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HomeAircraftHelicopterHelicopter Main Discussion › Understanding one-way bearings
07-19-2003 03:24 AM  15 years agoPost 21
Taipan

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Sydney, Australia

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Hmmm
The one-way in my X-Spec hub fits so tightly I have to tap it in with a hammer.

Isn't that meant to stop the sides of the bearing from flexing & fatiguing?

Btw, that hub & bearing was from my WC'99 - only 3 months flying with an OS61 then another 3 in the OS91 X-Spec before slipping. Found 7 hairline fractures, one on each side! One more & I woulda had a full house.

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07-19-2003 05:06 AM  15 years agoPost 22
jrice45516

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SoCal

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Deleted. The following post enlightened me.

Dances With Woofs

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07-19-2003 06:43 AM  15 years agoPost 23
AugustorrElite Veteran - US - My Posts: All  Forum  Topic

This is why I was reluctant to post the info. I just don't want to get into long discussions about it. I would ask for people to take as sharing info from my personal experience and take it or leave it. If it works for you great otherwise just disregard it.

jrice,

irq says that because we tried it in his heli and it also worked so he's familiar with the fact that the grease goes around the bearing case.

I think you may be misunderstanding what I'm trying to explain.

First, and to make sure we are talking about the same thing, the one-way bearing I'm talking about doesn't fit tight in my X-Spec hub. As a matter of fact when I take the ball bearing off it falls off the hub by itself.

Also you mention it locking. In my case it wasn't loking it was slipping.

Contrary to what you're saying a "floating" one-way bearing can work.

To illustrate how the principle works take a look at the following two diagrams.

Just imagine that the one-way bearing had some extra flaps that allowed it to hit the walls of an outer hub where it's floating.

As it engages, the bearing case (green) will freely rotate but only until the flaps hit the walls

Once in touch with the wall the bearing will lock in place and transfer the force to the outer hub or as in the case of helis the hub would be the one transferring the force to the shaft. This is a common mechanical device used in machines. The only difference is that they use rubber around the green area to make it into a dampened one way clutch.

As you can see the floating of the bearing doesn't prevent the transmission of the axial force. In the case I described before the outer flaps are replaced by the flat areas where the outer case rests.

Taipan,

I don't know if the one you are using from the W99 is the same I'm using. In my case it fits pretty lose. I also talked today to ja1010 and his is also lose and the one irq replaced was also lose. Maybe they become lose after a few flights, I don't know, I can only talk about the ones I've seen.

Augusto.

Avant Aurora Ultimate

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07-19-2003 11:54 AM  15 years agoPost 24
Taipan

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Sydney, Australia

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Ta mate
The WC'99 hub I'm using is the 0404-615 auto clutch assembly. The only mod I did to it was to file down the bottom to fit the DTDS 2nd main gear.

One-way is Hirobo 2500-048 12x16L one-way as for all 10mm main mast auto units. Just like the one in your pic;

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07-19-2003 03:14 PM  15 years agoPost 25
GMPheli

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W. Bridgewater, MA USA

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Every time I have had an auto bearing fail, it does not slip, it locks itself to the shaft. Upon dissassembly, I always find the plastic needle carrier has a crack in it somewhere. I always thought that when they fail in this manner, it was because the aluminum hub that the bearing is pressed into was not able to take the expansion loads, and allowed the one way bearing to expand too much, thus breaking the carrier. I noticed in MHW, that some aftermarket co. is selling a steel clamp that fits around the auto hub preventing this expansion.

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07-19-2003 06:29 PM  15 years agoPost 26
Augusto

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US

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Taipan,

The part# of the metal auto hub you're using is different than the one I'm using. Yours as you said is part # 0404-615 mine is part # 0414-229. I don't know if there's a difference.

Augusto.

Avant Aurora Ultimate

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07-21-2003 03:58 PM  15 years agoPost 27
yapjy

rrKey Veteran

Singapore

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Hi,
This is the X-Spec delrin main gear with the metal autohub.
Where shall I apply the grease?

