My reading of the forum and rules have cast a bit of doubt on the answer to this question. Are COTS venturi vacuum pumps allowed to be attached to the pneumatic system. R66 would seem to indicate no but the exceptions below perhaps indicate yes? Clearly vacuum pumps are ok when powered by legal motors, it is the venturi pump attached the pneumatic system I am hoping to clarify.
Rule 66 C:
The following devices are not considered pneumatic devices and are not subject to pneumatic rules (though they must satisfy all other rules): A. a device that creates a vacuum
B. closed-loop COTS pneumatic (gas) shocks
C. air-filled (pneumatic) wheels
I assume the “must satisfy all other rules” clause means you can’t use an electric vacuum pump unless you power it with a legal motor.
We experimented with a large Piab venturi vacuum generator. That worked well, but it’s specs state it requires 3.8 CFM (cubic feet per minute) of air flow. The FRC-legal compressor only puts out .88 CFM.
We found a much smaller Festo venturi (#547707) that also did the job, but still requires 1.8 CFM; about 2X the compressor’s output.
If we use it we’ll need to install quite a few air tanks and pressurise them in the pit before each match. We’ll also figure out a way to run the venturi only when needed and not a second longer.
We also experimented with a cheap small Shop Vac (assuming we’d replace the motor with one approved by FRC). https://www.shopvac.com/images_products/5872411.jpg
It generated a lot of flow, but very little vacuum - about 1/3 what the venturi generators could do. If we went that route we’d need vacuum cups with 3x the surface area.
Thanks for the thoughts Kevin. Mcmaster-Carr sells a venturi pump that is speced at 0.8 cfm, right in the specs of the allowed pneumatic pump. It’s vacuum is 28 in/Hg. It has low air flow but that is likely ok for simple vacuum cups. We’re moving away from the vacuum idea for a variety of reasons but you might want to check this out.