Spring loaded Pneumatic piston

[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.

[Al Skierkiewicz]

Originally Posted by Tristan Lall

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.

Tristan,
I was thinking along the same lines but this does need a little more research.

For those reading this thread, I know stored energy is going to a big concern during inspections. Springs, surgical tubing and pneumatics are all going to be used to direct the ball. Safety in the use of these devices is going to be of prime importance. Be sure you have the ability to release energy before leaving the field as in previous years and follow this...

<R01> Energy used by FRC ROBOTS, (i.e., stored at the start of a MATCH), shall come only from the following sources:
A. Electrical energy derived from the onboard 12V battery (see Rule <R40> for specifications and further details).
B. Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI in no more than four Clippard Instruments tanks. Extraneous lengths of pneumatic tubing shall not be used to increase the storage capacity of the air storage system.
C. A change in the altitude of the ROBOT center of gravity.
D. Storage achieved by deformation of ROBOT parts.

Teams must be very careful when incorporating springs or other items to store energy on their ROBOT by means of part or material deformation. A ROBOT may be rejected at inspection if, in the judgment of the inspector, such items are unsafe

[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.

[BJT]

the spring in these cylinders is usually very light. I was looking at a 1.5 inch bore single acting spring return cylinder and the specs said the spring had only about 6 pounds of force. I think the spring is always used to return a single acting cylinder, not to assist its push.

[Team2191]

Originally Posted by BJT

the spring in these cylinders is usually very light. I was looking at a 1.5 inch bore single acting spring return cylinder and the specs said the spring had only about 6 pounds of force. I think the spring is always used to return a single acting cylinder, not to assist its push.

if we were to use a spring loaded cylinder we would use the 2" bore with a 4" stroke and a front spring bias. this accomplishes the extra force needed and the extra velocity. the spring described in this system has 30 lbs. force by itself. with the pneumatics added this will be increased more. btw this is offered by clippard

[DonRotolo]

Originally Posted by Al Skierkiewicz

If these types of cylinders are used, some part of the robot can move when the valve is opened.

No different than if I tied some latex surgical tubing to the end of the cylinder rod, which would retract it if air pressure was released.

However, your point about safety is an excellent one: A gentle movement to a safe position with air release is one thing, but I can imagine some violent stuff that can happen when air is released (or lost) which could be quite dangerous and must be avoided.

[joeweber]

We are using a 2x4 piston (cylinder) with added springs to move a hamer type kicker. It would not kick fast until we removed the cylinder. We found that the exhause valve was not allowing the air to escape fast enough. Would a different valve work ar maybe a larger hose and valve? We were thinking of doubling up on the ehaust valve and hose to allow more air flow.

[DonRotolo]

Originally Posted by joeweber

maybe a larger hose and valve?

It may be helpful to peruse the rules.

<R72> In addition to the items included in the KOP, pneumatic system items specifically permitted on 2010 FRC ROBOTS include the following items. All included items must be “off the shelf” pneumatic devices rated by their manufacturers for pressure of at least 125psi, and used in
their original, unaltered condition (except as required for assembly with other components).
<snip>
C. Solenoid valves. All such valves must have a maximum ⅛” NPT port diameter, and a maximum Cv of 0.32 (if non-KOP valves are used, the team will be required to provide part documentation validating that the valves meet these constraints).
<snip>
E. Additional 0.160” inch inside diameter pneumatic tubing functionally equivalent to that provided in the KOP, with the pressure rating clearly factory-printed on the exterior of the tubing (note: alternate tubing colors are acceptable).