Robot chassis shape

[Herodotus]

Originally Posted by firebelly

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...

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.

[firebelly]

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! )

[Herodotus]

Originally Posted by firebelly

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! )

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.

[Cartwright]

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.

[kramarczyk]

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.

[Qbranch]

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! ) to see where weight could be taken out...

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

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