Singing the sticking autorotation hub blues

[wnor]

The autorotation hub/clutch on my Raptor 50 V2 (592 flights total) reliably fails to release during an autorotation. I've read many, many posts, etc., and tried many things, including replacing PV0019 Autorotation Clutch and PV0020 Autorotation Clutch Shaft at 550 flights. The new Clutch and Shaft have experienced no crashes. I definitely do not over-torque the lower Jesus bolt. The inner surface of the PV0379 Pully has been lightly sanded so it turns freely. I've tried as lubricants Tri-Flo, Hoppe's Gun Oil, ATF, white lithium grease, and combinations of these (I do remove the shaft and apply the lubricant directly to the needle rollers). I put the shim beneath the C-clip on the old unit as recommended by Raptor Technique. Belt tension seems fine. The clutch sticks even when throttle hold is set to kill the engine. I've never experienced similar problems with the three other types of helicopters I have owned. The only thing I can think of that I have not tried is TT's grease - is that stuff somehow magic? When stuck, both the old and new clutches are solidly stuck, requiring a good rotational tug on the pully while holding the head to get things free again. I do mild 3-D stuff, nothing exotic, with a nice-running OS-50 Hyper. What in the world am I doing wrong? Thanks for considering this problem.

[Mike SVOR]

When you hold the clutch and turn the main blades, do you feel it binding or hanging up?

Think about changing the one-way bearing?

[wnor]

Thanks for the reply. When I hold the main blades and spin AK0148 Main Spur Gear counter-clockwise when viewed from above, the Gear spins nice and free (when the autorotation clutch is not sticking, of course). When I hold the Gear and spin the main blades clockwise when viewed from above, the blades spin nice and free.

>Think about changing the one-way bearing?

I have changed PV0019 One Way Clutch and PV0020 One Way Clutch Shaft. Could any other parts be involved?

[Mike SVOR]

There are two one-way bearings. One for the starter shaft and one on the main spur gear. I"m guessing (didn't look at the part numbers) that you changed the main spur gear's one-way bearing.

A thought: Maybe your fan is backing off the threads and locking up the main shaft? Did you locktite your fan onto the motor?

[Funky]

Are you sure its the one way locking up and not the engine cluth. I had some problems with my one way locking up. I took it off, re-lubed it, but the problem kept coming back. I was sure it was the one way until someone told me to try pulling the main shaft and removing the gears while I thought the one way was still locked. I did and it spun freely once I removed the gears. Even though it definately felt like it was the one way locked up when everything was assembled, it was actually the engine clutch that was hanging up. Its worth trying and it is simple to check.

[wnor]

Thanks for the replies. I'm sure the problem is the PV0019 One Way Clutch: The helicopter idles normally with a jammed autorotation unit. After shutting down with a jammed autorotation unit it is possible to grab the main blade hub, grab the main gear, and torque the gear counterclockwise (as viewed from above) to break the autorotation unit free. Perhaps the new unit is defective, too.

[Funky]

After shutting down with a jammed autorotation unit it is possible to grab the main blade hub, grab the main gear, and torque the gear counterclockwise (as viewed from above) to break the autorotation unit free.

FYI, this is the same thing I did when it was my clutch was hanging up. I would grab the head and gear to break it loose when it was locked up. I swore it was the one way for the same reasons you are describing... until a friend made me test it by pulling the gears while it was still locked up. Like you I changed one way hubs first and the problem kept coming back despite the new one way.

Like I said, its a simple test and worth trying.

