Drive Train RPM

VEX Robotics Competition Discussion VRC
#1

Hey everyone. My team has just been allowed to start working on our robot after our school loosened restrictions and we are looking to save time so we can catch up with everyone else. We are aware that the only way to find what truly works best for us is testing, but I am wondering what drive train speed seems to be working for everyone so that we can hopefully save a little time. Any help would be great, thank you.

P.S. We have experience in VRC, we are just looking to cut down a little time from testing if possible.

#2

400 rpm is good. A lot of teams are doing 600rpm motors chained down to a 3:2 ratio on 3.25 inch wheels

1 Like
#3

400rpm is much faster than what is reasonable for a fully competitive VRC robot

5 Likes
#4

if you’re really looking to cut down time you could just do direct drive 200 rpm. it’s not very fast, but it’s super simple and there’s not much that can go wrong.

5 Likes
#5

One of the other teams from my school have a robot on 400 and it is very hard to controll. I would not suggest that. You will need a lot of practice for that to be kindof resaonbale. But in my thinking as well chain drives aren’t good with the amount of slop and friction.

#6

I would just suggest 4 inch wheel 200 rpm. That’s always been a good speed for me, at least.

4 Likes
#7

it’s not as bad as you would think

#8

Well I do know how bad it is because as I said another team from our school uses it.

#9

do not use a 400 rpm drive, unless you’re using the very smallest wheels. especially if you don’t know exactly what you’re doing. it will be too fast and way too weak.

2 Likes
#10

400rpm on 325s is nearly uncontrollable, even for veteran teams. Just do 200rpm 1:1 on 4" wheels.

4 Likes
#11

The slop isn’t bad if built well. IMO it’s actually better than some of the drives I have seen that have a geartrain of 5-7 gears if built right. As for speed, 400 on 3.25 = 325 on 4", which does require a lot of practice and commitment to control.

3 Likes
#12

Some common ones I’ve seen are 333 RPM on 3.25" wheels (200 RPM motor geared 5:3) and 257 RPM on 4" wheels (600 RPM motor geared 3:7). Like others have said, going too fast will make your bot difficult to control as well as cause motor overheating

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#13

Also very bad acceleration

#14

Definitely would not reccomend for rookie teams, as many veteran teams struggle with it as well

#15

This is false. If built right, it adequate/good acceleration

#16

my personal favorite drive ratio is 5:3 200 rpm on 3.25" wheels. nice and speedy, but still very controllable and has enough strength for some level of defense.

#17

7:5 on 4" is also good

1 Like
#18

Is that better than the acceleration on the 5:3 3.25. I have never been able to test the way you stated but 5:3 is good

#19

they’re pretty much the same. 7:5 on 4" is 280 rpm, 5:3 on 3.25" is the equivalent of 270 rpm on 4" wheels. so only a 10 rpm difference, probably not noticeable.

#20

Ok because I know the speed is about the same thing but not the acceleration. And techincally that way is more expensive with the motor inserts.