Tube Versus Channel

[MichaelBick]

We also like aluminum tube. Really, the best thing to use is 1 x 2 aluminum tube, welded. 1/8 in thick for drive base, and basically 1/16 for everything else. If used correctly it is perfect. Minimize the amount of frame material you need. Look at any 254 robot, and you will see how simple the frame actually is. It makes for lighter robots, and you really don't need anything more. Also, 1/4 in, waterjetted, aluminum plate goes very nicely with this. It makes building 20 times easier, and reduces the amount of tubing you need. Plus, you can make custom gearboxes. Really, it pays off to get a 2D sponsor, as they can turnaround parts amazingly quickly.

On the subject of sheetmetal, while a lot of good teams use it, there are plenty of good robots built out of tube, as long as you streamline the design process(254 again comes to mind). The nice thing is that the robot comes together lighter, more quickly, and more accurately than an aluminum tube robot. On the other hand, you need to have a good team of CADders, and have the sponsor to be able to do it.

[Gray Adams]

Originally Posted by MICHAELABICK

We also like aluminum tube. Really, the best thing to use is 1 x 2 aluminum tube, welded. 1/8 in thick for drive base, and basically 1/16 for everything else. If used correctly it is perfect. Minimize the amount of frame material you need. Look at any 254 robot, and you will see how simple the frame actually is. It makes for lighter robots, and you really don't need anything more. Also, 1/4 in, waterjetted, aluminum plate goes very nicely with this. It makes building 20 times easier, and reduces the amount of tubing you need. Plus, you can make custom gearboxes.

2 questions.

1) Is your 1/4" plate .25", or is it like ours and ranges from .22" to .24"? That made our gearboxes this year a little difficult to get fitting correctly (if you've seen the gearboxes, you know what I mean)
2) Besides custom gearboxes, how else do you use it in your frame? We have a lot more frame right now than I'd like, but I can't see how 1/4" plate would make it significantly better.

[FrankJ]

If your 1/4 plate is .22 to .24, you ordered a gauge thickness rather than 1/4 plate.

1/8x1 tube is virtually the same weight as 1" 80/20.

This year we used a lot of 1/8x1 angle. Half the weight of the equivalent channel & allows bolts to be properly torqued without crushing the section.

We use mostly 1/4-20 bolts. A little heavier than other options, but you don't have to worry about the inexperienced over torquing them. Carroll Smith has a great book about fasteners "Nuts, Bolts, Fasteners and Plumbing Handbook"

It is all about the details & trade offs.

[MichaelBick]

Originally Posted by Gray Adams

2 questions.

1) Is your 1/4" plate .25", or is it like ours and ranges from .22" to .24"? That made our gearboxes this year a little difficult to get fitting correctly (if you've seen the gearboxes, you know what I mean)
2) Besides custom gearboxes, how else do you use it in your frame? We have a lot more frame right now than I'd like, but I can't see how 1/4" plate would make it significantly better.

Our 1/4 plate is .250 ± .001. We got it from McMaster, because we actually had to get it CNC milled by our machine shop. We hadn't tried to get a 2D sponsor before the season, but actually right after the end of build season, we got industrial Metal Supply to sponsor us, and they have a laser cutter that we will be able to use for the offseason and any future games. This is just one of the laser cutters that they have available: http://www.youtube.com/watch?v=-k8JGL8Muq4

We use the 1/4 plate for our ground pickup, shooter hood, and elevator gearbox, which we also made custom. This helped to simplify our frame quite a bit. What I was really talking about though, is it seemed like a lot of teams have way more complicated frames than needed. I like using 1/4 plate, wherever it seems like it would be beneficial to use sheet metal, as it has a lot of similar capabilities, and it adapts to whatever you need it for very well.

[Madison]

Most of our machines are made from 1x1x.063 aluminum tube and 1/8" polycarbonate gussets that are fastened together with 1/4" rivets.

1/4" rivets are definitely overkill, but they make prototyping with 1/4" hardware and swapping in rivets at final assembly a cinch and our laser cutter doesn't always do such a great job when cutting smaller holes into some thicker parts -- a #10 clearance hole in 1/2" material gets pretty oblong by the end.

This year's drive pods were built from aluminum standoffs and 1/4" delrin plate; I was a bit worried about how well the plastic would handle side-loading, but it's been a champ so far.

With respect to tube vs. channel -- in almost all cases, I'd use tube if I could. Tube is much stiffer than channel in torsion.