Last night, I was placing our Clippard order, and realized that we may have an issue with some of our Solenoids.
We have an incredible sponsor who is a pneumatics specialist and not only donated some equipment, but taught us how to use pneumatics on our bot this year. However, we are still stumped by a few things.
R. 84.C. Solenoid valves with a maximum ⅛ in. (nominal, ~3 mm) NPT, BSPP, or BSPT port
diameter or integrated quick connect ¼ in. (nominal, ~6mm) outside diameter tubing
connection,
If we have a Solenoid with 3/8 inch npt ports and 1/4 inch Quick Connectors screwed into them, does this in fact violate this rule?
As a follow up, would that not make the Rookie Fiestos with M7 connectors also not legal?
Or, are we misinterpreting the meaning of integrated?
Also, are mufflers required? I thought I remember reading that somewhere, but cannot find it in the manual now. If they are, where would one find an m7 one? Neither Clippard nor Automation direct seem to have them.
Finally, Is it legal to have a lower pressure working circuit (say 30 psi) in addition to the 60? We may want to lower the pressure of our hatch intake mech.
I’m not sure for the first two questions, but to my knowledge a muffler is not required and it is legal to have a working pressure at anything below 60 psi (though I think the solenoids have trouble actuating below 20).
In addition to lowering the pressure you could also add in a flow restrictor to slow the cylinder actuation speed.
M7 ports don’t violate the rule because M7 is actually smaller than 1/8" NPT. The metric conversion is incorrect and shouldn’t be in the rule book, that is a direct conversion of 1/8" which is not how pipe/fittings nominal sizes work.
The reason for this rule is that a large port size allows for a larger flow size even with 1/4" tubing. The CV can be much higher on 1/4" NPT or 3/8" NPT solenoids.
Mufflers are not required.
Yes you may has as many regulators as you want as long as any additional regulator is down stream from your primary regulator that is set to no higher than 60psi.
The key here is that National Pipe Threads (NPT) are based on the nominal size of the pipe (that is, the airway), whereas M7 is based on a 7mm diameter of the stock into which the threads are cut. 1/8" NPT has a nominal pipe outside diameter of 0.405 inches, which is a bit over 10mm. https://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html
Just wanted to mention, running a second regulator to operate things at a lower pressure actually turns out to be a good idea because it can save alot of air volume.
But another regulator is more cost, more weight, more space claim.
Thank you everyone. This helps a lot. Is there a regulation on the cylinder ports as well? Or, is it legal as long as we interface using 1/4 inch or smaller quick connect pieces?
We have cylinders of various sizes and port configurations, but for each, we have NPT to 1/4 inch or smaller quick connect pieces.
The limit is only on solenoid port sizes, because a larger port will give a higher flow rate, so more air can be delivered at the same time, so more energy transfer which is what FIRST is trying to limit, where the cylinder port sizes will not affect that, unless you are using flow regulators, but even then the force will be the same, only extension rate will be affected.
Thanks, that is what I thought, but wanted to be certain. We have some time before our first event, and left the electrics board and first stage of our pneumatics setup out of the bag. This info will help us a lot as we move forward. We would have needed some changes to pass inspection that may have impacted our climbing mech.
The 1/8 NPT specification is safety driven in that the restriction to volume will prevent physical injury with larger diameter cylinders. The reaction time should be slower allowing a person to move before a large cylinder has time to fully move. The Cv specification was dropped as it was redundant to the port size.