My team is going to create a 450rpm 8 motor drivetrain. Two friction wheels are going to be in the middle on each side, and two omni are going on the ends. We are going to use 2.75’’ wheels. Would this setup work? Would it have a good balance between speed and torque? If not, what do we change, the gear ratio, or the wheel size?
Welcome!
OKAY- so, I just got like- really info-dumped there! Let me break it down for purely my understanding (and anyone else who may want to help you as well)
Summary
- Team is going to create a 450rotations per minute drivetrain with 8 motors.
- 2 friction wheels will be used in the middle on each side (assuming that 4 will be used in total)
- 2 omni-wheels on the ends (4 in total)
- Will use 2.75 inch wheels
Alright- so first off, what type of motors? 5.5? Or 11? Or are you in the unlimited life of VEX U?
I mean- I have no knowing but it worries me if you were to be in V5 and use only 11’s!
Now- Let’s make the assumption that you’re building a robot and not just a drive train! You’re using 5.5 motors for these and all!
So- the robots top speed would be wheel circumference times RPM over 60- which makes 64.8 in/sec!
Now- honestly, that’s really fast! Now- You can slow it down with a gear ratio (which btw, you didn’t list yours) like a 3:5 to like- balance it out (so gears like 36 to 60(?))
But- I’m not too sure, not an expert- Most motors I’ve ever put on a drivetrain is always 4! 
Hi. thanks for the reply. We are running six 11w blue motors for the drivetrain, which is 450 rpm and it has 2.75” wheels. I am just afraid of not having enough torque to push other robots or enough speed to move around quick enough to collect blocks. What do you recommend we change? The rpm of our drivetrain or the size of our wheels? We are using 36 to 48 for our gear ratio btw. I am a little skeptical about running 6 11w motors as a V5 team though. Sorry about the mistake. I meant 6 motors not 8.
450 RPM is a very solid ratio, it’s a good balance between speed and torque. Many other teams use 450RPM, so you will be on a fairly even field with a lot of teams. It should be a good ratio for you.
Why?
6 11w motors is the standard for V5, if you don’t use that you will definitely put yourself at a disadvantage…
Disadvantage? I’d like to just kindly ask why that puts teams to a disadvantage- Lot’s of teams use 4-motor drivetrains and do well!
I just need to be able to understand your viewpoint on this for a minute, 
No problem, just wanna help out!
Okay- so you want torque but also speed!
Now- I respect you for being skeptical about the 6 11w motors but- it happens way too often, you won’t be a new person in the crowd!
Math that sounds really important
Now- let me just break down a few equations so you know which components you would need to change to make influences!
So- To find the circumference you multiply the size of wheels (in your example, 2.75") by pi. This gets us around 8.639
THEN you put it into this silly equation, wheel circumference (8.639) by RPM (450) over 60 (to make a minute to second)
And that makes 61.792 -ish, (Chat i think I messed up on the math from that earlier equation)
Now- what affects it would be the wheel circumference (so wheel size) and RPM-
I would personally bump down the RPM because less RPM means more torque- and you want torque- But you also want SPEED! So maybe an RPM of 350 (or higher, lower??)
Was this written by AI?
Yeah I’m pretty sure my team is running an all-Omni 450 rpm 6motor and has immense pushing power, so it’s pretty solid in my opinion, would recommend
Nah, why (lowkey been avoiding that stuff since it’s errors on spelling strawberry with full r’s) ? Did I mess up on the equations? Or were my exaggerations too much (I’ve been told that I exaggerate with numbers a lil bit online-) ?
To my knowledge, every top team in my state for High School used a 6 motor drive. These were usually the only teams who really needed to be defended, and teams with 4 motor drivetrains almost always were unable to do so.
Really, it’s mostly the emdashes. Not a big issue though, just wondering.
Those aren’t em dashes!
Those are hyphens.
AI giving em dashes a bad reputation is just such a shame – they’re one of my favorite forms of punctuation…
On another note – we can leave the AI policing to post-flagging or the moderation team 
Wait-- Sir, I’m just gonna ask- Am I being accused of using AI all of a sudden? I was lowkey just tryna help?
No – we wouldn’t be approving your posts if we thought they were AI
I see, I see. So- what was happening (cause I’m now confused) Was that like- uh- Just like banter on the use of Em dashes?
Someone thought you were using AI to write your posts because you used hyphens/em dashes often. Many LLMs use em dashes as a preferred method of punctuation as opposed to semi-colons, and many consider even correct usage of em dashes to automatically be AI-generated text because of that.
I personally prefer to keep my eye out for excessive bolded text, posts that are formatted “too-well”, posts that read more like summarized notes as opposed to complete thoughts, etc. But maybe that’s just because I like using em dashes, myself. 
You’re good – don’t worry!
On another note – I appreciate the respect and politeness, but calling me ‘Sir’ on an internet forum just makes me feel older than I already do 
Sighhh, old habits are NOT going away- I used to use those back in 5th grade to make my letter count higher on my essays (my teacher for some reason graded letter count and not word count. She scared me.) And I’ve been using them ever since (cause commas are kinda over used rn [don’t mind that, that was a joke] and I really don’t feel like pressing shift for semicolons[that was also a joke, i really think its just the habit- like of using this -), guelp- I’m gonna work on tryna fix my amount of “-, --, —” and all
getting this back on topic…
plz note that if u are still planning on running with 450 on 2.75s then u have to half cut your 48 tooth gears if u plan on a 3 hole gap in your drivetrain. If u watch Ace 229V’s worlds robot explanation for high stakes on youtube they had that ratio and they mentioned half cutting their 48 tooth gears. This is because vex doesnt sell low strength 48 tooth gears.
There’s no need to half-cut them, just bevel the teeth on one side of the gear and it will fit inside the 2.75" wheel. Half cutting is just unnecessary effort.