pic: ABS-122, shifter-in-tube chassis

The major issue with this (for my team) is pushing matches: for example, during forward pushing you can easily have 100% weight on the back two wheels.

The back wheels are solely used on defenses. Happy we didn’t go 4 wheel.

Having un-powered wheels in your drive train is generally not a good idea. They create friction and make it really, really hard to turn. Replacing them with a caster or some low friction nylon for example, is also not a great idea because this year our back wheels help us get over defenses, and when you put something in place of a wheel that doesn’t roll, and hit defenses as hard as we do, it won’t turn out so well. Removing wheels and just replacing them would not be as good as just designing a drive train with 4 wheels only. In cases like this year, we needed 6 wheels to not get stuck on defenses so that’s what we went with.

When it comes to drive trains we go with something we are confident with. 6wd and 8wd are types we’ve worked with before and have given great repeatable results. Adding furniture sliders or caster wheels to our drivetrain is probably something we will never consider doing on our drivetrain.

To OP:

I recognize that this is a mostly theoretical drive train but have you thought about how you would remove a CIM, if it were necessary?

It looks like he oriented the motors in a way that you can access the bolts around the gears. But I am just assuming so I could be wrong.

I actually added a lightening pattern later such that a ball end allen key can access the bolts to remove the CIMs. As it stands right now, removing the gear in between the two CIMs would suffice to remove them.

I guess the question I was trying to get at is: How would you remove the idler gear with the bearing flanges to the inside of the tube?

Good point. That raises the other question: how would the shaft get in there to begin with? :confused:
The lightening holes might let you get away with not removing the gear. But IRL if I made this, all bearing flanges would be on the outside and/or I would use riveted bearing blocks to save space inside the tube. That particular spot is actually easy to put at least one of the bearings on the outside because I have space in there.