DFC Vibration from tail

[tonystevens]

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

wow, well that just shows how fine the line is between a good and bad mechanical set up!

[coolice]

So whats so special about the rail blades?

Hey buddy.

As above, lighter apparently.
Talking to Duncan O SAB tails also help with the buzz as he's tried a set he has.

What puzzles me though is that on the older 700E we were running a higher head speed to get snappy performance out of the model, all on stock tail gear with no hint of a buzz. Surely we must have had the tail rotor spinning at the same rpms that the current models experience this buzz at, so what's changed?
Unfortunately I think its a combination of things, tail blade weight, boom strut ends being fixed properly, less stiff booms perhaps, the list goes on.
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[raptorheli2]

Ian,

i don't know what upgrade parts i'm best with here?

i have 2 helis i need bits for, 700DFC-N and the 700E V2. can you please advise FL don't specify one for the nitro, they show the 700e/800e gears for tail? is this correct x2?

H70G005XXT Torque Tube Rear Drive Gear Set

so would it be wise to get diff tail blades as well? i really don't want to unless required though as i have loads of 105 aligns.

cheers

[coolice]

Ian,

i don't know what upgrade parts i'm best with here?

i have 2 helis i need bits for, 700DFC-N and the 700E V2. can you please advise FL don't specify one for the nitro, they show the 700e/800e gears for tail? is this correct x2?

H70G005XXT Torque Tube Rear Drive Gear Set

so would it be wise to get diff tail blades as well? i really don't want to unless required though as i have loads of 105 aligns.

cheers

Hey buddy.

This is the main upgrade for both machines;

H70G005XXT | T-Rex 700 Torque Tube Rear Drive Gear Set

Then if you wanted to change the front gears to, for the E;

H70G001AXT | T-Rex 700 M1 Torque Tube Front Drive Gear Set/22T

And the N;

H7NG001AXT | T-Rex 700 M1 Torque Tube Front Drive Gear Set/21T

I've got the front gears sat on my bench, haven't seen the need to fit them, only the new tail shaft and hub which beefs up the weak link.

Im with you on tail blades, I actually like the Aligns as they seem to work well, but will be trying some rails. Out of interest I'd cured my buzzing with the old tail shaft fitted, after fitting the new items it seems I have some back.
A thoughts just occured to me saying the above to swap the tail blades over to the opposite grip, might be worth a go.

Perhaps the best thing would be to fit the new tail shafts, then if you hear the buzz maybe try a different set of tail blades.
A little tip I can give is to fit longer tail blade bolts, the stock ones are too short and I'd had mine come loose after a couple of flights through the buzz thinking back now. One was so loose one time I could undo it with my fingers, lucky escape there as a low inverted auto had me clip the grass with the tail and luckily I inspected it and saw the loose tail blade bolt.

I forgot to say one of the improvements to the tail is thicker washers on the bolts keeping the tail blade grips on the tail hub. The old ones were cupping due to the centrifugal pull on them and allowing more slop to develope in the tail grips.
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[raptorheli2]

i already changed the tail bolts Ian as they are far too short.

i'll order a couple of the rear tail upgrades for both machines and see how i fair.

cheers

[raptorheli2]

just ordered the rear upgrade and a pair of rails just now. the 700e has edge tails on it already so hopefully those are ok. i must admit i never noticed a buzzing on that heli the twice i have flown it.

cheers

[Benjbrit123]

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.
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I can confirm that the rail tails do fix the vibe, everyone including me who have tried them all found it to work

[bikerflier]

I have never flown a 700 until my 700e DFC HV yesterday. 4 flights between 3 1/2 and 5 minutes duration each.

I don't know what sound to listen for or what is normal for this type of heli.
There was some type of noise I have never heard before but not sure where it is coming from or if this is normal for this size and type of heli.
Hear it more when the heli is coming towards me, when I hover tail in near me it is barely noticeable.
Would hate for something to break.

The main blades balanced spot on but one was 0.15 grams heavier.
The tails balanced spot on but one was 0.05 grams heavier.
I have since corrected the weight so they are identical.

Any sound tracks available with the noise plainly audible.

[muscleflex]

Sorry to bump but I kinda worry I have this 'Hum' but I really don't know what it should sound like. All I know is I have this sound that's started last night and it's kinda like a low pitch sound.... I have KBDD tail blades on my heli

[machasm]

I have read that the KDBB tail blades are one of the heaviest blades and can exacerbate the problem.

[coolice]

Sorry to bump but I kinda worry I have this 'Hum' but I really don't know what it should sound like. All I know is I have this sound that's started last night and it's kinda like a low pitch sound.... I have KBDD tail blades on my heli

Hey.

As above loose the KBDD tail blades, they are know to make matters worse.

The sound you're looking for is almost as if you were humming, it's a very fast humming noise like a very angry bee. Sort of a low droning noise.
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[ghost2212]

I have read that the KDBB tail blades are one of the heaviest blades and can exacerbate the problem.

+1 they will definitely cause problems, Get your self a set of rail blades and that should sort the problem.

[muscleflex]

Ok, found this video... around 35seconds into the video, I notice he gets this same sound like I'm getting... is this the tail hum I'm looking for?
700E DFC HV Tail Hum/Resonance - YouTube

[muscleflex]

+1 they will definitely cause problems, Get your self a set of rail blades and that should sort the problem.

Is this the right pair I need? 106mm? Rail Tail Blades 106mm R-106 / trex 700 / Blades - ALIGN-TREX.co.uk RC Model Helicopter Specialists in ALIGN, E-Flight, Blade, Goblin, Synergy, ALeeS, Outrage, ELY-Q

[ghost2212]

Is this the right pair I need? 106mm? Rail Tail Blades 106mm R-106 / trex 700 / Blades - ALIGN-TREX.co.uk RC Model Helicopter Specialists in ALIGN, E-Flight, Blade, Goblin, Synergy, ALeeS, Outrage, ELY-Q

Yep that's correct, They've solved the issue on 3 700's that I've seen including my one.