Just to close the loop as it were lol for inner tube isolation, the reason this DIY technique doesn’t work all that well compared to other techniques IMHO is largely due to the incorrect assumption that isolation is supposed to be "floating on air" whereas real isolation is obtained by the physics of the mass-on-spring behavior of most isolation devices/techniques, where the resonant frequency of the isolation system is equal to the square root of the total spring rate divided by the total mass. The resonant frequency determines the frequency of vibration where the isolation begins. The equation for Fr shows the advantages of high mass and minimizing the number of springs as well as spring rate per spring. That’s how I got the resonant frequency of my Nimbus air spring platform down to about 0.5 Hz (hel-loo!)- my using high mass and a single air spring (!) of the correct geometry and spring rate. A single air spring also allows for much greater horizontal and rotational isolation in addition to vertical isolation.
For air systems, bladders, airsprings, inner tubes, there is what is called a design (based on pressure under the load) for which they behave as true springs. If the air bladders, whatever are not filled enough or filled too much their spring rates will be incorrect. In addition there is the issue of air leakage through the rubber fabric. A much better DIY isolation technique that avoids the pitfalls of inner tubes is bungee cord suspension, a technique that obviously has challenges of its own.
For air systems, bladders, airsprings, inner tubes, there is what is called a design (based on pressure under the load) for which they behave as true springs. If the air bladders, whatever are not filled enough or filled too much their spring rates will be incorrect. In addition there is the issue of air leakage through the rubber fabric. A much better DIY isolation technique that avoids the pitfalls of inner tubes is bungee cord suspension, a technique that obviously has challenges of its own.