Optimizing the Trigger Piston Design

 

Optimizing the design.... or more appropriately, optimizing the manufacturing process in design.

In the picture, the above is a one-piece clone "piston" of the 2 stage trigger of an F-16. It's lathed on a mini-lathe, out of an OD=8mm brass.

First, it has to be turned down to OD=7.5mm, then, the middle section has to be turned down to 4.5mm, then one end has to be drilled with an D=1/8" hole. This whole thing has approximately the same dimensions as the real one. The blunt nose section's precise shape is not important. The original is a circular dome (plastic injection molded part). But, mine is... well, filed on a lathe. The curve? I have no idea... well, about there.

But... if you ain't got a lathe.... that is going to be very difficult to make. Just drilling a D=1/8" on an D=4mm hole is going to make you sweat. Any deviation on the center finding (or even wandering of the drill bit) will make it very obvious on these small diameter, thin walled part. Well, luckily we don't use this part for the looks, Ain't Moen.

So, when the prototyping with the one-piece proves that it works. Optimization by design comes in.

First of all... 7.5mm rods are f'ing difficult to find. Finding the right OD, ID together is even more difficult. OD=7.5 and ID=1/8" (or 3.5mm, or I will even accept 4mm) brass rod is difficult to find. Even OD=8mm and ID=4mm is difficult. So, how about increase the OD to 8mm? Then we chop it down into 3 pieces. Now I just need an OD=8mm brass rod, and an ID=5mm rod..... well... tube would be even better.

So, now, all I need to make it is to drill a 5mm hole in the 8mm rod, chamfer one end. Then, cut two piece off, one 3mm long, the other 22mm long. Take the long piece and chuck it into a lathe or even a cordless drill, and round that nose. Now, cut off a 19mm long piece off the OD=5mm tube... All I need now is to braze all three piece together, and done!

Sure the center hole is a bit bigger than I need, but this cavity is for the spring. As long as it's not way too big... an oversized hole is welcome, even required. Moreover, since I make my own spring, I can make a larger spring to fit the hole! Or you can pay an arm and a leg to Lee Spring for small quantity.