Robot chassis shape
 

I saw an old closed thread about the shape of robots' frames, and I was just wondering what was considered best particularly for robustness. Is a simple rectangular bot good, or a more abnormal looking robot best? Also what are the downsides to each shape.

One of the old posts talked about how the shape shouldn't be designed, but that it should just sort of evolve with you robot's creation. How about it?

There are many robots out there. Which shape is best for robustness, compatability, and effeciency in electrical organization and drive trains?

Re: Robot chassis shape
 

Honestly, it depends on your robots' functionality. The most common top-down shape is rectangular, but if you feel that your robot needs a different shape for your auxiliary to perform better, then by all means, go ahead, as long as you don't sacrifice your machine's stability and structural strength.

Re: Robot chassis shape
 

It depends on your desired role.

For offensive robots, 179 in 2005 had it about figured out--it was harder to catch a corner and stay on it. For defensive robots, we (being 1293) learned in 2006 that our ball intake was good for catching the aforementioned corners when we had to play defense.

Re: Robot chassis shape
 

Our Vex team tried using a Triangular shape for their robot. While our mentors thought it was a revolutionary concept (being more difficult to block and easier to control), it ended up simply being a hinderance. The team agreed the triangular shape made it harder to center and attach parts.
The odd shape design could potentially be a good idea, but only after it's been worked on extensively. Otherwise it's just for show.

Re: Robot chassis shape
 

For those of us who have limited experience in FIRST, could you please post links to pictures of what you're discussing?
Much appreciated,
-MT

Re: Robot chassis shape
 

I saw a team in Atlanta this year (can't remember the number, I think in the 900s, but can't recall right now) that I was very impressed with. They started with a rectangular base with rounded edges on the front and back and had two drop down sides that fell so it became a complete, uniform circle at about 3 inches off the ground. All the way around they had rollers so whenever a team tried to play defense on them they still could turn and do things that way without any issues... plus if the other team hit them at any angle but straight on they would "slide" around the robot. The driver said the added maneuverability it gave was amazing, and overall it's a very simple thing to create mechanically. Very, very cool idea and I wish I had a photo or the actual team number that did that. Definitely something to put in the memory banks for future years :)

Re: Robot chassis shape
 

I saw that in the pits too... I never got a chance to see it in action though, if anyone finds out the team number. can you link to videos?

Re: Robot chassis shape
 

That was team 95, the Grasshoppers. They won Xerox Creativity at GSR for that function.

The Blue Alliance has all but one match from GSR (and 95 isn't wasn't in that match).

Re: Robot chassis shape
 

We actually based our chassis design this year off that robot. The idea is great, since the chassis can be designed to shrug off hits from anywhere. With this design, at least for us, it was harder for other robots to pin us against the wall or the rack.

Our chassis: http://www.chiefdelphi.com/media/photos/27019

Swamp Thing 2005: http://www.chiefdelphi.com/media/photos/20152

Re: Robot chassis shape
 

Heh heh. Went against this one at nationals. My team was a little worried about it at first, but they turned out not not be a problem since they were coming after us. It was a really cool design, though.

As far as shape is concerned, you also have to keep weight in mind. In 2006, my team designed a great looking, extremely strong frame, but it ended up being super-heavy. *Shivers* so many holes...

Re: Robot chassis shape
 

I know how you feel. On the last day before shipping in 2006 we weighed our robot and found that it was 10 or 15 pounds(I can't remember exactly) overweight. We then spent that day and the next day and took the entire robot apart down to every individual piece of metal, drilled holes or swapped metals(replacing steel axles with aluminum ones for instance). So yeah, don't over design your frame. One thing also to keep in mind is that generally the maximum dimension you can be is a rectangular shape so to make the most of how much room you have a rectangle shape is going to give you the most space.

Re: Robot chassis shape
 

Well, while a rectangular shape may give you the most space, you have to ask yourself: do you really need it? I know that my teams robot next year is going to take a very minimalist approach. (I'll be a mentor, but I shall *help* with a iron fist! :cool: )

Re: Robot chassis shape
 

Well that is what you have to decide before hand. Last year we went with a very boxy approach so we could hold as many balls as possible. This year it would have depended on how you were handling tubes or how your ramps or lifts were shaped. Next year it will be different again and you'll have to think before hand what shape to make the robot.

Re: Robot chassis shape
 

We used it this year on our robot, but I was wondering if anybody else used stressed analysis to help design a chassis that could take the blows of defensive competition.

Re: Robot chassis shape
 

We did some... http://www.chiefdelphi.com/forums/sh...53194&p=569665
Coming up with the load cases was the hard part. We just ended up using a relative comparison. Now that I'm aware of the IRI definition for high speed ramming I've got something solid to work from. :D

Re: Robot chassis shape
 

Not so much this year, but last year when we were really having a tough time with weight I ran stress analysis on most everything (especially parts in the shooter itself) as well as the drivetrain (except for the wheels... something i would later regret! :eek: ) to see where weight could be taken out...

result: a very lightweight and cool looking frame, plus a shooter assembly total weight of 20lbs :ahh:

the stress analysis is also a great way to learn the limits of materials you use everyday; like plate aluminum, UHMW, etc. I ended up making the track guides for our '06 bot out of UHMW thanks to the ability to rapidly prototype in the ANSYS stress analysis system... cool stuff.

on the ultimate shape, it seems that for manipulators the triangle always looks to be the best shape ( 2005 bot ) since it allows for the longest arm. Other than our '05 bot we've always had a rectangular frame, boring I know, but easy to work on and build. Thanks to bumpers, one interesting frame option that really helps out in the pits is cantalievered wheels ( example ). bumpers also make it a little more feasable to use a welded frame since you don't have to worry about shock loading on welds as much, so we tried our first welded frame this year ( near complete 2007 bot ).

Still, for our team at least, it seems that rectangular frames for most everything but for heavy lifting the sheet metal triangle works best.

-q