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Main Discussion > Understanding one-way bearings
 
 
AugustoElite Veteran - Location: US - My Posts This: Topic  Forum
I finally decided that instead of sitting here watching people unsuccesfully trying to solve problems with one-way bearings I should stop procrastinating and write a post with drawings and pictures to share with other people what I have learned to make sure the one-way bearings work correctly in my helis.

As illustrative examples I take a look at three examples. The Freya auto hub, the Raptor auto-hub and the infamous KSJ starter wand with the one-way bearing.

This explanation applies to most helis and devices such as starter wands that use one-way bearings. I have had one-way bearing issues with several of my helis in one way or another other helis and there are several posts in here where people keep having problems with their one-way bearings in almost every brand of heli under the sun. In most cases is not as much a problem with their units as it is more of a consequence of a lack of understanding of how they work. Hopefully this post will bring some better understanding of how the one-way bearings work on our helis and it will help us assemble and adjust them correctly.

1) The Freya one-way:

Initially, during the first couple of weeks I had my X-Spec, I blew a few one-way bearings (auto hub one way clutch bearings) making them slip after a few real hard flights. To prevent being grounded by this problem in the middle of a weekend I bought a few of them to keep them in my toolbox just in case.

The problem was that the bearing case developed a micro-fracture (not easy to see to the plain eye) and under torque load the case started to expand so the rollers wouldn't be able to lock against the center shaft sleeve with enough force hence the slipping.

Concerned with why this was happening, I started thinking about it and then I realized what the “why” was. As a matter of fact once I understood it, it became pretty simple to fix.

From past experiences with metal parts I knew micro fractures are usually some problem with metal fatigue induced by repetitive loads in the section that kept developing the micro-fracture.

Looking at the geometry of the one-way bearing I realized that being securely fixed it wouldn't work the way it needed to for this application. A one-way bearing is a self-centering and self aligning device that without the self centering feature won't work correctly. I'm of course refering to the shaft in the middle being able to find its center when rotated inside a one-way bearing. That's what I was used to look for but in this case I had to look at it from a different perspective.

The problem that initally bafled me in this case was that according to what I was looking, the shaft wouldn't be able to find its center because the shaft (or sleeve) is held centered in place respective to the hub by the two ball bearings on top and below it.

Initially I thought that to make it a bit lose as I needed I would need to find a way to introduce some play such as replace the ball bearings with something less precise such as brass or Teflon bushings. I also though of other more involved and complicated solutions but then I realized that in this case the solution was to think of it in a different way and instead of expecting to see the center shaft find its center I should expect to see the outer casing find its center.

This is the reason why:

When you look at the way a one-way bearing works you realize that it's nothing more than a bunch of roller pins that when rotated “climb” the bearing case “walls” pushing the center shaft away from the walls. This “climbing” and consequently the pressure they exert on the center shaft is the reason why they lock. When rotated in the opposite way they “climb-down” releasing the center shaft from the grip.



Now the trick to understand why a secured one-way bearing where neither the outer case or the center shaft are allowed to move won't function or will develop problems is to realize that at the very begining and for a very short period of time until the one-way bearing locks all the roller pins are free and ONLY ONE roller starts the effect by being in contact with both the shaft and the case wall.

When rotated this roller starts “climbing” its own case wall and by doing so it “pushes” the shaft towards the center but you can also see it as the roller pushing the wall or climbing plane away from the shaft. This pushing away makes the whole outer case move away from that first roller pin point of contact and at the same time it brings the opposite side of the outer case closer to the shaft until the opposite roller starts the contact between its wall and its side of the center shaft.

Keep in mind that in the above drawing the outer case off center offset is a greatly exagerated to illustrate the point. In real life the case is off-center only a few thousands of an inch. Also the “climbing planes” are not that steep. They only need to bit a couple of degrees in inclination for them to work. As a matter of fact the lower the inclination the greater the pressure the exert on the center shaft. Also in many cases there's not even a need for a climb, the geometry of an hexagon shaped outer case gives enough climbing effect for it to work so bear with me and look at the drawings as more illustrative than engineeringly accurate.



This produces a sort of “embracing” effect among all the roller pins that makes all the pins climb their respective “walls” and start pushing against the center shaft until there's no more climbing possible at which point the bearing locks into its one-way effect.

