What's the coolest (or most complicated) linkage ever used in FRC?

[RogerR]

Originally Posted by s_forbes

I recall team 67's 2008 robot as having one of my favorite linkage mechanisms (at least conceptually... implementation looked painful ). Spring loaded extending member in a single DOF mechanism to achieve a very unique path and stay within size constraints, very cool!

Also a big fan of 1625's over-center launching mechansim, though I've yet to use it on a robot. I'm sure a time will come.

The Thunderchickens arm from 2007 is very unique, and another favorite of mine. I used it as one of my "pick any mechanism and do a report on it" style of exams for free-body analysis in college. I wish I remember more details of my analysis, but I wasn't very good at documenting things back then.

67: http://www.chiefdelphi.com/media/photos/30680
1625: http://www.chiefdelphi.com/media/photos/31538
Short analysis on 217's arm attached as well.

Looks like you went through and picked all my favorites.

I'd add 148's 2011 four-bar, because of the clever use of the cylinder as part of the upper link.

I guess I could mention that lame 842 arm from 2011 (and its predecessors mentioned in the below thread): http://www.chiefdelphi.com/forums/sh...ad.php?t=90284

[s_forbes]

Originally Posted by RogerR

I guess I could mention that lame 842 arm from 2011 (and its predecessors mentioned in the below thread): http://www.chiefdelphi.com/forums/sh...ad.php?t=90284

That was one of my favorite mechanisms for a week or two, right up until we tried to build the darn thing.

Another cool linkage system that I've only ever seen used once: 1565's linkage drivetrain from 2008: http://www.youtube.com/watch?v=RvN4K2ieR5g

[dodar]

Originally Posted by s_forbes

That was one of my favorite mechanisms for a week or two, right up until we tried to build the darn thing.

Another cool linkage system that I've only ever seen used once: 1565's linkage drivetrain from 2008: http://www.youtube.com/watch?v=RvN4K2ieR5g

DING DING DING, I think we have a winner. I have never seen that video before or any video of 1565's 2008 robot and I say that takes the prize. That is actually very innovative. Not to sound demeaning to the team, as I am giving them tons of praise, this seems like a poor-man's swerve; all be it it is only bi-directional, it still works on the same concept. I wonder if you could use mechanum wheels in the same setup.

[Foster]

Originally Posted by s_forbes

Another cool linkage system that I've only ever seen used once: 1565's linkage drivetrain from 2008: http://www.youtube.com/watch?v=RvN4K2ieR5g

We built this during one of our Summers of Robot Fun for Drive trains we built a "twitch drive", like 1565's linkage. (See the Power Point on the page) One of our VEX teams then built one a year later for competition It had all the features of wide and short bases, and worked well for them. With the grippy wheels it was a winner in any pushing contest. Downside was the huge force on the upper part of the pivot and the shaft. The force applied by the wheels on the standard VEX shaft was the weak point. If I had to do it today, (and I might since this has triggered the thought) I'd use the VEX small turntable as the pivot point.

More on topic for the linkage was a team at "Overdrive" that could pick the ball up off the floor and swivel it up and over the bridge, either placing it or tossing it over. I want to say it was Rolling Thunder 1511, or Moe 365 since they are awash in engineering coolness, but I'm not 100% sure.

[Peyton Yeung]

190 in 2008 had a crane like appendage. If i can find a picture i'll post it later.

[Nuttyman54]

Originally Posted by Tubatroopa

190 in 2008 had a crane like appendage. If i can find a picture i'll post it later.

While this was a very unique system, the crane was essentially a very long version of 233's famous arm, mounted vertically. It wasn't a linkage by any sense of the word, so I don't think it qualifies for this discussion.

190's 2007 championship winning robot did have a 7-bar linkage on it, in the gripper:

Open position, closed position

It was operated by a single piston which when extended would first actuate the "finger" linkage, gripping a tube and pulling it back into the claw. Once 13 lbs of grip force is achieved, the continued extension of the piston would lift the entire arm up to a 45 degree angle (all while maintaining a constant grip force on the tube).

Video here, best shots are from 0:30 to 1:00

[Chris is me]

Might be a bit of a minority opinion here, but I actually think the replacement for 67-2008's adjustable link made for a really cool linkage. The required placement for the link was in the middle of where the arm had to go through, so HOT used a unique combination of shapes and materials to make a "hollow" pivot point that was really cool. http://frcteam67.dyndns.org/HOTPhoto...s/P1010001.JPG

I've always been envious of some designers' abilities to seemingly pull cool, complex linkages out of their heads and onto a robot. Does anybody have neat resources to learn more about synthesizing and designing linkages for various tasks? I'd love to learn more as that's essentially the most fascinating part of mechanical design for me right now.

[Adam Freeman]

Originally Posted by Chris is me

Does anybody have neat resources to learn more about synthesizing and designing linkages for various tasks? I'd love to learn more as that's essentially the most fascinating part of mechanical design for me right now.

Chris...thanks for linking to the picture of our re-designed linkage. I didn't get a chance to really look for a good picture of it.

As far as linkage design....it's all 2D AutoCAD and circles for me. Basically, just have to pick a starting pivot point and sketch away. For 2008 it was a three position design. So it was basically iteration (trial and error) to find pivot points and link lengths that fit the three positions we were trying to achieve.

I am sure there are more ingenious ways of figuring it out, but that's how I do it.

[AdamHeard]

Originally Posted by Adam Freeman

Chris...thanks for linking to the picture of our re-designed linkage. I didn't get a chance to really look for a good picture of it.

As far as linkage design....it's all 2D AutoCAD and circles for me. Basically, just have to pick a starting pivot point and sketch away. For 2008 it was a three position design. So it was basically iteration (trial and error) to find pivot points and link lengths that fit the three positions we were trying to achieve.

I am sure there are more ingenious ways of figuring it out, but that's how I do it.

I like to do the reverse process in SW. Draw the same linkage 3-4 times (depending on number of desired positions) without dimensioning any lengths, just dimension where we want to end up and what angle we want there. This then "solves" for the correct link lengths. It's also nice to leave it partially constrained and move it by hand around so you can see the tradeoffs of various mounting points.