![]() Safety WireĪC43.13-1B goes into great detail on how to safety wire various nuts, bolts, screws, hose fittings, turnbuckles, and just about anything else you can imagine safety wiring. Never substitute a stop nut for a castle nut and cotter pin at joints where fully tightening the nut would stop the joint from rotating. For firewall-forward installations don’t forget to use AN363 all-metal stop nuts if you decide to go that way. Their vast experience with this arrangement makes it hard to argue against it, recommendations of AC43.13-1B notwithstanding. The concept of forcing rotation into the rod end rather than around the bolt underlies Van’s recommendation to use standard AN365 nylon insert stop nuts at most rotation joints such as aileron hinges and control push/pull tubes. Verify the correct size with your propeller manufacturer. 032-inch, but with practice a neat job is possible. This larger wire is harder to work with than. The recommended fix was to dab some epoxy or JB Weld on the cotter pin tail so it couldn’t be pulled loose. This RV-4 brake pedal is subject to a service bulletin because the cotter pin nearest the pedal face often got caught on the pilot’s shoe. A recent EAA Hints for Homebuilders video highlighted this method. An alternate method of protecting the tails of a cotter pin is to orient the pin sideways and turn the tails into slots adjacent to the one through which the pin lies. This issue came up with the rudder pedals for RV-4s and resulted in a service bulletin. JB Weld or a similar product will also work. If the tail of a cotter pin sticks out in such a way that it may snag on shoes or clothing, it may be necessary to put some epoxy over the tail of the pin to keep it in place. ![]() Sometimes changing a washer from thick to thin will help get proper alignment. This is generally allowed unless specifications say otherwise. The nut may need to be overtightened a bit to achieve the proper alignment. When using a castle nut, the slot of the nut needs to be lined up with the hole in the bolt. For convenience cotter pins are usually longer than needed and then cut off. This idea was suggested by an EAA member in a Hints for Homebuilders video.Ī properly installed cotter pin will be 1/64-inch smaller in diameter than the hole in the shank of the bolt and will be long enough so that when it is bent over, it will extend at least to the center of the bolt or clevis pin. This alternative method of securing a cotter pin works well when there is poor access to the top of the nut or where snagging of the cotter pin is a concern. ![]() Even though it is sometimes inconvenient to use cotter pins in these instances, it is critically important that these nuts and bolts do not come loose in flight. Engine mount bolts are also good candidates for castle nuts and cotter pins to secure them from the heavy vibrations they typically experience. However, depending on the way the connection is assembled, a stop nut may suffice. Control linkages and the attachment of control surfaces to wings commonly call for drilled bolts and castle nuts with cotter pins. They are especially needed when there is rotation at the bolt or heavy vibration. Cotter PinsĬotter pins are used in conjunction with drilled-shank bolts and castle nuts or with clevis pins. For these situations we need safety wire, a cotter pin, or rarely but occasionally, a chemical thread locker. In many cases a nylon insert or all-metal stop nut may well provide the necessary holding power and peace of mind. If they aren’t, something vital might come apart and cause a crash. In airplanes there are lots of parts that really, really need to be secure. They are also used to secure ceiling fans to prevent falling if the mounting nut loosens.Shown above is an assortment of cotter pins and an AN3 bolt with both the standard and thin (shear) castle nuts. These cotters have a short threaded section at the narrower end of the taper, which is used to hold the cotter in place with a washer and nut. The angle of the wedge determines the position of the parts being held therefore, on a bicycle, the pedal arms will only be at 180 degrees to each other if the angle of the cotter pin's wedge is the same on both pins.įormerly, it was common to mount bicycle cranks using a cotter, although now usually a more easily maintained arrangement is used such as a square tapered or splined interface. Typical applications are in fixing a crank to its crankshaft, as in a bicycle, and a piston rod to a crosshead, as in a steam engine. In British usage cotter pin has the same meaning, but in the U.S. Another view, with scale, of bicycle crank cotterĪ cotter is a pin or wedge passing through a hole to fix parts tightly together.
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