[wnor]

Thanks very much for the reply. I think I have done as you suggest: After removing PV0020 One Way Clutch Shaft from PV0019 One Way Clutch, lubing this time with ATF, and reassembling, I went flying. On two of two flights, the autorotation function of the helicopter did not work correctly, and the stuck "whatever" described above was present on landing. On landing, the engine idled fine with the blades stopped. After stopping the engine, the one-way bearing in the start shaft was observed to work normally. Between flights I broke the "whatever" loose by torquing the main gear as described above. Following the second flight, I completely removed the autorotation unit from the machine, removed the white gear from PV0019, and observed the hub to be solidly locked up - to be clear, PV0020 One Way Clutch Shaft and PV0019 One Way Clutch were stuck together. The engine's clutch bell was observed to spin freely as it should, and the one-way bearing in the start shaft was observed to be functioning correctly (engaging in one direction, and spinning free in the other). So I think I have held the problem in my hand, isolated from the rest of the machine and confined to only two parts. So, how to proceed? Return these two parts locked up to Ace for their consideration and possible replacement? Try some other lubricant than the list cited above in my first post?

[Funky]

Check out this post for more ideas http://www.runryder.com/helicopter/t55473p1/?highlight=auto+hub+grease

[wnor]

Thanks for the interesting link. A comment in it about excessive belt tension possibly jamming Raptor auto hubs caught my eye, along with the emphasis on grease as the ideal lubricant (too bad he did not mention the specific make/model of grease he uses). So, I bought some new white lithium grease (AGS Company, Cat. No. WL-1H, 1.25 oz tube, at True Value Hardware), thoroughly washed out the hub with acetone, thoroughly dried it, and thoroughly packed it with grease. Then I set the belt tension as loose as I dared, and went flying. Yep, the hub jammed hard on two of two flights.

Well, the scientific method seems to have let me down so far, so perhaps I should resort to magic: buy another new hub and TT's grease, then hope for the best.

[ferincr]

along with the emphasis on grease as the ideal lubricant (too bad he did not mention the specific make/model of grease he uses). So, I bought some new white lithium grease (AGS Company, Cat. No. WL-1H, 1.25 oz tube, at True Value Hardware), thoroughly washed out the hub with acetone, thoroughly dried it, and thoroughly packed it with grease. Then I set the belt tension as loose as I dared, and went flying. Yep, the hub jammed hard on two of two flights.

Well, the scientific method seems to have let me down so far, so perhaps I should resort to magic: buy another new hub and TT's grease, then hope for the best.
Did I get it wrong or it says to put the grease outside of the one way and not into it:confused::confused::confused:
Please correct me if I'm wrong but it seems like the grease is for the whole bearing to "float in it and not to put it inside to lubricate the pins.
I'll look at it one more time.
As far as what type I think it says triflow grease (unless I read that in some other post about auto hubs)

[ferincr]

The one-way bearing below should be completely surrounded with grease on the outside to allow it to "float" when installed inside the hub.
Yep, that's what I thought I saw...

[Funky]

You are correct, they aren't talking about the actual bearing. The grease goes on the lower plastic part of the main gear where it inserts into the tail drive gear. It is supposed to help the hub center under load without jamming it up. I have been doing this since I read the article and I haven't had any locking up issues... although I am not sure if this is helping or not.

[ferincr]

Ok, now how do you take the R60/90 one way bearing off?
I managed to get the two brass bushings off but not the one way.
Any tips??? Should I heat it, or this would ruin it?

[ferincr]

I've been doing a little bit of thinking (not a lot since I'm very brain limited:OK) so please feel free to correct me but...
What is the worst it can happen if the auto hub locks?
It seems to me that the only problem there is that it will drive the clutch bell in an auto but I can't think in anything else (although there should be more reasons why engineers decided to go the extra mile and put one there I guess... )
Oh, I'm talking in a driven tail heli here, since I'm not familiar with belt driven ones.

[ferincr]

Well, after taking it apart and cleaning it, plus I put the shim as per Raptortechnique, plus loosen the lower jesus bolt and the reinforced ring a bit I flew today all day and had no more problems with the auto hub locking (it would have been good to know which one of all these things was the solution:confused: )

[ferincr]

Well, that was it.
Few more flights in ti and it got stuck again, not as hard since I was able to unstuck it rotating it backwards while holding the main gear with the other hand.
Anyway the new one is here, it came in a beautiful crumpled box with a pair of brand new CRUSHED main blades:soapbox

[Mike SVOR]

What is the worst it can happen if the auto hub locks?