Now to understand the problem I was having you need to imagine that either the outer case is not allowed to move freely or it is severely restricted from movement. The result is that the particular roller whose side of the bearing case (wall) is closer to the center shaft will always be the first to be in contact but won’t be able to push the outer case away making it be under a lot more pressure than the other ones. If you repeat this over and over it will subject that single wall spot to excessive and repetitive flexing and consequently it will develop a fatigue crack. This problem is exacerbated when using a metal hub because they're more rigid than the plastic ones. In both cases, whether it is metal or plastic, a rigidly or even semi-rigidly mounted one-way bearing will ultimately develop a crack when flown real hard over and over.

I imagine this is why the design engineers put some play into the fitting of the bearing and I kept misunderstanding it as a lose fit. Then we the american lunatic pilots started playing pogo stick with our helis bouncing them hard on power pitch takeoffs, piro hovers, piro tic-tocs or any of that crazy pitch pumping we do, so some more freedom of movement of the bearing case is required especially for 91 sized motors and their new higher power levels.

To fix the problem I just had to find a way to let the one-way bearing case move more freely so it could center itself when engaged distributing the load among all roller pins equally and lock in it's ideal center every time. Doing so would prevent one of the rollers from getting the entire load over and over. The solution was amazingly simple.

ENTER GREASE

Those extra loads force the issue of making sure that extra play works under even the more stressful conditions. To do so just pack a lot of grease (I used white tri-flow grease) around the outside of the bearing case so that you guarantee it's lubricated ebough so that it can move freely when it needs to find its center.



The one-way bearing below should be completely surrounded with grease on the outside to allow it to "float" when installed inside the hub.




This problem happened mostly when I was flying it real hard. I don’t have direct experience with the 60 versions but I don't believe that a 60 size engine would have enough torque to break them as often. The 91 engines have considerable more power and consequently we fly them harder and harder subjecting parts to a lot more abuse than before.

This is something I have done and it worked for me. I went from blowing them frequently to never ever again. I also told some friends in other states about this mod with excellent results and a few weeks ago I also told it to one of the guys that I fly with and so far it also seems to have fixed the problem for him. Lucky enough for him I had one of those extra bearings I had bought for myself that I had'nt had any use for again . I have also found that this assembly tip works both for the metal and the plastic hub.




Now for the perfectionists even though this is not required for it to work you can also use some 400 grit sanding paper to sand the sharp edges of the “fingers” that holds the one-way bearing case in place to make it even easier for the grease to let it move freely.




2) The Raptor one-way bearing:

As an example of a different approach the Raptor also uses a one-way bearing with a sleeve centered by two brass bushings. In the case of this bearing the brass bushings usually have a bit of play already so the lock should be solid from the begining. If it's not a little bit of wear in the bushings gives a bit more play making it more solid.




3) The infamous KSJ starter wand:

Most people that bought the KSJ starter wand have found that after only a few uses the wand stops working and the one-way bearing fails to lock.




In the case of the KSJ wand you have a shaft being held in the middle by two bearings just like the Freya metal hub does but unlike the Freya hub the bearing itself is not allowed any play for self-centering. What happens is that once there is a bit of wear in the shaft the bearings stop working because the roller pins fail to start the centering effect since neither the shaft nor the casing are allowed to move.

Using the concepts explained above and unless it's really worn-out, you can get it back to work. The idea is to allow for some play so that the shaft can move a little bit inside the one-way bearing making it engage into a lock.

The way to do it is to take one of the bearings off and allow the wand to rest on only one of the ball bearings and on the one-way bearing.



Here you can see the back ball bearing and the shaft that goes inside the one-way bearing.



Here's the front bearing. Between the two of them the shaft is securely held in the center of the one-way bearing not allowing it to do the required self-centering to engage into a lock.



Here's the one-way bearing. As it can be seen the one-way bearing is also firmly held in place so unlike the Freya hub no play for the one-way bearing is allowed.



Using a torch to heat the unit it can be easily dissasembled.



The front unit it taken out and now there's enough play in the shaft fo it to move inside the one-way bearing and find it's center. Re assemble the unit and remember that since now there's nothing to prevent the wand to be pushed inwards you need to supply some spacer such as a few washer in front ot the starter motor shaft the so it will hold the shaft in place by pushing it from behind. After this modification the unit now is back in service.


Comments

There are several schools of thought as to what system is better. Some prefer ball bearing supported sleeves because they feel that under load the main gear plane has no possibility to lose it's perpendicularity with respect to the main shaft creating misalignment in the gear mesh with the driving pinion. Others preffer the simplicity of the brass bushings. I believe that as long as there's play both systems are good. The reason for my belief is based on the observation that one-way bearings are not only radially self centering as explained above but also axially self-aligning devices. In other words a Hub with only a roller pin based one-way bearing and without either bushings or bearing will not only self-center but also self-align with the center shaft because when engaged all the roller pins being straight cylinders will force the hub to align parallel with the center shaft. Being this the case the wear on the bushings will be limited to the initial wear and not continue to increase afterwards.

Notes:

This is an extremely over-simplificated explanation. The actual operation of a one-way bearing from a strict engineering point of view is a lot more complicated but the principles explained here are the same. There are several factors such as surface roughness, brinell hardness coeficients, torsional shear and all kind of details that determine additional factors. For instance when I say there's only one pin in contact I don't mean it literaly what I mean is that there's only one that has significant force being applied to it while others have negligible force but they might still be in contact. If I start making all kind of side note explanations the post loses its purpose of being clear to most people. In most cases the pre-loaded pins should engage correctly but as the pre-load wears and becomes less solid the described play becomes more important. There are other issues to consider such as the fact that in most cases there's a pre-load in the roller pins to start the contact, there are also cases where the pins are not circular cilinders but pre-loaded pivoting lips with a progressive curve shape that gives them a transition from fast engagement to high force but in all cases the same principles explained here apply so the post still works as a guideline to understand and rectify problems commonly found.


Conclusion:

When faced with a one-way bearing issue understanding the way a one-way bearing works will allow you to make the right diagnostic and it will also give you the knowledge required to devise a solution or a corrrection. Most issues with one-way bearing are easy to resolve. Just think how the concepts explained above apply to your particular problem and you will probably be able to figure out a simple solution.


Augusto.

Avant Aurora Ultimate
07-18-2003 Over year old.
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FastR1Red
Senior Heliman
Location: Melbourne Australia

My Posts This: Topic  Forum		Augusto,,

Excellent!!!!!Thanks very much for the article, very informative.
Can I have permission to reprint in the club newsletter???? With credits to you of course..
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bluefronted
Veteran
Location: South Africa

My Posts This: Topic  Forum		As usual AUGUSTO , you go all out for this hobby.

thanks
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Steve Campbell
Elite Veteran
Location: Baton Rouge, LA

My Posts This: Topic  Forum		Most informative. Excellent work.

One question, and one comment:

What's the difference between a Sprague bearing and a Torrington bearing?

I was told that a medium-viscosity oil was better on these roller bearings, because grease could "pack up" in one spot and "throw" one or more of the roller pins. And this is a commonly-held belief in the heli community.

I've never had one fail, on over a dozen helicopters and a tired old KSJ adapter just like in your photos. I use a petroleum-based particulate gun oil; i.e., one that has teflon particles in suspension, like the popular Break-Free/Tri-Flow (both are the same stuff- different label).

Steve
07-18-2003 Over year old.
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WMac
Veteran
Location: Skotlande

My Posts This: Topic  Forum		Really interesting post Augusto.

Now where's that grease.....

Will


Beep Beep! One Road Travel, with Dominic Byrne!
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stardotstar
Senior Heliman
Location: Sydney Australia

My Posts This: Topic  Forum		Excellent Augusto. Thank you.
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Doug
Elite Veteran
Location: Naples Florida....

My Posts This: Topic  Forum		Nice job, great illustrations and pictures

First member of Member of Bearings Anonymous
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davehour
Key Veteran
Location: Guayama, Puerto Rico

My Posts This: Topic  Forum		Terrific information. Thanks Augusto!
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z11355
rrMaster
Location: 10000 is enough time wasted.

My Posts This: Topic  Forum		The other machine are Robbe's.

