G570 Tail Belt Vibration / Boom Slap Under Load

[rando]

Thanks for the help

[felborn]

did you try this without tailblades on?

[pert]

you have a 570? put that tail on the 500, see if it works, if so you know its some thing wrong with the tail. ill bet the 500 tail and the other side plate holes are off. making shaft not sq. worth a try

[rando]

Without blades it is fine.

I dont have a 500 as I sold it. It flew fine but was just smaller than I prefer

[P.I.Engineer]

how is the boom attachment to the frame, solid?, it looked like the boom was flexing a bit in the 2nd video.

[alexmit]

Originally Posted by rando

Without blades it is fine.

I dont have a 500 as I sold it. It flew fine but was just smaller than I prefer

That tells a good bit. There is a possibility that one or both of the grips are not machined properly, or your tail dampeners are just too loose.

My first impression was that the thrust bearings were in the wrong order. I'm still wondering if the thrust bearings are contributing to this since it only shows up under load. I can't remember if you said you tried replacing them.

[rando]

I've replaced the entire tail rotor hub with new parts, grips, radials, thrust, spindle, dampers and blades -- no observed change in the behavior. The thrust bearings are installed properly with the smaller ID race on the outside. The shim/spacer is installed on both sides between the grip and damper and likewise between the thrust and radials. I could double up the dampers or toss more shims in there to tighten them up but would be kinda surprised that two sets produced this problem for me yet nobody else is reporting the same problem.

The boom is attached firmly. I think you're just seeing video artifacts from the vibration that create the digital illusion that it's flexing. I could swing the model like a baseball bat from the end of the boom and it wouldn't budge or flex.

[rando]

Originally Posted by P.I.Engineer

how is the boom attachment to the frame, solid?, it looked like the boom was flexing a bit in the 2nd video.

Come on over and take a look first hand.

[P.I.Engineer]

pushrod guide moving?

i'm looking through the manual for anything that jumps out at me.

[rando]

Originally Posted by P.I.Engineer

pushrod guide moving?

i'm looking through the manual for anything that jumps out at me.

I've looked long at hard at the guide as the most probably interference target. I pulled it out and don't see any indication/wear marks from the belt slapping it. I haven't observed the push rod to have a more aggressive vibration than does the boom itself, like you might expect if the belt was somehow hitting it. As a test, I did consider mounting the push rod external (temporarily) or otherwise securing the tail in a deflected state to see if rod/guide interference were involved. I haven't tried it yet.

[cjpainten]

Its gotta be the boom... Nothing left lol

[DominicD]

Get a vbar.



Only old timer HF'er will get that joke

[alexmit]

Originally Posted by rando

I've looked long at hard at the guide as the most probably interference target. I pulled it out and don't see any indication/wear marks from the belt slapping it. I haven't observed the push rod to have a more aggressive vibration than does the boom itself, like you might expect if the belt was somehow hitting it. As a test, I did consider mounting the push rod external (temporarily) or otherwise securing the tail in a deflected state to see if rod/guide interference were involved. I haven't tried it yet.

Look on page 22 of the manual (bottom right corner of the page). Do you have HC026-S installed? That should take out any flex or play in the tail pushrod. Also be sure the rod is actually run through H0394-S.

[rando]

Originally Posted by alexmit

Look on page 22 of the manual (bottom right corner of the page). Do you have HC026-S installed? That should take out any flex or play in the tail pushrod. Also be sure the rod is actually run through H0394-S.

H0394, H0395 are both installed and secured by HC026. The push rod is running through H0394 and captured by H0395.

[FlightTime500]

You said you looked at the tail plates at the front? Mine became loose after a couple flights and made the same sound, see if your tail plates are secured at the drivetrain where the belt goes, same goes with the other plates form your main belt... Sounds like a hard one.

[rando]

Nothing is loose.

[Lompma]

Building mine now. I see you have Logos and if you can get those tails working good you can get any tail working. Just wondering if you measured the 3 metal stand offs that separate the tail case halves? To see if they are identical. I had this issue with a Logo.

[rando]

I spent a couple of hours at RC Depot Hobbies today. We've now replaced everything from the boom back, including the belt and front pulley (except the push rod and hanger). The symptom remains. The head, main shaft and main gear wasn't installed for any of this testing so it can be ruled out.

I've previously removed, inspected and re-installed the secondary shaft and can find no issues with its installation. It turns butter smooth and has no play in any direction. Likewise the one way and gear. The motor belt is centered on the one way gear and tracks strait as shown in the video.

I'm nearing my wit's end on this one and the gents at RC Depot Hobbies are equally baffled. It sure seams like this bird needs a tensioner to keep the belt from going nuts under load. Can anyone out there demonstrate that their G570 does NOT behave like mine in the video? If yours were doing the same thing, it's quite possible you might attribute the strange sound hard tail loading as the "normal Goblin tail sound". Spool up on the bench without your mains and deflect your tail to the sides and give it a test. I'd be very interested to see some results.

[birdcrazy]

I have been looking at the g570 as one of my next machines, so don't have one yet, nor the manual to correctly describe the parts.

But, my 2c are a bad bearing in the shaft at the front pulley for the tail belt. Take the bearings out and apply heavy lateral pressure while turning with a shaft running through them.
If you feel ANY notchy-ness or if they are sloppy chuck them and try a higher rated bearing.

Worth a shot? Hope to help.

I have had a similar issue with the set up and seating of gears on some torque tube installations where if the mesh is too tight it puts too much lateral pressure on the radial bearings exposing early bearing notchy-ness.

[birdcrazy]

what is the need for the dampened tail system? Is there a resonance in this particular size Goblin that needed equalizing? If so, then maybe you need to lube your tail dampeners.