View Full Version : Team 842,The Forbes Arm, Mach-1
falconmaster
27-01-2011, 19:43
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!
Its designs like this that make me see why some people were disappointed to see the 60" rule leave.
Beautiful!
Mike Betts
27-01-2011, 19:57
Elegant...
woah...wasn't expecting that!! engineering and creative thinking at its finest!!
Chris is me
27-01-2011, 21:15
To put it simply, Steve Forbes is a genius. Awesome arm this year.
I'm really impressed with how simple and effective this design is. Great work you guys.
Aren_Hill
27-01-2011, 22:10
I highly approve of this, I'm a fan of more linkage use past 4 bars, more fun to watch.
liam.larkin
27-01-2011, 22:14
The elegance is overwhelming
I can imagine how effortlessly this will go from the floor to the scoring pegs.
I am a fan
Very sweet solution. Nice work.
Very nice design. Can't wait to see that in action at a competition.
s_forbes
27-01-2011, 22:37
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 (http://www.youtube.com/watch?v=EqK_XTSoc1w) 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. :)
MrForbes
27-01-2011, 23:09
He takes after his mom :p
falconmaster
28-01-2011, 11:14
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 (http://www.youtube.com/watch?v=EqK_XTSoc1w) 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. :)
You are too modest! Your contribution has been invaluable, I wish you were here every day!
Hopefully the banebots come soon!
JamesBrown
28-01-2011, 11:16
Any chance we can get a picture or description for those of us stuck behind corporate firewalls?
bladetech932
28-01-2011, 11:17
:D Great work guys hope to see you at the championship!
Jon
Steve_Alaniz
28-01-2011, 11:28
Oh wow! Original and a thing of beauty! Very cool!
Steve
MrForbes
28-01-2011, 11:38
cropped screen shot from the video
Tom Line
28-01-2011, 11:42
cropped screen shot from the video
The picture doesn't do the elegance of that design justice.
falconmaster
28-01-2011, 12:18
http://lh3.ggpht.com/_lPKnNMUfSS8/TUIQlvLmTdI/AAAAAAAA2A4/uG9WacVOGXU/s720/IMG_5846.JPG
http://lh5.ggpht.com/_lPKnNMUfSS8/TUIQlxCjjLI/AAAAAAAA2BA/iJdcX156ikg/s720/IMG_5847.JPG
http://lh4.ggpht.com/_lPKnNMUfSS8/TUIQmRU8r4I/AAAAAAAA2Cs/1x7MOSN6Irc/s512/IMG_5848.JPG
Lil' Lavery
28-01-2011, 13:43
Reminds me of 1595 in 2007 (http://www.thebluealliance.net/tbatv/match/2007or_qm41).
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!
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 :cool:
Very cool. Nice work 842.
sanddrag
28-01-2011, 14:50
Very nice and simple. Good geometry. Almost makes me wish we weren't doing our arm the way we are.
Tetraman
28-01-2011, 14:51
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
28-01-2011, 15:08
Reminds me of 1595 in 2007 (http://www.thebluealliance.net/tbatv/match/2007or_qm41).
Aha! I knew this concept must have already been used before... it's not very complex. Thanks for the link!
AdamHeard
28-01-2011, 15:29
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
28-01-2011, 15:57
Ok so then its the second time this arm design is used....
AdamHeard
28-01-2011, 16:27
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
28-01-2011, 19:06
The non 1:1 ratio is where the mechanism gets its "magic", really. Still seems like the first of its kind.
chris janney
31-01-2011, 18:25
speaking of competition, where is everybody going?
Tetraman
31-01-2011, 18:53
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.
The non 1:1 ratio is where the mechanism gets its "magic", really. Still seems like the first of its kind.
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
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.
Brandon_L
31-01-2011, 19:47
Its designs like this that make me see why some people were disappointed to see the 60" rule leave.
Beautiful!
I thought you still had to be within 60" at the start of the match?
Rangel(kf7fdb)
31-01-2011, 20:09
I thought you still had to be within 60" at the start of the match?
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.
I thought you still had to be within 60" at the start of the match?
I was talking about the 60" cylinder rule, which has since been expanded to 84" Height limit is and always has been 60"
s_forbes
31-01-2011, 22:35
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
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:
http://img534.imageshack.us/img534/7317/robot1.png
...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! :)
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.
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
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
MrForbes
16-02-2011, 11:00
I found an interesting video this morning
http://www.youtube.com/watch?v=icp1w9PYQYk
Timz3082
20-02-2011, 11:10
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.
jakegorov
20-02-2011, 17:36
Good Job.
Does the robot have to be under 60 inches this year?
MrForbes
20-03-2011, 02:09
I guess it works, eh?
:p :D ;)
billbo911
20-03-2011, 02:32
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!!!
Chris is me
20-03-2011, 08:03
I guess your super fancy linkage arm beats out our claw on a stick, huh. :)
falconmaster
20-03-2011, 14:54
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!!!
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!
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