I wanted to reach out to the forum if anyone has good recommendations on the best way to have a faster chassis for this years game. I know gear up the chassis can lead to motor burn outs but wanted to know if there is an optimal solution out there. I have notice team having 257rpm chassis and wanted to know how some are accomplishing this. We are currently using the standard 4 motor direct drive at 200rpm.
There are lots of post about gear trains already. This is one that comes to mind.
However, this late on the season I wouldn’t recommend messing around with drive train speed, unless you have already had state and are prepping for virtual worlds.
The best way to be faster is to have a lighter robot. This year robots are very lightweight (mine is 10.9 lbs), so it’s easy to have a light robot. I have 333 rpm 3.25” omnis, which translates to 4 ft/s. Going faster this year is really about getting lighter, and it’s not too hard to cut off weight. That being said, achieving a higher skills score isn’t about raw speed, so you’re probably better off keeping your slower drive and getting really consistent
Thank you for the link. Virginia has not has their state competition yet it is in about a month. So we are making the best of the time we have.
So the lighter your robot is the higher speed chassis it can support without burning out too quickly. There are a couple of different ways to increase speed. The ratio you mentioned (257) is made by using a 600 rpm motor, and gearing down, 3:7. Some other common ratios are 333 rpm ( 200 cartridges 5:3) and 280 rpm ( 200 cartridges 7:5). Now wheel size also affects speed. The smaller the wheel the slower the bot will travel at the same rpm. Usually, people use 4’’ or 3.25’’ wheels. I use 333 on 3.25’’ which is roughly equivalent to 280 on 4’’.
I would recommend practicing and coding as by changing your drive train you will have to rewrite your auton which can take anywhere between a week to a month.
are you running a 60 to a 36?
Thank you this was exactly what i was looking for
This is not true. It’s a simple matter of doing the math to figure out the ew distance to travel
I have 200 rpm cartridges geared 3:5
Here’s a video of some of my skills runs so you can get an idea
Im pretty sure this end up being closer to 4.7 ft/s.
3.25*pi for circumference, times 333 rpm for inches per minute divided by 12 for feet per min divided by 60 is aprox 4.7 feet per second.
take consideration of friction and weight
I believe it is also possible to get 300 rpm with 3:1 on a 100 rpm motor. Also might want to recategorize this, it’s in IQ.
In theory, yes. However, you are also adding friction with a gear train, and likely moving motors or wheels resulting in a change of the center of mass. You are also decreasing the torque of your wheels which makes them accelerate slower and could lead to wheels slipping at speeds that were fine without the ratio.
While that is true, that’s an easy fix that won’t take over 30 minutes, unless they have a complex auton
wheels slipping at speeds that were fine without the ratio.
Slipping depends on traction, not speed. Simply gearing up a drive for higher speed without changing any other factors should not result in wheel slippage
Slew rate would be helpful in the case of slippage…
This is correct, however, by increasing speed, you are decreasing torque. Traction depends on torque.
Traction has nothing to do with torque. Traction is the friction between the wheels and the ground. You’re not going to start slipping because of gear changes
This is simply untrue. The usable acceleration of a drive system is directly limited by the traction. If you try to accelerate beyond the traction you have, you will slip. Traction is the limit to the amount of relative acceleration the surfaces can handle before slippage.
You are correct however that mr. 9motorgang’s comment
The amount of traction a surface has is not dependent on the torque, but the usable acceleration IS limited by the traction.
A word of warning:
Make sure you build your Drive Train with a general idea of how much you want your bot to weigh. We didn’t take this into consideration and our motors burned out during the state finals!