Un-Wanted House Guest: Low Speed Bob

[Qema]

I have a house guest that has over stayed it's welcome. Ever since I re-built my eco8 after it's crash " Low Speed Bob" has moved in and I can't evict him no matter how I try.

He is not that bad of a guest as he only shows himself at the end of the battery pack and its time to land. However this makes landing a bit of a annoyance as the tail is slowly bobbing up and down about 2-3 inches.

I replaced all the shaft's with new after checking them for straightness first. All the links are loose, flybar paddles are even, new blades main and tail, balanced CG, and weightwise etc. New blade grip bearings also.

I read all the posts about this un-wanted guest and just can't get rid of Bob. I know it's crash/re-build related because it was never there before the crash and the configuration is the same.

Mega 22/20/4 14 tooth, Jeti 40-3p, 10 cells 2400, wood blades, 120 alum. SP. HS-85 servo's, AR gear , Boom Supports, PG-03 gyro.Tail mounted servo.

Anybody have a new ideas on how to get rid of this pest. Need more info ?
TIA

[BertVK]

Inviting Mr. Add-a-tooth-to-the-pinion-to-get-the-head-speed-up over for coffee should solve the issue as Low Speed Bob only come in when the head speed has dropped low enough.

What kind of line drawing do you use on the Throttle invitation to Mr. Low Speed Bob?

[Qema]

I never invited mr. up-a-tooth before, was worried mr,&mrs. to-hot-battery/motor might show up
My throttle curve is 0-45-98-99-100
Pitch is 0-40-58-67-100 , with 58 giving me exactly 6* pitch

[HARRomeo]

I'm curious as to why it wasn't there before and is now with the same setup.. are you landing on the same surface? Is your CG the same? Low speed bobs are caused by headspeed dropping.. maybe you're hovering out a little longer than before? [img]/ubbthreads/images/graemlins/grin.gif[/img]

[BertVK]

Hmmm, I think you are bogging down your motor because of a low head speed. Try a 15 tooth if you can, that will get the pitch and the drag down a little.

Who else is flying this combo? What pinion sizes do you guys use?

[Qema]

[ QUOTE ]
maybe you're hovering out a little longer than before

[/ QUOTE ]

Thats a possibilty. Maybe the reason I can't find anything wrong mechanically is because there isn't anything wrong mechanically.

I will order a 15 and 16 tooth pinion and try that also.

Now I am beginning to wonder about the shape of the mainshaft bearings. I did not replace those. hmmmm

Maybe it's bobbing now because everything is perfect. Could be that before the crash there was a problem. I have the same problem with all of my heli's. By the time Mr. Bob shows up, there isn't enough power left to do anything anyway, other than hover a foot off the ground.

[Bejay]

[ QUOTE ]
By the time Mr. Bob shows up, there isn't enough power left to do anything anyway, other than hover a foot off the ground.


[/ QUOTE ]

I was going to say exactly the same.....infact I treat it as a "flat battery" indicator.

Try check the o-rings for your feathering spindle. If they are worn out then your head dampening is too soft and will get a low speed "nodding".

[Erez]

Wobbling is normal on your setup. Its too low an RPM. I have run that setup on an 18 tooth and it was fine so don't worry about heat. Also set the throttle curve to 0-50-100-100-100, unless you really hate Mr. High End Bogger.