Valve Index Trigger Reinforcements

The Valve Index “Knuckles” controllers have triggers that are prone to breaking along the internal hinge axle due to very thin plastic used in the hinge design. This is an insert you can add to the trigger that will add about 60% more plastic (0.6mm x2) to the main weak areas, plus spread out the upward hinge forces across more area using two tabs. This will theoretically increase your trigger's durability, but I have no way to actually test how much of a difference this makes in practice. 

Taking the controller apart to access the trigger is a huge pain, so I recommend only doing this if your trigger already broke and you have to take it apart anyway to repair or replace it. The following resources will help walk you through the disassembly process:

• Teardown guide images for trigger replacement
  • I didn't have to remove the screws near the charging port, mine flexed enough without doing that. 
• How to  remove the top components (first 9 minutes)
• How to take apart the side components (first 4 minutes)

Please note that I can't provide any help taking your controller apart, it's a complicated process and you do it at your own risk. It will probably void your warranty if you still have one. 

Printing

I printed these in PETG because I figured the extra flexibility compared to PLA would be more durable. 

Inspect the pieces after printing and clean up any blobs or stray filament. Ensure that the hinge bar can easily slide through the holes in both pieces. 

I made two different versions. The first one has an extra retaining block that helps hold the spring in place when re-assembling the trigger (which is a really difficult process). I recommend that one, but if you run into issues with it you can try the version without that. 

Assembly

Follow the guides linked above to get your trigger removed from your controller. 

If your trigger assembly is broken you'll need to fix it first. Some people say you can superglue broken pieces back together, but I recommend contact cement as a more durable solution. 

The pieces are designed to slide into place as shown in this picture. It may require a little bit of gentle force to get them to pop in. Be careful not to break (or re-break) the existing hinges when doing this. 

For best results glue them in place, but be VERY CAREFUL not to get any glue in the circular holes. 

You'll have to slightly squeeze the spring together to get it to fit in the middle now. Ensure the spring holes line up with the plastic holes. 

Now pray to your favorite deity and try to get that thing back onto the main controller housing. I had the best results by carefully wedging the square end of the spring into the metal cutout marked in red below (sort of locking it in place), getting the rod through the first plastic hinge (where it gets stuck on the spring coil), then using a small flathead screwdriver to release the spring from that slot that it was wedged in. Then I could wiggle things around until the bar make it through the other plastic hinge and could be screwed back in place.