3D+ Slow tail wag?!

[rcnut]

Hey guys!

Just recently my Compass 3D+ has developed a somewhat slow tail wag. I've tried increasing/decreasing the tail gain with no success. I talked with Eric Brandenburg about this and he mentioned the possibility of the soft motor mounts causing this oscillation effect. Like the dampers needing to be replaced every so many flights (mine...~100 flights).

Anyone else notice this? And what did you do to fix it?
"I love the smell of Nitro in the morning!"

[Ah Clem]

I would listen to Eric, he knows his stuff.

In addition...

Have you taken the grips apart to make sure that there is grease in the thrust bearings and that the races are oriented the right way?

Can any of the wiring entering the FBL unit flap or tap against the frame, anywhere?

Does it only do it at one RPM?

[rcnut]

Ah Clem,

I will check the blade grip bearings and thurst bearings. It does this at all head speeds, but seems to be more noticeable (faster wag) at higher head speeds. John Cook's 3D+ is doing the same thing!

Thrust bearings are installed properly, and the wiring is good. I'm very anal about my wiring...ask John, LoL

[skunkworx]

I also would advise going with Eric's recommendation. They should be replaced on a somewhat regular basis (at the same time as maybe your fuel line or dampers, or once a year maybe?). Slow wags are also a good example of bad gyro tape in some cases. Like if its soaked up too much fuel or got torn up by weathering effects, etc...

I also wouldn't rule out the wiring so quick. I've fixed several people's helis that had been flying for a while with no issues and found that they either shift a little over time, get pulled ever so slightly through zip-ties, get knicked up, or the wires themselves harden up a little (especially on nitros). I'm pretty meticulous with my wiring as well. But sometimes it does the heli good to take everything off and do a fresh re-mount on it and clean all the gunk off of them.

[rcnut]

I'm new to this brand of heli and learning what needs to be replace after so many flights. I have over 100 flights on it and have only changed the dampers...so far. Now that the colder weather is here, I guess it is time strip it down, clean and check everything.

I noticed the soft motor mount parts are getting old, so maybe it's time to change them out.

I read on one of these heli forms that Compass is discontinuing the Compass 3D+. I haven't confirmed this yet, if so...I wonder how long Compass will make parts for the 3D+. The 3D+ is my favorite! I'd hate to sell it when parts become unavailable.

[skunkworx]

You shouldn't have to replace much, but if you're having the problems described then it certainly can't hurt to swap them out. 100 flights is around 2 cases of fuel and likely 25% to 50% of the life of the motor so it's a pretty fair amount if you look at it like that. I personally put a Knight 3D motor mount on my 3D+. They seem to hold together for quite a while and are a little easier to work with IMHO.

The only other real wear item you have to worry about is the clutch liner and maybe the clutch shoes. It's a pretty solid machine and nothing really wears out on them unless they're allowed to get really sloppy. Even then, I barely take care of mine at all and have had less problems with it than any of my other Compass helis (other than motor tuning anyways).

Yes, unfortunately they did discontinue the 3D+. But parts will never be a hard thing to get ahold of. They share a lot of major components with the 6HV so the peculiar parts won't be hard for Compass to keep up with. The only major loss in the discontinuation is that if you crash bad enough you can't just re-kit and start over again. Barring an insanely bad crash, I don't think this should be a major issue since most of the parts are realy affordable, but that's just how I see it. Might be different for others out there.

[rcnut]

Ok, it has been awhile! I've replaced the clutch, clutch bell, and motor mount. The clutch problem is fixed, now I need to solve the slow tail wag.

I thought replacing the motor mount would have fixed this, but not. So I will continue until I find what it is or just live with it.

[Ah Clem]

One more thing to look for in the tail grip thrust bearings, which may or may not apply to the3D +, but did apply to early versions of it predecessor, the Knight 3D...

The thrust bearing races are supposed to have different I.D. and O.D. as you know. Some of the Knights had different I.D., but the O.D. on both races was the same, causing binding of the outer edge of the race furthest from the hub, with the blade grip (someone else discovered this, not I).

My Knight developed a slow way (oddly enough, especially when hovering inverted) after a dozen or so flights. I found out about this and mic'ed the O.D. of the thrust bearings, Sure enough, all the same O.D.

I passed a both through the offending race, chucked it in the drill press (I don't have a lathe) and turned the O.D. down about 1mm overall.

After reassembly, the problem went away, forever.

Not sure if this one affected the 3D +, but it is possible, as the tail grips are the same.