Of course, just to throw some gasoline
on the smoldering fire, the Robbe one
(in this price list) is $27, about 20% more
than MA. In the NEW pricelist, it rockets
up to $38, almost 50% more.



http://www.ronlund.com/Merchant2/me...duct_Code=S4448
07-18-2003 Over year old.
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Obsessive
Key Veteran
Location: 41.73N 71.41W

My Posts This: Topic  Forum		Folks may also find a more general "bearing" trip of discovery here:

http://science.howstuffworks.com/bearing3.htm

and Z, just sell the dang Robbe or crash less often
07-18-2003 Over year old.
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z11355
rrMaster
Location: 10000 is enough time wasted.

My Posts This: Topic  Forum

Probably the former instead of the latter.

I'm having a season like the one you
had early on.
07-18-2003 Over year old.
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Heli-Driver
Elite Veteran
Location: Arlington, TX

My Posts This: Topic  Forum		I always thought a Sprag bearing was a shouldered bearing like Augusto shows in his photos, they roll upward and tighten in one direction..

I thought Torrington bearings had a spring steel arm in it to keep the rollers tight or free depending on the rotation direction.

I know one thing for sure.... The one way bearings in MA are some of the best I've seen.



Raymond

Predator Gasser SE/231 X 2
Century Helicopters
07-18-2003 Over year old.
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WMac
Veteran
Location: Skotlande

My Posts This: Topic  Forum		So how does the Sprag (?) bearing in the previous link work, it seems there are pressure pads that press against the shaft by means of a spring, is that how it works and if it is wouldn't it slip under high load?

Will


Beep Beep! One Road Travel, with Dominic Byrne!
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FlyinBrian
Veteran
Location: USA

My Posts This: Topic  Forum		Hi,

The spring is there to create friction between the sprags and the shaft/sleave they ride on. Look at inside ends of the sprags, the friction / rotation of the sprags one direction will slip and the other direction the sprags are designed to climb themselves closing down the id untill it locks the shaft / sleave. Rotation of the carrier & sprags plays a part in this as well but that is the general idea of how they work.

The main benefit is the pressure is on the sprags themselve instead of an outward pressure on the housing as augusto has shown above.
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WMac
Veteran
Location: Skotlande

My Posts This: Topic  Forum		Thanks for enlightening me Auger !

Will


Beep Beep! One Road Travel, with Dominic Byrne!
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irq
Key Veteran
Location: San Diego, CA

My Posts This: Topic  Forum		I think some of you are confused.. Augusto is talking about putting grease on the outside of the bearing, i.e. between the block that is holding the bearing and the bearing itself. NOT between the shaft going into the bearing and the inside of the bearing itself.

And thanks, Augusto
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sharam
Elite Veteran
Location: Northern California

My Posts This: Topic  Forum		Nice Job Augusto. Thank you.
07-18-2003 Over year old.
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Jagboy69
Key Veteran
Location: Texas

My Posts This: Topic  Forum		Thanks for the hard work... see who needs to buy the crappy heli magazine when I learn more here on RR.... Nice job explaining how this interesting little bearing works..
Thanks, Jason

Jason /// Sceadu50/9chp WWW.Jagboy69.com
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Augusto
Elite Veteran
Location: US

My Posts This: Topic  Forum		David I think you might be right.
I have found the Sprague terminology used in the one-way bearings.
I'm going to check on that. In the meantime and to prevent confusion I changed it all to one-way bearings.

Augusto.

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Sar
Elite Veteran
Location: Kingston, NY

My Posts This: Topic  Forum		This should go into the RR articles section.. oh wait, there isn't one

--
Jon
07-18-2003 Over year old.
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Taipan
Elite Veteran
Location: Sydney, Australia

My Posts This: Topic  Forum		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.
07-19-2003 Over year old.
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jrice45516
Heliman
Location: SoCal

My Posts This: Topic  Forum		Deleted. The following post enlightened me.

Dances With Woofs
07-19-2003 Over year old.
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AugustoElite Veteran - Location: US - My Posts This: Topic  Forum
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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Taipan
Elite Veteran
Location: Sydney, Australia

My Posts This: Topic  Forum		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;

07-19-2003 Over year old.
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GMPheli
Key Veteran
Location: W. Bridgewater, MA USA

My Posts This: Topic  Forum		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.
07-19-2003 Over year old.
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Augusto
Elite Veteran
Location: US

My Posts This: Topic  Forum		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.

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yapjy
Key Veteran
Location: Singapore

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

07-21-2003 Over year old.
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jdgee
Heliman
Location: Central Pennsylvania

My Posts This: Topic  Forum		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
07-21-2003 Over year old.
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irq
Key Veteran
Location: San Diego, CA

My Posts This: Topic  Forum		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.
07-21-2003 Over year old.
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TMoore
rrProfessor
Location: Cookeville, TN

My Posts This: Topic  Forum		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
07-23-2003 Over year old.
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Billme
Elite Veteran
Location: MS

My Posts This: Topic  Forum		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
07-23-2003 Over year old.
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daggit
Elite Veteran
Location: Waseca MN

My Posts This: Topic  Forum		Billme

I have not run into any smoothness problems with my gasser but I was wondering about what you said
Quote 
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?
09-20-2003 Over year old.
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Billme
Elite Veteran
Location: MS

My Posts This: Topic  Forum		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
09-20-2003 Over year old.
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trickle
Heliman
Location: On Road

My Posts This: Topic  Forum		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.
09-20-2003 Over year old.
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docramage
Heliman
Location: Warlingham, Surrey, UK

My Posts This: Topic  Forum		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
09-21-2003 Over year old.
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Ivan
Veteran
Location: Hutchinson Kansas

My Posts This: Topic  Forum		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

I came, I saw, I hovered
09-21-2003 Over year old.
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slant911
Veteran
Location: Las Vegas, NV. Hirobo, Magnum Fuels, MAH

My Posts This: Topic  Forum		Awesome post Augusto. I didn't realize how important this post was to me until just recently


John B. McNamara
12-12-2003 Over year old.
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heliman41&1/2
Heliman
Location: Florida

My Posts This: Topic  Forum		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
12-12-2003 Over year old.
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Fisherman
Senior Heliman
Location: Hong Kong

My Posts This: Topic  Forum		Thanks for sharing.
12-18-2003 Over year old.
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IAF
Senior Heliman
Location: Israel

My Posts This: Topic  Forum		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 :)
12-29-2003 Over year old.
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Mitz
Senior Heliman
Location: Crystal Lake, IL

My Posts This: Topic  Forum		I tried the grease!

The grease in my Evo 50 one-way is wonderful. I immediatly
noticed an improvement in performance and the rock-solid
proof was the extended time it took to spool down after shut-down.


Dick Sceadu or Don't
10-14-2004 Over year old.
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Alistair
Key Veteran
Location: no where land

My Posts This: Topic  Forum
Quote 
Understanding one-way bearings


this is easy..... the go one way

squigle
10-15-2004 Over year old.
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mrNoodles
rrProfessor
Location: Borlänge, Sweden

My Posts This: Topic  Forum		And breaks after X hours of use



/Fredrik
'Hm now I just have to find out where to connect the GV1 sensor to the Jazz80 ESC.
10-15-2004 Over year old.
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Alistair
Key Veteran
Location: no where land

My Posts This: Topic  Forum		yep, see...... easy

squigle
10-15-2004 Over year old.
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Crusty Commie
Senior Heliman
Location: Wales

My Posts This: Topic  Forum		Mitz is the evo one way different to the original sceadu?, looking at my one-way there is no way to do the mod without modifying the main gear...thx

I am dsylexia of borg..resistance is fruity...your arse will be laminated
10-15-2004 Over year old.
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mrNoodles
rrProfessor
Location: Borlänge, Sweden

My Posts This: Topic  Forum		The oneway housing on the EVO is plastic.
You can sand down any eventual sharp edges and apply grease on the outside of the bearing.
But I guess plastic is doing less harm to the bearing, and less force being applied on it due to smaller engines.

Wouldnt hurt to try the mod though.

/Fredrik
'Hm now I just have to find out where to connect the GV1 sensor to the Jazz80 ESC.
10-15-2004 Over year old.
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Crusty Commie
Senior Heliman
Location: Wales

My Posts This: Topic  Forum		Noodles, I still cant see how, the bearing is a tight fit, greasing the outside would do nothing in this case

I am dsylexia of borg..resistance is fruity...your arse will be laminated
10-15-2004 Over year old.
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smegs
Veteran
Location: Hacienda Heights, CA

My Posts This: Topic  Forum		Awesome article that's how you write a awesome article.
11-18-2004 Over year old.
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hepsibar
Senior Heliman
Location: Lancaster, Lancashire, UK

My Posts This: Topic  Forum		Raptor 60/90 bearing adjustment, gear mesh issues

Excellent explanation! Thankyou for this info. Very very interesting and well researched.

A question though for raptor 60/90 owners. If I increase the internal diameter of the bushes on the 60 hub above and below the bearing to allow some float/ free play of the bearing will this not affect the gear mesh of main gear & pinion and tail take off gears?

Am I barking up the wrong tree? I realise tolerances in your diagrams are greatly exagerated but approx how much play is required to free up my hub - do I ream it out a little at a time till it does not lock?

From the diagram it seems that the freya bearing has flats which allow freeplay in the hub without allowing the bearing to spin unlike the raptor bearing which apears to be round.





Empty Coffee Cup
11-18-2004 Over year old.
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hepsibar
Senior Heliman
Location: Lancaster, Lancashire, UK

My Posts This: Topic  Forum		The point I was trying to make is that from what I perceived Augusto's post on the free hub auto bearing is that the bearing needs to be able to float around the shaft in order for it to engage/ disingage smoothly.

The bushes on the raptor hub are there to ensure correct gear mesh but because of this the auto bearing cannot float about the main shaft therefore is the answer to remove a tiny amount off the bushes thereby allowing a small amount of free play without adversly affecting gear mesh? - Reduced lock up problems with increased gear wear!!!

Perhaps someone knows of a sprague clutch which may fit the raptor with or without modification.

Or maybe the raptor auto hub is a lost cause.

Empty Coffee Cup
11-18-2004 Over year old.
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rstacy
Key Veteran
Location: Rochester, NY

My Posts This: Topic  Forum		Augusto,
I just did the bearing mod to my KSJ start shaft.
It did the trick!

Thanks!
Ray
06-21-2005 Over year old.
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SubSailor
Veteran
Location: Austin, TX.

My Posts This: Topic  Forum		Good info, wanted to bump this.

Fromeco Field Rep.
A day without sunshine is, well.., alot like night time.
04-11-2006 Over year old.
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MrT
Heliman
Location: Dawson Creek, BC, Canada

My Posts This: Topic  Forum		One way bearings

Does anyone know how the one-way bearings work on the Suprex-3D Pro 450 is installed? I had a major crash and dismantled my Heli before making a detailed diagram of the gears.



Thanks in advance?

Is anyone else trying to fly one of these?
09-02-2007 Over year old.
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CitationX
Senior Heliman
Location: Danville, IN

My Posts This: Topic  Forum		Need Help Understanding 1 Small Issue

Augusto did a fantastic job explaining the one-way bearing theory. The 1-way bearing in my KSJ wand has begun to slip over the last few weeks and therefore the modification is imminent. I would like a bit of clarification on 1 issue Augusto made. It is in regards to this statement:

Quote 
Re assemble the unit and remember that since now there's nothing to prevent the wand to be pushed inwards you need to supply some spacer such as a few washer in front ot the starter motor shaft the so it will hold the shaft in place by pushing it from behind.

Will someone give me some help on understanding this point? I was looking at my KSJ trying to figure this out but I am not seeing it.

Thanks for any help guys.
09-04-2007 Over year old.
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PietervA
Veteran
Location: New Zealand

My Posts This: Topic  Forum		Undo the bolts in the conical connector, thus releasing both the hex starter shaft and the stubby one-way shaft. Heat up the wand piece with the two bearings, and allow the front one to drop out. Make sure the back one remains in place as the piece cools.

Now replace the stubby shaft, screw the wand base onto the part mounted on the starter motor shaft, let the stubby shaft rest up against the front of the starter motor shaft, and replace the conical piece on the stubby shaft. Tighten the caphead bolt, making sure that the conical piece does not rub against the wand base when you push down on it.

Now replace the hex wand and voilá, you get another year or more out of your KSJ unit.
09-04-2007 Over year old.
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CitationX
Senior Heliman
Location: Danville, IN

My Posts This: Topic  Forum		Got It!

Sounds good. I have made the necessary modifications and will give it a shot tomorrow on a fresh charge.

Thanks for the help!
09-05-2007 Over year old.
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