Changes from MK III (Last Built Octocanum):
• 8 Motors
• In 4 Motor Configuration, lighter than MKIII
• Single Stage Reduction rather than Toughbox Nano
• Frame Pieces are laser cut .09
• Colson Modules are bent 1/8”
• Piston is now 2” stroke rather than 3”
• Bearings are press fit and Loctite-ed in
Matt, You are welcome anytime.
To answer your other question: we haven’t really tested that. It’s something we can do, though. I’m not that concerned, however. If we were to be hit in that way pulling the tractions up and running on the mecanums should solve that issue. We used that maneuver to good effect in Aerial Assist.
There seems to be a decent amount of extra space between the frame rails and the modules themselves. One thing you could try is to put some delrin on either side of the modules and move the frame rails closer together to basically pinch the module between them. You’d then get horizontal support for the modules.
Hopefully we both make it to the DCMP so I can see it in person if the game calls for a drivetrain like this again.
In addition to what Mr. Wilson said, we are planning to run more tests on it. We have not yet sideloaded it, but plan to do that and a few other tests, including running it with SD540s.
Awesome! I love your music choice, I knew I wouldn’t be the only person to use Knife Party music in a robotics video! I also love the design, I think I’m gonna look into this being one of my team’s off-season projects for 2016!
We have restrained the modules with retaining rings. This will be the third year we have used them without a failure (as long as they were installed properly). We did this get away from spacers. Might rethink this if it’s a really defensive game.
Looks really nice! Have you guys seen how well it can traverse obstacles like a scoring platform? I know it’s unlikely that there will be an object EXACTLY like that, but it does look pretty close to the ground.
Yep, pretty sure at the moment the frame is low enough that you could place a penny in front of it and push it around. We are evaluating a few options for raising it up.
Thanks for the idea! Just tried that out, and at speed it could make it over, but moving slowly it gets stuck every time. I got a video of it with colsons down, but it can do it with mecanums down (it just gets stuck much more often.) As Alex said, we are contemplating a few different ways to raise the clearance. I will edit in the video when I get home.
EDIT: Here is one test.Here is another. Both of these videos are with traction wheels down. I didn’t get video of it going over with mecanums, but it works, just less consistently.
Just wondering: what is the ground clearance on that thing? I’m designing my own octocanum modules and I’m having trouble getting the ground clearance I want. Looking at these videos, what I have may be good enough.
That was actually one of the things we were testing with this set up. Right now, you can write anywhere on the bottom of the frame with sharpie and it will get wiped off. We are sitting at about .24 of an inch (this is at the rivet). We do know we need to raise it because usually game elements have supports under the carpet that raise the carpet about a 1/4 of an inch.
We performed sideload and push tests to check the durability using our 2014 robot. Overall we did not notice any damage to the modules or frame. Our CAD will be available later this week once it is cleaned up. https://youtu.be/ABcCZot--OA
Our CAD is up. If you have any issues with opening it, or any comments/concerns on it please comment. It is a slightly different version, which has a higher ground clearance. Link to the files.
We are trying to think about how we can adapt this to a terrain game without changing wheel locations or diameters. If you have any suggestions, please let us know.
What made you decide 16fps with such a powerful drivetrain? With the equivalent of 6.7 CIMs on there, how much of an advantage do you get over a 4 CIM drive?
How heavy is this version? The lightening pattern looks wonderfully aggressive.
16 FPS was chosen as this is the same gearing we used for 4 cims, and with the extra power we have a much more responsive strafe and higher acceleration, however if we decided to we could remove the mini-cims for weight and still have a perfectly functioning system. In traction mode it is friction limited, so it will burn a hole in the carpet before stalling. Because there is less friction on the mecanum wheels, you can’t stall the motors in either of the drive states.
Our weight is at about 45lbs (I believe it was 45.8lbs). This includes all 8 motors, a full control system, a big pneumatic compressor, a metal tank, and a huge excess of wires and pneumatic tubing. With four CIMs, this would come out to approximately 36.6lbs for a functioning octocanum.
