Am I correct in stating that the current KOP Drive Base Chassis only includes a gearbox with input for 4 CIM motors (2 for each side)? If so, are there any gearboxes that mesh well with the KOP Drive Base that offer 6 CIMs? If 6 CIMs is not easily done using the KOP pieces, can’t we achieve the same level of torque by sacrificing speed? Obviously you’d be a better defender with more pushing power, but you’d decrease your cycle time of delivering balls to the front lines.
We’re also debating whether or not it’s necessary to have a 2 speed option, so I’d appreciate any feedback about that. Any comments about how difficult that might be to implement (and keep in mind that we are rookies!)?
I’m not sure how much 6 CIMs will help you on the field, but I do know they will help you get selected as a 3rd robot. I’ve been on alliances where teams made our short list of 3rd robots just because they had 6 CIMs.
My previous post wasn’t suggesting teams shouldn’t be more than just a drivetrain that plays defense. I’m advising teams to not sacrifice their drive train or driver practice to add additional capabilities. Spending 5 weeks on a high goal scorer or climber while their drivetrain isn’t reliable and drivers aren’t practiced is a bad idea. Building a new, untested, articulated drivetrain (look back at some very good teams that struggled in 2010 due to fancy yet ineffective drivetrains) to weaken defenses instead of building a more simple tank drive is also a bad idea.
I was alluding to some of these things in my comment but was far too brief so let me elaborate.
KOP only allows for 4 CIMs as you pointed out. You would need something like: 3-CIM 3-CIM with Shifter
While these don’t come with a Kit or anything to integrate into the KOP you can integrate them without a ton of trouble and a few teams can probably give you a step by step if you decide on that route.
You are correct that one of the easiest and most often overlooked changes that you can make is to change the ratio on the KOP gearbox. Andymark includes details on how to do this in the KOP assembly instructions. As mentioned it will be a power/speed tradeoff but blindly accepting the ratio that the KOP provides doesn’t allow you to tailor things to the strategy you are trying to achieve.
I think putting teams on a short list because of 3 CIMs is silly. I have seen many 3 CIM robots be pushed around by a 2 CIM shifting gearbox just because of the ratios. Don’t forget brownouts being a higher possibility with 3CIM drivetrains and everyone can agree that a robot dead on the field is a big red flag for alliance selection.
This doesn’t mean that a shifting gearbox is within your capabilities as it will take pneumatics and some additional code to do it right. I know some rookies and a bunch of second year teams have been able to do this so it isn’t out of the question.
I completely agree with Xaul in his comments about driver practice though. Getting a driver who is comfortable with the robot and who can control it well outweighs probably any of these changes.
I am curious how high ranking teams view a 3CIM drive vs shifting (or maybe neither of these is important)?
Yes, you can get the same torque by sacrificing speed. You then have the problem of catching the faster bot. You can’t push what you can’t catch. Adding a shifting gearbox adds complexity as jdaming discusses very well. It also adds a lot of cost. An effective driver will likely make more difference than two extra motors regardless of what role their robot plays. A good example is how 610’s driver dealt with defense in 2013.
With proper planning and design, it should be possible to start driver practice within the first few weeks of the build season. The mechanisms that give your robot additional capabilities can be installed later in the build season or be brought to your tournament in your withholding allowance.
Advice to rookie teams for Stronghold: Spend a lot of time perfecting a drivetrain that can traverse all of the terrain-based obstacles (not gates) including the low bar. If you are successful with this, you will make the playoffs at most events. The low bar will be a valued skill because it’s consistently there (allowing for consistent alliance strategy) and it is very quick to traverse if you’re low enough. If you perfect driving over obstacles, design a way to grab and release boulders. If you can do that we’ll enough, you will be very successful.