I have had this issue with my KX2 paddle and have two observations: On my paddle, the screw that is meant to hold the standoff to the plastic body will actually screw tightly into the plastic body *without* the standoff. When this happens, additional torque applied with a screwdriver has no effect on the standoff.
When my paddle got loose I tightened the screw with a screwdriver, but then later (after it got loose multiple times) I realized that the screw felt tight because the threads were *gripping the plastic. *The connection with the standoff was still fairly loose, the torque I put on the screwdriver was blocked by the tight fit of the screw's threads to the plastic. The solution I used was to turn the standoff while jogging the screw back and forth with a screwdriver until I felt the standoff grip against the other side of the plastic, then continue to jog the assembly while tightening the screw about another quarter turn, to the point where the screw was nice and tight against the standoff and *also* tight against the plastic. This approach has kept the screw and standoff stable without the need for glue. I think that if future releases of the paddle were manufactured with a slightly larger hole in the plastic, then it would be easier to achieve a tight fit between the screw and the standoff. I'd also be curious if a small lock-washer on the standoff side might help make the assembly more immune to vibration. 73, Matt NQ6N On Tue, Jul 25, 2017 at 11:12 AM, Ron D'Eau Claire <r...@cobi.biz> wrote: > It's useful to remember that a screw (or bolt) is a spring. When tightened > it stretches lengthwise. Like any spring, it offers the best "grip" when > subjected to the right range of pressure. > > Way back in my High School days (1950's - before Mercury was a toxic > substance) I watched a demonstration using a bolt and nut made of frozen > Mercury. Mercury is not elastic. Liquid Mercury was poured into molds for a > nut and bolt and hardened with liquid nitrogen. Using gloves, the > demonstrator assembled the nut and bolt using a large wrench to apply a > great deal of torque. That done, anyone could loosen it without a wrench by > just twisting the nut or bolt with minimal finger pressure (inside the > gloves of course). There was no resistance since Mercury does not stretch. > > It's easy to over torque (stretch) small screws. That's why the Elecraft > kit > assembly manuals do not recommend using power screwdrivers. The Elecraft > factory in Watsonville is equipped with special torque-limiting power > screwdrivers to allow quick assembly with screws not so tight they are > damaged or broken. > > Since a screw is basically an inclined plane that stretches the screw when > tightened, vibration will allow the screw to turn (slide along the plane of > the threads), hence the use of lock washers or chemical compounds in such > environments to stop any movement. > > Perhaps the issue with the KX2 paddles is the vibration as the contacts > collide allowing the screws to turn. Working remotely on the Elecraft > manuals I've not been directly involved with the issue, so that is pure > speculation. > > 73, Ron AC7AC > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to m...@nq6n.com > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
