Tail blade holders

Logo 600 SX
I purchased some new tail blade holders last week as there was a split in one of the moldings on the existing ones, I have done this several times before and have also built five logo kits, when tightening down the bolt onto the bearings and blade holder it becomes tight and won't rotate freely. I have never has this before so I checked and double checked that the thrust races were the right way round. I flew the model as I thought it might all settle in but the tail was wagging as I thought it would. I purchased a complete tail assembly yesterday as I thought this might solve it, but as soon as you tighten down the bolt the blade holder goes tight on the tail rotor hub, has anyone got any thoughts on this or had the same problem?

Robert Cole

Hi Robert,

I only recall vaguely, but I think I had it once and had either put some wrong (thinner) bearings in the blade holder or there were the wrong bearings in the bag.

Can you please check the width of your bearings?

Please lay out all the parts in a line, screw, shim, thrust bearing, ring, outer radial bearing, blade holder, inner radial bearing and take a pic so I can see what you have on your desk.

Kind regards

Eddi

Born to fly ...
forced to work.

Edi,
pictures as requested

robert Cole

Hi Robert,

looks OK. If you pull on the blade holders, do they possibly click a bit (bearings settle) and then turn freely?

Can't imagine what else it could be, only the hub but you seem to have two and I doubt both do not have proper dimensions.

Kind regards

Eddi

Born to fly ...
forced to work.

Eddi,
There is no free play on the blade holders at all, you cant pull them, I know what you mean as all my other loge tails are like that.


Robert

Hi,

OK, then please measure the hub and compare both if possible.

With the data I can measure one here and see/compare.

Curious what we find

Cheers

Eddi

Born to fly ...
forced to work.

Eddi,

Which part of the hub do you want measured


Robert

Hi,

there are only so many relevant dimensions, the steps where the thrust bearings and the radial bearings go on, to see where it can possibly bind.

Usually, there is no pressure to the center of the hub, there's a little axial play. But something _is_ binding, either the thrust bearings or the radial bearings.

You can also put the bearings onto the hub without the blade holder, and tighten the screw and see if there is anything out of the ordinary. We have to narrow it down ...

Kind regards

Eddi

Born to fly ...
forced to work.

Eddi,
Just tried it without the brass shim and its perfect, is the shim to thick or is the moulding wrong?

Robert

Hi,

for the molded parts, there is almost no margin for error, and those parts are bulk items where hardly ever any issues were reported.
Only if there were burrs interfering with the bearings so they don't just slip in all the way, it could be necessary to pull so they 'click in'.

The shim should be 0.5 mm, the radial bearings 3 mm and the thrust bearings 3.5 mm in thickness. This adds up so you usually have slight axial play, as you already know.

So the thrust bearing sits on the first segment which is 3.6 mm and can technically not bind.
The brass ring separates the thrust bearing from the radial bearing and puts the load on the outer ring so the inner ring can rotate freely.
The radial bearings (2 times 3 mm spaced by the 2 mm ring in the blade grip, 8 mm in total) sit on the second segment which is 8.5 mm, which gives the axial play and should not bind either.

So please check the hub(s) and parts you have again, please, so we can find out where the difference is?

Kind regards

Eddi

Born to fly ...
forced to work.



Edited 1 time(s). Last edit at 04/26/2017 11:12AM by Eddi E. aus G..

Eddi,
I have to go out, but will measure the hub when I get back. I found a 6x8x.25 shim last night in a bag of shims that Rainer sent me a couple of years ago for third motor shaft support on a 550sx, this is perfect, just a small ammount of play and rotates freely, only have one though,

Robert

Eddi,
All measurements okay, I have just put the blade holder radial bearings in with an arbour press (very carefully) and now it's all okay, but I have never had to do that before, so alls well that ends well

Robert

Hi Robert,

OK, maybe the bearing seats in the blade holders were just tighter than ever before ...

Happy flying now!

Kind regards

Eddi

Born to fly ...
forced to work.



Edited 1 time(s). Last edit at 04/26/2017 04:51PM by Eddi E. aus G..