[Andy Baker]

All,

I'll post my opinion here about pneumatic vs. servo shifting.

If you have ANY pneumatics on your robot, then you should use the pneumatic shifting setup for 99% of the applications in FIRST Robotics. The only reason that servo shifting is better than pneumatic shifting IF pneumatics are already present is that servo shifting can provide a neutral gear. This seems to be a trivial feature, and therefore I suggest using a pneumatic shifter to anyone who asks me, unless they have no pneumatics on their robot.

Here are the advantages and disadvantages as I see them:

Pneumatic Shifting:
Advantages: 20-25 pound shifting force; very, very fast shifting (under 0.5 sec), will shift while under a pushing or accelerating load, mechanical adjustment available so that dog gear is not bottomed out
Disadvantages: requires a pneumatic system* on the robot, no neutral gear

Servo Shifting:
Advantages: no pneumatic system needed, provides a neutral gear
Disadvantages: weak shifting force (5 lbs), slower shifting (1-1.5 seconds), shift may hang up under a pushing or accelerating load, software adjustment needed to set high and low positions, requires a charged backup battery, wears out servos if the servo is constantly pushing on dog when software is not telling the servo to go to the correct position.

We did not offer a servo shifting solution until 2007, after the 2006 FRC game that required little or no use of pneumatics. We only offered it after MANY teams said that they really wanted a servo solution.

I wish that FIRST would let us use solenoids on FRC robots so that we could use a solenoid instead of a servo to shift.

* - for a pneumatic shifter, an entire pneumatic system is not required. I have run systems that use 2 accumulator tanks and an off-board compressor. These systems can shift for more than 20 times during a match if no other pneumatics are being used on the robot.

For what it's worth....

Andy B.