Auto Unit feels very tight

[sookainian]

After flying a while my auto unit feels very tight. Compair to last time when i first bought it, it is very smooth and can turn easily.

But now is like very tight when u turn it, is like very STICKY

What can i do to lossen it ?

Kenny

[DavidH]

I would suggest taking it apart and servicing the sprag clutch. Use a light weight oil to lubricate the sprag clutch. Also check the delrin rings to see if they have worn and allowed the parts to bind together.

David

[sookainian]

hmm i am not sure about this, but i have took it out to wash it with oil. Then later i lubricte it and put it back. But still the same.

The delrin rings seems fine.

Last few days when i was trying to figure out what's wrong, i took out one shim, and the clutch seems to be looser but there is some play.

But it seems to me like it is to tight, but i didnt touch it from day one ( very smooth ) till now :arggg:

So what should i do ?

[Alfred]

What oil are you using?
Use sawing maschine oil or automatic transmission fluid if you can't get your hands on thin teflon based oil.
If you used thick oil, flush the sprag bearing out thoroughly with methylated spirit.
When re-filling, follow the instructions to a "T". The clutch will take quite a lot of oil.

Other thing..you haven't installed the Main Shaft upside down, have you ?
Some (or all..not sure) have only one end hardened to withstand the forces of the sprag clutch.

[DavidH]

Other thing..you haven't installed the Main Shaft upside down, have you ?
Some (or all..not sure) have only one end hardened to withstand the forces of the sprag clutch.


Sprag clutch does not come in contact with the main shaft. The main shafts used in the helis that come with the MA constant drive tail auto unit. Do not have hardened main shafts at all. The sprag clutch grabs a sleeve that the main shaft goes inside of the auto unit.

Davikd

[sookainian]

What oil are you using?
Use sawing maschine oil or automatic transmission fluid if you can't get your hands on thin teflon based oil.
If you used thick oil, flush the sprag bearing out thoroughly with methylated spirit.
When re-filling, follow the instructions to a "T". The clutch will take quite a lot of oil.

Other thing..you haven't installed the Main Shaft upside down, have you ?
Some (or all..not sure) have only one end hardened to withstand the forces of the sprag clutch.

Yap, i used the sawing maschine oil to wash the dirt out. Then later i use teflon base oil to lub the wayone bearing.

But somehow i FEEL like something is like BEND because when i hold the gear and turn my head, So is like an auto. I notice like the one way hub is bend, but i dont know which part. I also notice when i turn the gears, when i turn it will some part is smooth, then come to a point, it become tight then lose again.

So could it be bend some part inside the one way unit ? any idea ?

[Alfred]

Your right David
I completely fergot, even that I just done a major overhaul on my Fury Expert constant drive unit.
I still have an old 1001 Heli with the black Maingear. It runs directly on the Mainshaft and I remember seing the instruction pointing out that just one end of the Mainshaft is hardened.

sookainian
All I can think of is for you to use a Micrometre or Vernier Caliber. Put it onto the Steel Sleeve that the Sprag bearing runs on and rotate it. It should tell you very quickly if the sleeve is distorted for whatever reason.

[sookainian]

ok guys, i just took out the whole unit again and wash it and lib it. Then i put everything back. It turn smoothly. ONLY when i put in the Retaining collar and lock it with the pin, then when i turn the unit it will feel tight and some part it will become tighter then loss again.

What should i do ? :arggg:

[MAIONX]

try removing one of the shims between the retaining collar

[sookainian]

i remove it and it is slightly better, but it is not as smooth as last time. when i turn it, still got abit of 'jurking'

But MA menual say it is a MUST to put the shims

[sookainian]

i remove a shim between the gear ( in the pict ) and the one way work very smooth

But when i fit it up into my heli, there is abit of left and right free play. is this all right ? or what i did is not allow ?

[Alfred]

sookainian

How about if you jump into the chat room.
I wait there for you.
I haven't used chat before but it's real easy to get onto.
Juts go to the top of this page and click onto chat..and I wait for you there.
Anybody else that would like to help with this..please join us there.

[sookainian]

hmm tonight at around 9 can ? coz i am going to see my doctor. Sorry guys

[Alfred]

Okay...

[sookainian]

let me know if u can 'chat' now

[Alfred]

It's 23:30 PM here, but hop onto chat anyway..see you there.

[sookainian]

o guys, i remove one shim yesterday and the auto unit can spin smoothly. So today i went to fly.

AFter flying 3 flights, and 3 autos, when i reach home, i check my auto unit, it seems to be tight back. Anyidea why will it become tight ? when yesterday it was smooth :arggg:

[heliroller]

Just a question? Is the crown gear mesh consistent as you rotate the main? One more thing to look at just for grins.. Make sure your crown plate has not come unscrewed from the hub unit. The crown gear will bind if this happens.. This will happen if you rotate the tail hub in the opposing direction.

[Ernie]

How much wear does the sleeve have on it? Can you see damage or excessive wear to the hub which rides inside the Sprag?

[sookainian]

i will try to take a picture of my auto unit and post here

[Zilly]

sookainian,

have you ever dissasembled the auto hub before now, by that I mean have you stripped the unit down?

z

[sookainian]

Here is the pictures.

[sookainian]

any idea guys ?

[DavidH]

All pieces in the pictures look normal to me.


David

[sookainian]

i also think so too, that's why it's like so hard to solve what's causing this 'sticky' unit.

But what i know is the unit spin smoothly with out the retainer collar and pin. But when u put this 2 teogether, it become tight :arggg: