how does a one way bearing hub works in the main rotor gear

[eric tung]

Not sure where I should post this question, but here it is.

can anyone show me how one way bearing works ?

the problem I have at the moment is : I have a small heli and crashed (of course , I am new in heli ) , since then the main rotor gear turns when the motor drives it, but it doesn't drive the smaller gear which drives the main shaft and the tail blade. so the heli motor runs but the bird stay on the ground... :arggg:

so I am interested in how this thing works together.

thanks

[BarracudaHockey]

If you replaced the main gear the bearing has a right way and a wrong way to install, yours is probably upside down, in the future mark things with a felt tip marker so they go back together correctly.

[eric tung]

The heli is prebuilt ARF type, the bearing was alright before the crashed.
I took the whole gear and bearing apart and there is only one way to install them together , otherwise it wont fit.

thanks for your reminder anyway.

how does the one way bearing looks like inside ?
when the shaft go through it , how does it allows one way turn and stop other direction. :?:

[BarracudaHockey]

Spin the blades, they should spin the way they will in flight with nothing moving and backwards they should spin the gear, if its opposite then you got the bearing in wrong.

If thats correct you probably got two wires reversed on the motor and its turning the wrong way.

As for how it works
A sprag is a freewheel clutch used in a number of applications. It resembles a roller bearing with rollers shaped like a figure eight and cocked with a spring as it turns one way they stand up and bind because of oil friction and slip in the other when the shaft is running.

[spork]

The one way bearing is a sprague clutch. Basically there are roller pins that get wedged against the shaft when it's turned in one direction, and they're free to float away from the shaft when it turns the other direction. I'll look for a picture - or maybe draw one.

[BarracudaHockey]

Sprague is a town in Manatoba, and a river in Oregon.

Sprag is a one way clutch :glasses2:

[spork]

Sprague is a town in Manatoba, and a river in Oregon.

Sprag is a one way clutch :glasses2:

I've always seen it spelled "sprague". I get plenty of hits for "sprague clutch" on Google. I think "sprag" is short for "sprague".

In any event, here are the best pics I could find. In the pic on the left you can see how the rollers would be wedged against the outer race when the inner race is turned CCW. And they would simply fall into the recessed areas when the inner race is turned CW.

[eric tung]

many thanks , The pictures helps a lot

so, if I put the shaft through the spargue/sparg clutch , it should only move in one direction, but reverse.

I will post a picture of my clutch tonight , may be you can tell me if the "things" inside ( like the roller or whatever ) are broken.

[spork]

It would be nearly impossible to tell by looking (even in person) on our little one-way bearings. The easy way to tell is to simply put it on the shaft and see if it turns freely in one direction and locks in the other.

[eric tung]

you are not wrong !

I am hoping to compare the normal good one with mine to see what happened after the crash..

The heli I have is a Blackhawk 450EP. I set the Gyro direction wrong and spin very fast after taking off. and ends up in my lemon tree upside down. :(

[eric tung]

I try to turn the main gear, it goes both directions.

hope you can see what's wrong..

[spork]

I try to turn the main gear, it goes both directions.

hope you can see what's wrong..


motor drives the main gear,
Main gear drives the small gear through the one way bearing,
small gear then drives the main shaft which turns the blades. but the small gear doesn't follow the main gear when it turns

I'm having a hard time reconciling your picture and description. I don't see a small gear in the pic. I would think that the motor would have a small gear (the pinion gear) directly on the motor shaft. I would expect that to drive the main gear (the big red one), and then I'd expect the main shaft to go right through that steel sleeve, which goes through the main gear. The only thing the one-way bearing needs to do is to make sure the sleeve can turn in one direction inside the gear hub, but not in the other. I can think of two possibilities off hand. Either the one-way bearing IS working correctly, but the main shaft is turning in the sleeve itself, OR the one-way bearing isn't working because it appears to be greased (it should be nice and clean).

I don't see a "small gear" in the picture. I can't make out what the smaller red piece is. It appears to be some sort of hub?

[eric tung]

yeah, it isn't very clear.

but more photos ...

and

my problem shown in this tube..

when I turn the main gear, it supposes to turn the main rotor blade by driving the small gear below, but it doesn't .

http://www.youtube.com/v/yktm49b95sk

[spork]

Try this... forget about the small gear. Stick the steel sleeve into the one-way bearing on the big gear. That sleeve should turn freely in one direction and not at all in the other direction. Sometimes you can fool yourself if the sleeve is going into the small gear, but isn't bolted to the smaller gear - because it's simply spinning in the small gear.

[eric tung]

Thanks Spork. I tried what you suggest already, and they spin in both direction. so it is definitely the bearing :roll:

I went int your Gallery. you have a lot exciting moments...

[spork]

Thanks Spork. I tried what you suggest already, and they spin in both direction. so it is definitely the bearing

Sorry to hear it. You might find a good cleaning in mineral spirits will cure it. It appears to be greased.

I went int your Gallery. you have a lot exciting moments...

Thanks. I try to get out and have some fun. I should put the latest pic in my gallery... I met a young lady from the Bunny Ranch on the plane to N.Y. last week, and invited her to join me at a taping of the Colbert Report. Ended up being a unique experience. (by the way, I explained to her that I got ordained on the internet, and would be redeeming her. she insisted however there would be no redeeming) :mrgreen:

[eric tung]

I will try to clean the bearing up , no harm done anyway. thanks for your advice ,Rev Spork.

by the way, what is the Colbert report ?

I have never heard anyone can be ordanined on the Internet as well, I don't think she would believe you... :lol:

your website is also useful. Bob's video is great. I watched the build for logo , lepton and Trex, and other general things. I hope he is going to do a build on Logo 500 3D , that will be mine next heli

[spork]

...by the way, what is the Colbert report ?

:shock: :shock: :shock: :shock: :shock:

Stephen Colbert has a show immediately following Jon Stewart on the Daily Show. Comedy Central. Colbert basically acts like O'Reilly just to be sarcastic. It's gotta be the best thing on TV. I got to see Colbert last week, and was lucky enough to see Jon Stewart a few weeks earlier. If you get to N.Y. you HAVE to go.

I have never heard anyone can be ordanined on the Internet as well, I don't think she would believe you... :lol:

Sure can. I got the idea from Homer Simpson. I've committed marriage twice so far. I'm thinking of having the Bob's (my hermit crabs) ordained as well - but I don't know if they'd take it seriously. :dontknow

[eric tung]

you added two more photos, what's that ? put them in the bin, quick...

[spork]

you added two more photos, what's that ? put them in the bin, quick...

That's an ex-LiPo. Always wondered what kind of magic they put in there.

[eric tung]

I found a site that explain the workings of one way bearing.

hope it is useful to someone.

http://www.rctek.com/info_bearings_one_way.html