Need general drive train expertise

[EricH]

Originally Posted by jimmers205

Also, more general questions:
How do different shifters work?
How does the pneumatics work with the gearbox?

Originally Posted by Richard.Varone

My team only has experience with the Dog shifters so I can't really comment on Dog vs Ball.

Two aspects of the same question. One has to do with the actuation, one with the actual shifting.

Dog shifters have small "dog" that is designed to engage either of two gears that it is located between. Moving the dog out engages the outer gear, moving it in engages the inner gear. The gears have some form of machining that the dog can engage. The upside of this is that anybody can do it with fairly basic machining resources (a mill). The downside is that it can take a split-second longer than a ball shifter to shift, and sometimes a lot of force.

Ball shifters work like ball-lock pins: small balls will pop out into small holes in the right gear when a shaft is moved to the right spot. They're a little newer to widespread FRC use than dog shifters.

Now, on to the pneumatics. Or, should you choose to be so brave, the servo. You'll notice that both types of shifter have something moving in and out, often inside an axle. A short-throw pneumatic cylinder is connected directly to that pin/shaft/whatever you want to call it, and then powered. Move the piston one way, you get low gear. Move it the other way for high. You can use a servo, but it takes longer and you'll want more than one servo per gearbox.


You'll notice that I make no recommendation as to type of gearbox. That's deliberate. First, I have minimal experience with ball shifters; second, some things are a personal preference. Which is actually better is, therefore, left as an exercise for each reader. (Though I do recommend pneumatics, specifically pancake cylinders, over servos for shifting.)