VIBE RATIONS !!! OS 55 PROBLEM ???? THE VIBE HUM ? HELP Please !

[derrick]

The vibration is before the blades start spinning.

[Steve]

[QUOTE=rachel;640062]From new I have chased a small high frequency Vibration which can be clearley heard in flight at a certain rpm , roughly 1750 ish.[/QUOTE]

:confused::confused::confused:

[derrick]

[QUOTE=rachel;640062]

I have noticed the fuel is absolutly boiling in the tank upon starting the os 55 up and the vibes from the engine are making the tail pushrod and fin vibrate hugely at just idle !!!

Forget engaging the clutch I am not getting that far !!!!

Oh I also replace the bearings in the OS 55, as just to get the fan off you have to push the crank out.

What can I do next should I change my balancer , a highpoint one as to my surprise everything was bang on and needed no balancing.

Things are much worse since removing the fan and changing bearings.

Any Ideas ?????


Thanks X Rachel[/QUOTE]
Swap the motor

[Eckchaz]

You didnt mention the fan rachel.. has that been balanced and dialled in? Also to throw one more thing in.. could you have a bent starter shaft?

Have you got a vid of the tail vibes/fuel on Idle..

[Mslater]

Rachel,

The vibe is present before the clutch grabs so....

1. Bent Crank
2. Front Bearing failure
3. Pushrod on backwards ( only relevant if you changed the piston recently
4. Cracked ring
5. Exhaust baffle failure
6. Bad mounting/cracked frame


My bet is no 5 you would have noticed the others.

[Steve]

Or, try hovering it.

Vibes at idle could just be irritating harmonics at tickover. They may well disappear at quarter throttle and smooth right out. At least try it once surely?

[Steve]

Ok, other things that could go wrong with the V50:

All the bearing blocks are aluminium - starter stack and main shaft. Check to see if the bearings are turning in the blocks. If so, new blocks and bearings.

The starter shaft on just about all JR helis including this one can float up and down inside the clutch assembly. If the starter shaft has slipped down then you will be able to pull the starter coupling up and down. Reseating the shaft is a pain as you have to take the engine out, but it's worth first turning the heli upside down to see if you can get it to drop into the correct place before re-attaching the starter coupling from below. If it has slipped down, then it will be rubbing on the clutch shoe which could be the source of your vibes.

[Steve]

Off topic, but worth a gander to anyone interested in a Vibe 50 - [url=http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=250799413387&ru=http%3A%2F%2Fshop.ebay.co.uk%3A80%2F%3F_from%3DR40%26_trksid%3Dp5197.m570.l1313%26_nkw%3D250799413387%26_sacat%3DSee-All-Categories%26_fvi%3D1&_rdc=1#ht_500wt_1156]JR VIBE 50 HELI KIT PLUS 53 REDLINE ENGINE+BLADES ECT on eBay (end time 14-Apr-11 16:12:38 BST)[/url]

[rachel]

[QUOTE=Steve;640172]Ok, other things that could go wrong with the V50:

All the bearing blocks are aluminium - starter stack and main shaft. Check to see if the bearings are turning in the blocks. If so, new blocks and bearings.

The starter shaft on just about all JR helis including this one can float up and down inside the clutch assembly. If the starter shaft has slipped down then you will be able to pull the starter coupling up and down. Reseating the shaft is a pain as you have to take the engine out, but it's worth first turning the heli upside down to see if you can get it to drop into the correct place before re-attaching the starter coupling from below. If it has slipped down, then it will be rubbing on the clutch shoe which could be the source of your vibes.[/QUOTE]

Thanks steve and thanks all inc dave (pitman ) for your help & kind offers.

I have allways had a small vibe from new that was just a tail fin shake and a noise in flight that is hard to describe but sounded like a police siren an out of balance type of thing.

It was livable but annoying , so in my attempt to cure it I have made it worse.

here is what I did, first I reaserched hear and on helifreak (the Americans love the Vibe) and found the Vibe Fifty is prone to miss alignment of the engine and clutch hub balance issues .

So I have balanced the hub , clutch & fan . they were fine if my balancer is ok .

I replaced front & rear engine bearings.

I dialed in the hub to under one thou, and was super carfull with the engine alignment.

now the vibes are so bad I am seriously worried the tail pitch wire will fatigue and snap.

I was going to do a video but I am now 100% sure the problem is with the hub/clutch/ crank.

Just a Dumb question but as I didn't have the rod off the piston could I have put the poiston in backwards ? The engine runns fine.

Once again thanks all.

X Rachel

[Steve]

[QUOTE=rachel;640217]could I have put the poiston in backwards ? The engine runns fine.[/QUOTE]

Doesn't the piston have a curved cutout along the bottom edge that clears the inside of the backplate? If it does then it wouldn't turn if it was in backwards.

[Steve]

Is the main bearing seated properly in the crank case?

[rachel]

[QUOTE=Steve;640257]Is the main bearing seated properly in the crank case?[/QUOTE]
yes sure it was , crank was very smooth on re-assembally ,engine coming out tomorrow morning.

[Steve]

When I built my V50 a few years ago, I didn't own a dial gauge like I do now, and I just bunged it all together by eye to the best of my building experience and knowledge. It's been absolutely fine since day one in the engine stack department. I did chase a vibe when it was a year or so old which turned out to be the torque tube bearing. It was then that I put two in at unequal spacings.

Just luck I guess with the engine. Makes me wonder now if I should take it out when the new one arrives.

[electricsceadu]

did you replace the fan mounting brass collets?
i was told by a sponsored jr pilot to always replace them after the fan has been removed on my vigor
after installing the motor on start up the fan hub can slip (that was the problem with the vigor, it either gripped and started or just slipped and wouldn't start) and any dialing of the fan hub is then wasted as its moved

the tip i was given
use new upper and lower collets
apply a little washing-up liquid on the tapers face
lightly tighten
dail in the hub
once dialed in tighten the hub fully (do not over tighten)
and re-check its run out

if the fan hub has any marks or damage to its tapers replace the hub

(the fan and hub should be balanced before fitting)

i don't know the vibe 50 set up on the hub, ie if it uses two tapers and collets, a thread, a thread and one taper or a thread and a stepped collar
so those that have built one could answer if the info is any good to you
but i hope it helps

[Steve]

Two taper collets - [url=http://www.modelhelicopters.co.uk/acatalog/plans/jr_vibe50/clutchFanShroud.htm]JR Vibe 50 plans from Midland Helicopters at www.modelhelicopters.co.uk[/url]