700 woes!

[ChrisB]

One thought Pete and i know its a long shot and dunno if it makes no odds,is the bearing on the TT in the centre because they say to offset it,mine is offset..


Edit

No the more i think about this its gotta be in the engine drivetrain as the low gain obviously causes the kick on punchout and loose hold but the vibration is stopping you running a decent gain..

[t-rex pedro]

One thought Pete and i know its a long shot and dunno if it makes no odds,is the bearing on the TT in the centre because they say to offset it,mine is offset..


Edit

No the more i think about this its gotta be in the engine drivetrain as the low gain obviously causes the kick on punchout and loose hold but the vibration is stopping you running a decent gain..

TT bearings are as per the manual Chris (23cm from each end I think).

Your edit sums the problem up nicely. I'm leaning towards the clutch stack and fan as the culprit.

[Britflyer]

I may have missed it but have you had this problem from day one or has it just started?


Paul

[Britflyer]

A good way to find out if it is a vibration related problem try changing your gyro damping/mounting or position of mounting on the model (where is it mounted?)

If a change of gyro mounting effects the performance it is probably a vibration related problem.

If a change of gyro mounting has no effect it is probably a mechanical related issue, like loose boom clamp/boom supports etc.

Paul

[t-rex pedro]

I may have missed it but have you had this problem from day one or has it just started?


Paul

Thinking about it the wag in funnels has been there a while but has gotten worse recently. Maybe I hadn't noticed before as I have only recently started doing tail first flying. I changed a rumbling rear bearing as thats when the problems really started but it didn't improve things at all. I've even changed another bearing yesterday just to make sure but still the same.

[3dbasher]

fan or fanhub

[barney]

If it's a tingling like vibration it's got to be your clutch, as thats about all thats spinning at high speed and is heavy. Getting hold of a dial Indicator is highly recommended as even new parts often need fettling to run true.

My YS doesn't create the storm in a tea cup unless it's running a little lean and gets a a bit harsh sounding

[t-rex pedro]

No 1/ Busted boom stay. The little pins at each end can snap internally or pull through the tube after very little airtime..very common I might add. You need to really pull the boom firmly side to side and watch for the slightest movement at the boom stays ends..The plastic ends also compress after a little time and the bolts usually require nipped up or the boom end wanders in its own bolt hole.

Just checked the boom stays and found a loose one. Not by much though. I was also running an alu brace but removed that tonight. Epoxied the boom support and allowing to set overnight. It was only moving a tiny bit but it was moving. Could this cause such a tail problem?

[Steve]

Shim the engine head with an extra head gasket. Smoothes out the SR a treat and only costs a couple of quid.

But I also agree strongly with all the hub/fan dialing comments.

[raptorheli2]

i think you'll find that boom support is the reason. it doesn't take much for the tail to start wagging when those supports are loose. i'm going through a set of align boom supports every 2-3 weeks atm with this exact problem. i'm doing reverse chaos and as soon as you do anything like that the boom supports go like you have found. my ear is very adept at hearing it now as it's a familiar buzz not like gyro gain.

try and and report back, hopefully all is well.

if not then need to be looking at other things possibly causing it. tail rod guides, tail grips/bearings (i've had a set lock up causing wag) and dial the clutch, do no harm. a dial gauge is one of the best things you will ever buy in this hobby.

cheers

[t-rex pedro]

i think you'll find that boom support is the reason. it doesn't take much for the tail to start wagging when those supports are loose. i'm going through a set of align boom supports every 2-3 weeks atm with this exact problem. i'm doing reverse chaos and as soon as you do anything like that the boom supports go like you have found. my ear is very adept at hearing it now as it's a familiar buzz not like gyro gain.

It's not so much a buzz associated with a loose boom support, it's aggresive tail wag in backwards/funnels. I've epoxied the suspect support. Hopefully that will sort it. Maybe the boom support brace accentuated things? I'll try give it a test later and will report back.

Thanks for all the replies guys.

[SRH990]

Might be worth checking the end points on the Spartan using the USB link, if it's too low then it can be difficult to balance between to high or low gain, running the endpoints over 100% helps. My 700 has always been a shaker with the 91SZ-H fitted, I've noticed that the 91HZ a few other guys have in their 700's is much better in this respect. I did have a slow drift with the Spartan and tried the recommended two layers of tape under the metal plate which made a small improvement. At the moment I've swapped to the Align blue gel (Zeal Gel) with two layers under the metal plate and it definitely seems much better.

[raptorheli2]

if you need that many gyro pads your defo hiding a bad vibration problem steve. both my 700's have shz's and i use only a single gyro pad without the plate FYI.

as for the buzz pete, have a look at the tail grip bearings. mines were cocked with loctite i discovered and caused similar.

cheers

[SRH990]

if you need that many gyro pads your defo hiding a bad vibration problem steve. both my 700's have shz's and i use only a single gyro pad without the plate FYI.

as for the buzz pete, have a look at the tail grip bearings. mines were cocked with loctite i discovered and caused similar.

cheers

You should see the fuel tank I've been unable to tack down the vibration, it's always been the same through around 3 different sets of blades, 3 new mainshafts, a completely new clutch stack with brand new non-Align bearings, new clutch bell and new Quick UK clutch plus new main shaft bearings The engine recently had a new rear bearing fitted and is perfect inside after over 18 months of running. I've got a DTI but couldn't see how it was worth using it as nothing is adjustable.

[barney]

Pete the chances are your epoxy will be a waist of time as the carbon tube will already be slotted or the pin broken internally

The cure for the boom stays is to unscrew the flimsy little Allen key, and replace with the threaded end of a pushrod..drill the hole on the tight side, end and stay. Clean/roughen said end, add epoxy and screw the rod in till its flush then cut the remaining part away.