N5 "Buzzing"

[Spanner]

Ok, New longer N9 boom supports, no fix. 92mm Radix tails, no fix. New bearings in the tails blade grips, no fix!! New mainshaft, no fix. balanced the fan, no fix. revlock counter weight, no fix. Another new back bearing in the 55, no fix. (£50 for nothing, at least I now have a few spares for when she goes in!)

So now at a loss as I think I've balanced everything I can, and changed everythin that has been mentioned.

Aside from engine tuning which I'll have a proper go at at the weekend, could it be the back bearings I use from RCBearings.co.uk?

What I would really like is for someone else more experienced in all things whirly to have a look and give it a once over and see if they can point me in the right direction!

[robgt]

Have you glued the flanged bearing into the vertical fin?
Sorry if that's already been suggested!

Cheers,
Rob

[Spanner]

Have you glued the flanged bearing into the vertical fin?
Sorry if that's already been suggested!

Cheers,
Rob

Nope, but it will be tomorrow!

[ROSSCO]

^^^ I have to agree with what Rob has suggested, i remember some people reporting an issue with the flanged bearing on the vertical fin causing a slight vibration or 'Buzzing'.

Also with regards to the bearings your using, what are the specifications of these bearings? are they exactly the same as OS spec bearings? I tried some 'Cheap' bearings and also Ceramics a few years ago in the 50Hyper i was running and i found i was going through bearings very quickly and after talking to a local transmission specialist he told me that the cheap bearings i was using might be exactly the same in size but the tolerance or fit is the key factor and that engine bearings require a 'C3' fit due to the environment they are operating in. The 'C3' fit allows for the correct operation of the bearing with the expansion/contraction due to heat build up etc..

I would check the flanged bearings in the vertical fin and opposing side as a first port of call before you start dropping the engine and changing bearings again. I believe there were only a small number of kits that slipped through the net with this issue but its worth a check to rule it out as the cause of your issue.

Hope this helps, and if you need any further help just give me a shout.

[Spanner]

I know when I built her, the flanged tail fin bearings were a very snug fit.

[Spanner]

Bearings I've been using these, both in my 55 and my 50 when I had my Raptor, which thinking about it, it did the same thing...............hmmmmm I hate being at work and not able to try things, my mind goes into overdrive!!

[ROSSCO]

Have you checked/replaced the tail output shaft at all?

[ROSSCO]

Bearings I've been using these, both in my 55 and my 50 when I had my Raptor, which thinking about it, it did the same thing...............hmmmmm I hate being at work and not able to try things, my mind goes into overdrive!!

Those bearings look like standard 6902 opening bearings, it does'nt say anything about the tolerance or fit of the bearing so it might be worth changing out the bearing for an original OS bearing just to rule these bearings out.

[Spanner]

Have you checked/replaced the tail output shaft at all?

No not yet as I've buggered the grub screw so can't remove it! It was going to be the last thing I changed as I'm going to have to drill it out! But looking closely whilst it its rotating in the heli it looks to spin true. The vibe looks to be a horizontal one rather than a vertical one I would expect from the tail?

[ROSSCO]

No not yet as I've buggered the grub screw so can't remove it! It was going to be the last thing I changed as I'm going to have to drill it out! But looking closely whilst it its rotating in the heli it looks to spin true. The vibe looks to be a horizontal one rather than a vertical one I would expect from the tail?

What i usually do with a rounded M3 grub screw is to get a good hex wrench with a good top on (Not rounded etc.) and then warm up the area where the grub screw is with a hot air gun or hair dryer, and then with the hex wrench in the grub screw i twist the wrench at an angle so that it bites into the grub screw and then whilst still holding the hair dryer or hot air gun on the area i twist the grub screw by using the friction of the hex wrench and usually it will loosen itself of with the heat and i can remove it and then just get a new grub screw.

It's hard to explain how to do this but i could sort a couple of pictures if it helps, as they say a picture is worth a thousand words!

It could be something like this that is affecting the gyro and it is showing itself as a horizontal vibration as the gyro will respond to the vibration.

[Heliblerk]

I dont know if this has been suggested before but here is an extract from Matts website reference tail problems:

Tail output shaft should not have excessive play within the flange bearings. If you think there is too much play then I would recommend green or red loctite to secure the shaft within the bearings. Make sure you take the tension off the belt before securing the shaft into the bearings.

Its seems that even the slightest play could case problems - might be worth a try.

[Spanner]

All good stuff to try, but for the weekend it seems, work is getting in the way!