Double Reverse Four Bar


assuming everybody is an absolute rookie. so try not to be biased. what is easier to design? an elevator (2 stage) or a dr4b?


There are numerous COTS solutions for elevators, and rigging for a two stage isn’t difficult. For those reasons I’d lean towards and elevator if I didn’t have experience with either.


can you suggest any? links?






I only have experience with the VEXpro one, but the others look fine as well. My team made an elevator with the VEXpro system in the fall of 2017 as an R&D project. We used what we learned to design a more custom elevator for the 2018 game.


What’s everyone’s thoughts on DR4B vs. Single 4 bar with a pivoting wrist? Seems to me like a single 4 bar arm would likely be faster and lighter, though you don’t get a consistent “end effector to bumper” distance as it raises and lowers, whereas a DR4B would.


we considered this. our main issue is that it extends out of the frame perimeter and then goes back up. so some of height is essentially useless. (travels on an arc). dr4b let’s you keep it all in line


We were considering a four-bar lift for this year because it isn’t much harder to execute than a simple arm, but we’re starting to lean towards a DR4B for two reasons:

  1. A single arm would be quite close on the height restrictions and requirements, whereas a DR4B can gain a much higher height while keeping the drive arm’s pivot point lower.

  2. Our original four-bar linkage design, when elevated to 90º, would make our robot (from the front of the arm to the back of the chassis) nearly 6’ long. That’s a bit hard to fit and maneuver with on the field, especially when considering that the distance between the cargo ship and each rocket is only 9’. A DR4B, on the other hand, lifts nearly vertically and should be much easier to fit.