I was pretty impressed by the actual walking “Thing” from the Netflix Wednesday! program. The behind the hand view is amazing.
Watching it, and more specifically the finger movements, showed how little I know about complex bar linkages. Yeah, I can toss together a 4 bar linkage for lifting with the best of them, built a few working scissors, but more complex linkages are hard.
Most of the linkages in VIQ / VRC are pretty simple. I did more when pneumatics didn’t exist to change rotary motion into linear to open/close claws, shift PTO, etc. This year’s Rapid Relay to arm/fire a catapult is a good example of rotary to linear motion.
This site has links to built models which is easy to then conceptualize how to build some common linkages. (scroll about 2/3 the way down).
This encyclopedia of linkages has 1700 YouTube animations to go along with it. It’s the best so far, it’s just mesmerizing. I recommend starting here.
Can you recommend other sites or books that cover the design of linkages that you have used? You can also drop in the most complex linkage you’ve built in the chat.
Linkages are very fun to get into! The concept of an over-center linkage is, in my opinion, one of the most fundamental things to learn about linkages. It’s very versatile and the concept can apply to all sorts of things, especially climbing claws or anything else that clamps onto stuff, or deploys and needs to stay deployed. If you have a pair of locking pliers, those are a great example.
Optimizing leverage and making a linkage strongest where you need it to be is a pretty great skill to have, and can make you a very valuable mechanical team member.
Anyways, here’s the claw I made last year for over-under. I compete in VexU, so these parts are made from CNC aluminum plates, 3D prints, and cast urethane rubber, but these concepts still apply to vex parts.
Notice how when claw is closed, the over-center is straight and the claw’s lever is perpendicular to the over-center linkage. This means that the only way to open the claw once it’s closed is by pulling the over-center back away from the plate (or breaking things I guess). The fact that the lever is perpendicular simply gives it the maximum possible amount of leverage. It’s not a very complex or impressive linkage system, but the simplest solution is often the best.
I sometimes feel sad when people go LLM will be the future. I love what mechanical things can do (linkages is just one small part of mechanical engineering) and feel like it’s a cop-out to go “So add microprocessor here, add a H-Bridge, attach a motor and we are done”). I don’t see LLM being able to design some of these complex, yet simpler solutions to mechanical designs.
There is a Lego series on Power driven books that I page through at least once a season to refresh ideas.
Robotics is exciting to me, since that is the bridge between mechanical and human worlds. Do we teach robots to climb stairs or rip out the stairs so robots can get to us?
