|some words about the so-called clutches...|
Message #3 Posted by Hans Brueggemann [GER] on 31 Dec 2005, 8:05 a.m.,
in response to message #1 by David Ramsey
...of the card readers. following the many posts here in the forum that deal with card readers of 67 and 41 machines, you can find two major opinions about how the worm gear is attached to the drive motor.
fact is, that the worm gear is simply pressed onto the motor shaft. the two opinions either state, that the attachment tube of the worm gear serves the extra function of protecting the card drive against too much torque, in case the card movement is blocked somehow. the other opinion is, that there simply isn't any purpose of the attachment tube other than attaching the worm gear to the motor in a fashion, that it can be dismantled and reused in case, say, of a motor fault. i'm of the same opinion. there is *no* protective function designed into the whole drive, other than the weak motor itself. you doubt? try the following: connect the motor to a proper power supply, start it up and try to block it with your bare hands. no bloodshed, though you might have expected that. the generated torque is so low, that there is not the slightest chance to damage anything inside the card reader if the card is blocked. furthermore, you simply won't find *any* card reader, that, with a stuck card, keeps the motor running (until shutdown) and, on the other hand, is able to properly drive a card through the reader.
that's why i consider the "safety clutch" nothing more than an "urban legend". it is just an inexpensive means to connect a worm gear to a motor. that's it. just my two cents to the everlasting discussion about "loctite or gelee royal?"