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07-21-2003 06:07 PM  15 years agoPost 28
jdgee

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Central Pennsylvania

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Hello Augusto,
Thank you for sharing this information. I hope that you can continue to do so, with other topics which relate to our hobby. I understand and respect the wish to post a topic and not care to spend additional time and energy with further debate and instruction. You've done an excellent job ! To prove my sincerity, I'll offer an option for the folks that did not grasp the concepts that you put before us .
~~~~~~~~~ option ~~~~~~~~~~~~~~~~~
Should you have problems with a part that contains a one-way bearing or sprang, order a new replacment for the worn part . Thank You, Jon

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07-21-2003 06:16 PM  15 years agoPost 29
irq

rrKey Veteran

San Diego, CA

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yapyj,

Take the sleeve out of the center. Then take the top and the bottom bearing out. Then take the one way bearing out. Put grease inside what's left of the metal auto hub. Then put it all back together again.

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07-23-2003 05:14 AM  15 years agoPost 30
TMoore

rrMaster

Cookeville, TN

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The one way bearing on my Freya is a tight fit at the top of the bearing to hub fit due to the stamping process used to roll the outer case over at each end. If you relieve the milled slots in the hub so that the bearing has float you will also have to relieve the tops and bottoms of the hub to clear the upsets in the one way bearing shell. This will give the bearing more clearance to float and still not impede the bearing from locking against the hub. In my case I chucked the hub up in a lathe and skimmed a couple of thou out of each end about .06" back.

The grease will definitely help the one way bearing to float as long as the hub is properly cleared relative to the swaged surface of the bearing. In my way of thinking this fix only works for this particular type of one way bearing and won't do much for the auto hubs that use a round cased one way bearing that is pressed into the hub like the old Futura hubs. In the case of the Futura hubs the sleeve was too undesized and the bearing locked up.

In this instance, clearance between the auto hub and one way bearing is a good thing. Nice job Augusto!


Terry

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07-23-2003 07:41 PM  15 years agoPost 31
Billme

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MS

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Augusto!

This has been a problem for years concerning the gassers, where most thought they had engine problems... I run up on this from time to time...It took me a while to catch it though For those who just can't get the gasser smooth, just run it up on the ground, you will notice the machine smooth till the pitch starts loading the system...As a matter of fact, at bham get together last weekend I found this problem on a new machine...
I didn't see this like you have desribed, which is awesome BTW...I just washed them out and re-oiled them.. This was only a temp fix, because it does come back to haunt me, hehe
Thank you so very much for opening my eyes a little more with this fantastic article
Many Regards
Bill

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09-20-2003 07:31 PM  15 years agoPost 32
daggit

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Claremont, MN

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Billme
I have not run into any smoothness problems with my gasser but I was wondering about what you said
This has been a problem for years concerning the gassers, where most thought they had engine problems... For those who just can't get the gasser smooth, just run it up on the ground, you will notice the machine smooth till the pitch starts loading the system.
Are there some tell-tale signs that point towards one-way bearing issues? Is the bearing slipping and causing the illusion of an engine tuning issue?

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09-20-2003 11:05 PM  15 years agoPost 33
Billme

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MS

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Its not so much slipping as is its slipping, and crabbing like a lightbulb is going off and on 60 times/sec, its hard to see..Anyway, the above exsample is the only way I could find it while looking at the horizonial tail- fin. Its more common with the non constant tail hubs because of the way they are mounted in the hub... In the constant tail drive, the bearing is fitted more loosely inside with no up and down play in the gear itself when mounted properly....Since I'm talking about it, when I first got the new constant drive hub, I tried the Transmission fluid..On the gasser its just slipped, and sounded like a 53 chevy taking off in 2nd gear...So I cleaned it, and put some Remington lite silicon gun oil with Teflon...It worked great..Don't ask me why, because the instructions also recommend transmission fluid...
