Legality of pnumatic ball launcher systems

[Tytus Gerrish]

I've been reading about the different ways to create devices based on pneumatic cylinders to launch the ball. i would like to explore a few of the methods and rules and question what first is going to say about some the pneumatic rules issues

First i would like to question the use of pneumatic cylinders as Gas springs witch are allowed by R87. this means plugging an end of a pneumatic cylinder and using the trapped air as a working gas. and by some means cocking this mechanism either by a winching it in with a motor, or manually cocking the device by hand before a match.

 <R87> .For the purposes of the FIRST competition, closed-loop pneumatic (gas) shocks are not considered pneumatic devices, and are permitted additions to the ROBOT.

the question here is do you consider a pneumatic piston with an end plugged a gas spring?

if the device described above is considered a pneumatic component then the cocking action of this device would be compressing air and is therefore in violation of R93

<R93> Compressed air for the pneumatic system on the ROBOT must be provided by the Thomas Industries compressor provided in the 2008 Kit Of Parts. Compressed air shall not come from any other source.

Also a device like this could be capable of generating more than 60psi witch would be a violation of R98 but only if you considered that sealed in air as "working" air pressure. perhaps this should be elaborated on further

however if this device is cocked by pressurizing the opposing side of the cylinder to a greater pressure with your pneumatic system, then venting that pressure to release the device. Is this trapped air considered part of the “Working” air pressure described in R89?

<R98> “Working” air pressure on the ROBOT must be no greater than 60psi. All working air must be provided through the Norgen adjustable pressure regulator, and all other pneumatic components must be downstream from this regulator. A pressure gauge must be placed adjacent to the pressure regulator and display the downstream pressure.

this is one of the reasons that the regulator provided in the kit is required. it is designed to vent gas to the atmosphere when the working side exceeds the set value

additionally if this device were considered a pneumatic component it would need all the Required equipment dump valve, pressure gauge, etc...

i suppose if a cylinder were plunged in the opposite fashion in order to pull a vacuum while cocked, this would not apply to R93 as pneumatic pressure is not being generated, rather a vacuum is being pulled in the empty space and then the device is allowed due to R87

<R87> For the purposes of the FIRST competition, a device that creates a vacuum is not considered to be a pneumatic device and is allowed. This includes, but is not limited to, venturi-type vacuum generators and off-the-shelf vacuum devices (as long as they are powered by provided or permitted motors).

no matter the ruling i above all concerned with safety and then secondly with teams allowance to accomplish what they desired for their machines. I always Hate sending teams away from the inspection table with the mandate "make your robot legal so you can play"

[MasterMkanik]

I think they are talking about gas shocks, like used to hold up hatchback trunk lids and such, not an actuall cylinder. we used a pair of shocks last year, they are completly closed and dont require air input or output, it just compresses ther Air allready inside.

[dlavery]

Tytus-

Excellent points. The FIRST Q&A system has addressed many of the concerns that you raise. Those that are considering a pneumatic launch system would be wise to familiarize themselves with these Q&A answers. Your concern about making sure a team with such a system is prepared and not surprised when they get to the inspection table is right on target.

The topic of using pneumatic cylinders as gas springs is addressed in this Q&A answer (you can't do it). Mechanically compressing the cylinder to create a working pressure higher than 60 psi is addressed in this Q&A answer (you can't do it). And the idea of mechanically restraining a pressurized cylinder and rapidly releasing it to launch a Trackball is addressed in this Q&A answer (you can do it under certain conditions).

-dave


.

[JesseK]

I'm curious as to if you can depressurize an end of the cyllinder such that it's actually less than atmospheric pressure, theoretically achieving the same results but also technically within legality of all of the Q&A answers. Depressurisation would be achieved in a similar (but reversed) manner to what's described.

[jskene]

Update #6 says that the rules say that a solenoid must be connected to a cylinder with 1/8" tubing. I can find no reference to this in the rules.

We were planning to connect the valve directly to the cylinder, using "off the shelf" 125 psi fittings, as permitted in rule R88.

