pic: Team 148 - 2011 - Raptor

[Adam Freeman]

Originally Posted by Chris is me

I've never learned much about arms and I don't understand the advantage or disadvantage of either system, other than CG placement.

When we did it in 2007, it was specifically for CG purposes. I did not want to mount a gearbox near the top of the arm. I also did not want to run chain from the gear box to a sprocket at the top of the arm.

There is also a design elegance to doing something different than running chain.

I can tell you there are advantages and disadvantages to it. CG is probably the biggest advantage...other than 4 bar linkages are always cooler. In my mind the biggest disadvantage is the amount of packaging room required to allow the push link and connecting link to swing in the bottom of the robot.

In 2008 we wanted to use a double 4 bar, but could not get it to package... so we mounted a sprocket to the arm and ran a long strand of chain.

[MrForbes]

Originally Posted by AdamHeard

I would imagine their goal is to keep making cool, great performing stuff, while never having to do repair or maintenance.

If they don't have to repair or maintain the robot, they can spend their time and talent improving it. I like that idea.

[JaneYoung]

Originally Posted by squirrel

If they don't have to repair or maintain the robot, they can spend their time and talent improving it. I like that idea.

While true, when at the actual competitions, 148 can be found spending their time helping other teams. That's another way of spending their time and talent, improving.

It's going to be fun seeing the looks on a lot of rookies' faces when they see Raptor and 148 in action for the very first time.They'll wonder just what this FRC thing is all about and they'll want to learn more.

Jane

[JVN]

Originally Posted by JesseK

Those of us who never saw 67's linkage are left to ponder the way the 148 linkage works. Is it like the locomotive linkages on old-school trains?

I just put up a blog post highlighting how the linkage works:
http://blog.iamjvn.com/2011/02/insid...hip-joint.html

-John

[Akash Rastogi]

Originally Posted by JVN

I just put up a blog post highlighting how the linkage works:
http://blog.iamjvn.com/2011/02/insid...hip-joint.html

-John

Very cool. Thanks for explaining.

What's driving the hip joint on your robot?

[Brandon Holley]

Originally Posted by JVN

I just put up a blog post highlighting how the linkage works:
http://blog.iamjvn.com/2011/02/insid...hip-joint.html

-John

If you can't appreciate cool mechanisms like this, you probably can't appreciate anything!!

I especially like the use of sheet metal for everything, including the stacked plates to create the gear teeth on the smaller arm driven by the gearbox.

Thanks for sharing JVN.

-Brando

[JVN]

Originally Posted by Akash Rastogi

Very cool. Thanks for explaining.

What's driving the hip joint on your robot?

The shoulder joint is driven by (1) Banebots 775 motor, and (12) bands of surgical tubing.
You can see the 775 in this pic:
http://1.bp.blogspot.com/-rFQ0CRqTKR...0/IMG_8024.JPG

-John

[Brandon Holley]

Originally Posted by JVN

The shoulder joint is driven by (1) Banebots 775 motor, and (12) bands of surgical tubing.
You can see the 775 in this pic:
http://1.bp.blogspot.com/-rFQ0CRqTKR...0/IMG_8024.JPG

-John

You guys obviously rivet a lot, I assume you have a pneumatic rivet gun.

Any recommendations on one that is pretty reliable?

-Brando

[JVN]

Originally Posted by Brandon Holley

You guys obviously rivet a lot, I assume you have a pneumatic rivet gun.

Any recommendations on one that is pretty reliable?

-Brando

We buy the crappy ones from Harbor Freight -- they last about a season before they break. We replace them every year. Students are hard on riveters.

-John

[Garret]

This robot is amazing.

I would think that the double fourbar linkage would actually simplify the arm's joint design (at least in my mind it seems so much easier to deal with weight and taking loads) in that you would have to worry less about powering the pivoting point (gearboxes and chain) and instead focus on the making the actual joint stronger and more stable. I also could see it as isolating the motors and gearboxes from the abuse (as in side loads) the arm could take in a match, which I see as beneficial seeing how much defense this robot will likely have to put up with. Those are some of many potential benefits that I thought of when I first saw it.

[JVN]

Originally Posted by JVN

Yes, we are proud of some of the more subtle features inside Raptor. I know there are some that most people totally ignore that will be impressive to a mechanical designer with a good eye...

-John

After receiving a number of requests in response to this post, I decided to highlight some of the subtle parts of this year's design on my blog as part of an "Inside Raptor" series.

Here is a glimpse at one of the SIMPLE subtle features that I think makes Raptor special... press-on CIM pinions:
http://blog.iamjvn.com/2011/02/insid...ion-gears.html

-John

[thefro526]

Originally Posted by JVN

Here is a glimpse at one of the SIMPLE subtle features that I think makes Raptor special... press-on CIM pinions:
http://blog.iamjvn.com/2011/02/insid...ion-gears.html

-John

Wow, that's a really good idea. I can't tell from the picture, but does the pinion have the Key Shape cut into it, or do you just rely on the press fit to transfer the torque?

[IKE]

Wow. The press on pinions are very elegant. Did you guys do any slip calcs or tests?

[Brandon Holley]

Originally Posted by JVN

After receiving a number of requests in response to this post, I decided to highlight some of the subtle parts of this year's design on my blog as part of an "Inside Raptor" series.

Here is a glimpse at one of the SIMPLE subtle features that I think makes Raptor special... press-on CIM pinions:
http://blog.iamjvn.com/2011/02/insid...ion-gears.html

-John

Hell. Yeah.

Awesome idea Greg. Kudos to team 20 for producing the parts.

-Brando

[Chris is me]

That's a cool idea! I wish we had the resources to try cool things like that.

What's the easiest way for Low Resource Team to get press on CIM pinions?