Introduction: K'nex Piston Version 2
Welcome to my instructable on how to build a k'nex piston! This is my second version, also check out my original K'nex Piston.
This is a video of the K'nex piston version 2 operating.
This k'nex piston converts rotational motion to linear motion. (or vice versa). This piston has a smaller range of movement than the previous version, it is able to retract/extend 51mm (about 2 inches). The original version is able to retract/extend 65mm (about 2.5 inches).
It has always been a challenge to create linear movement with k'nex. But no longer! I have designed a rack gear (something which k'nex should have made a long time ago in my opinion) built completely out of k'nex. A rack gear is a rod with teeth on it which allows a round gear to push the rod back and forth.
This video demonstrates how a rack gear works:
Step 1: The Parts List
These are the parts you will need to build the piston:
109 - blue spacers (many can be substituted for grey spacers)
9 - black clips.
3 - blue clips.
6 - brown clips.
21 - grey clips.
8 - orange connectors.
40 - blue 3D connectors.
2 - white connectors.
6 - yellow connectors.
2 - green connectors.
8 - red connectors.
2 - blue gears.
5 - grey grip gears. ( finally found a use for those things :P )
2 - yellow gears.
2 - red gears.
20 - green rods.
13 - white rods.
39 - blue rods.
6 - yellow rods.
1 - red rod.
3 - grey rods.
Step 2: Starting the Frame
This is the back of the frame which you will start building off of.
Step 3: The Rack Gear(s) Parts
These are the parts you will use to assemble the the rack gear in the next step.
Build though pictures 4 - 9 twice. you will need two of these parts.
Step 4: Rack Gear(s) Assembly
Assemble and mount the rack gear as shown.
Note: There is a small issue with the yellow rods disconnecting from the red connectors in the rack gear assembly. my solution to this was to rap a rubber band around them to hold it together.
Step 5: Upper and Lower Pinion Gears
This version of the piston uses 2 pinion gears to drive the rack gear. This helps keep the rack gear in place and increases power output.
Please read picture notes.
Step 6: Gearing
In order to power both pinion gears from a single input, I built a gear train connecting them. The challenge of this though is that both pinion gears had to spin in opposite directions. building a 3 gear train would have made them spin in the same direction. To make things even more challenging, both pinion gears had to spin at the same speed, which required a symmetrical gear design. So I had to design a symmetrical 4 gear train to solve this problem.
- Connect 6 blue rods to the blue and red connectors.
- Add the 2 red gears to the blue rods on the red connectors.
Step 7: Gear Supports
These gear supports hold the gear axles in the proper position to keep the teeth of the gears interlocked.
Step 8: Final Assembly
Just add the spacers and the final structural panel.
Congratulations on completing the K'nex Piston V2!
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