This is absolutely nuts. Please build this, at least a small one, simply to say you did. I mean, how many people can say “I used a rover drivetrain design for a robotics competition… and it worked.”
Legal… who knows with bumpers. Awesome? Well, that’s a given.
I love it. Crazy enough, there is actually more gearing required in this to make it work. You have to have a differential gear box set in between the left and right side on the front pivot so that as one side goes up the other goes down to compensate on rough terrain. I had to build one of these with banebots gearboxes for a lunar mining competition. It does get heavy quick and there are some other things you have to do to keep the chassis level but it worked swell at Kennedy Space Center.
**Challenge accepted.
**
We seriously considered building something similar in 2016. A rocker-bogie suspension at least, not one that slapped swerve drive on top of it.
As to making bumpers work… in 2016 we did build an actuating drive train to help us clear defenses. One drive rail was an integral part of the frame. Then the frame was lifted a couple inches on opposite side. The second drive rail was mounted on a pivot underneath the frame. The bumpers were mounted to the frame and the frame was deemed by inspectors to be non-articulating (the drive rail articulated) as such the bumpers were non actuating as well.
I expect you could design a similar system for the bogie suspension. You mount both suspensions to a solid frame and mount bumpers to it. The question becomes, if both halves of the drive train articulate does the frame articulate?
Yeah… I haven’t really figured out what to do about bumpers. Mounting them at normal height would also make the suspension pretty useless, so I have no clue what to do.
I haven’t selected a gearing ratio yet, but the drive motors have 2-stage VP’s on them, allowing for a range of different ratios.
My plan for getting the frame to stay put is to have a differential bar running across it. This way, when the left side goes down it rotates the bar, causing the right side to go up and cancel out its motion. Because of this opposite reaction, the frame will be able to hold itself up mechanically and without the use of motors or weights.
Yeah, the amount of gearing on this thing is insane. Instead of using a gearbox for the differential, though, I plan on using a bar that will act as a differential. This way, when the left rotates down, the right will rotate up proportionally and cancel out any tilt, allowing the bot to stay upright without the use of motors or weights.
Best of luck to you.
I’d really love to build this, but… it costs like $2000 just for the drivetrain, and I’m not even sure if it would work. I’m prototyping a swerve drive using a 3D printer, but even that requires a lot of components. I think it would be cool to 3D print a little model of this for my desk, though…
I chose to put the 775’s vertical mostly just for the aesthetics, to be honest. Curiosity has some kind of hubbed (or very small and hard to see) motor for its wheels, so I wanted to try to imitate that. Also, I heard that my team had a really bad experience in the past using VP’s horizontally directly to the wheels.
Also, how would you recommend utilizing CIM’s for drive in this design? As far as I’m aware of, CIM’s can’t be mounted to VP’s and creating a custom gearbox for this would be either too big or an absolute nightmare.
Thanks a lot!
CIMs absolutely can be mounted to VersaPlanetaries using a CIM Adapter. You have to pay attention to the load rating guide to make sure you don’t use them above their rated torque, but other than that it’s no problem. You should also pay attention to that guide with the 775pros, because I would think you are starting to approach that limit with (what look like) 6" wheels driven 1:1 off the VP.
As far as directly connecting the VP to the wheels, you’re right that that’s not such a good idea. VPs don’t like much axial or radial force on the output shaft, and direct driven wheels tend to give both of those (especially if not well-constrained). You could, however, use a small spur gear or belt or chain reduction between the VP output shaft and the wheel shaft so those forces aren’t transferred. All of those options are more efficient than bevel gears, and would allow you to rotate the modules 360*. That would also allow you to lower the reduction in the VP, which will bring you further from the max rated torque and maybe even make your VPs smaller.
If you’re not set on using VPs, you could use CIMs with a Toughbox Micro or Nano. They’ll give you plenty of reduction and no worries about forces on the output shafts. The hardest part would be integrating them into your design, but they aren’t too big so you should be able to find a place for them if you so choose.
Yes CIMs can be mounted to the VPs if you’re willing and able to cut the hardened shaft of the CIM motor.
It really isn’t that hard to cut. My team has cut a number of them over the years with just basic hand tools.
This method hasn’t failed is yet, and it’s basic enough that any team can do it. If you’re really worried about safety, you can cut the shaft without turning on the motor using a good amount of cutting fluid and elbow grease. It really doesn’t matter if the end isn’t perfectly flat for this application.
Wow, really?! I didn’t know you could do that 
I’m working on finishing the full model of this first, and I’ll integrate that in the second revision!
That looks absolutely amazing! I’m a freshman with no money though.
It’s for university/college students, so there is time to plan your design. 
This will work nicely with the replay of the 2010 bumps in next years game.