Bimba Cylinder Dimensions

Hello all!

I have been designing a custom two speed gearbox, and I have a question regarding the dimensions of the bimba cylinders.

What is the total length of this bimba cylinder while fully retracted? Fully extended?

What exactly is the difference between these two bimba cylinders?

Does the latter maintain an extended position when no air is pumped into the cylinder? If so, can the spring-style cylinder be used as a fail safe, in the event that the pneumatic system ruptures or the robot is undergoing a stall load situation?

Thanks everyone!

Go to McMaster and search “air cylinders”

You can select all your options.

One is spring return. You only need to put air in one direction. We have tried these in the past, the issue is that when shifting back in with the spring, the two sides don’t spring right. And most of the time you don’t have enough “spring” to shift under load.

For what its worth and how much air your consuming, your better off with the normal cylinder.


The -R cylinder is a reverse single action cylinder (spring loaded in one direction), the -D is a double action cylinder (no spring).

For total dimensions and more explanations of these cylinders, see the Bimba website (they have CAD models too), and the catalogue.

I’d recommend the one shown at this link.

It’s already used for the supershifter. If your design doesn’t deviate too far from the AM model then it should be a good fit.

If you can’t find the dimensions for this cylinder on the website, pm me and I’ll measure the piston next time i’m in the shop (Saturday).

I was planning on using this exact cylinder. However, I’ve been having problems understanding how the Poofs (254) have used this piston mount interfaced with the cylinder as you listed above to connect to the dog.

Since this piston mount seems to mount directly to the side plate, how does the piston connect to the dog gear? (On the super shifter, there is a big spacing between the face of the cylinder and the rod that connects the dog to the cylinder.

Basically how 254 does it. They use that cylinder and it nose mounts/threads into that piston mount. From there it threads into a cone that pulls the rod that pulls the dog.

The only difference between 254’s and the AM one is that this guy threads into a block while AM’s requires a nut. Both setups do the same thing mechanically.


Hmmm, so as I understand it, their piston mount is firmly attached to the sideplate.

If that is correct, where do they have room to add the “cone” in the gearbox?

I would assume that the cone would have to be on the outside of the gearbox.

The piston mount is attached via standoffs, so the shifter bearing block mounts between it and the sideplate.

Ahh, this makes complete sense now. Just one final question: what is the reasoning for a “cone” shaped bearing block as RC had mentioned?

I’ve taken a look at 973’s bearing block, and they use the exact same cone that has been mentioned here.

Here is a CAD file that should help you design the mount for the cylinder.
I haven’t had a chance to look through it, but I think that it’s the right one.

Not much reason other than weight and aesthetics. The AM one is functionally identical.

There is also the tradeoff in cost versus in house fab time.

Adam, what we did for our first series of gearboxes was reuse the AM shift shaft, block, mount plate, etc… We later switched to our own custom setup.

It may save you time and make the process a lot more painless by reusing his components, and going custom when you feel comfortable doing so.

Alright, what we plan to do is make a custom output shaft, but reuse AM’s dog and shaft assembly.

Thanks for all your input.