This is a CAD drop of some of the projects team 4776 worked on in off-season 2019 and some designs that we may or may not modify to use in this next build season. I’ve only uploaded the STEP files for these models.
As a part of a shift to a CAD oriented team, several weeks were spent doing basic prototypes to get an estimate for how long it will take to design, build, and test them to better fit prototyping into our overall schedule for build season. There’s also a prototype west coast chassis that we have manufactured and are in the process of assembling.
In addition we have designed a west coast chassis that we hope to be able to quickly and lightly modify after kickoff, making work easier for the CAD team. Our wheel shafts are held by 1/4" bolts screwed into the hex with a washer. We anticipate seeing how this will perform on our practice chassis that we’re assembling, but are cautious about their ability to fly off in the middle of a match. E/C clips are being debated instead of bolts. We’re also aware the radio and main power switch aren’t in the CAD.
Inside of our chassis we have an electronics “hub” that we have just recently designed. One of the features we’re interested in the performance of is our mounting of the Spark Max’s and Victor SPX’s. On each mounting set, the middle four cells are able to swap out between Spark Max’s and Victor’s. The Victor’s are simply bolted to the back plate. The Spark Max’s however are retained by a little lip that is extruded from the sides of each cell. The lip is large enough (hopefully) to retain the Spark Max, while still allowing a Vicor SPX to fit if we want to hold that instead.
Honestly, I don’t get the idea behind the electronics hub. It seems to me that it would make the diagnostic lights on the motor controllers hard to see, block access to the ports on the front/side, and make replacing a motor controller under pressure extremely difficult. If you’re already making a custom CNC’ed bellypan, why not just add mounting holes for the motor controllers there and mount them normally?
Also, I personally wouldn’t recommend stacking the roboRIO over the PDP like that, especially with the motor controllers on the sides like that. The stacking makes accessing the PDP for inspection/repairs more difficult than need be. And when you have the motor controllers flanking the sides as well, getting a WAGO tool in there to switch a branch circuit is going to be very hard.
The Chassis looks great, probably because we’ve done many of the same features for the same reasons. I hope it works well for you, which would bode well for us.
While I love the modular electronics, our Electrical Mentor who was also a Robot Inspector would never allow it. There is such a strong desire to have easy access to the electronics we limit what will be on the Belly Pan if a mechanism limits access in any way.
It looks like the axles may need some extra clearance so the screws are not tempted unscrew; along with Thread Lock should be fine. We are testing Clips. I’d feel better with both Screws & Clips, but I’ve seen so many successful teams with just clips done correctly.
Including the side gussets with the Belly Pan add to cost of the plate; but making separate gussets and notching the pan weaken it… Tough call. I changed our outer band from 1" wide to 1/2" for weight because there is strength in the frame. One last thought is wondering if the Elec module window in the center allows more flexing/bouncing.
The design of the electronics hub ranks very low for manufacturability, and serviceability and the ability to troubleshoot your control system. There is a lot of empty space around the bellypan that could be used to spread out the motor controllers.
How much “bend radius” are you allowing for the wires coming out of the motor controllers, especially at the bottom? Bending larger wires sharply puts a lot of stress on the strands on the outside of the bend. If the wires in the motor controller are the very flexible, high-strand count type, the individual strands will be very thin making them more vulnerable to this type of damage. The broken strands make your wire function as a smaller wire. Unfortunately, the breaks in the strands tend to be covered by the wire insulation making the damage very difficult to detect.
@Sam_Dare suggested hinges for getting access to the PDP. If this is not done just right, you will stress out the small wires that span the hinge and break the wires inside the insulation (where it will be very difficult to detect) or you will pull the wires out from the Roborio. Hinged panels are only used in industrial applications as a last resort.
If you start adding mechanisms above the motors and gearboxes, the difficulty of getting access to your PDP and motor controllers will be even greater.
You are best off just developing the chassis and not committing to the control system layout. After Kickoff, you may find you want to use the space currently occupied by your battery and control system for some sort of scoring system. In that case, you are better off installing your control system somewhere else, perhaps spread out on some vertical surface that is easily accessible from outside the robot.
