Drivetrain Basics

[akeisic]

Originally Posted by Jared341

In general, limiting yourself to 40A before you lose traction is overkill. You almost never need to push against a "wall" for more than a few seconds at a time, in which case you can use a much higher figure (easily 2x as much) before worrying about tripping the breaker.

While it may seem overkill, we definitely we're spinning our wheels pushing for nearly 10 seconds strait this year.

We had a 4 CIM base with 7" diameter wheels and use the AndyMark Super Shifter with the optional gear package.
Low Gear: 30.1:1
High Gear: 7.5:1

I just posted the latest version of our analysis file as it is significantly better then the previous ones. We used it to determine all of our gear ratios: http://www.chiefdelphi.com/media/papers/2292

I also have posted a Drive Train Fundamentals presentation: http://www.chiefdelphi.com/media/papers/2294

Another design consideration is your operating voltage. Your motor power is proportional to the square of your operating voltage. We've started to monitor our voltage during the matches and found it can easily drop below 11V under load (in some cases 7V! [bad battery] ). Hence - much to my dislike as a mechanical guy - we've started to design with a nominal voltage of 11V.