Limiting Drivetrain Motors

[cbale2000]

We used a 6 motor drive train (4 CIMs, 2 Mini-Bike Motors) back in 2006 on a similarly open field with no bumpers on the robot. We also built the frame out of solid sheets of 3/16" aluminum, needless to say we had no durability issues with the frame.

Rules that try to limit drive motors are really just limiting mechanism options, and rules putting a cap on drive system power will make inspections more complex, and likely longer.

The game animation for as long as I've been in FIRST has included the line "Robots should be built robustly", IMO teams simply need to design with robot durability in mind, otherwise the exciting contact sport that is FRC eventually becomes a dance recital.

[Billfred]

I don't think the kitbot is obsolete by the available power, but it does require a little work to tap the power. We did switch in the AndyMark 3CIM4U gearboxes ($150 for the pair, if I recall) and ran our underweight robot just fine all season. Total BOM on the change would probably be around $260 with the two extra CIMs and a pair of speed controllers (which IFI has a PDV for if you want to split hairs). If a sub-$300 parts order is causing major insomnia, I'd question whether the team was really prepared to compete in FRC.

The other notion: 6-CIM setups have fewer parts (and fewer small moving parts) compared to a shifting design. Could this be FIRST's subtle helping hand to ensure drivetrains stay mobile?

That said, if FIRST was worried about it I say limit teams to five CIMs. Teams will either do without, shift gears, or learn a thing or two about matching motors to party like it's 2004.

[AllenGregoryIV]

Originally Posted by Billfred

The other notion: 6-CIM setups have fewer parts (and fewer small moving parts) compared to a shifting design. Could this be FIRST's subtle helping hand to ensure drivetrains stay mobile?

I don't think this is FIRST's plan but I do think it is an advantage. I've never been on a team that has used shifting gearboxes in competition. Our setup this year shifted the wheels to get speed reductions but we haven't used something that can fail in the same way as your standard two speed gearbox.

[colin340]

I would hate to see the arms race end, fast robots and harder hit are way more fun for all parties, other then rookies.

[Andrew Schreiber]

Originally Posted by colin340

I would hate to see the arms race end, fast robots and harder hit are way more fun for all parties, other then rookies.

And anyone trying to actually play the game. It gets old going out and spending most of the match being smashed into by teams that are incapable of playing the game.

[colin340]

Originally Posted by Andrew Schreiber

And anyone trying to actually play the game. It gets old going out and spending most of the match being smashed into by teams that are incapable of playing the game.

Fair point, but this year we got called for hitting the defense bots back too hard. Teams that are blockading / pinning a partner should design for 13 fps hits or get out the way.

i'm sick of playing tea party games / soccer.

[Chris is me]

I think the assumption being made by a lot of posters in this thread is that 6 CIM drives are a large competitive advantage. People have stressed this to the point of saying the Kit of Parts is "obsolete" because it has a 4 CIM drive.

While a 6 CIM drive definitely has some benefits, they are not magic. 6 CIMs do not increase your pushing force when you are traction limited. While most single speeds aren't geared to run indefinitely under traction-limited load (pushing against a wall), they are usually geared to be traction limited at SOME point before stall. Thus the pushing force "cap" for robots isn't determined by the number of motors.

Acceleration is trickier, as it's very hard to model several dynamic factors in play to make a general case situation for all robots.

Honestly, I think tons of non-top teams faced extreme defense for the first time this year. Their robots got damaged, they want something easy to blame, so the first guess was more CIMs in opponent drives. The game design sucked and we're scapegoating the motors.

[AllenGregoryIV]

Originally Posted by Chris is me

Honestly, I think tons of non-top teams faced extreme defense for the first time this year. Their robots got damaged, they want something easy to blame, so the first guess was more CIMs in opponent drives. The game design sucked and we're scapegoating the motors.

I agree, motor limit or not, high speed ramming would be in issue in this game. We have bumpers for a reason, hard clean hits between two robots that can take it is very entertaining and have been a part of most FRC competitions over the past two decades. Finding game designs that limit destructive actions is hard but should be part of every game design.

[Tungrus]

"More is better"? A good engineering is doing more with less (no, not Target's catch phrase). It would be awesome if some team can design an efficient and powerful drive train without adding more hardware.