A simple subjective evaluation I decided to toss together as both an example of how folks could represent design choices as well as to help students evaluate options or at least provide a jumping off point for research.
What is a “2+2” drive system?
Two omnis, two traction. 971 has one this year.
Can we call parallel omnis “Asteroid Drive” ?
I’m not sure how your defining power. I’d argue that it’s pretty independent from drive train type (except if your accounting for efficiency losses).
For example, you have 2+2 listed as low power. Our 2014 bot had 6 CIMs, which most would argue is plenty (or more) power than you need.
I confess, I’m not at all a fan of 2+2. The turning center is nowhere near the center of the robot, which makes maneuvering very strange. It also has a nasty tendency to fishtail. Calling it “more mobile” than a standard 6wd is…a bit of a stretch.
Not sure but I am guessing something like pushing power. All other factors equal. Maybe
KoP drive gets dinged on complexity? That thing can get done in a couple of days if not within a few hours. Have any Kitbots really broken yet?
I doubt it they are extremely tough
I like this - it’s a nice visual guide for those who would be confused by a weighted cost/benefit table.
My only question is what examples did you use as a baseline for this? Of course it’s subjective, so this is all based on a team ability/skillset/resource capability that you had in mind, so it would be interesting to have that information on the graphic for context.
I think you’re reading it wrong. KoP isn’t getting dinged on anything.
In terms of pushing power take a look at the matches I’ve posted below:
https://youtu.be/i9-eH3Iym38
https://youtu.be/imPp9DMwEOg?t=42s
A 2+2 can have pushing power.
OTOH, if you do it right, you can use that fishtailing to maneuver around one end of the robot, all the time, which might be important if you are trying to maneuver a tall, unstable stack of 5 totes +1 can around. If your traction wheels are around the stack, it simply spins…
It can be done.
There’s also the 2x2 which would be putting omnis on opposite corners paired with tractions on opposite corners.
+1 to this. 1625’s 2014 drivebase was one of 1058’s inspirations for going 2+2 this year and we absolutely love it, a great blend of speed and pushing power. Spinning around the traction wheel side is actually an upside, if you get T-boned or hit from the traction wheel side spinning out of the pin is very easy, moreso than a standard 6WD.
This is nice for those who wouldn’t understand a weighted cost-benefit table. However, I don’t believe it’s a very good substitute for it at all.
First off, it lacks granularity and makes certain drivetrain types seem better than others from a numerical standpoint when they really aren’t. Parallel Omnis seems like a great choice for a drivetrain on paper, better than tank drive (hint: it really isn’t. I like different drivetrain designs, but go with a 2 x 2 or butterfly or something if you want better turning).
Speaking of tank drive, KOP isn’t really the baseline you want it to be. Any decent custom tank drive is more reliable than the KOP chassis, has more pushing power, and more mobility.
To properly explain drivetrain design, it’s best to come up with a long-winded post on why tank drive is the best and you should never use anything but tank drive (that’s not really what I believe, but it’ll go over well on CD). Explain that every single drivetrain other than tank will break down by the end of every match or be so complex that you wouldn’t get done with it by the end of build season (again, sarcasm intended, but this is how CD feels).
Seriously though, best way to explain drivetrains is to justify your claims.
So as posted you make general assumptions and imply that most of CD would choose tank drive as best. For many teams it is the best choice for many reason. We are a 6th year team and have run a KOP drive train all 6 years. For recycle rush we took the tread off the center two wheels and ran omnis with an additional pair of omnis in the center, last year we ran aluminum 8" wheels with stock gearing. I would put our bot up against any other bot and I can guarantee that our driver can play hard core defense on you no matter what drive train you have.
We are in New England and it gets rough. We have never broken any drive train component and have gone head to head against 8wd 6 cim, swerve, West Coast, just to name a few. In Waterbury we were pushing not one but two robots across the field at the same time with a 100% KOP drive train.
In Greater Boston there was a second year team that opted out of the KOP and built a swerve drive because the thought the stock drive train wouldn’t work well. Because of their budget and team resources they had a very maneuverable robot the could could place 3-4 gears and do nothing else. This was their second event and our team got them climbing by Sunday morning. They didn’t do much time and money on building and programming their swerve drive it left no time for any manipulators.
Drive train is just one part of the whole robot. If you don’t have the time, money or team resources a fancy drive train is a luxury you can afford if you can’t play the game.
If we could we would love to try a different drive train type but until we build, develop and test one before build season it will not be part of our design. We have a simple rule, “If you can’t move, you can’t play” so until we have another proven design that we can build and program just as quickly with a 100% non-failure guarantee we will be using a KOP drive train because it works.
If you want proof just look for matches at Waterbury or Greater Boston District this year or any event from 2014 that we played defense and you’ll have your proof. If we’re playing against 558 you can almost certainly see some defense between us and they run 8wd colsons with 6 cims most years.
This is correct, the KoP is my baseline for everything. From there each attribute is graded as either better, worse, or equal.
I was more working from staying power which is where it gets dinged because it can be more easily spun.
You’re right, this doesn’t replace a good WOT or a good discussion. However, one of the goals was to distill a design/prototyping process to something that can be seen at a glance. Things like this are useful for showing to judges or as documentation.
KoP is a baseline because it’s about the only thing every single team can see the performance of. It’s a baseline precisely to get everyone on the same page.
Parallel Omnis seems like a great choice for a drivetrain on paper, better than tank drive
I’m not sure if you’re quite reading this chart properly. On paper Asteroid Drive (I’m trying Nate!) is about equal to the KoP drive, it’s a bit more mobile but has less staying power.
Zebracorn Swerve - Taking Unicorn Swerve and making it more complicated with ROS, Stereocameras, and White Papers.
Just for clarification on where 900’s drivetrains fall:
hey now, those harpoons are undefeated
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