The most important part of any robot
This year, 7226 decided to go with a custom built mecanum chassis.
This chassis was designed by me, with the help of my old team, 308.
This style of chassis was largely copied from Team 67 - HOT. I believe they have been using this style chassis since 2008. The Monsters 308 used it as a large influence for our 2014 robot, and we loved it. It was a light chassis that had tons of space for the cRIO, talons, and pneumatics. All of that was kept at a super low CG.
The problems with the 308 chassis: Thin metal and mecanum wheels don't always play along nicely. We ended up warping our chassis and powdering our gearboxes, which we found at lunch at our last district competition.
Bill Clark and Mike Sulkowski added a steel plate that came with the gearboxes to reinforce it for the next iterations of that chassis.
Some design considerations:
- Mecanum chassis = 4 gearboxes in each corner
- Some treads to take care of bottoming out
- Elevator requires sturdy mounting
- Low CG
- Battery Placement
- Master Power Switch placement
- Battery connector placement
- Routing holes for wires
- Lightening holes
- Tons of mounting space for other mechanisms
To be honest, we didn't exactly know how everything was going together. I designed both the elevator and the chassis, so those two subsystems mounted nicely. However, I can't design everything, and I got pretty burned out, so I left some designing to the other mentors and students. That is the reason there is so many mounting holes everywhere.
Show us the design already
Okay, here is it naked (no powder coat):
In this state, it's pretty sharp on the edges since they're not chamfered. No big deal, it's getting paint. I was on an interview trip and it probably didn't get all the TLC it needed. The bends were out of spec slightly which threw a lot of it off. No big deal, however. I designed the chassis to have a 119.5" perimeter. When it came together it was exactly 120". Next time I'll design it to be 119" even.
Lots of the holes didn't line up, so the team just drilled more holes. Wasn't too happy about that but there wasn't another solution.
Here it is all powdercoated before welding it:
Why white? Because white is clean. Every team has their own color. 308's is always red or black, 118's is always white, gold, red, 148's is always all black. I decided that ours was going to be white with purple accents.
Here it is welded and powdercoated (again):
What I learned from making this chassis
This chassis is far from perfect.
- Mecanum is not a good choice for a game with a lot of non-flat surfaces
- Wires are thick. Bigger holes for wire routing
- Create more space for RoboRIO and PDP
- Make sure the bends are better. Not our team's fault, more of a manufacturing defect, but it hurt us slightly
- More ground clearance more better
- White looks good
- Purple is hard to match
- Invert the outside panel so the inside of the C is facing outwards. This can help with the nuts and fasteners that need to stick out
There are so many things that could've gone better, however there are tons of things that went so right.
- The wire planning was excellent. Small, but excellent.
- Having a battery mount and battery connector mounted to the chassis is sweet.
- The chassis looks damn good. And it has been holding up to our 2nd-year-team abuse
- The mounting points, although not perfect, really did help
Some other things not related to chassis:
- Wet noodle wire is so fun to work with. Seriously, if it's in the budget, get it.
- PID loops are so easy to run on Talons. Do that instead of the RoboRIO
- NEO Motors (brushless) are a pain and inconsistent. Make sure those drivers are update (again)
- Make your elevator light. Our is way too heavy. I'm not sure how it even goes up, but it does.
- Elevators that allow for the intake to go on either side are awesome, however they are not very stable or rigid
- Make things lighter. Next year I will experiement more with polycarbonate
- If you can machine things, do it. Students are not the most accurate at making holes
Alright, time for the late night rambling to end