e-copter
Senior Heliman
Location: Nice, France
| Hi Eury,
i've checked your heli pictures and could found some reasons why the SK360 does not work properly.
Below my text is the picture with the points which casue problems to you.
A: The blade grips extension for the ball linkage are too long. There is an insane lever effect twisting the blade grip arm between the ball link and the main body of the blade grip. This causes an erratic answer to the SK360 inputs. it's a little like having a carbon torque tube for the tail completely delaminated as a result: waggy, at low gain, and "kicky" at higher gains.
B: The main hub is totally empty in the middle. The flybar pivot is not there to link the two sides of the rotor head, and i would say that you get 5 / 10 ° of unphasing when the main hub twists. with the blades trainee (airfoil, sorry i do not know the exact name in english), it's like if you had a brake disck on the top of your head and it unphases it by twisting the hub backward when you apply pressure on the brake, and forward when you release it; Imagin the effect with backwarding and forwarding blades + the torque handled by the hub.
C: i can not se very clearly, but it seems you are full neg pitch with very little elevator; The part seems very "straight" and the ball link is close to bind on the swashplate. Be carefull with pop out of the linkage.
D: according to full neg pitch, your servo arms look not very angled. I would recommend removing or reducing the brass inserts you have on the blade grips for the ball linkage, and bring the servo arm ball link closer to it's center if possible. As well, teh Eflite servos are not very powerfull and have natural slope .
If you add the fact that your main hub twistes on itself, that your blade grips arm twisst as well and that your servos will act as bumpers for all of that, it will be very hard for the Sk unit to ake it"s job properly as each input you will give to it will be then translated for the rotor head and the problem is that the SK unit will not be able to "feed back" the desired input. And the more it will try to compensate with inputing some wider orders, the more the entire head hub / blade grips arms will twist and give erratic answers as everything will be delayed and amplified.
Anyway, i think that with a simple main metal hub and metal grips ( you cna find some aftermarket very easy and very cheap), you should solve 99% of your problems. Important is to try to find blade grips where the ball link is fitted with it's screw parrallel to the feathering shaft and not perpendicular to it. It avoids linkages pops outs.
That said, you have a very clean setup on your heli and before switching your SK 360 to a nem heli, i would encourage you to try to find a Zoom 400 like metal hub and metal grips to make more tests.
For the 450 heli sizes, the best hub / grips combination existing on the market is the Mini titan main hub ( it's wide, it's good for flybarless!) with the metal grips. They can be fould cheap everywhere.
The Kasama head is not bad but honnestly the aluminium quality and milling precision is not as good as on the original thunder tiger parts ( i had to setup one, full of small bugs like too long screws ripping on flybar and so on..)
Another hub you could try for very cheap is the Walkera 60#B metal hub( the small MFS head) with it's blade grips , i must have one somewhere i'll take pictures for you later.
Hope you will finnish to find the bugs and solve them, the SK 360 is a nice thing and i'm building it in my Bell 222 fuse now (it's a 450 size) with a custom mechanics. Crossing fingers  ))
Best regards,
Fabien
Too much is not enough.... |
