swift crazy head shake!!!

[yoshgixxer]

hey guys im fairly new at helis,especially .30 size, i have a century swift 16 and got it all ready to go today,i placed it on the ground, turned off the throttle hold, and id say at about 75% throttle it started shaking violently for a breif second then as the rpm's climbed higher it smoothed out, (by the way i have it set up in idle up mode and i had it at half stick so roughly 0 pitch upon spool up) is this normal,it was definatly scary,i dont rember this on the flight sim!!! haha,i checked the distance from the paddles to the collets on the fly bar,both distances are equal, and i made sure the paddles were level with the mixing arms,also made sure the blade grips were set so the blades could mover freely,with a little resistance, it scared me so bad i almost had to put it away for the night!!! i just want to see if any other swift owners have this problem and if its just somthing i have to get used to, thanks alot!!!

[scarr]

Yes, mine does exactly as you describe although it is the 550 CF version... I have moved the boom supports off the landing gear legs and that helped a little bit. It has been crashed and rebuilt about 4 times and the resonance is always there. When spooling up it is minor as I tend to get past it quickly and it smooths right up once past it. Winding down is another story. Sometimes it shakes a lot.... I have tried everything to eliminate it but have not found an answer yet. Gear to motor lash, tail belt tension, tail drive gear lash all have been checked and altered to try to eliminate it but it is always there.

My set up is with the Century 600+ motor, 6s1p Lipo, metal tail case, metal boom support, almost all metal rotor head, current landing gear struts.

[JustPlaneChris]

Yep, it's a Swift Thang. :) Mine does it even with aftermarket struts (Hirobo) Here's another thread with more info:

http://www.helifreak.com/showthread.php?t=30782&highlight=swift+shake

-Chris

[RAV50]

Many helis (electrics/nitro/gassers) do the same as they come up to flight rotor speed and as the blades find their natural lead/lag that cause resonances at various rpms.

This is why full scale helis will have rotor speed areas that are marked in red or amber on the rotor tach.These are rotor speed areas of resonance that one must insure to pass through and not remain at.

Also of consequence, is that the closer the Chordwise CG of a blade is to the center of lift and the better they are matched to the same CCG, the less pronounced this will be. That is another reason why I really like using the Rotor Tech C/F blades and the Funkey composite blades. these blades are very well designed in this area.

If the hobby shop you got yours from had it on the shelf for awhile, it may have an older version of landing gear struts.

Also of consequence is the length of the landing gear struts and their rigidity. The current versions of the Swift have a more rigid landing gear then did the early versions, so they are less effected by such resonances. Be sure to insure your landing gear struts are the V3 versions and not the V1 or V2 versions.

[yoshgixxer]

yea actually i got my swift from george b. aka rcgrinch,it already has i believe raptor landing gear, and the heli it self dosnt seem to " wobble" on spool up just the head it self,so im assuming the landing gear is nice and sturdy,and im 100% positive he set it up correctly, i was just nervouse somthing could have been damaged in shipping even though everything seemed ok ,well im glad this is normal, i was just waiting for a blade to fly off!!! like i said im new at this,and the size sound and speed of those blades is a little intimidating!!! i really appreciate all the help and info from you guys, now i can go learn to fly with one less thing to worry about, and chris i seen some of your youtube vids,and really got me liking the swift,nice work, and flying, thanks again,

[JustPlaneChris]

Thanks for the kind words! I really need to shoot new video of the Swift, it's flying much better now with 550s and more headspeed. I'm getting more comfortable with it too, so it's seeing more "unusual attitude" time as well. :D

I still really like my Swift, but may end up selling it in a couple of months since I'm buying the new "425" size MSH heli that will be released in March...

-Chris

[philiusm]

I don't profess to be an expert but I cured the shakes on my Swift by running the blade grips tight. See the other post "Swift 16 Shakes".

I've got two Swifts one doesn't shake the other does. I think it's down to uneven blade lag when it spools down. I balanced everything on the head to 0.01gm. I built the head up piece by piece and ran up the heli each time to see if I could see what was causing the shakes. It's not until I put the blades on that the problem manifests itself. Tightening up the blade mount bolt in the grips so that the blades are stiff to move cures the spool down shimmy almost completely. When spooling up, the heli will shake untill the blades centre themselves properly so I accelerate the head up quickly to avoid too much shaking.

Regards,

Phil M

[aramsdell]

You can power through the shakes on spool-up. On shut-down I'm lucky enough to have a Tx that will let me bring the throttle slowly to 0 wtihout affecting pitch. Royal Evo 9. It has a slider that you can use for 'direct throttle control'. It works great and lets you adjust Thr/pit curves.