Is a shifting transmission really necessary?

[Andy Baker]

Originally Posted by Jay TenBrink

What are the risks rewards of having a shifting transmission?

Risks: Reliability, robustness, weight, packaging space, cost, complexity, time and energy required, etc.
Rewards: Maximum low end torque / top end speed.

Jay,

Good question.
This thread also discussed the same issue. As I stated in the other thread, we have shifted gears every year since 1999. While you point out the obvious rewards, there are more. Robot driving control and voltage conservation are two major rewards that come from shifting from a high gear to a low gear. These are two benefits that you did not mention.

A robot with 2 speeds can be driven more precisely than one with just a high speed. From my experience, FIRST robot drivers who have 2 speeds to work with can have more control over their robot as opposed to drivers with only a high speed. Also, if a driver wants to move their robot into a tight position, it is easier to do while in a lower gear.

Also, a typical FIRST robot that is geared to go above 9-10 ft/sec gets hot when running multiple matches in an elimination scenario. If a robot is using a 4-motor drive setup, it is good to have a low gear to switch over to, in case motors get hot and circuit breakers begin to trip.

Originally Posted by Jay TenBrink

In 2003 we had a 4 motor system with a robot weighing 115#. This year we weighed 130# and had a 6 motor drive.

I do think that this explains much. The 2003 game was unique in that it did not require much precise positioning, and allowed for less control of robots. The 2004 game required more precision, and I can see why a single-speed, 6 motor drive base was successful.

I still like the 2-speed design. There are good 2-speed designs that are reliable, robust, and lightweight... and they don't cost too much either.

It really does depend on the game. If a game comes around like 2002, a 2-speed will be a hot commodity.

Andy B.