tail binding when spooled up?

[semperfib400]

I'm having an issue on my 70 tail... when the blades are still, the tail is very free and no binding at all. When I spool up the heli on the bench the tail will bind and not respond to any rudder input. I can see the servo straining to try and push it one way or the other.

Now, the other night I did remove the tail grip hubs and very lightly sand the ends to help reduce some of the lateral slop in the tail. I'm curious if I perhaps went to far and when it comes up to speed and then it's binding?

Thrust bearings are installed correctly too.

[zelman]

Try redoing the end points in your Tx or in the fbl unit

[semperfib400]

I guess I should have been more clear.

The binding is not at the endpoints. The tail can be at it's center position and bind when I'm spooled up to full head speed. When the blades are not spinning the tail moves freely.

It's like there is something that's binding only when it's spooled up. It's like the tail get's locked into position and you can see the servo arm straining to move the tail slider.

I'll try and get a video of it.

[semperfib400]

Here's a video showing what's happening:

700L Tail Binding? (0 min 31 sec)

[Ukhan24]

This was a post by Derrick in another thread.

"I frequently see improperly assembled tails that are binding due to loctite seeping into areas it shouldn't be during assembly, or the pitch link "dog bones" are tight in the pitch slider yoke.

I would ensure your tail mechanics are border line "sloppy" loose"

I would go through the tail one more time if I were you.

[semperfib400]

That's what my plan is... I must have missed something... there is just no reason it should be binding like that.

I did the same process on my 450 to remove some lateral slop in the grips and that one works perfectly! Something must have got into something somewhere...lol. I'll report back with what i find.

[ShlomiB]

Hi, my guess is the bearings. That was happening all the time on the old align 450/500.
Make sure that the bearings are seated right, they are ok, and the in and out on the thrust bearings positioned right. The thrust bearing must be lubed (greased).
Good luck.

[semperfib400]

Originally Posted by ShlomiB

Hi, my guess is the bearings. That was happening all the time on the old align 450/500.
Make sure that the bearings are seated right, they are ok, and the in and out on the thrust bearings positioned right. The thrust bearing must be lubed (greased).
Good luck.

Would filing down the hub make it do this? I did it to remove some of "in and out" slop on the grips. There is still a very small amount of play....but maybe went to far?

[ShlomiB]

Might be, but if you have in out play it's fine as long as it's ~1mm or less. Try reassembling the grips while checking the bearings. They might be "send like". Try removing the spacers u've added check for gaps.

[ShlomiB]

Another thing might be that the new spacers press on the wrong part of the bearing, causing it to jam. I'm just thinking out loud ....

[semperfib400]

I pulled the tail off over lunch and the ends of the hub are not perpendicular to the the shaft or the hub body.

I'm speculating at this point it could have jammed as the outward load increased on the hub and since the hub is not square it was bearing more on one side of that thick washer... causing a bind.

We'll see if my theory is correct when I reassemble it. I trued up those ends so they are completely perpendicular to the hub shaft.

[semperfib400]

Turns out the issue was the thrust bearings were binding. When I would tighten down the grips on the hub, the thrust bearings where bound tight (filed too much on the hub I guess..lol) When it would spool up the centrifugal force would naturally cause the hubs to contact the thrust bearings... but they were bound tight so it would not allow the grips to spin freely!

[Larry227]

Glad you figured it out that quickly.
Years ago I had a Blade 400 that would randomly lock the tail slider all the way to one side during flight after full right or left input. It took me awhile to figure out it had a bad radial bearing in one grip that would bind up.

[semperfib400]

It's been a good learning experience... really understand how all the mechanics work now!