What Type of Thread Lock to use on a Trex 450 Heli

One of the most important tasks in building a RC helicopter is applying thread lock to all metal to metal screws. These machines, with their many moving parts, create ultra sonic vibrations that do their best to loosen screws which will quickly lead to a crash of your new bird.

For this reason, it critical that you inspect each and every screw that has come installed in your kit. Don't rely on the factory installer. Every builder that has put together an Align helicopter kit will tell you that they have found screws that did not have thread lock applied.

I use the Locktite brand of thread locker which comes in several different types. Each has it's own characteristics as far as color, holding strength and applications. The primary types of Loctite are as below:

Locktite Purple #222: This is a low strength thread locker that is used on screws that require easy disassembly.
(See Technical Data Sheet)

Locktite Green #648: Is a wicking type designed for bonding cylindrical fitting parts like bearings and motor shafts.
(See Technical Data Sheet)

Locktite Blue #242: Designed for medium strength thread locking where disassemble might be required.
(See Technical Data Sheet)

Locktite Red #271: Designed for high strength permanent locking of threads.
(See Technical Data Sheet)

From my experience, you'll want to use Blue Locktite#242 for all metal to metal screws on your Trex 450. Watch Finless Bob's thread lock 101 video and see how he applies a small amount to the end of the screw then wipes the excess off with his finger. A little goes a long way. Apply it in this manner and you will have no problems getting a screw out for maintenance. If you do find a stubborn screw, don't try to force it out, you will scrip the head. Instead, take your soldering iron and put heat to the head for about a minute and it will break the locktite down so that the screw will come loose.

A word of caution, there is no need to use red locktite anywhere on a Trex 450. The red creates a permament bond that will create havoc as you need to remove parts during future repairs. Bob mentions that you might want to use purple thread lock in high service areas as it is easier to remove, but I've never had any problems getting blue lockite to release after a little heat.

The green can be used to secure bearings so that the outer race doesn't spin in it's housing. Be careful as you don't want thread lock inside the bearing. Green can also be used to help lock the pinion gear to the motor shaft. I grind a flat spot on the motor shaft where the pinion's grub screw lands which seems to eliminate the need for thread lock on the shaft.

One last note, you need to clean all screws before you apply thread lock. During the manufacturing process oil is applied to the screw threads as they are being cut. This oil can retard the thread locks holding ability. I use denatured alcohol for this process. Acetone will work also. I soak the screw in a small glass bowl of alcohol and then take the screw, put it on the end of my hex driver and turn the threads into a paper towel removing any oil residue. Once all the oil has been removed, I make sure the alcohol has dried before applying thread lock.

Working on RC helis is a craft that comes with experience. Leaning just how much and how to apply thread lock is part of this craft. I hope this post help you on your way to becoming an expert RC helicopter mechanic.