Team 971 proudly presents our 2023 robot, Doffle, which will be competing at the San Francisco and Monterey regionals in California.
Special thanks to everyone who made this robot possible!
Introducing Doffle (link to reveal video)
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why still go tank?
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They wanna keep the bot within a reasonable number of DOFs.
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They used up all the DOFs on the arm and intake, any more and it would just turn into Doffleception anytime they ran the bot I imagine
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Why such a big sprocket?
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So no turreted davinci surgery robot for the 2023 game 
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bravo! 971 singlehandedly keeps me inspired every year, this may be the coolest robot ive ever seen.
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The call of the Falcon is strong with this one.
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Reduction, or helps reduce impacts of slack in chain, lower forces, lots of reasons.
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The larger sprockets increase the rotational stiffness of the system (r^2 has a big impact), which is one of the driving factors of the system’s natural frequency.
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Am I going crazy, or is the shoulder free-rotating on a lazy susan inside of the (closer) elbow sprocket and driven by then farther back sprocket?
Also, what drove the decision to use steel cable to drive the elbow instead of using chain on another sprocket connected to the current elbow sprocket?
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Yes, the proximal rotates independently of the capstan for the distal link. That’s a fun stackup.
Cable has higher stiffness. We looked at using chain but that was too much of a compromise for the spec we were targeting.
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Nick, I am but a simple man, with a simple mind. What is the layman’s version of this statement?
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Fair enough - the proximal (near) joint that is coupled to the inner rotating assembly is independent of the capstan (cable pulley) for the distal (far) joint. They are independently driven by their own sprockets, despite being packaged rather tightly together which may give the appearance that they are the same/connected.
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Maybe some of the same reasons why they’ve never used their differential swerve:
Though maybe the door is now open given that it seems to be legal now to use PWM over MXP to control motors, unless I’m misreading the rules.
971 drops their robot and gets memed
#BagMotorGang going strong. Love it.
-Ronnie
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Here is, perhaps, an ugly Midwest version of this concept…kinda sorta. The dual #35 sprockets surrounding our shoulder joint arm member ride on hex bearings that permit the assembly to freely rotate dead axle on the steel hex shaft running through it. The coupled #35 and 25 sprocket assembly for driving our elbow is joined via versahub to the same steel shaft. This is driven only for the purpose of connecting a hollow bore encoder for seeding the absolute angle for motor PID control; otherwise, the elbow sprocket assembly could ride dead axle on the steel shaft as well. So 10 pounds of crap packed into a small space, and 2 separate link drivers being driven on the same axis.
PS - our arm design was inspired in large part by a certain 2018 robot, so…yeah.
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Judge, “Could you please explain your robot?”
971:
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