Dulce's First tele-op tube

[falconmaster]

Here is our first test of the prototype arm hanging a tube.
http://www.youtube.com/watch?v=N415TOE45Fk

We are building a gearbox to hopefully give the arm more torque

[Josh Fox]

We had issues with torque on our "virtual four-bar" (I think that's the term) last year. We were putting it under considerably more load (trying to elevate our robot), but we were never really able to explain where our mechanical losses were coming from.

It got to the point where #35 chains were breaking and hex shafts were shearing before we threw in the towel on it, but I was just wondering if you guys had any insight as to what sort of mechanical advantages/disadvantages go into an arm like this? I've been curious about the math behind it ever since.


It looks like your gripper is pretty solid and not too finicky about the orientation of tubes it's trying to pick up. I also love the geometry the arm goes through, this is such a cool concept. Good luck!

[billbo911]

Originally Posted by falconmaster

Here is our first test of the prototype arm hanging a tube.
http://www.youtube.com/watch?v=N415TOE45Fk

We are building a gearbox to hopefully give the arm more torque

Looks like you are on the right track.

You are spot on about needing more torque. What are you currently using for a motor and transmission? What is the load on the mechanism as it is built right now?

[Michael Corsetto]

Have you considered sticking a gas shock between the upright and first segment of the arm?

Awesome design, way to get it working, can't wait to see the final result!

[Jon Stratis]

4-bar mechanisms can benefit greatly from the use of supporting springs. One of the designs our team originally considered was a 4-bar mechanism, and to help demonstrate it to the team, I brought in an old desk lamp that utilized that mechanism. The lamp in question had several springs stretched in place, and one of the more interesting parts of investigating how it worked was moving it with and without the springs in place. With the springs, it was easy to lift up, and it held its position perfectly. Without the springs, it was a lot harder to lift, and would drop back down immediately.

I would highly recommend looking into how springs could be used to help provide the added torque needed to neutralize the weight of the arm, allowing your motor to work a lot easier.

[thefro526]

Torque issues aside, that arm looks fantastic.

Is it just me, or does the gripper stick out past the chassis on one side? I'm assuming this will be fixed down the line?

[Chris is me]

Are you concerned that your arm will get caught up on the bumper when pulling up / back?

[kgzak]

Is the arm fully inside the robot when it is up? It looks like it might be but The tube blocks the bottom of your gripper. Also can you reach the top peg?

Otherwise it looks nice. Hopefully I can get video of our lifter up soon

[falconmaster]

Originally Posted by thefro526

Torque issues aside, that arm looks fantastic.

Is it just me, or does the gripper stick out past the chassis on one side? I'm assuming this will be fixed down the line?

Its a prototype. We will fix the dimension issues.

[falconmaster]

Originally Posted by Chris is me

Are you concerned that your arm will get caught up on the bumper when pulling up / back?

It is adjusted for the bumper.. . will have that on soon

[MrForbes]

I know 842 has gone thru a lot of calculations to figure out what size and how long of latex springs to use. There might be more friction in the arm than anticipated...although I think the joints use ball bearings.

It's neat to see it running at last! I know they'll get it sorted out...hopefully I'll get to see it Feb 19 at Duel in the Desert