Chassis Materials

[M. Mellott]

Team 48 has used welded aluminum box tubing for our base frame for years, 1/8" wall for the outer box and 1/16" wall for inner bracing. Aluminum takes some practice to weld, both to weld it with proper penetration without burning through it, and to weld it without warping the frame. We've had ours welded up at a local machine shop before, but last year one of our team member's father who works at a steel mill offered his services.

We feel the base frame, the foundation for your robot, is very important to make as solid and strong as possible, even if it means spending an extra couple pounds. That way, it's one "sub-system" that we don't have to worry about down the road, even after many matches. The last thing you want is to have to tear apart your robot to repair a bent/broken frame in the middle of a competition--it could make for a long weekend.

[joeweber]

The 2004 and 2005 season we used HDPE. Pictures @ http://team1322.org/pictures.htm It can be heavey but it has alot of give. This was befor bumpers, other robots would just bounce off with out damage. We found a local place that would weld the plastic together.Our robot was completly plastic except the arm. The plastic was very easy and safe to work with, students could cut it and not get shavings in there skin or cut themselves on the edges. You could use a jig saw, router, hand saw, and drills with ease. We still use HDPE (High Density Poly Etholean?) as mounts for motors or structure supports between aluminum frames. This seasons robot we used two blocks 2.5 x 5 x 6 in. and cut it into a fun looking "Y" to get around some items so we could mount the motors in a particular spot. The stuff is strong and easy to work with. Also you can use it as a low speed axel support or make pillow block out of it. Look close at this picture @ http://team1322.org/DSC00703.JPG you can see the motor mounted to it.

[redbarron]

Team 1270 used 6061-T6 4"x4" box tubing (3/16" wall) last year and we are using it again this year. We integrated the AM Transmission with the whole drive train into each side tube. The CG of the bot with the tube 113 inches in the air was in the center of the robot and about 7 inches above the floor, we didn't add any extra weight or heavy materials to the base just kept as much of the weight as low as possible.

[falconmaster]

http://www.creativepultrusions.com/

Pultruded Fibergalss

1/5 the wt of steel/ 1/3 of alluminum for same strength!
Electromagnetically transparent
Non conductive
non corrosive

the best stuff!

[JesseK]

Originally Posted by falconmaster

http://www.creativepultrusions.com/

Pultruded Fibergalss

1/5 the wt of steel/ 1/3 of alluminum for same strength!
the best stuff!

What's the cost compared to 6061 Aluminum? I'm thinking along the lines of 1" square tubing that's 1/16th thick for aluminum (since we know it's strong enough) vs. 1" square tubing that's 1/8" thick for the fiberglass.

Also, what do you use to reliably "weld" the components together? Also, being that you're from a NURC team, how well does this stuff hold up under water?

[falconmaster]

If you sand it epoxy works great. We use 1/4" bolts with 3/8" lock nuts, and it works great. We use all the same size nuts and bolts. You need stainless for the underwater bots!

In most cases the cost is more, but not that much more, especially if you count in the labor time and repair time you save.
1 1/2" x 1 1/2" x 1/4" is $2.74 a foot

1" x 1" x 1/8" $1.20 per foot

6" c-channel $7.34 per foot

The water has no effect on the material at all!

[Molten]

Originally Posted by squirrel

If you are interested in keeping your robot from falling over, go heavy on the chassis.

I definitely think he has a great point. Alot of teams struggle with weight, but we have never had troubles. We use 1 1/2 inch aluminum tubing. I remember our first year(2006). We was at the Boilermaker regional and a team made it to the final rounds(I think). And their robot fell apart on them. I felt so sorry for them. They made a great robot, but they did not consider structural integrity as much as they should. Our robots have been tipped time and again, and we have yet to see any damage. So, worry about weight. Just not as much as the structure.

[Doug G]

Oh so many techniques and materials...

2001: We used Bosch 30 series extruded Aluminum and steel sheet metal for mounting the lightweight components. The connectors for the Bosch got to be a bit pricey.
2002: We switched to 80/20 1" extrusion and T-nuts and such. Great for new teams, easy to make adjustments. But in the end it can get used for too many things and your robot is heavy. Used 1/8" Aluminum plate to mount things to.
2003: 80/20 Extrustion 1" extrusion again with some 1" Al angle here and there. Used 1/4" Lexan to mount electronics to.
2004: 1" Al 6061 Tubing (1/8") welded together by students. Used 1/8" Lexan to mount electronics.
2005: 3/4"x1.5" Al 6061 Tubing (1/8") and C-channel welded by students. Used 1/8" lexan for mounting components
2006: 1"x2" Al 6061 Tubing and C-channel again welded by students. 1/8" Lexan for the electronics
2007: 1"x2" Al 6061 Tubing and C-channel again but welded by sponsor. Custom made Fiberglass panel that when under the robot. Used 1/4" foam core and included hard points for mounting compresser and electronics. Now we now how to do this, we will be doing this each year.

[legotech25]

We used 1/8" polycarbonate for the entire robot, including the chassis!!!

[joeweber]

Do you have a link to Pictures, I have though about using it, kind of like unibody construction ?

[Rapt0r9]

We always used some type of aluminum. Whether is it 80/20 or the kit frame, rarely do we need to use anything else. Ocassionally we have used harded steel for things that need to be extremely strong and we used lexan for all of our electrical work, but if you saw our robot this year, you would understand what I mean when I say we are all aluminum.

[MrForbes]

Originally Posted by joeweber

Do you have a link to Pictures, I have though about using it, kind of like unibody construction ?

go to google.com

click "Images" at the top left corner, then type

FRC 1714

into the box, and click "search images"

you'll find lots of pictures of their neat robot, and links to the morerobotics web page.

(note that this search technique works for finding pictures of just about anything you want to find pictures of)

[joeweber]

Thanks, Looks good, I wished their site had some thumb nails of the robot so I could get a closer look.

Off subject: Is their a site with a picture of every teams robot. Wouldn't that be a good idea for the First web site, when you enter you teams info you could also add a picture of your robot when it is built and first could forward it to a Page with every teams robot per season.

[MrForbes]

I agree that that is a great idea, my guess is that others have tried to do it but have not succeeded, because it is a daunting task!

When our team goes to regional competitions, I take pictures of all the other robots the first day, and put them on our web page that night. I doubt this happesn at every regional event though, and I haven't tried to coordinate my efforts with those of other people.

First place I'd look would be

http://www.thebluealliance.net/

[JesseK]

Originally Posted by Doug G

Oh so many techniques and materials...
...
2005: 3/4"x1.5" Al 6061 Tubing (1/8") and C-channel welded by students. Used 1/8" lexan for mounting components
...

I noticed that you use nylon/plastic sprockets on the drive train. How did that work out for you, were they strong enough to last the whole season?