HS Produkt VHS-2 Airsoft Replica Build [Part 3: Grip and Fire Controls]

Okay, so now we get to a real pain in the ass part of this build: the grip, trigger, and fire selector.

 

The grip and fire controls are comprised of the following parts:

• Grip (housing)
• Trigger
• Trigger PCB button
  
• Trigger switch mount
• Trigger spring
• Rotary potentiometer
• Rack
• Pinion x2

As you may have figured out from that list, the trigger just activates a PCB button. The real meat and potatoes of this fire control group is the fire selector. We're spinning a rotary potentiometer to select the firing mode, but this introduces challenges. 

Namely, I can't just hook up a potentiometer to the selector switches themselves. This would employ two potentiometers that are not synchronized (one for each half). There are rotary pots that allow a keyed shaft through the center, but this requires more machining than I'm capable of doing with my current setup. 

The solution, of course, is a rack-and-pinion:

Imagine another pinion sitting between the trigger and that pinion on the potentiometer. This translates the rotation from the fire selector downwind to the potentiometer, allowing an Arduino to pick up the position. Also imagine a PCB switch on that little shelf in front of the trigger - that translates trigger movement into a readable position as well. Clever, huh? Big shoutout to janssen86 on Thingiverse for the parametric helical rack and pinion model he made, though I did modify the hell out of it to fit in the grip and to not be helical. 

I printed the rack and pinion out of Dr.3D ABS-like resin, which I have been VERY impressed for at the price (it costs about as much as normal UV resin, but comes in 500g bottles instead of 1kg).

 

That's it for the grip and fire controls. Took far too much effort, too many re-prints of tiny resin parts. See you next time for the lower receiver. Worth noting, there will possibly be a significant amount of time before the lower receiver part is published - I have to do more test fitting prints, which means more hours into printing parts destined for the garbage can. I have queued posts to release once per week to prevent this from being too bad, but if you're keeping up with the project, just be aware.

-Craig, ETW