MadModder
Gallery, Projects and General => Neat Stuff => Topic started by: Tinkering_Guy on August 04, 2010, 06:50:33 PM
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In rummaging through my bins looking for bearings, I found some peculiar items as shown below in the first photo.
Each hole is lined with what look like rollers, which is why I originally thought they were bearings. However, insert a piece of 1/4" round stock in them, and their true magic shines forth: they only allow the stock to turn in one direction!
That's not strictly true; the inserts can be pressed out, and as the second photo shows, they're grooved with detents for the spring-fed steel ball shown. It's not clear in the photo, but on the little shoulder under the word 'INITIAL' there's a wax-sealed threaded hole. Clearly there's a grub screw in there that puts a set tension on the ball, so at some point the torque overcomes the spring and the handle turns around the insert rather than with it.
So, adjust the spring as desired, and you can tighten something to a particular point -- but no farther -- when the force of turning the stock becomes greater than the force holding the insert's detent against the spring's resistance.
They came from a defunct computer company's labs, so I suspect they're for tightening drive shafts or something. The ones marked 'FINAL' are tougher to overcome than the ones labeled 'INITIAL.' Some of the units are hand-labeled "6 in.-lbs. / 2½ in.-lbs." and the like, which is nice to know.
Odd beasties, but now that I've looked at 'em in detail, I can see potential uses for them..
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Funny things. Might they have been used to adjust tape drive reel spindles? One side for an empty reel, the other side for a full one.
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Great. Now you can torque all the bolts an a model steam engine's piston cover. :D
Bernd
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Also known as a "sprag clutch". http://en.wikipedia.org/wiki/Sprag_clutch
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One way roller clutch. used to make a ratchet drive on equipment.
John S.
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They are very good for making starter 'handles' for model ic engines.
You can either mount one onto the flywheel of an engine and use a bit of the correct sized rod in an electric drill, or have a spigot on the flywheel, and the bearing mounted in the drill.
They automatically freewheel when the engine starts and the speed exceeds the drill speed, and are then just pulled off.
Bogs
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I use Sprag-type clutches with fair regularity. If you use dowel pins rather than balls, you can get a lot more torque transmitted. Properly designed, the roller elements act like a roller bearing when the shaft over-runs the applied torque. It's a bit harder to make them under-running, but it can be done -- I have only run into that requirement a few times. The main thing is to be sure that the angle on the locking reliefs has a tangent greater than the coefficient of friction between the roller element and the mating shaft.
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One of the features of a roller ramp type clutch is that there may be very little, near as darnit no, backlash. I have an old electric clock with such a clutch which is vibrated at 50hz by a mains coil. The clutch causes the shaft to turn very slowly but with considerable torque to wind up a big spring.