How fast is too fast?

So when we are designing our drive train and we usually never stray away from our tank drive we always want to know how fast is too fast. Last year our drive train was 6 direct drive turbo 4" omni wheels which was roughly around 3.5ft/s. This year being no defense and pushing matches we want to go faster around 1ft/s now using JVN design calculator for a single speed drive train we came up with a way to do this using 4 motors per side. Is this doable we want to ask the veteran teams here on the forum. Attached is a screenshot of the excel sheet detailing all the info.

Well, I would say Nothing But Net have a lot of control so you could aim better. But this year I don’t think you a whole lot. If you went 3.5 ft/s and did well, I think if you have a good driver you could easily do 5 ft/s and do amazingly, but I would go above 5.5 ft/s.

So you wouldnt go above 5 or 6 ft/s I was thinking going higher cause you can always go lower in programming. Yeah our drivers are all COD fans and play on high sensitivity so transitioning that to a super fast robot was not hard.

Ok then your fine. But me myself wouldn’t want to go above 7.5.

A senior from my school designed a vex car. Geared 625:1 with twelve motors. That my friend, is too fast

Do you have video. :slight_smile:


Sadly no. They decide to take it apart after they shattered almost every 60 tooth geared we owned and twisted an axle around at least a dozen times

Oh, I remember we had a robot last year at our school that was a simple arm, but when we took it apart the axle was like a screw.

Honestly, I would say that if you are using 4 motors, the fastest you should make it is the motors being high speed.
If you were using 6 motors, I would suggest no high speed internal gearing, and a 2:1 gear ratio for them.
If you were using 8 motors(Which some do), I would suggest having a 3:1 gear ratio.

With 6 you could easily go turbo internals direct drive

Yeah, good point! :slight_smile:

With 6 motors you could safely go 1:4.5 on 3.25" wheels, but 1:3 with only 4. I would stay less than or equal to 1:4 only because the game objects are designed like caltrops, which were used to stop tanks, and they don’t slide easy. You want some pushing ability without stalling, and games like toss-up didn’t need such crazy speeds to be competitive.

You should only build a drivetrain as fast as you can control.
During tossup, the VEXU team OYES had 3:1 ratio drivetrain on 4" wheels.
Even though their driver had many years of world class driving experience, they had trouble maintaining their skills.

(The robot starting in the hanging zone.)

I personally can’t confirm since I haven’t received my game elements yet, but other posters remarked that there wasn’t a whole lot of friction between the stars and the mat. The stars seem to have a kind of “finish” that makes it easy to slide something underneath them.

I don’t think pushing should be a significant problem, though I feel you should always have a “margin of error” to ensure that your robot doesn’t stall in a match.

No you cant. I built a 1:4.8 on 3.25 wheels and it only ran on 8 motors. With 4 you can only go a Max of about 1:2

4.8:1 requires more than 6 motors on 3.25" wheels. When we had a 14 pound robot for NbN, our drive stalled at 4.8:1 but worked fine at 3.2:1 with 6 motors.

link text So here is our drivetrain from last year it was 6 turbo motors direct driven to 4" omnis and it was fast around 3.5ft/s. This year we have settled on a 6 motor drive train that is turbo geared then we will have it be 3:1 over all should be 10 ft/s free speed but around 8.25 ft/s adjusted the biggest thing as someone said earlier is having someone who can handle it. Our design is a slip gear catapult with no intake and a high hanger that is still being worked on but will be very unique

You just gotta go fast. Cause Sanic

We were experimenting with drive trains in the NBN season. One design, was a six motor (internally turbo), externally geared 5:1 (I think) on 4" wheels. That thing was so fast. If you were to stop it, it would drift 3 feet-ish. I feel that the only thing stopping how fast you can go, will be your driver, and of course the stalling problems.