pic: Robot Concept CAD

[Siri]

Originally Posted by MikeBrock

This is very true. How about waterjetting 1/8" plates for the top and bottom to hold together 2x1 tubing?

You could, but what are you gaining with that? (Besides weight) I think you may well find that welding/riveting/bolting the 2x1" together with corner gussets will save you significant money and waterjet time. You also might want to put some more thought into the drivetrain before committing to 1x1" instead. Certainly plenty of robots drive with great 1x1" frame members, but attaching your wheel axles directly through 1x1" profile doesn't leave a whole lot of metal around most axles.

In places where you decide you need aluminum in non-stock profiles (a taller frame or a wider baseplate, etc), you can definitely get really creative. Also remember that it doesn't have to by aluminum, though. Many a nice electrical panel was made of plywood, carbon fiber, and many things in between.

With reference to the shooter: First, please, please, do not cantilever that axle. But more systematically, "non-continuous" shooters (as opposed to easy-to-turn-on wheels, cam-arming shooters, etc) in which you have to execute separate actions to load, arm, fire, etc can often be more complicated, especially with such a huge moment arm. (They weren't uncommon in things like Breakaway, where the travel distance was usually minimal.) It leaves you things with a few more challenges than normal.
- Where and what is the cylinder? And how precisely do you plan to use it? Is it providing the actual launch power?
- Where is the roller/how do you store and pickup balls and get them in the cradle?
- How long will it take to reload, and what's the range? (adjustable?)
- Most importantly, what are your design requirements? Are you meeting them with this?

On a catapult specific level, how far are you planning to shoot? Without knowing the specifics (CG), I'd be a little surprised if your back wheels stayed on the ground when launching for considerable distance.

Also, are your mecanum wheels mounted correctly? In the iso view it looks like they don't form an "X" from the top. Not a big issue in CAD, but your robot won't like it much.

Still your CAD is quite solid and your idea (even if I disagree with it) has a nice conceptual start. I can't say I'd do it, but if you've got a valid strategy, strong design requirements, excellent testing data, and the wherewithal to overcome the non-continuous shooter challenges, don't let us push you down.