Chassis Connections

[Billfred]

Most of the robots I've had a hand in were held together with bolts--then again, most of those robots have used the kit frame.

What 1618 did in 2008 (and 2815/1398 in 2010) was use rivets. 1618 used the IFI kit frame that year and simply substituted a rivet in each place where a bolt was used originally. The result (click for the big image) was rock-solid, with no problems the entire Chesapeake Regional. (Bumpers likely aided that.)

2815 and 1398 used a custom sheetmetal frame, which naturally I can't find a good photo of this morning. (The next best thing is this photo.) We had about five 3/16" rivets on each edge of the frames, along with support from running dead axles. There was then a back plate and a belly pan, also riveted together. While I wasn't in the pits as much this year, I can't think of a single report of frame trouble across two teams and five events. And just as a bonus, we were able to rip apart both drivetrains to shake out drivetrain bugs by drilling out ten rivets and undoing three bolts holding the axles in place. (Okay, fixing the drivetrain issues didn't really seem like a bonus at the time...)

I wouldn't consider rivets an automatic decision on the frame, but they're certainly a strong choice each year.

[Brandon Holley]

In the past couple of years I've developed a pretty cool method for putting our frames (chassis) together.

Basically we have our own gussets made out of ~.060" aluminum and make them in two varieties, 'T' or 'L' (this is usually done by waterjet, and we can get the parts for around ~$1/piece). The Ts have 4, 1/8" holes and are 3" long while being 2" tall. The Ls are 3 holed around 2" X 2".

We pretty much use 1" box beam for all of our framing needs. This then allows us to put a simple hole pattern of 1/8" holes 1" apart, and 1/2" from any edge to rivet our frames together. For most applications the riveted frame is strong enough as is. However, the nice thing about doing it this way is that you have created a welding jig once riveted. If you then want to go back and beef up certain or all joints, you simply just start welding. The gussets will hold the frame extremely square, especially if you put the holes in the frame members on a bridgeport or mill.

I'll try to dig up some pictures to make life easier, but in the meantime if you have any questions feel free to ask.

EDIT: Picture found




-Brando

[Jon Stratis]

We welded a custom chassis in our second year, but have stuck with the kit-bot frame bolted together ever since. For us, welding the frame together ended up taking too long and was too mentor-intensive (and less student participation) than we want.

[JamesCH95]

My team has used bolt-together frames, typically plywood with angle-aluminum brackets or the kit frame. For 2010 we welded the kit frame together (saves several pounds of weight over fasteners) with some custom wheel brackets. Took 1 mentor (me) less than two hours to do at work (we had no welder at our work space). We then bolted on everything else, including some 3/8" plywood for a deck.

I would highly recommend welding the kit-frame together for the weight lost and stiffness/strength gained. It's 5052 aluminum, so it has no temper to lose through welding. If you are just welding the kit frame together it should take less than 1 hour to assemble, prep, and weld. The kit hardware holds it in place very nicely.