Planning to build this over the next couple of months…
Compact “Killough drive” chassis
Intent is to be a test platform for software development, and later for “demo bot” use.
Specs:
– 19" square x 9" overall height with battery
– 4x AndyMark Toughbox 14.88:1 gearboxes, one CIM per gearbox
– 4x AndyMark 6" aluminum omni wheels (with option to expand to “dualies”)
– ~7.5 ft/s in the cardinal directions, ~10.5 ft/s in the ordinal directions
– Arduino Ethernet microcontroller + RobotOpen Control Shield
– Plywood chassis construction (should let me get some good use out of my tablesaw)
– Access to internals by removing drop-in battery tray (transparent magenta subassembly)
– Close to optimized for minimum moment of inertia
– ~3/4" ground clearance
– Less than 60 lbs
– Less than $2,000
Looks like a pretty solid design. Though I don’t think just removing the battery tray will give you good access to the internals, all those CIMs and gearboxes are going to make it hard to get at the PDB, and I don’t see how just removing that panel will let you get at the Talons.
Could you maybe replace the bottom panel with some simple aluminum framing (to hold the gearboxes) and have a removable electronics panel?
This is a good point-- something I’m worried about as well. I’m fairly confident that I’ll be able to reach the Talons, but I’m already considering raising the battery and placing the PDB into the recessed spot above the motors.
One great benefit: this would leave a nice open area, right below the center of rotation, to place a gyro & accelerometer later on.
Honestly, I’m much more concerned about overheating my CIMs, seeing as though they’ll be:
– mounted to gearbox plates made of polycarbonate (which has a thermal conductivity3 orders of magnitude less than aluminum)
– inside a mostly-sealed box
– run at a 100% duty cycle for much longer than a 2-minute match
I expect to make a lot of changes from this initial design as it’s being built. I’m a huge devotee of the “plans are worthless, but planning is everything” school of thought
Yeah, I’d agree, moving the whole electronics panel above the toughboxes would be a good step.
Here’s what I’m thinking:
Instead of the small angle bracket attaching the toughboxes to the top panel, attach the tops of the toughboxes to the side panels with standoffs or long bolts through some spacers.
Stick to a simple electronics board. PDB, Talons, Router, Arduino, Breaker, all of it, that sits just above the toughboxes. Hold it down with a couple of wingnuts or some other easy-detach method.
Get some standard 120mm PC case fans, and mount one right under each CIM (obviously this will require holes in the bottom panel too )
One thing I would do is use toughbox Nanos instead of the fullsize toughboxes. That would allow you to drop the CIMs down further and give you more space. Then put electronics and the battery up above, and some fans down below.
I considered this, and it would have been a more graceful solution, but I really wanted the slightly-higher gear ratio.
I’ve only seen one FRC robot with a truly modular electronics board in my life, and I didn’t like what I saw. Instead of focusing on consolidating my electronics into one neatly-organized board, I’d much rather prefer to think about (1) reducing the number of required connections-- and therefore potential failure points, (2) reducing the sum of the wire run distances, and (3) allowing more than one type of maintenance activity to occur at once on the same robot.
)
