Team 842,The Forbes Arm, Mach-1
 

Here is an arm that Steve Forbes, a former NERD 1726 helped us to develop. He works for Intel now and is in town so help mentors here now.
http://www.youtube.com/watch?v=cYP4pshmW3k

Motors, and grabber coming soon!

Re: Team 842,The Forbes Arm, Mach-1
 

Its designs like this that make me see why some people were disappointed to see the 60" rule leave.

Beautiful!

Re: Team 842,The Forbes Arm, Mach-1
 

Elegant...

Re: Team 842,The Forbes Arm, Mach-1
 

woah...wasn't expecting that!! engineering and creative thinking at its finest!!

Re: Team 842,The Forbes Arm, Mach-1
 

To put it simply, Steve Forbes is a genius. Awesome arm this year.

Re: Team 842,The Forbes Arm, Mach-1
 

I'm really impressed with how simple and effective this design is. Great work you guys.

Re: Team 842,The Forbes Arm, Mach-1
 

I highly approve of this, I'm a fan of more linkage use past 4 bars, more fun to watch.

Re: Team 842,The Forbes Arm, Mach-1
 

The elegance is overwhelming

I can imagine how effortlessly this will go from the floor to the scoring pegs.

I am a fan

Re: Team 842,The Forbes Arm, Mach-1
 

Very sweet solution. Nice work.

Re: Team 842,The Forbes Arm, Mach-1
 

Very nice design. Can't wait to see that in action at a competition.

Re: Team 842,The Forbes Arm, Mach-1
 

Great to see it coming together guys! Hopefully we can get power to it (and a driving base underneath) this weekend and the coming week.

Another fun point to mention about this arm mechanism is that the gripper will fit in the starting dimensions, so no hinge mechanism or "unfolding" will be needed at the beginning of the match. I was pleasantly surprised to see it all work out that way. Certainly a fun concept! Though I think Falcon Arm might be a better name. :)

Re: Team 842,The Forbes Arm, Mach-1
 

He takes after his mom :p

Re: Team 842,The Forbes Arm, Mach-1
 

You are too modest! Your contribution has been invaluable, I wish you were here every day!

Hopefully the banebots come soon!

Re: Team 842,The Forbes Arm, Mach-1
 

Any chance we can get a picture or description for those of us stuck behind corporate firewalls?

Re: Team 842,The Forbes Arm, Mach-1
 

:D Great work guys hope to see you at the championship!
Jon

Re: Team 842,The Forbes Arm, Mach-1
 

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

Steve

Re: Team 842,The Forbes Arm, Mach-1
 

cropped screen shot from the video

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

Re: Team 842,The Forbes Arm, Mach-1
 

Reminds me of 1595 in 2007.

Re: Team 842,The Forbes Arm, Mach-1
 

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!

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

Very cool. Nice work 842.

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

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!

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

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".

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

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.

Re: Team 842,The Forbes Arm, Mach-1
 

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

Re: Team 842,The Forbes Arm, Mach-1
 

speaking of competition, where is everybody going?

Re: Team 842,The Forbes Arm, Mach-1
 

I was talking to all the other mentors about how this arm will be used all of next season by tons of teams. They didn't believe me there could be such an arm design. So I shown them the video.

"Yeah...prototype that arm for next season."

We'll make sure to always call it The Forbes Arm.

Re: Team 842,The Forbes Arm, Mach-1
 

First time in FIRST? Maybe...

However, no offense to Steve -- this is just an example of a grounded link, or as some people might call them a "virtual 4-bar" linkage. It is pretty darn cool, but this technology has been around for a long time.

One of my hobbies is researching cool mechanisms and linkages from history. Back in "the day" when computer control was non-existent, engineers designed machines which turn constant rotary motion (from a stem engine, or water wheel, or whatever) into all sorts of different motions -- including linear motion.

In fact, I know a company in NY involved in a design which utilized something similar to this for an oscillating shower-head on a paper machine.

Call it the Forbes arm if you want, but to me this is similar to the people who used to say Paul Copioli invented the 4-bar linkage...

Again -- no offense intended to Steve Forbes on a beautiful design.
I love it when someone takes a cool linkage or mechanism and uses it with great success on an FRC robot. Now if only I can find an excuse for a Geneva Mechanism (I keep trying to find one).

-John

Re: Team 842,The Forbes Arm, Mach-1
 

These are definitely cool mechanisms....

To echo John's comments, this mechanisms has been deployed before.

Team RUSH used the same system in 1997 for the very first inner tube game.

I can't find a picture right now. :( We call it a passive arm.

Re: Team 842,The Forbes Arm, Mach-1
 

I thought you still had to be within 60" at the start of the match?

Re: Team 842,The Forbes Arm, Mach-1
 

You have to be within your frame perimeter at the start of the match. You used to have to be within a 60 inch cylinder after the start of the match. That cylinder is now 84 inches.

Re: Team 842,The Forbes Arm, Mach-1
 

I was talking about the 60" cylinder rule, which has since been expanded to 84" Height limit is and always has been 60"

Re: Team 842,The Forbes Arm, Mach-1
 

John, no offense taken at all. I'm fully aware of the linkage concepts involved and know they're nothing new. When we had it modeled up in solidworks we were talking about how we had never seen an arm mechanism with this geometry used before on a FIRST bot... the name was jokingly suggested by another team member. Seeing that it was already implemented by 1595 in 07 shows that we're not actually the first to use it, which comes as no surprise.

I'm also fascinated with linkages and rotational/linear power conversion systems (Selectric typewriter, anyone?). This mechanism actually came from a somewhat structured problem solving approach. Sometime on Saturday (kickoff) night I sketched something like this on a piece of paper:

...with the thought that the ideal* arm would be a single DOF mechanism that followed that path. Floor to top peg, passing through initial starting position. After that it was easier to narrow the motion down to possible mechanisms. Form follows function! :)


Sounds like it was first implemented ages ago, I'd love to see a photo if you happen to find one!


*no such thing in this competition, but you know what I mean

Re: Team 842,The Forbes Arm, Mach-1
 

Here is a model of the arm that was done in GeoGebra (free program). You can change all of the lengths of the members and the gear ratio of the sprockets between the shoulder and elbow.
http://concordrobotics.com/arm/

Happy modeling.
Mark

Re: Team 842,The Forbes Arm, Mach-1
 

I found an interesting video this morning

http://www.youtube.com/watch?v=icp1w9PYQYk

Re: Team 842,The Forbes Arm, Mach-1
 

Our team saw this idea and was really enthused about it, I spent hours in inventor planning it out with all of the ratios. It is finally complete though it looks much different than this we reach the top pegs with ease. We will be posting videos and pics after ship along with our deadly deployment.

Re: Team 842,The Forbes Arm, Mach-1
 

Good Job.

Does the robot have to be under 60 inches this year?

Re: Team 842,The Forbes Arm, Mach-1
 

I guess it works, eh?

:p :D ;)

Re: Team 842,The Forbes Arm, Mach-1
 

Congratulations!!! I was following the Arizona Regional from afar via FRC Spyder. I had you tagged for score notifications. It was really nice to see you do so well and ultimately win the regional!

Again, CONGRATULATIONS!!!

Re: Team 842,The Forbes Arm, Mach-1
 

I guess your super fancy linkage arm beats out our claw on a stick, huh. :)

Re: Team 842,The Forbes Arm, Mach-1
 

Thanks for the gearbox, We went through 4 of them, We are switching to pneumatics. Its too high maintenance to keep using the gearbox. Thanks for helping us win!