Prototype of Mechanism

For our first prototype, we modeled a single piston in our grid to focus on how each one would handle the motion and various forces individually. To create the transition from input rotational motion to output vertical motion, we used a gear train that was attached to a threaded rod. On this threaded rod was a large nut and cover which was locked from rotating about its vertical axis, limiting its movement to purely vertical motion. Next we implemented a Grashof crank rocker in the input of the system so the input rotation could have a singular direction while the output would oscillate up and down. This prototype was not as smooth as we would have liked because of the lack of precision in our laser-cut gears as well as the loose manner in which they were mounted, causing wobbling that did not allow the gears to mesh completely. It did create the desired motion, however, so we moved on to our final prototype that would incorporate a series of these piston mechanisms.

First Prototype (Single Piston)

Our final prototype was improved from our original by the use of additional worm gears to garner vertical motion in multiple locations. For this rendition, we opted to square off the shoulders of the threaded steel rods in order to promote a better torque transfer from the surrounding gears. We also used bolts as our pin joints, which we felt would increase the stability over our first prototype, and lowered the gears to make them mesh a little better. Unfortunately, stability was still a serious issue, as the bolts acted as cantilever beams and deformed under the load.

Our final prototype features a set of three worm gears that drive platforms vertically. These are connected via multiple gear trains and a set of three grashof crank rockers to the single rotary input. In our first (failed) version of our final prototype, the outer rockers were built to rotate approximately 45 degrees, and the inner one 90 degrees. We believe this design failed because the acrylic could not withstand the forces needed to gear up for the final ratio of approximately 8. We rebuilt this using wooden linkage arms, and modified the gear trains to produce a ratio of roughly 2.5. This, however, resulted in a final vertical motion of roughly 2-3mm, much less than our desired output of 10-15mm. While multiple separate sections of the mechanism operated correctly (gear trains and crank rockers not yet attached to the entire system), when finally put into position these sections could not handle the forces of all the counter-torques and friction being applied at once, resulting in a lack of movement.

Original (Failed) Design

Failure of rods due to large reaction forces

Final Design 

Ultimately, we were limited by our choice of using acrylic as our main material for the gears and linkage arms and by our decision to use human input instead of a motorized input. Looking forward, a future redesign would be to use metal for all of the components and incorporate a motor into the system (thereby necessitating gearing down instead of gearing up). We would also design and implement some sort of plate that could hold all of the currently cantilevered pin joints, which would increase the stability significantly.