4886A Sack Attack Progress (VT Design)

Hello, we have decided to share our work so far on the new game in the interest of accelerating learning and progress for teams. I came up with most of this design on the flight home from California.




The intake is made from leg wheels.
Features (hopefully)
-score all goals
-descore all goals
-extremely high capacity
-drive under trough

Here is a video of the various features of our robot:
[http://www.youtube.com/watch?v=EmNQ1YqUM1g

Feel free to use elements of our robot, but be sure to credit us.
Enjoy!](http://www.youtube.com/watch?v=EmNQ1YqUM1g)

Wow, I can’t believe you guys released your design so early. It looks pretty cool and I’m sure will help some teams who were at a complete loss for ideas.
A few questions:
Do you have any ideas for a hopper yet / how many do you expect it to hold?
Did you go with H-drive over X or mecanum so you could use the planetaries?

Overall it looks like it will be an awesome robot.

Yes, we are using H-dive so that we can take advantage of the planetaries. As for the hopper, we havn’t tested that much, but I am thinking of some sort of ramp.

Hmmm… I don’t see any benefit of the 8 bar over a 6? A 6 bar just allows a longer arm, so I don’t see how putting another extension on helps? Because you get maximum length with a 6 bar?

The 8-bar allows us to reach the high goal, and still fit under 15 inches. With a 6 bar, you wouldn’t be able to drive under the trough.

Yes, but how? Its not like your arm can be any longer than a 6 bar?

It is though. Because we have 2 extra linkages, we get more height. It’s hard to explain, but once we get our field and stuff, we’ll show you guys. After May 23rd we can actually start the real building of our robot. (We have to keep our gateway robot intact so we can get school credit from doing a robotics challenge course.) But the 8 bar lift does allow for the robot to be under 15 inches tall, but still reach about 34 inches.

Wait… Let me think about it for a while and then either come back and explain why I’m right, or why I’m wrong and why I thought I was right :stuck_out_tongue:

It gets more height for the same reason that a six bar gets more height than a four bar. In a six bar, the top bar becomes the bottom bar, with another bar above that one. With the eight bar, the bottom bar becomes the top again, again creating another one on top to keep the end of the arm in alignment. Basically, every time the top becomes a bottom, the height you can reach rises by the distance between the bars.

Hope this helps, and sorry if it was hard to follow.

Nice work but pretty standard thinking. I was hoping to see a crazy design from you guys! I know my team is currently planning to stay away from intake rollers because they simply don’t allow the capacity we want to pass through.

How are you planning on scoring on high goals with that intake? It doesn’t look very precise(I may be wrong)

Anyway, thanks for getting the ball rolling! :smiley:

trollface.jpg

:slight_smile: maybe we have a crazy design?

Also this was just made today. Once we get out polycarb we can start to do what we really want to do.

Who says we don’t have a crazy design in mind for later in the season? :wink:

We are still brainstorming about how to score accurately (or stack) in the high goals. I have a few ideas. Same thing for the capacity issue.

I will post updates when we build the whole working robot.

It’s easier than you think. If you imagine the n-bar link as a scissors lift turned on its side (and kind of at an angle) you will see that adding more sections will give it more reach, just like adding more sections to a scissors-lift is how to make it reach higher.

I think you guys are over thinking this (or I’m unaware of some other advantages to 6/8 bars), but why not just use a basic 2/4 bar? 15in high start + 18in C-channel at a ~45 angle connected to your scoring device gives you 32in? You could probably even use those new C-Channel expander pieces that they released recently to make your lift longer. I believe you can up to around 23 in + 15in = 38in max in a 15x18 box.

The intake seems pretty solid, I think that’ll be pretty standard for this year.

If the vertical distance between the upper and lower pivot points of your arm are 15 inches apart (which wouldn’t even fit with the size of bearings, etc.), then if you lift the arm up so it is 30" off the ground, you will be at the same horizontal location at which it started. If you want to be able to go above the high goal to dump, this won’t do. And if you want to be able to reach out from the front of your robot at all, this won’t do even more.
http://img192.imageshack.us/img192/3798/15ine.jpg

With a 6-bar, your bar can actually be the full 15" by 18", but if you have a 4-bar the vertical distance between the pivot points is 15" minus the vertical distance between the two horizontal bars. An 8-bar lets you lift up past 30" because you have the 15" plus the vertical distance from the end of the normal 6-bar to the bottom of the parallelogram that you add with the 2 new bars.

Ah yes that makes sense. My original thought was that you could go under the troughs so the horizontal distance wouldn’t matter to much. I also wasn’t thinking of something that “dumps” the sacks either. I was thinking more of a low-friction titling bucket that the sacks could just slide off from. Thanks for the explanation. :slight_smile:

What is your plan for de-scoring? My team had a similar idea and we where just going to use metal to create some sort of hook. Anything you’d like to share?

I was hoping to just have the intake roller go into the trough and suck out the sacks, using pneumatics if necessary. I don’t actually know if this would work though, because we don’t have troughs yet. It will definitely be able to descore somehow.

Wow guys, you read my mind! This is basically the same design I came up with once the game was released!

Great video though!

Edit: How wide is the intake?

The intake can either be 3 large c-channels wide, or 4 c-channels wide.