Extending a 4 Bar? Design/Resource Help

[Saketh123]

Hi Everyone, I am a little stuck on a design my team has been wanting to prototype. We have been thinking of the advantages of a 4 bar and lifting parallel to the ground, but we cant figures out how to make it extend. Some ideas were folding it up like the robowranglers in this video or something similar Robowranglers 2011: Raptor - YouTube . Or using a screw drive in the center, maybe a telescoping system. Has this been done in the past? Does anyone have any ways that are fast and not too complicated? Thanks for the help

[Skyehawk]

All you have listed could work, another option is to have an arm fold on itself. i.e.

Just to add to the options:

1. robonauts 2011 (but this was on an elevator)

2. Instead of independent actuators you are looking for maybe 2 degrees of freedom. Movement at the “shoulder” (attached to base of elevator) and moment to extend (actuator and rigging over “elbow” and “wrist” to pull those out from a coiled up state to a more linear one.

You are looking to do the opposite of what Myth busters did with the arrow catching hand this would need to be sprung back with springs… which is another thing entirely.

[Jen_Lawrie]

My team used a lead screw in 2015 to extend a 4-bar. There are some photos here on TBA. I would not recommend it for this game, however. While it was stable, simple, and reliable, it was also pretty slow. You can adjust the starts and motor speed to get it moving faster, there are some big tradeoffs that will keep if from getting all that fast.