A liquid or semi-liquid compound that is applied to the threads of a screw or bolt to help prevent the screw from loosening. Commonly referred to by the trademark name "Loctite", threadlocker comes in different strengths for different applications, typically identified by their colour:
- Purple : Low strength retainer useful for screws which are frequently undone;
- Blue : Medium strength retainer, useful for most helicopter purposes;
- Red : Strong retainer. Used for screws that should never be removed.
- Green or Black: 'Studlock' or 'bearing retainer', used to hold bearing in their sockets.
Threadlock should be applied sparingly to the end threads of a screw, so that the threads hold the fluid by capillary action. Too much will just create a mess, and when used in close proximity to bearing (for example, on the feathering shaft) risks contaminating the bearings. It is not necessary to use threadlock when using nyloc nuts.
Bearing retainer should be applied sparingly (for example, using a toothpick) to the outside race of the bearing before it is pushed into place. Carefully wipe away any excess after installation. Red threadlock is probably a sufficient substitute on smaller electric helicopters.
Threadlock and studlock should only be used on metal-to-metal fastenings, as it can degrade plastics. If extra security is needed on plastics use cyano.
Threadlock (and especially studlock) can make it very hard to remove the screw or bearing when it becomes necessary. Usually it can be broken down by heating; holding a soldering iron against the item for a few minutes usually allows it to come out easily. Large items with no plastic can be put in the oven for half an hour!
- Always go over the head and make sure everything is threadlocked on RTF and ARF helicopters. Bolts can come loose very fast in a model due to the vibrations of everything, so check them often and threadlock everything that makes metal to metal connections.
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