I use this all the time:
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What chassis base should we use for our wheels
Nobody can answer this question for you, you need to figure it out for yourself!
VEX has a great resource for beginning teams to learn the design process and how to make decisions. Take a look here, and especially look at the “engineering” section to see how experienced teams have worked through making their design decisions: https://kb.roboticseducation.org/hc/en-us/articles/8373753632407-Students-Start-Here
and:
https://kb.roboticseducation.org/hc/en-us/articles/4460497609751-VRC-Engineering-Design-Process
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what is GR in the table
I believe it is the gear ratio of the drive
Gear ratio
202029837392029chqr
We are going 400RPM 6M 3.25” 6 Wheels: two front and two back are Omni, 2 in the middle are the new tractions. Anyone have any thoughts on that? Feel free to share if you notice that this could have a major flaw.
We may have an intake PTO off of the drive to make it 4M drive. Would that cause the motors to burn out at 400RPM 4M?
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That sounds viable
Im using 6M 450rpm on 2.75 wheels with the same PTO configuration and it works nicely
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Drive speed is good for 6m, new tractions are good (they are very grippy).
4m drive for long periods of time might be too far of a stretch, depending on how light your robot is.
In this game, since you’re driving pretty much all the time, it’s more of an advantage if you could just dedicate 6m to the drive all the time.
The constant torque and acceleration boost when driving with 6m is worth it, imo.
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Alright for sure, thank you
I personally don’t want the middle wheel (because tokyo drift vibes), but thats seems good, but thats just driver preference.
400rpm so good 
I can vouch for 6m 400 rpm 3.25". The speed is so good and the gearing is super convenient, very easily done without any idler gears at all.
It’s subjective of course, but this was by far my favorite drive speed out of all the ones I tried.
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Yep, in this game I don’t see how anything less than a 6 motor drive will be competitive.
It’s definitely viable to use a 4m drive, but I figure the most efficient use of motors is to include them on the drive base rather than on subsystems.
Just because it’s not as efficient (using 4m drive) doesn’t mean it’s not competitive. Matter of fact, 4m drive won MoA !
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The best thing about VRC is that it’s a long season. What work early may not work later in the season. Competitive teams don’t aim to beat last week’s best robots, they aim to beat next month’s best!
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Heyy, I see you sound experienced when it comes to this. My team and I started last year. We had no experience at all, and this year we are expected to build a working robot that shoots disks, spins rollers, and expands. ( last year I was the programmer so I didn’t know much abt building and still don’t ) So far we have nothing. We don’t know how to build our drive train, the intake. I know what components out rib needs to have j just don’t what would be a good starting point. I’ve watched several videos but I’m still confused. Not sure about the different types of drive trains, but I do know the middle of the robot while be spacious so the in take could be there. Tips and advice is much appreciated and needed!!! Thank you
Welcome to the Forum!
If you are pretty new, my advice is to build a pretty simple 4 motor drive bot. Simplest chassis is to direct drive 4" wheels with 200 rpm (green) motors. This will be very simple, and a decent speed to start out with. It will also be super easy to program. Some topics about designing good drives have been posted by @Xenon27.
You should also check out these:
MENTORBUILT - A Robot Made in 12 Total Hours For Your Enjoyment
Harvard-Westlake Robotics: BLZ-i Reveal
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if you’re completely new to building and you just want to get a drivetrain that works, going direct drive 200rpm (the green cartridges) on 4" omni wheels is a solid place to start, and although there are much better options, there’s nothing wrong with starting at the basics.
if you’re more stuck on the structural layout of the drive frame, I go into some detail on this in this topic: Designing Another Quality Drive
But I also used some more advanced techniques that I wouldn’t necessarily recommend to someone not confident in the very basics of build techniques.
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If you are new to vex, build 4 motor direct 4" omni tank drive (i.e. Vex Classic) and start practice driving it as early as possible.
You can never underestimate the value of an extra month of drive practice!
Then go to early comoetitions, see what other people have, and start rebuilding your next version of the robot.
Once you get more experienced, you can upgrade to a faster drive like @Xenon27’s
In short, the best chassis for your robot is the one your driver is most comfortable with.
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Joins thread to share opinion
Illyana and Xenon27 posted
Illyana and Xenon27 posted everything I was going to say
All jokes aside, I cannot stress how important it is for teams to:
- Build a simple and robust drivetrain early,
- Test it thoroughly,
…and … - Get lots of driving practice and autonomous programming in well before competition season really gets going.
Learn how its going to get stuck. Learn how its going to fail. Learn how to service it. Reduce friction. Tune your turning coefficient (multiply your turn axis by something like 0.8 to reduce how aggressively they turn). Run into walls, repeatedly.
If you want even more practice… stick a wheel on a post as a stand-in roller roller. Lash/tape a laser pointer to a piece of structure and practice aiming. Figure out how to ram and roll or juke and roll when another team is defending the rollers late game. Learn endgame defensive/positioning strategies by scrimmaging against a cardboard box or clawbot.
Many people do not begin designing for the human element (driving) until its late in the season. Get practice in, document/notebook it, reflect on it, review footage, and be the best dang 4m 200rpm driver you can be.
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