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

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.

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

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

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

Unfortunately, that linkage never made it past the build season. We had some major controls issues dealing with the transition between when the link was compressed and when it started to expand. We ended up removing the adjustable link and creating a new lower link with a different pivot point that provided the same motion, at our first event of the season. I think it ended up being a lot more robust too. I am not sure the adjustable link would have held up to the abuse.

It was a decent idea, but the execution was lacking a little bit.

148's 2011 adjustable 4-bar linkage had much better execution.

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

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

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

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.

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

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.

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

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.