Team 842,The Forbes Arm, Mach-1

[Steve_Alaniz]

Oh wow! Original and a thing of beauty! Very cool!

Steve

[MrForbes]

cropped screen shot from the video

[Tom Line]

Originally Posted by squirrel

cropped screen shot from the video

The picture doesn't do the elegance of that design justice.

[falconmaster]

[Lil' Lavery]

Reminds me of 1595 in 2007.

[JesseK]

The beauty in this design is the coaxial sprockets on the joint at the very top. The one that hooks to the wrist can be hooked to a non-backdrive motor on the very bottom of the robot -- keep ing c.g. low while also adding another degree of control/extension. The beauty in that is that the drivers shouldn't have any extra buttons to control it since the wrist movement is limited enough that software can pre-determine its positions.

I tried to get our team to prototype something like this (not a criss-crossing one) this Fall, yet was overriden by a mentor who borrowed a compound lift from 116 that we used as a teaching tool instead....

Best of luck in 2011 842!

[TEE]

Originally Posted by JesseK

The beauty in this design is the coaxial sprockets on the joint at the very top. The one that hooks to the wrist can be hooked to a non-backdrive motor on the very bottom of the robot -- keep ing c.g. low while also adding another degree of control/extension. The beauty in that is that the drivers shouldn't have any extra buttons to control it since the wrist movement is limited enough that software can pre-determine its positions.

Best of luck in 2011 842!

The beauty in this design is that the wrist/elbow doesn't need to be powered

[Racer26]

Very cool. Nice work 842.

[sanddrag]

Very nice and simple. Good geometry. Almost makes me wish we weren't doing our arm the way we are.

[Tetraman]

Pending success on the arm, which I expect there to be much, I figure this to be the new arm design many teams will utilize for years to come.

Great work!

[s_forbes]

Originally Posted by Lil' Lavery

Reminds me of 1595 in 2007.

Aha! I knew this concept must have already been used before... it's not very complex. Thanks for the link!

[AdamHeard]

It's a cool mechanism, but I'd like to give credit to team 60 for doing it all the way back in 2000, and carrying it on for years and years.

Granted, 842 did a different take on it by fixing the "wrist" sprocket and do a non 1:1 ratio. A clever way to use the same mechanism to get two rotations from one motor.

We've used it a few times in the past (with a 1:1 ratio) and always called it a "virtual 4-bar", I suppose this would be a "virtual uneven 4-bar".

[falconmaster]

Ok so then its the second time this arm design is used....

[AdamHeard]

Originally Posted by falconmaster

Ok so then its the second time this arm design is used....

It's the first time I've seen it nondriven and a non 1:1 ratio, but it has been easily used on 30+ robots. It's been used nondriven with 1:1 ratio and driven with 1:1 ratio most commonly.

Not criticizing at all, it's a cool twist on the mechanism to simplify the control a great deal. We're doing the same chain method but doing 1:1 and driving both, and I'm starting to regret that choice after seeing what this gives you.

[Chris is me]

The non 1:1 ratio is where the mechanism gets its "magic", really. Still seems like the first of its kind.