The Right Drive Train?



How does your team decide on “the right drive train” for each game? As someone stated in this thread, with 2019 you need the right drive train to have an effective defense strategy. What is considered the right drive train for 2019?


Generally speaking, the best drive train is the one that you’re most experienced building/fixing, unless your chosen game strategy demands you pick a different one.


We considered different DTs, but settled on 8 wheel WCD for a number of reasons: 1. It’s what we know best. We have experience building/repairing WCDs and we wanted to finish our DT asap so we could spend more time on the more complicated elements. 2. 8 wheels gives us maneuverability but also the ability to drive off of level 2 hab without damaging our belly pan. and 3. WCD is hard to defend against.
We knew going into this season that lateral motion would be incredibly important for hatch alignment. Instead of a laterally-moving DT, we chose to create a moving hatch mechanism, and it’s worked out great for us so far.


For us we eliminated a swerve right off the bat because we haven’t built one before. We also took out butterfly and mecanum because of potential heavy defense. We considered butterfly or octacanum but again we hadn’t built one before so we settled on a wcd. One of our design constraints was that we wanted to drive into hab level 2 without the possibility of beaching. Using a bunch of layout sketches we found out that an 8 wheel wcd with 6” wheels was basically the only way to do this.


We went with the AndyMark 8” mecanum chassis with the NEO motors and with the Blue Banner we brought home from week 1, I’d say it worked well. This combination gave us the power and agility against defense ( which we got a lot in the playoffs), but also made it relatively easy to align on targets. The brake system in the NEOs was added bonus.


We like to stick with our starting question being “wide or long chassis?” Then next year we will have “Standard, Mecanum or Omni?” Because of the growing interest and parts we are starting to get. We’re really simple about it and we order the best kit recommended for what we want


We went with the kitbot default config, although I can’t remember if we dropped the centre wheel down slightly (I think we did), but we cut it to a custom dimension. A lot of designs for other drivetrains were eliminated due to complexity and/or the manpower required which we simply didn’t have. Swerve drives in defense heavy games are also too prone to burning out/defended against, so that was out as well.

Generally we plan out our centre mechanism, then we design the base dimensions, before choosing a drivetrain based on the game. And budget.


Kit bot is center dropped out of the box


What are your thoughts about a custom drive train??


I don’t think it is possible to go wrong with 6 wheel tank. You will always win pushing matches against every drive train except for a higher reduction 6 wheel tank. The thing you sacrifice is maneuverability/agility which, in my opinion, is easily overcome with a few hours of practice.


I am partial to 6 wheel tank with solid center wheels and omni front and back. It is by far my favorite drive train to drive, and when skilled at driving it can be more maneuverable than mecanum drive up to a certain point of driver skill.

I think it ranks number 1 in what I call “specific defense attribute” (Maneuverability to Traction Ratio).

Only Issue we had with it was in 2017 when the driver rammed into a gear against a wall and broke 2 of the rollers off.

In 2012 when I was a student we went from just driving the center wheels to driving all 6 wheels which gave us better ability to get up on the balance, and made us one of the top defense bots.


Do you know what this ratio is?


Once you answer three questions, you’ll be down to a short list:

  • Does your strategy require you to drive sideways?
  • What irregularities do you intend to drive over/off of?
  • What are our machining and development capabilities, and how much of them are we willing to devote to the drive train?


We only have experience with west coast styled drive train, so we generally only focus on improving that. We decide the drive train ratios by the end of day 1, generally by figuring out whether the game would be defense intensive or not. We always add a 1/8’’ drop, and inspect the field for drive train dependent items (such as the platform). We then sketch out the wheel spacing to ensure we won’t beach on field elements. We used a 2+4 style drive train this year and it has been fairly successful.


Traction is easy to calculate, but Maneuverability is more subjective. I wonder if we could make that value the time it takes to rotate 360 degrees. That would require a standard gearbox/motor combination, and it doesn’t tell that much in terms of being able to get around the defenses and get game pieces.


We decided to go with a drivetrain we could build quickly and optimize on a 25-foot sprint. That meant an AM14U4 (because a custom frame burned us hard last year) and 3CIM4Us at 7.31:1 with Mini CIMs (as verified in the ILITE drivetrain spreadsheet versus other 3CIM4U ratio options). Best drivetrain the team has built in at least a decade.


What data are you using to draw this conclusion?


I think a good general rule to follow is if you haven’t built something similar during offseason or a previous season that you know works, go with something you know works or the KOP chassis.


4774’s drive looked like a barbecue just bu running itself. Plus swerve drive modules are usually powered by a smaller motor, so any stalls would cause it to burn out.


When would one say is a good time to try going to swerve drive?