The blades would then slow down with the engine rpm instead of 'free-wheeling' while the motor drops down to idle/shuts-off.
Basically, if your motor dies, it will drag your head speed down till the clutch disengages. Not good on autos.

[ferincr]

Basically, if your motor dies, it will drag your head speed down till the clutch disengages. Not good on autos.
But if the engine dies, wouldn't that disengage the clutch automatically, I mean the engine needs to be spinning at quite some rpm's for the clutch to engage so if it dies my thought is that you'll only be dragging the clutch bell (I know, it would be better not to but it doesn't seem that bad).:dontknow

[Mike SVOR]

But if the engine dies, wouldn't that disengage the clutch automatically,


nope. The clutch won't disengage untill the motor drops below a certain rpm, and that can't happen until the rotor falls to an rpm low enough to allow the motor's rpm to release the clutch.
Basically, if the one-way is locked, you will have bad auto rotation attempts.

[ghtracey]

I can see where you're coming from Mike, the clutch can't disengage becuase the rotors are forcing it to turn at a speed high enough to keep it locked. I'm just wondering how it all would work in a properly functioning system, The motor idles, the auto hub allows the pinion to slow allowing the clutch to dissengage I imagine.

Nobody mentioned that it if doesn't work and your fan manages to back itself off that you could be in for some ugliness as well.

[ferincr]

Ok I understand now, especially the thing with the possibility of the fan backing off:WOW:WOW:WOW
I knew that if the heli designers decided to put one there there should be a reason for it, especially when you find it in every heli, not just one brand.

[Mike SVOR]

just wanted to say check tail belt tension also.
yesterday, i was putting my tail back on by slipping the belt over the main shaft pulley and turning it. This caused the one way bearing to lock up. I got it free by hand turning it although it took some force to do so. It's fine now, but thought you might want to check that.

[wnor]

Problem solved: The problem described in the first post of this thread was caused by defective new parts PV0019 and/or PV0020. Having tried everything I could think of to fix this problem, I returned the items to Ace, and Ace promptly replaced them (thank you). The new auto hub is working fine. So it is possible for a brand-new auto hub to stick. One thing to check if you encounter similar problems: While installing the replacement hub I noticed that the upper Jesus bolt had fractured. The bolt head was completely gone, and the only thing holding the rotor head on the main shaft was a tiny stub, held in place by the nut. This was a new Miniature Aircraft part, not the original TT bolt. Apparently, in the course of doing a lot of autos from a hover with a stuck auto hub, a great deal of stress was being placed on this bolt when the throttle hold switch was flipped and the engine suddenly transitioned from being a driving force to a brake. So, if you are singing the stuck autorotation hub blues, check those Jesus bolts!

[ferincr]

Problem solved: The problem described in the first post of this thread was caused by defective new parts PV0019 and/or PV0020. Having tried everything I could think of to fix this problem, I returned the items to Ace, and Ace promptly replaced them (thank you). The new auto hub is working fine. So it is possible for a brand-new auto hub to stick. One thing to check if you encounter similar problems: While installing the replacement hub I noticed that the upper Jesus bolt had fractured. The bolt head was completely gone, and the only thing holding the rotor head on the main shaft was a tiny stub, held in place by the nut. This was a new Miniature Aircraft part, not the original TT bolt. Apparently, in the course of doing a lot of autos from a hover with a stuck auto hub, a great deal of stress was being placed on this bolt when the throttle hold switch was flipped and the engine suddenly transitioned from being a driving force to a brake. So, if you are singing the stuck autorotation hub blues, check those Jesus bolts!
:WOW:WOW:WOW