Great question. The ideal internal pressure depends on several factors - the size of the tube or bladder, the number of bladders and the total weight. Design height is the technical term for an airspring height where max isolation is achieved. Design height is a function of air pressure for a given load. However, in terms of sound quality the height and internal pressure can vary. I find a stiffer air tube or bladder or airspring is better than a floppy one. So, the objective is not to have the component “floating on air” as it were but to achieve an optimum mass-on-spring effect, which usually means stiffness is desired. A resonant frequency of 2 to 3 Hz would be a good target. Having said that my guess at inner tube pressure could have been too high, it depends on load. If the load is relatively low then the internal pressure could be low and achieve proper stiffness.
You can measure the Fr by bouncing the component up and down on the air tube and timing the cycles per second. But because there are a lot of variables involved, including how the component is mounted on the air tube, how the air tube itself is mounted, where it’s mounted, etc.
Furthermore, an inner tube is not an ideal geometry. An ideal geometry is low surface area on top and large volume. A long vertical tube would be ideal in terms of geometry but would be very difficult to work with because it would be very floppy. My original Nimbus Platform used a single air spring, which is relatively floppy so the design needed a secondary horizontal sprung system to build up lateral support. The Nimbus airspring was fitted with a large auxiliary air canister to provide a high effective internal volume of the airspring.
You can measure the Fr by bouncing the component up and down on the air tube and timing the cycles per second. But because there are a lot of variables involved, including how the component is mounted on the air tube, how the air tube itself is mounted, where it’s mounted, etc.
Furthermore, an inner tube is not an ideal geometry. An ideal geometry is low surface area on top and large volume. A long vertical tube would be ideal in terms of geometry but would be very difficult to work with because it would be very floppy. My original Nimbus Platform used a single air spring, which is relatively floppy so the design needed a secondary horizontal sprung system to build up lateral support. The Nimbus airspring was fitted with a large auxiliary air canister to provide a high effective internal volume of the airspring.