OT: Ratcheting bearing?

The clicking sound on multi speed bikes is a ratcheting device that uses dogs to engage teeth when pedaled and slip when coasting.

I believe you are looking for a Torrington bearing. These don't use teeth and grip a smooth shaft in one direction and slip when the shaft rotates at a faster speed than the bearing is being turned.

similar?

A 'spring clutch' would give you unidirectional gripping

AWEM

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Well that's enlightening.

Many many spring clutches used in electromechanical type writers such as the old IBM 'golfball'. To acutate all you need is a slight friction drag on the free end of the spring so it tends to 'wind up' and grip the shaft. They could operate as amazing speeds both gripping and releasing.

AWEM

Perhaps that's what you want -- but I think what you *need* is a worm gear.

I dont know strong you need it to be - fishing reels have anti reverse bearings in them to stop the handle reversing. It is usually a self contained bearing unit - If you where near South Africa I could give you a bunch :)

Tim South Africa

TMN fired this volley in news: snipped-for-privacy@x35g2000prf.googlegroups.com:

That's all one line. It's page 1092 in the McMaster-Carr catalog.

"one-way locking needle bearings".

LLoyd

It's more on topic than a lot of others.

The bike devices are called freewheels ("free wheels"?), see also "overrunning clutches".

Bob

Search for a "sprag clutch" or "sprag clutch bearing" instead of a "spring clutch", and I think you'll find what you are looking for. There are a number of sizes and styles available, from a number of manufacturers. Basically, they all use asymmetrical cams between the inner and outer races to lock up in one direction and freewheel in the other. Some have just the cams and must be used with ball or roller bearings, others have one or two rows of ball or roller bearings built in.

John Martin

it is called a sprague clutch.

On Fri, 17 Aug 2007 05:26:08 GMT, with neither quill nor qualm, John Doe quickly quoth:

Google "Sprag clutch". They're used in automatic transmichigans, conveyor belt systems, etc.

Ayup.

-- Seen on a bumper sticker: ARM THE HOMELESS

Sprag is the correct (or at least more common) spelling.

The spring clutches and roller clutches are suitable for light duty, non-critical applications. Sprag clutches are available with much higher torque capacity than either spring or roller clutches.

There are devices out there that look like roller bearings but the rollers are egg shaped instead of being round. Had an electric starter on a Gravely tractor years ago with this set up. It allows free rotation in one direction but locks up in the other. No ratchet pawls to wear or break, just a series of cam shaped rollers between two smooth surfaces. Don't know the name for them but I bet someone here does

Much depends on how much power/torque and speed you are transmitting.

for light duty use RC model helicopters use something that may be useful.

also click on

Let the group know how you make out and what your project was.

Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.

Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.

F. George McDuffee fired this volley in news: snipped-for-privacy@4ax.com:

Hey, Unca. You might be slightly misinterpreting "light duty". A decent ABC .30 will turn out well over 1 HP at 18 to 20 grand.

LLoyd

Wow, thanks for the link, that was my next question. What I asked for was probably more like what Andrew Mawson first provided, but the one-way bearings (with or without radial load protection) might be even better for my project.

Whatever, it has to be something discussed in this thread. Very useful information, examples, and terminology, thanks.

I do, unfortunately.

Gravely call them "cams" or "roller cams", I can't remember which and I'm too lazy to look it up. What they ought to be called is RCAYBBSDWYSTPs. That is "roller cams and you'd better be sitting down when you see the price". They are about 1/2" long, maybe 1/4" to

5/16" diameter. Not much to them. They wear out primarily because the tit on the sprocket hub that you put the hole in the hand starting strap on looks somewhat like a grease fitting, so a previous owner has often removed it and replaced it with a real grease fitting and then pumped the hub full of grease. The last ones I ordered listed for $28 and change. That's EACH, and there are 21 of them in the clutch. The dealer double checked the price, apologized for it, and then sold me 3 of them at about $20 each. Which was enough to get the clutch to lock up properly, at least for the time being. If it goes again, I'll consider machining the sprocket assembly to take an off-the-shelf sprag clutch.

John Martin

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Must the shaft they are stuck onto be very smooth?

If so.

Any suggestions locally (USA) for a short 1" or 2" piece of 1/4" diameter smooth steel rod? I guess it has to be "ground".

Or do I have to order that online too? I was in a hurry (to have the bearings shipped today) and bought them without thinking much about what those bearings might require to be usable. All I have is some ordinary steel rod purchased from Lowe's.

Thanks.