Is anyone aware of any rule in section 8.3.9 that would preclude this?

Also, we are planning to store air in the Clippard tanks downstream of the regulator, at 60 PSI, instead of 120. Is anyone aware of any rule that would preclude this?

[Tytus Gerrish]

Originally Posted by JesseK

I'm curious as to if you can depressurize an end of the cyllinder such that it's actually less than atmospheric pressure, theoretically achieving the same results but also technically within legality of all of the Q&A answers. Depressurisation would be achieved in a similar (but reversed) manner to what's described.

My thoughts exactly. is that allowed through R87?

however i haven't tried this for myself yet and weather or not it works is still a mystery to me. prehaps someone else could tell us about their oun experment in this thread.

Originally Posted by Tytus Gerrish

i suppose if a cylinder were plunged in the opposite fashion in order to pull a vacuum while cocked, this would not apply to R93 as pneumatic pressure is not being generated, rather a vacuum is being pulled in the empty space and then the device is allowed due to R87

[EricH]

Originally Posted by jskene

Also, we are planning to store air in the Clippard tanks downstream of the regulator, at 60 PSI, instead of 120. Is anyone aware of any rule that would preclude this?

Nope. You will get less air in the system, but that is your choice.

[IndySam]

Originally Posted by jskene

Also, we are planning to store air in the Clippard tanks downstream of the regulator, at 60 PSI, instead of 120. Is anyone aware of any rule that would preclude this?

Question, why would you want to do this? I can't think of any advantage to it.

[JesseK]

It would seem that a tank that simply stores air would allow for faster response times if it's closer to the target consumer than all other consumers, espeically during times of large air consumption. Not sure of how much performance gain there is overall, but if the target consumer is short stroke and/or timing critical I can imagine it's a big enough difference.

[IndySam]

Originally Posted by JesseK

It would seem that a tank that simply stores air would allow for faster response times if it's closer to the target consumer than all other consumers, espeically during times of large air consumption. Not sure of how much performance gain there is overall, but if the target consumer is short stroke and/or timing critical I can imagine it's a big enough difference.

No, the limit is the size of the pneumatic line. You would be much better served by having a tank at 120 back stream. You could buy a second regulator and run the one important cylinder off of that.

[jskene]

Thanks for your replies regarding the legality of using the Clippard tanks for low pressure storage.

How about the first question?:

Update #6 says that the rules say that a solenoid must be connected to a cylinder with 1/8" tubing. I can find no reference to this in the rules.

We were planning to connect the valve directly to the cylinder, using "off the shelf" 125 psi fittings, as permitted in rule R88. Is this legal?

[EricH]

Originally Posted by jskene

Thanks for your replies regarding the legality of using the Clippard tanks for low pressure storage.

How about the first question?:

Update #6 says that the rules say that a solenoid must be connected to a cylinder with 1/8" tubing. I can find no reference to this in the rules.

We were planning to connect the valve directly to the cylinder, using "off the shelf" 125 psi fittings, as permitted in rule R88. Is this legal?

The applicable rules are:

<R87> Additional pneumatic system items specifically permitted on 2008 FRC ROBOTS include:
[...]
 Additional 0.160” inch inside diameter pneumatic tubing functionally equivalent to that provided in the Kit Of Parts, with the pressure rating clearly factory-printed on the exterior of the tubing (note: alternate tubing colors are acceptable).
[...]
<R88> There is no limit to the number of solenoid valves, pressure regulators, pressure gauges, and connecting fittings that may be used on the ROBOT. All such devices must be “off the shelf” pneumatic devices rated by their manufacturers for pressure of at least 125psi.

I don't see anything against this. (I am also not on the GDC.)

[SteveJanesch]

I'd think the main disadvantage in using a vacuum in a cylinder for energy storage is that you only get -15 psi (negative one atmosphere) pulling pressure at best, or a quarter of the pushing pressure available with a +60 psi line. You just can't pump it down any more than that.

Steve