Bad vibrations

[beans07]

Hi guys, got myself a seconhand mini protos and have some vibration issues.

After my test flights I checked the vbar log and found some high vibration even whilst hovering. I ran it all up on the bench and found that possibly the spindle was bent so I replaced that. It did help on the bench and the vibration dissapeared from that area of hz but now have found some seriously high vibrations I think in the tail area.

I have tried now 3 sets of new tail blades. 1 x black gorilla, 1 x radix carbon and 1 x kbdd tail blades all with very high vibration.

With tail blades off I get very little vibes around 80 os so on the vibe live screen with them on I get very high. It seems only when loaded up that it happens.

All in the one run I got

314 vibes @ 206hz ( 12,402 rpm)
254 vibes @ 222hz (13,388 rpm)
417 vibes @ 237hz (14,274 rpm)
717 vibes @ 257hz (15,444 rpm)

There are also more spikes in and around that area.

So far I have changed tail blades, tail shaft, tail gear pulley (metal), tail belt, complete tail assembly (grips, hub and bearings), tail belt pulley (2 different metal ones).

I have also tried varying tensions on tail pitch slider arms where they attach to grips, tail blade tensions, pulley tensions, belt tensions.

Not sure where to go from here??

All help appreciated!

[SMJT]

is the tail pitch lever straight? they mention in the instructions that they can be warped not sure weather it will cause much vibration issues but worth a look

and check your boom support braces if they are still connected to their ends and not just sitting in the slots.

[baui2000]

The pitch lever doesn't produce vibrations.
Check my older post here - https://www.helifreak.com/showthread...04#post3835104

I'd try tightening the vBar first, it might be all you need if you have it mounted on the gyro tray.

[beans07]

Thanks for the suggestions. I have been running it up and seems that either the metal tail gear or the belt is the likely cause. The shaft seems fine. I can see the metal gear wobbling a little on spin up but only happens with the belt on it.

There is only vibration when there is load on the tail.

I got another couple of each to try, hopefully here tomorrow.

[beans07]

Fitted new tail pulley and tail shaft again which has fixed the wobble on the pulley.

Vibes still exist. I ended up using 2 pieces of gyro tape and the vbar strapped down hard and this reduced the vibes to around 120 which came from the motor area. I played with various tensions on the belt until the vibes were that figure which is the lowest I could get it.

Then mounted the tail blades back on and the vibes went through the roof again up around 800-900. Tail belt idler is getting quite hot not matter if it is loose or tight.

The only things that haven't been replaced in the tail is the pitch slider and the tail case. I have a spare slider so I will try that but it must just be that the load caused by tail blades causes bad vibrations. Maybe the tail case bearings are binding up with the load of the belt causing issues?

The major problem is that when flying the heli drifts and randomly gives aileron input quite severly.

Anyone got any suggestions?

[JustPlaneChris]

Make sure you have not over-tightened the tail case halves, which could put things in a bind. Just snug it down, the bolts don't need to be super tight.

[scott s]

Bearings on the way out in the tail grips could be a cause also and also bearings in the tail case.

[Dylwad]

I had to balance my tail assembly as a unit on a magnetic balancer off the heli to get the vibe numbers down to an acceptable level, after that I did bench runs and added tape randomly to the tail blades until I got things in check. It was silky smooth with the hub and grips off, through the roof with just the hub and grips, and could barely get to half throttle with the tail blades on out of the package. Both blades were within .01 grams out of the package, and I now have 1 tail blade almost completely covered in scotch tape to get the vibe levels under 200. I also tried replacing the hub, grips, blades, pulley and tail shaft before going to extremes.

Really the only issue with my build. I dont notice vibes when the tail grip bearings get worn, I just notice a stop bounce on hard piro stops. Luckily the grip bearings are cheap and easy to replace, I use rubber sealed bearings from http://www.gobrushless.com/shop/inde...how&ref=B-3625 and replace every 30 flights or so.

BTW I used a chunk of 4mm hardened drill rod with the ends ground to sharp points in the balancer, and spun the tail assembly up with a drill to get the blades to extend before placing the unit in the balancer.

Also have the Mini Vbar mounted to the top of the boom block with 1 piece of 3M 4011 tape. Night and day difference in flight after getting the tail vibes in check!

Dylan

[beans07]

Thanks for the suggestions guys it all helps.

The tail case is not all that tight but I will play around with that as it could be a little too tight.

Bearings sholdn't be on the way out as the whole hub and grips are brand new before running up on the bench.

