Pneumatic Proportional Control Valve

[DavisDad]

Our team is prototyping a pneumatically driven catapult shooter. We're copying the design generously shared by team 2073 (see this thread: 2073 Pneumatic Catapult

We'd like to control the cylinder supply pressure with a proportional control valve (aka I/P). Has anyone done this.

In the past, I've modified a regulator by changing the diaphragm spring and replacing screw with driver rod: illegal for FRC. Here's an idea of how to adjust a regulator via a servo without directly modifying the regulator (see pic below). Would this be allowed?

[magnets]

I've seen a team do this in the past. I have no clue if it was legal then, or if it legal now. However, I'm concerned that a servo doesn't have enough torque to turn the knob on the regulator. The team that did this in the past used one of the mabuchi motors (wow, that was a long time ago) with a huge pulley reduction.

[DavisDad]

Originally Posted by magnets

I've seen a team do this in the past. I have no clue if it was legal then, or if it legal now. However, I'm concerned that a servo doesn't have enough torque to turn the knob on the regulator. The team that did this in the past used one of the mabuchi motors (wow, that was a long time ago) with a huge pulley reduction.

Roger that on the torque power. Will probably require a gear-motor. Just wanted to show in a quick sketch...

Thanks for the reply; much appreciated!

[Tem1514 Mentor]

Aside from needing a more powerfully adjuster as the primary 60 psi I would call it as a real no-no since you have no way to prove the maximum 60 psi working pressure is controlled by sensor feed back.

If this was another regulator AFTER the main 60 psi regulator then go for it.

[DavisDad]

Originally Posted by Tem1514 Mentor

Aside from needing a more powerfully adjuster as the primary 60 psi I would call it as a real no-no since you have no way to prove the maximum 60 psi working pressure is controlled by sensor feed back.

If this was another regulator AFTER the main 60 psi regulator then go for it.

Right- pneumatics would be downstream of regulation set-up:

Compressor --> Safety Relief (125 psi) --> Pressure Switch (124 psi) --> Reservoir tank(s) --> Regulator (60 psi) --> Solenoid --> Prop. Control Assembly --> Accumulator --> Cylinder

Thanks for the input.

[Gdeaver]

I wanted to do this some for some time. There are other regulators that have a t handle and do not require as much force at the almost full pressure setting. One I looked at was 10 turns for the whole range. Almost could use a 10 turn pot for positioning. Never went further. There are commercial electronic regulators that would do this. Price is the biggest problem.

[DavisDad]

Originally Posted by Gdeaver

...There are commercial electronic regulators that would do this. Price is the biggest problem.

HVAC control valve "I/Ps" aka "V/Ps" are cheap on eBay but probably not legal: link -->

It may be possible to create a feedback control loop by adding a pressure transducer and pulsing the legal solenoid.