How do you shift??

[Mike Nawrot]

I've started prototyping a 2-speed gear box for next year, which i may expand in different directions, be it more speeds, or brakes, or other functions, it doesn't matter. I need to know how most teams decided to shift gears. Obviously, the most popular solution is a pneumatic cylinder, but I am looking for an alternative, because I do not find the need for pneumatics if they are not being used anywhere else on the robot. I've looked at electronic linear solenoids as a replacement, and i found one type that has the equivalent force of a 7/16 bore pneumatic cylinder at 60 psi. Two problems. 1: the model i was looking at can only be on continuously for 1 minute at a time, which may be an issue if we're in low or high gear for more than a minute at a time, and 2: I'm not sure if linear solenoids are legal in FRC. I will continue researching various linear solenoids, but in the mean time, i would like to keep an open mind about shifting mechanisms. Also, if you find any useful information about linear solenoids, please leave me a link. Thanks.

[Alan Anderson]

Solenoids have been consistently put in the "not legal" slot for many years.

Consider using a servo, or a motor driving a cam, or a geneva wheel connected to a rack and pinion.

[Mike Nawrot]

Hmmmmmm.... thats very unfortunate.... Out of curiosity, why are they illegal? I guess I'll have to look at the servo idea.... Of course, another question, do you really need alot of force to hold a dog gear in place? If it is a low force application, which I am pretty sure it is (if you're hit hard enough, you may stall the motors.... which is next to impossible with CIMs... from what i understand..... but the force on the dog gear is perpendicular to the motion of the shifting mechanism... so not much force can be applied) I can easily shift the dog gear with a servo..... Although I easily solved the problem, your suggestion of a servo made me think, so thank you. But i am interested in what other things people will say. Thank you, again. Time to update some CAD drawings.......

[lukevanoort]

Why not attempt to make something that doesn't shift in the normal sense, like a CCT (Crazy Chicken Transmission - A CVT style device the Thunderchickens thought up)?