Spring loaded Pneumatic piston

[Team2191]

ive been looking for a solution to our kicker problem and i looked into clippards products for the solution. they offer a pneumatic piston with a spring insdie which would help with the power and initial speed of the piston. are they allowed?

[Peter Matteson]

Traditionally we have not been allowed to use them but I have to say I don't see any rule against it this year.

Normally the GDC's round about way to get prevent use of spring return pistons is that you can only use cylinders equivalent to the free order form parts from Bimba which did not include spring return, bore size and stroke. This year <R73 D> only has a maximum bore and stroke.

I'm actually surprised they opened it up this way finally.

Edit: I guarentee that it is asked at least 6 times in the official Q&A anyway because this question is asked every year.

[IndySam]

Originally Posted by Peter Matteson

Traditionally we have not been allowed to use them but I have to say I don't see any rule against it this year.

Normally the GDC's round about way to get prevent use of spring return pistons is that you can only use cylinders equivalent to the free order form parts from Bimba which did not include spring return, bore size and stroke. This year <R73 D> only has a maximum bore and stroke.

I'm actually surprised they opened it up this way finally.

Edit: I guarentee that it is asked at least 6 times in the official Q&A anyway because this question is asked every year.

They opened it up last year. Teams did use spring return cylinders. Please don't call them pistons.

The problem with spring return cylinders is you are stuck at the return rate the manufacturer gives you (unless you find someone who will make custom ones.). It's not hard to use a little surgical tubing and make your own spring return where you decide how much spring to use.

[Al Skierkiewicz]

If you are talking gas shocks then those were allowed last year. If you are talking a spring inside a pneumatic piston that is connected to the pneumatics system that is another thing. I do not remember that something like that was allowed last year. From this year's rules
R72
I. For the purposes of the FIRST competition, closed-loop pneumatic (gas) shocks are not considered pneumatic devices, and are not subject to the pneumatic rules (although they must still satisfy all other appropriate rules).

[Team2191]

No not the gas shocks. A pneumatic cylinder with a spring bias forward or backward.

[Al Skierkiewicz]

Do you have a part number and supplier?

[Jared Russell]

Al:

McMaster sells spring loaded air cylinders. See: http://www.mcmaster.com/#pneumatic-cylinders/=5dun1p

The single acting, spring-loaded cylinders look to me to meet all of the pneumatic rules this year (assuming the bore and stroke are within the limits in the manual, and the cylinder is rated for sufficient pressure).

In my opinion, the main advantage of these cylinders (besides simplicity and one less air connection) is that you are guaranteed that they will return to a known position in the event of an air loss event. In the case of a two-speed, air-powered, dog-shifted transmission, this means that you will always be in gear even if you lose air pressure.

[Al Skierkiewicz]

Thinking.....
This raises some safety issues. Does anyone have other types they are thinking of using for a larger data sample?

[Jared Russell]

Originally Posted by Al Skierkiewicz

Thinking.....
This raises some safety issues. Does anyone have other types they are thinking of using for a larger data sample?

Al,

Could you elaborate on what safety issues you foresee with spring loaded cylinders of the type I posted? If anything, I could see them being safer than traditional double acting cylinders. (In extension, the total force is reduced by the amount of spring force; in contraction, only the spring is providing force).

[Al Skierkiewicz]

Jared,
Although there are no rules that prevent operation without power, I have never liked robots to move when the system is vented. If these types of cylinders are used, some part of the robot can move when the valve is opened.

A personal wish for safety.

[Tristan Lall]

As of last season, the pneumatic cylinder rules were greatly relaxed—the best robot rule change in a while—and seem to pretty clearly permit all sorts of strange and wonderful cylinders. (Your stroke, diameter and pressure rating are still restricted.)

Since the GDC didn't say (in this year's or last year's rules) that single-action cylinders were distinct from double-action models, I don't think there's any issue with using the manufacturer's definition of a cylinder (which happens to be accepted in industrial practice). I therefore don't think there's any point in asking this one on the Q&A.

Of course, the robot must still satisfy safety rules with regard to energy storage, and the spring in a single-action cylinder will be inspected as such. That shouldn't be a major obstacle, however—lots of teams use springs.

[JesseK]

Originally Posted by Al Skierkiewicz

Jared,
Although there are no rules that prevent operation without power, I have never liked robots to move when the system is vented. If these types of cylinders are used, some part of the robot can move when the valve is opened.

A personal wish for safety.

It's about the same effect as a robot with a single solenoid valve when the robot turns off.