Pirouetting 500 3d.

[Streeker59]

Hi guys. It's been awhile since I was on the forum.
Started with a nano, mcpx bl, 130x, 130x redbull, trex 250,450 3d and my latest acquisition , a 500 3d .
Third flight in ( hovering mainly) as I find the 500 intimidating compared to my 450, the bird pirouetted very fast like the tail blades had stopped though they hadn't.
No input from me would stop the spin. I managed to land her with no damage cept a broken front skid edge.
I checked the tail servo, tail set etc. no explanation. I flown her twice since and no reoccurrence as yet.
Any ideas as to why she spun chaps. I'm crap scared to start flying circuits incase it happens again.
Your thoughts would be appreciated.
Grant.

[Paulos]

Hi Grant,
May be it's the tail servo failing due to a dirty failing pot. I have had them perfect on the bench and then play up during flight due to load/vibration. A bit of a long shot but the tail hub bearings can stick or seize, it may be worth checking them. Not sure what else to check other than that there is no general binding of moving parts.
Cheers
Paul

[Pj1969]

Had the gyro initialized properly? Was it fine before or has done it 3 times??

[Paulos]

Also another long shot but check that the servo wires have not chaffed and shorted against the frame.

[Streeker59]

Thanks for the help chaps. All wiring is good, no chaffing. I bought the bird second hand so no idea of it's flying hours.
The tail case bearings are fine so I guess the tail servo must be playing tricks. I'll replace it just in case.
Many thanks.

[tomatwalden]

Have you checked the belt tension? Could be that the belt slipped that one time, but re-engaged once landed ?


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[milly0812]

Check your mounting pad too, if the gyro comes loose it loses it's reference point and the tail will whip round

[Streeker59]

Thanks for the tips. I've checked belt tension and servo mounts, it's all good.
I'll run a few more batts through it with low hovering until I'm satisfied it'll behave.

[Leigh Beaumont]

Make sure there is no wear on auto rotation gear as if this slips you lose tail drive which makes tail let go, also check boom not lose or moved again you would lose drive to Torque tube, both of these have happen to me on a 500.

As you brought 500 second hand you don't no history a strip down and rebuild might be a good ideal that way you can check for wear or failing parts and alignment of parts all piece of mind as last thing you want while learning is that thought in back of mind will tail fail again

[Leigh Beaumont]

Sorry just seen its a belt drive, still worth a rebuild and belt inspection for wear you don't no if its a genuine belt or not

[tomatwalden]

Given your description if the symptoms, I'd still be suspicious of the belt! Have you tried posting in the 500-3d section on helifreak? Many of the Blade designers are active there and might have some good ideas?


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[Pj1969]

As it's belt drive, make sure that the belt is going the right way, if it's been apart and twisted the wrong way, that will make the blades spin wrong and have no effect on holding tail. Take it from someone that's done it lol

[pgkevet]

If it's intermittent then it cant be a wrongly twisted belt. It could be a slipping belt but they're suually obviosuly loose befre that happens. My money is on a loose servo plug/solder joint or a dodgy servo or a gyo that's either mouted wrng or has a loose sensor.
You check what you can and also spin it up on the groudn without blades to observe etc.

Work on autos on the sim..if it happens again grab height, TH and auto down - at least the spinning will stop in TH nd at least learnign autos will hold you in good stead for the future - best thing to learn.

[Streeker59]

Thanks for all the help guys, it's appreciated.

[Streeker59]

Hi guys. I replaced the tail servo and took her flying last Sunday.
The bird behaved perfectly until 4 mins into the flight when the tail went again !!!!!!
I wasn't so fortunate this time. Crap loads of damage as my £60 carbon blades hit the deck. Twisted and bent tail boom, broken blade grips, etc. I was gutted. Got it home and started stripping. Guess what I found ? Yup, a buggered anti rotation bearing.
mmm, I recall a nice chap warning me to check for that lol ...
Thanks to Leigh Beaumont for the advice. Pity I didn't follow it.

I have a new anti rotation bearing and collar. It feels so notchy. What do I lube it with?
Fine machine oil or a dob of fine grease ?