I will try and balance the hub and grips assembly together.

As I said the vibes only come about when the tail gets loaded up (tail blades on).

I will post back when later on.

[beans07]

Found that the pitch lever was not quite right when using the Spacer A. So I used a little heat and bemt it so that they both contact at the same time.

Tail hub (brand new) is way out of balance.

What is the best way to balance the tail hub? Glue? or file?

I have never had to do this before on any heli.

[beans07]

I checked the balance of the tails as a full hub and tails and it was fine. Checked just the tails and they were ok. A couple of the bearings in the tail blade grips had gone bad. Suprising considering they actually haven't had a flight at all only bench testing.

There is something definitely wrong and not to do with mounting as you can feel it along the boom and there is a wur sort of noise (don't know how else I can explain it). IT sounds like the tail is going to explode. The vibes are way up around 1000 and different belt tensions, blade tightness, different blades nothing seems to solve it.

Possibly a bent tail hub. I have actually replaced every part in the tail including the belt. Nothing else to replace unless I got a bad replacement part?

The tail part I installed was MSH41046 http://www.msheli.com/Item.aspx?IDItem=214

I have pretty run out of ideas and patience with this heli.

Anyone got any more suggestions?

Anyone know how to get in contact with MSH?

[scott s]

Some tail hubs have had problems with the hole for the tail shaft drilled at off center or at an angle where it is centered on one side and off set on the other which will cause an imbalance and or the tail blades will not track in the same plane. It happens and they sometimes slip thru. Examine it closely. Can't you contact your vendor and see if they will back it ? I personanly would not bother with it and not use it period but that is me

[beans07]

Yeah I can get another one sorted through the local importer if that is the actual issue. I might even be able to get to their shop tomorrow.

I do have an older silver one here I could try to see if that helps.

[beans07]

I took the new black hub off and put on an old used silver hub with the gorillas and even unbalanced the vibes reduced from 1100-1200 to about 350. A hell of a lot better but should still be half that. With a new hub and new bearings and balanced it should be about fixed.

What gyro tape is everyone using in their mini p and vbars?

[Lompma]

I had a bad hub and had to replace it. Bad new in kit.

[Dylwad]

Originally Posted by beans07

What gyro tape is everyone using in their mini p and vbars?

http://products3.3m.com/catalog/au/e...er/output_html single layer

[beans07]

I tried to fly it with the old hub and the tail was wagging back and forth. Still has at keast 350 vibes on the vbar analyser. Can't have 2 bad hubs I wouldn't have thought.

I did some further investigation and the motor bottom bearing is really notchy. The little bearing that goes on top of the motor shaft is again really notchy but the pinion bearings are not. I guess they are better supported. Maybe the motor shaft could have a little bend in it as well.

I think main frames and plastic trays, landing gear as well as the head hub are the only parts so far not replaced. Motor hasn't but will be now rather than replacing the shaft and bearings which is a pain getting the bearings out on the little motors.

At this stage I have spent $170 on it with new parts plus new parts I have used that I already received in packets when I got the heli. I will also need some more bearings aswell so it will become a very expensive 450.

I guess it serves me right for buying a seconhand heli that had "no more than 30 flights on it".

Motor runs rough and sounds rough when away from the frame. It also starts and stops the ESC aswell so I think it cactus.

Probably will go 6s and stretch kit I think.

[bravedave]

I had exactly this issue with my Blade 400. Bad tail vibes... The left side of the horizontal tail fin would blur up and down 5mm or so. Drove me nuts. Part by part I replaced the whole rear end of the heli. Lots of other parts too. In the end I gave up, stripped out the electrics and sold it for spares. Later I read somewhere that in a crash (yes I had a few) the main frames can get twisted causing the vibe. Must have been it in my case as id already repaced tons of stuf....

[scott s]

well I fly beastx but did some quick research and have pretty much found that a vibe level of 350-400 on v-bar is pretty normal for a 450 though it can be a little lower. Is your tail fin vibing so bad it is a blur? Can you see the boom supports vibing visualy? Are you absolutely sure your tail wag is not just to high gain or some binding in the linkage somewhere. I would for sure fix the bearings in the motor however. I got cursed at one time for making the following statement but I will not buy a used heli unless it is from someone here localy and pretty much know what has actualy happened to it.
Oh I would also make sure the motor can is not out of round or severely unbalanced if you do take it apart.

[Lompma]

Beans I have a brand new never used 3S motor I will sell you for $40 shipped. It came with my kit and I went 4S so never used it.