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prop size problems on tri copters

#1
heiio i have been fiying rc planes for 25 years and have no probilem with any aspect of the hobby however ive been
flying multirotors for about a year i use 1200 kv motors normaly with 8-4 props ive bult a new tricopter with 800 kv motors witch should use 10-45 props but when i put these props on the copter is bouncing all over.it is fine with 8-4 props ive even tryed to use a kk2 bord and its still the same.i was using multiwii pro with 3329 gps can anyone hellp my new tricopter is the hobbyking g3 fiberglass and it needs bigger props i am pulling out my hair please HELLP!!!!:mad:
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
Sounds like vibe is getting to the board -- accelerometer based boards are all sensitive to vibrations to some degree, and it might sound smooth, but still vibrate enough to confuse the control board. My copter lost one of it's shock mounts on the board and would fly fine at low throttle, but if I goosed the throttle briefly, it would go into a pumping behavior and proptly find it's way to the ground. There's a handful of symptoms for the diffrent flavors of vibe attack, but it usually involves the board inexplicably deciding it wants to surge and/or cut throttle at the worst possible times.

Two ways to fix this -- isolate the board and remove vibrations. Might want to check:

Isolate -- Board properly shock mounted: Don't hard mount -- it'll just amplify vibe going onto the board. Use foam backed doublesided tape if you don't have any better ideas.

Remove -- Props balanced: Most common offender. don't forget to ballance both blade and hub. I imagine you know to keep your props tight and centered -- a loose prop is an unballanced prop.
-- Motors balanced: usually not that bad, but sometimes trouble, especially if you've increased the loading. Fix one boom to the table at it's base, with the prop on, power up one motor WOT and check for any vibe on the boom, repeat on the other three. if impallanced add a pair of zipties around the bell, run, and if better move it a little, if worse move to the opposite side. repeat until balanced.

These boards *can* survive a little vibe, so it doesn't have to be perfect, but some boards and firmware versions can tollerate more than others.

BTW, welcome to the forum. Hopefully this'll sort it out and and you can get to showing off your success, instead of crying out in frustration.