingPhisher]

Originally Posted by trillian

Well now I'm slightly puzzelled because I can spin up the tail blades here with no main blades and there's no vibrations at all, not even a little bit.

So the vibes appear to not have anything to do with the tail blades or TT. I'll just have to watch it closely next time out.

Sounds like your vibes are coming from your main blades?

[trillian]

Originally Posted by TheKingPhisher

Sounds like your vibes are coming from your main blades?

I don't see how, the frequency would be so much lower.

[TheKingPhisher]

When you spun up you tails without main blades there is no load on the tail? Did you hold the heli in place and apply rudder to see if there is vibes under load?

[Boris the Blade]

Originally Posted by thefrog

The kit comes with a bronze coloured grease - no idea what it is, I've never used it. I use a white Lithium grease and have a syringe with which I dab a bit of grease on. Whatever you decide to use, stick to the same base. I suggest that before you mess around balancing tail blades first check and lube the tail gearbox. I looked at the Dune manual online and it seems you can't adjust the crown gear mesh like the Srimoks. Perhaps Dune owners can confirm?

Do I have to wash gear box each time or just add a bit of grease? I have "Molygrease EP 3% General purpose NGLI 2 Lithium Grease containing solid Molybdenum Disulphide". Is it OK i wonder?

[thefrog]

Originally Posted by Boris the Blade

Do I have to wash gear box each time or just add a bit of grease? I have "Molygrease EP 3% General purpose NGLI 2 Lithium Grease containing solid Molybdenum Disulphide". Is it OK i wonder?

Just add a touch of grease. The one you had should be fine.