450 HK 450 4 blade

[lennyapplegreen]

Hi Guys, I have a problem with my 4 blader, the tail is very sensitive and difficult to keep centred, I can fly it but it is far too unstable, my standard HK 450s use the same HK401 gyro and I have swapped the gyro from the 4 blader to one of the others and it works perfectly.
Any suggestions would be welcome, thanks.

 

[Tony]

With a 4 blade main head, it's putting more torque onto the tail. So the gyro is having to compensate more to correct this torque.

With that said, I"m not sure what Tx you are using, but make sure your endpoints are set to 100/100 and adjust them DOWN (ie, 80/80) until you no longer get any binding. Make sure your tail slider is in the middle of the tail shaft (you should have pitch on teh tail blades when it's centered. If you don't, make sure you set some pitch into the tail blades pushing air out the right, or nose right). Then, make sure you are in HH mode and raise your gain up until you get a wag, then back it down.

With all of htat said, I HATE the HK401 gyro. I purchased 3 of them and all 3 of them sucked. Look at the HK250 gyro which used to be the Assan GA250 gyro. This one I had great luck with. It's not a piezoelectric gyro like the 401, it's a MEMS gyro which is MUCH better and doesn't require you to acclimate it to the temp from in the house to outside.

 

[danhampson]

the instability is due to not having a flybar. It is possible (as long as your head phase is perfect) to fly a multi blade head this way but from what i have read you will be fighting it all the time, you could try to reduce the throw of your cyclic servos with the dual rates in you tx, because with the increase in blade count also increases cyclic response and torque (as Tony stated). I personally would change the gyro for a FBL controller it will make it far easier to fly and if it is still too sensitive you can tone it down with the flip and roll rates.

At the moment im using a 3GX with a 4 blade head with the flip and roll rates set at 30% (i still feel that this if a tad sensitive)

To make the tail hold better you could try some 500 tail blades on it (taller skids and some filing are required) or you can make a cascade tail up, which doubles the blade area this is not too difficult to make.


I agree with Tony on the HK401, when i first started in the hobby i had one and couldn't get it to hold and quickly changed it out to a spartan quark, which held solid as a rock.

 

[murankar]

If your looking to keep tour setup upgrade the gyro to a better tail gyro and servo. If you have a quality tail servo then leave it as is. I do have a gyro and servo combo for sale in the sale adds.

Your best option is the fbl controller.

Sent from my LG-E980 using Forum Runner

 

[Admiral]

I agree with Dan it is possible to fly four bladed without an FBL controller but you must get the blade phasing exact and it is still pretty hairy, and FBL controller and either 500 tail blades or a four bladed tail rotor will give you a far better experience.

 

[lennyapplegreen]

Thanks Tony, I use Dx6i which I`ve found to be excellent , I have one Assan which I haven`t used as yet but will try it as the 401s do seem a bit variable.
So basically as there is more torque reaction to the 4 blades the tail rotor needs more pitch to counteract than it would for 2 blades for a given rotor speed, now I have watched your vid for the GA250 I can now maybe understand how to get it working, the translation is very poor indeed.

- - - Updated - - -

Hi mate, yeah its just the yaw instability I couldn`t get sorted, the overall handling isn`t that bad just a bit more responsive than flybar version, I will upgrade to a better tail servo and gyro , I`m not interested in 3d flying so don`t have to go overboard thats why I use HKs , they are cheap lol.

- - - Updated - - -

The pitch and roll wasn`t an issue it was just the tail not holding steady but given the fact that the heli is so much more responsive it was slightly unmanageable , I am going to get upgrade to a quality gyro fit bigger blades ( tail ) and a better servo, cheers,

 

[Tony]

Try this, get a ZYX gyro and stick on that bird. It's a 3 axis gyro. I was (and still am) so tired that I completely overlooked the fact that you don't have a flybar on that bird. Once you put that gyro on there, it will be MUCH more stable. I suggest an AR7200BX or an Ikon, but not everyone can afford one. If you can, then do that. Otherwise, just get the zyx.

 

[lennyapplegreen]

Hi Tony and all , thanks for the advice, the heli is now flyable ( just ) with the rudder axis not as bad as it was, I am waiting for some new digital servos so I can switch to the GA250, as a tempory measure I have fitted a large Futaba servo for the rudder.
Also I have reduced the control throws on the swash to 50% this has made it far more stable , secondly reduced the positive pitch so it doesn`t come in until after half throttle position so reducing torque reaction until the tail rotor is at a higher speed.
Next step is longer tail blades and then a 4 blade tail rotor which I am going to make myself to better tolerance than the commercial ones.

 

[Lee]

Try this, get a ZYX gyro and stick on that bird. It's a 3 axis gyro. I was (and still am) so tired that I completely overlooked the fact that you don't have a flybar on that bird. Once you put that gyro on there, it will be MUCH more stable. I suggest an AR7200BX or an Ikon, but not everyone can afford one. If you can, then do that. Otherwise, just get the zyx.

+1 Do yourself a favour and get a FBL unit. Cyclic and tail control all in one. The heli will fly 100% better than no FBL unit and a cheap tail gyro.
ZYX is good. Also Robird and a few more for between $50 and $100

 

[lennyapplegreen]

Might just do that , all axes gyroed seems a good idea, I assume its the same as tail gyro whereby the FBL is first off the receiver then the servos follow?

 

[Lee]

RX>FBL>Servos
If you get something like the AR7200BX, the unit is a FBL and RX in one.