Regards,
Bill

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09-20-2003 11:33 PM  15 years agoPost 34
trickle

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On Road

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Biggest problem I have seen is people hammering the bearing in place. It should either be pressed in or the aluminum should be heated so that the bearing will slide in. I'd guess if the aluminum was a loose fit than that would cause problems every time the head was unloaded and loaded again. I guess the grease dampens this? I'd have it replaced with one that has a light press fit as per the specifications of the one way. Mine was a light press fit and no problems so far.

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09-21-2003 12:39 AM  15 years agoPost 35
docramage

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Warlingham, Surrey, UK

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Excellent explanation Augusto.

I too have had trouble with WWBs. In the Raptor the bearing is integral with the clutch, and following your explanation I suspect it's failure to centre when there is minor mis-alignment of the engine/clutch/start shaft that causes the problem.

(I think the correspondent who suggested greasing the inside of the bearing was probably rightly offering a simple solution - surely a thick grease would at least encourage all the rollers to engage)

My 2ry old Freya has a Torrington bearing as the input for the starter wand - a 6mm hardened shaft. I feel this is wrong - a bearing with rollers instead of balls fails to work like a constant-velocity joint, and it is almost inevitable that there will be mis-alignment with a hand-held start wand.

Nevertheless, I've replaced the Torrington with a hex, and use a standard hex wand without an integral one-way bearing. This is better in some ways, in that a ball-ended hex does (almost) act as a CVJ, so alignment is not a problem. However it does mean of course that the shaft is rotating when it is pulled, and it tends to get thrown...(which is OK as long as it doesn't hit the throttle/collective stick)

What I want to make is a start wand with a ball-ended hex, but that has a one-way bearing close to the ball. This way one could have a "freewheel" function, but there would only be a few grams of mass to withdraw on the engine firing. It somehow seems more of an engineer's solution to have the one-way mechanism where you can see and service it, rather than expending fuel carrying it as cargo.

Brilliant diagrams!

Incidentally - can you tell me :

With any kind of one-way bearing, if you suddenly accelerate the input shaft to catch up with an already-rotating output, does this place any more stress on the bearing? Engagement surely can't take place until both shafts are at (almost) identical speeds. I'm thinking of the situation where you have landed briefly, throttle at idle and the rotor rpm is still high-ish, and you then kick in throttle to take off again. Thirty years ago I drove a 1947 Rover with a freewheel function, and it didn't seem to harm that. If it is harmful, shouldn't our start motors have a "softstart" ?

Philip

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09-21-2003 02:38 AM  15 years agoPost 36
Ivan

rrVeteran

Wichita

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this is why I think the raptors wah wah. side load on the one way bearing causing it to slip, and the elasticity of the tail belt working against eachother make the tailrotor speed up and slow down and cause wah wah.

one way bearings don't like side load, as is put on by the tail belt in a raptor.

Ivan

Back to it!

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12-12-2003 12:13 AM  15 years agoPost 37
slant911

rrVeteran

Las Vegas, NV. Hirobo, Magnum Fuels, MAH

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Awesome post Augusto. I didn't realize how important this post was to me until just recently


John B. McNamara

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12-12-2003 12:38 AM  15 years agoPost 38
heliman41&1/2

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Florida

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Good Lesson.
Augusto, If you have the time, will you give me some info on why my Raptor 50 auto rotation bearing sticks. What can I do to fix the problem besides replace the hub?

Thanks for the work you put into helping everyone.

Rusty

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12-18-2003 09:03 AM  15 years agoPost 39
Fisherman

rrApprentice

Hong Kong

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Thanks for sharing.

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12-29-2003 07:37 AM  14 years agoPost 40
IAF

rrApprentice

Israel

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Thanks Augusto,

I'm going to do the greas thing in my Freya90 and hope I will not loose any more one way bearing.

Eran.

Have a nice day :)

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