DFC Vibration from tail

[j2tgw]

Hi
My misses bought ma a nice new 700n dfc for xmas
Was flying it today and there is a funny sort of humming noise that
seems to be comming from the tail
Ive checked all the nomal things !
But im sure I read somewhere this is a problem wih this heli??
Can anybody help ??
Tom !!

[Stanley Speel]

I don't have a 700 / DFC but I rembember talking about this at my field that the tail-shaft-snapping problem that the 700DFC has is always preceded by a low humming noise from the tail.

EDIT: Oops sorry didnt see it was a 700N DFC - thought it was the 700e.

[Jamin_00]

Do a search on here for it before it causes you heli to crash??

[smokingtommy]

T-REX 700 700E DFC tail vibrations - Page 1 - RunRyder RC Helicopter

[Delarado]

Yes apparently this will cause the heli to crash. Something about the tail shaft retaining washers going conical shape and causing vibrations, which will eventually cause the tail shaft to shear and fly off completely. I suggest not flying the heli till youve sorted it.

Dismantle the whole tail shaft spindle (Bearings and all) and I think youll find something in there. Also apparently some of the tail shafts themselves are machined so they dont rotate centrally which also causes the vibration.

it could be a problem in the tail assembly itself or it could be the tail shaft not being machined properly. jjust take the tail apart and if you dont see a problem i suspect it is probably a dodgy tail shaft. align are releasing an "upgrade" that fixes this issue.

[j2tgw]

Is the upgrade the new black gears ??

[coolice]

Is the upgrade the new black gears ??

Hey.

Yes, however machines with the new shafts fitted also suffer with the buzzing on occasions. I'd eliminated mine using the old shaft setup, but on flights today with the new parts fitted, I was told it could be heard once again.

One major fix has been the fitment of different tail blades, namely lighter ones apparently and Rail tail blades are a firm favourite.
Also run your choosen tail blades quite loose in the holders, as this allows the blades to lead/lag nicely in flight.

Fit the all aluminium boom as well, seems to be stiffer than the carbon skinned one.

Also the 700N DFC seems to suffer less as it is running the lower tail gear ratio, it's not totally immune to problems as I know of one MK Club guy who had an N failure, but it's less prone to it than the E version running the faster tail speed.

In any case I would fit the new tail output shaft and hub set to bullet proof the tail assembly.
.

[Ryan-Henson]

DFC Vibration from tail

It may have been mentioned or tried, and I have missed it, but, could it be lower quality bearings at the higher RPM's becoming notchy and/or locking up, causing vibrations, or because of locking up, irregular consistent movement putting more stress on the shaft causing fatigue and failure.
Just a thought?

[j2tgw]

I have put the new tail gears ,main gear and front drive gears on !
I have also put a set of rail tail blades on
Weather permiting I will see what the outcome is at the weekend !!
Cheers Tom !!

[raptorheli2]

so there is no doubt has anyone got links to the new parts to fix this?

i have a 700e v2, is this one of the problem ones or if is purely the dfc-e? i have the dfc-n and not flown it yet so wondering what to do before risking the helis.

cheers

[coolice]

so there is no doubt has anyone got links to the new parts to fix this?

i have a 700e v2, is this one of the problem ones or if is purely the dfc-e? i have the dfc-n and not flown it yet so wondering what to do before risking the helis.

cheers

Hey buddy.

Unfortunately the 700N DFC is also prone to it, I know of one machine which suffered a broken tail shaft within its first flight :-(

The new tail outout shaft adds strength to a weqk point by removing the turned down step that the tail hub clamps onto. The main problem appears to be the tail blades going out of track, I've been told by a fellow club member he's seen it happen on the bench.
This same friend tried the rail tail blade trick I'd seen mentioned on HF and confirmed it helped. Myself I am yet to try it, I'm currently on the Align tails still.
It does have me wondering if there is a bad batch of tail blades even, with weight added in the wrong place. The buzz appears to be rpm related, somewhere around the 2k mark it appears, go above or below and it's none existant. Past models have run similar head/tail speeds without issue which is what's got me thinking it could be the tail blades.

To be safe I'd fit the new tail shaft/gear set and go fly.
.

[Ryan-Henson]

DFC Vibration from tail

Is this the new set, that needs to replace the kit parts?

http://www.fast-lad.co.uk/store/h70g...r-p-22024.html

Thanks.

[ghost2212]

I had this problem on a 700eDFC i built for someone, It was only at certain RPM's but the vibration was so bad it would remove loctited bolts. Fitted a set of rail tail blades and the problem has completely dissapeared

[tonystevens]

So whats so special about the rail blades?

[Ryan-Henson]

DFC Vibration from tail

Lighter and according to a post on another website they are a little closer on individual blade weight within the pair of blades.