[Al Skierkiewicz]

Richard,
The two Q&A answers do cover your question. The GDC's response is related to devices that produce movement. The hose expansion produces movement by the introduction of air pressure. The only devices that may do that are defined in R72 as cylinders up to a specific size and rotary actuators.

The last paragraph of section 8.3 gives you a little statement from the GDC that might help.

"In addition, another intent of these rules is to have all energy sources and active actuation systems on the ROBOT (e.g. batteries, compressors, motors, servos, cylinders, and their controllers) drawn from a well-defined set of options. This is to ensure that all teams have access to the same actuation resources, and to ensure that the inspectors are able to accurately assess the legality of a given part."