Non-Rectangular Frames

[Lil' Lavery]

As mentioned in this thread (and plenty of other places), the new frame perimeter rules helped encourage the use of non-rectangular frames. Sure, we've seen a handful of them before [insert obligatory nonagon comment here], but never in the quantity we saw in 2013 (or some of the irregular shapes). From circles (3574), to hexagons (2851), to v-shaped septagons (1425), to adding irregular pentagons (4334), there was a lot more creativity in frame design this year.

This thread is to discuss the obstacles and advantages presented by these unusal frames. Why did they come to this design? How did teams use them to their advantage? What challenges did they face along the way? How did they solve those challenges? How to did they build their bumpers? Where did they place their wheels, and why? How did it change their approach to maintenance? How did they perform structurally? Etc.

[joelg236]

Our frame was a blessing and a curse. It was fantastic for lining up, but terrible for shooting anywhere else. Bumpers were pretty straight forward, we just built them in the segments around the frame. Driving was somewhat off-balance, since more weight was on one side.

Everything else was basically the same as a normal rectangle-bot. I'm curious what it was like for circular bots though.

[Joe Ross]

Team 585 made a rounded rectangle

http://www.idleloop.com/frctracker/p.../2013/3651.jpg

[Gregor]

Multiple times this season I've seen oddly shaped frames that had no obvious or apparent reason. Occasionally I could see why (4334), but to those other teams, why? What am I missing? And to quote JVN,

Remember to ALWAYS use physics in engineering discussions. There is really no room for "feelings" in this sort of thing. I don't care how you feel about an 8WD, or what you "think" might happen. I only care about your physical justifications for how and why things happen.

[NXTGeek]

I've seen my share of parallelogram frames... not sure wether that was the original design, though...

[Ryan Caldwell]

Our hexagon shape came about when trying to package a very wide hanging mechanism to stay level, along with a 28" wide arm to pick up two disks easily in Auton.
The wide hanger was proposed to allow for stability so that we could shoot off our last cycle while hung.

We had originally thought about a round bot but decided bumper time would be unjustified when a hexagon could house everything.

Our wheels were also very wide which made our zero radius turn incredibly fast & smooth. We were also able to hit and role out of contact fairly well.

The Shape was beneficial when playing defense making it harder for teams to brush off and making it easier to wedge them into the boards without technically pinning them as they could still back strait up.

Structurally it was awesome no real issues. We had a little bending on the back of our bot, thanks to some awesome smash mouth defense by 3098 at Waterford. But nothing that created any issue.

[Levansic]

Originally Posted by Joe Ross

Team 585 made a rounded rectangle

http://www.idleloop.com/frctracker/p.../2013/3651.jpg

Yes we did!

We started with an elongated octagon, but rounded the corners to better match the fiberglass fabrication. We figured that if we fell, we would like to bounce and not have to repair chassis damage.

We use fiberglass as our base medium, because we don't have a metal or wood shop to use, and have sponsors and mentors with composite experience. Fiberglass needs only scissors and spatulas for spreading epoxy. It also gives us a lot of volume to play with for locating components, as we design our chassis as a stressed skin.

We were not prepared for the mid-build clarification/change to the bumper rule that required us to block our center trough with the bumpers. By that point, we didn't have time to change the overall design for other purposes. We still got to make really cool (and light) curved bumpers, and got to be pretty good at defense, by the time our season ended.

[DampRobot]

Originally Posted by joelg236

Our frame was a blessing and a curse. It was fantastic for lining up, but terrible for shooting anywhere else. Bumpers were pretty straight forward, we just built them in the segments around the frame. Driving was somewhat off-balance, since more weight was on one side.

Everything else was basically the same as a normal rectangle-bot. I'm curious what it was like for circular bots though.

I never got a chance to see your drivetrain up close, could you describe in a little more detail how it worked out? Was one side of the wheelbase longer than the other?

[jacob9706]

I'm an alumni from 3574 and as a 3rd year team I am ecstatic to see that their unique design of a perfectly circular robot with a 8 wheel tank, shiffters an not one ounce of chain got some national recognition.

One thing that struck me as a unique solution to the bumpers was the use of a industrial vacuum bag to bend the glued together 1/4 in (?) pieces of wood to create curved bumper pieces that fit perfectly around the frame which was made from Nomex honeycomb (carbon fiber airplane flooring) and cut on an Omax water-jet. We like to say that we grew a round tree though.

The drive was CAD'ed by a self taught student in the off-season and was implemented into the circular frame.

Another fun feature of their robot was the ability to filter discs within the collection mechanism. It had no sensors to do it, just a mechanical toggle that the disc would trigger if it was upside down.