Metal Hobi MH-245 kit as Hitachi ZX245 excavator

[Blender]

Thanks Egronvold.

Time to step away from the ZX and tackle the barrier lift mechanism. The full scale looks to operate with a bi-stable latch which allows the jaws to engage every second plunge. Well suited to RC play with no electronics needed. Completed the CAD work to carve a path inside the housing. A 1mm spring pin is what follows the groove and keeps the plunger from falling out.

Parts look great and assembled well, but the latch only advances to the next position on rare occasions. Everything is internal, so there is no real troubleshooting i can do. Full redesign is in order

[frizzen]

I'm not 100% sure on your design of that last piece, but think i've got a basic enough idea.

Instead of doing a full redesign for the bi-stable latch I might try to file some directional ramps on the lower side of the plungers 'paddle looking section' to help them ease into next position. Then cross-drill the plunger shaft for a pin near the coupling sleeve maybe like 45 degrees out of phase with the paddle, so that at weight-released full-down it can act against a couple bumps on the collar to start rotation to advance next position?

If it still doesn't want to advance, you might be able to mill a zigzag path in plunger shaft, then a pin in the collar rides in zigzag to keep it moving.

I dunno, worst case you could take apart some 'pop-up bathtub drains' for some other design ideas.