"Modular" Chassis

[Jon Stratis]

Originally Posted by AdamHeard

If you do this then all configurations combined must be under 120 lbs unfortunately.

Some inspectors (incorrectly in my mind) even consider modular swaps of identical components to be something that requires re-inspection.

dmaciel10123 - Please note that the combined 120lb weight limit only applies if the modules are different (different wheels, gear ratios, etc), per the 2014 rules:

R5
The ROBOT weight may not exceed 120 lbs. When determining weight, the basic ROBOT structure and all elements of all additional MECHANISMS that might be used in different configurations of the ROBOT shall be weighed together.

emphasis mine.

Adam - something like this would definitely warrant a re-inspection. This isn't something small and simple like replacing a COTS gearbox with an identical item... this is a large, complex portion of the robot that impacts several areas of the inspection sheet. Off the top of my head, a team could do this replacement and fail re-inspection for overlooking simple items in the following areas:
- Weight (How do I know that the modules weigh the same? I've seen teams with identical looking red/blue bumpers weigh in over half a pound different!)
- Size (are the modules all exactly the same size? Were the modules attached without any gaps? Do they still fit within the 112" frame perimeter? Do any other structures still retract within the starting configuration?)
- Bumper mounting (Are the mounts all the same? Are the bumpers attached securely? Are they within the bumper zone?)
- Bumper backing (are there any gaps that are introduced with the swapped module? Do the bumpers still fit snug against the frame perimeter?)
- Risk of damage to the field (is there anything different about this module that would cause it to damage the carpet? Different wheels? Different gear ratios? A dragging chain or idler sprocket that'll hit the ground?)
- Safety (Is it still safe to operate? Same/minimal risk of getting fingers caught in chain? Was it attached properly so it won't come off mid-match?)

Ideally, it wouldn't be an inspection issue - replacing one module with an identical module shouldn't be a big hassle for teams. In the real world, however, modules are rarely identical, and those small differences (even something as small as having a weight holes in one plate but not the other) can make a difference when it comes to compliance. Regardless, a re-inspection for it shouldn't take more than a few minutes.