First of all, I love this chassis. Let me get that out of the way. Looks very nice. I suppose you're in for a ton of awards which you justly earned even if you guys do nothing more than just put bumpers on this chassis and compete with it as is.
Here are my concerns. I don't want to rain on anyone's parade. I am just trying to have a real discussion as though this was something that our team was designing themselves.
1st Comment
If you slow down the video, you can see that the chassis is flexing a bit as it turns. That long arm on the single trailing arm suspension and also the spacing between the dual rocker suspension give the wheels a big moment arm when they scrub over the carpet. That in turn puts some high loads into that chassis. I suppose that 842 has done some calculations to design the reinforcement plates. I just worry that over a season either the rivet will work loose or that someone will T-bone them against some field element where one of those gorgeous yellow tires will get "tripped" and then you've got the full push load of another robot trying to pretzel your robot.
2nd Comment
You can see the aluminum bits coming into contact with the defenses at a number of points in the video. It is not catastrophic because the robot clearly gets over the defense, but it DOES cause the robot to momentarily stop as a few points in the video. Why didn't you lower the wheel axles with respect to the aluminum bits so that this was less of a problem?
3rd Comment
When you have suspensions. Springs and torques from the drive belts and tire/carpet forces matter. Sometimes they matter A LOT. And they are not so easy to figure out (in theory they are but in practices, it is easy to screw it up and not consider all the loading cases).
Looking at the photo, it seems that the dual axle arm is completely unsprung while the trailing arm has a gas strut.
I don't have all the dimensions of things but my back of the envelope calcs (and scaling some photos which is not the most accurate way to get dimension, I assure you) show that the dual arm loads shift 10-20% depending on what direction the wheels are driving (said another way the normal load on the center tires is equal to the normal load on the front tires plus/minus 10-20%). This is probably not going to affect things during a pushing match -- I was afraid it might lift the entire robot but that seems unlikely unless the tire gets traction much greater than a CoF of 1.
BUT... that trailing arm is another story. Again, I don't have all the right dimensions and I don't even know the spring output or travel but the back of the envelope calcs estimate that the when pushing forward, the normal force of that rear tire is going to go up by as much as 50% (when pushing the friction on the carpet tends to lower the wheel, making it bite harder into the carpet). This could kinda be a big deal depending on the rest of the robot and the situation.
4th (and final) Comment
Suspensions are designed to keep weight on all the wheels. All the wheels. That means that the front and the back wheels have weight on them when turning. If you play the video you can see that this robot is not having a great time turning. I know I am like a dog on a ham bone but really all ya'll should read
Dr. Joe's Seven Stages of Dealing with a 4WD Robot with Grippy Tires
So... ...842, hats off to you. Very cool. But there are a lot of details to making suspensions work and work well. Think hard before you decide to follow them down the suspension path.
Callin' 'em as I sees 'em.
Dr. Joe J.