Pneumatic Rotary Vane Actuators?

FIRST General Forum
1

Hello, fellow FRCers! I hope that this build season is finding you well and that you are in good position to finish your robots on time.

Our team was considering using a pneumatic rotary vane actuator on our robot (for reasons that will be revealed when we do our showcase thread). This is a part that has been legal in previous seasons, but the updated [R78] throws its legality into some doubt.

Here is an example of the kind of part we’re talking about:http://www.mcmaster.com/#6508K142

A previous question in the Q&A, Q186, asked:

Is a pnuematic rotary cylinder the same as a pnuematic cylinder?

and received the answer:

For the purposes of FRC, yes.

Unfortunately, the question was rather poorly worded. There is no such thing as a “pneumatic rotary cylinder”–there are “pneumatic rotary actuators” that are cylindrical, but “pneumatic rotary cylinder” is not the correct term. Furthermore, there are two kinds of pneumatic rotary actuators: some vane type, others piston type. We think that the answer to [Q186] can be interpreted to mean that our part is legal, but we wanted to make absolutely sure.

I know what you’re thinking. “Why ask Delphi? The Q&A is faster and more reliable!” Good idea, but we thought of that. We attempted to register our team’s account with the Q&A, but it’s been five days since the registration and we are still not allowed to submit any questions. Clicking on the “Team Questions” button on the Quextit site yields the message “your request is in pending state”. Effectively, we cannot submit our question.

If you have a working Q&A account, we would be extremely grateful if you would submit the following question the the Q&A using said account.

The response to Q186 clarifies that a “pneumatic rotary cylinder” is a pneumatic cylinder under R78. There are multiple types of rotary pneumatic actuators. Are rotary vane actuators such as the following (http://www.mcmaster.com/#6508K142) considered legal pneumatic cylinders under R78?

If you are willing to submit the question, please do so, then post a message in this thread notifying teams that you have submitted the question (to avoid double-submissions) and identifying the question number (so that teams can follow it).

Thank you very much for your help. Good luck with the rest of build season!

2

You should have a password in TIMS. That should be all you need.

3

You are correct that the term “pneumatic rotary cylinder” isn’t the most descriptive. But, having worked with pneumatics for years, this phrase brings to mind two types of pneumatic actuators. The first is a rotary actuator where a cylinder drives a rack gear, which is mated to a circular gear connected to an output shaft or stage. The output axis is perpendicular to the axis of the cylinder, and has only rotary motion. These are often used to actuate a rotary joint through 90 or 180 degrees.

The second type has a pneumatic cylinder that drives a rotary cam through a coarse pitch helical track. The output shaft is coaxial with the cylinder and moves both axially and rotationally, usually 90 degrees. These are usually used as hold down clamps in automation, and especially fixturing applications.

Both types are shown in a google image search for “pneumatic rotary cylinder”. If I were an inspector, I would allow both types as allowed under the rules, even without the clarifying QA question. Similarly to how any transmission mechanism or gearbox is legal, as long as it is driven by a legal motor, as long as the device is powered by a pressure cylinder, I would consider the form of the resultant motion to be irrelevant.

It sounds like what you are asking about is commonly referred to as an “air motor”. These commonly convert air flow into continuous rotary motion. The most familiar examples of air motors would be those in dentist’s hand pieces or some air powered hand tools. There is no way I would include air motors within the definition of “pneumatic rotary cylinder”.

4

To extend:

Only official FRC team accounts may submit questions to the Q&A; other accounts are not allowed to do so. The password for the team account is in your TIMS account; the username is FRC####. See here for more details.

5

Thank you all for your help.

6