Atmostrack Linear Seal
The linear seal is obviously a critical component.
In Brunel's day, he had to use materials to hand. This meant strips of leather weighted with cast iron.
Local rats greatly appreciated Brunel's gift of gourmet rat food. They were even more appreciative when he seasoned the leather with tallow (which he thought was just to keep it flexible).
But rats weren't Brunel's only problem. With his system the linear seal had to perform over the full length of the drive tube between pumping stations.
Starting with the latter problem, we note that with Atmostrack the linear seal needs to perform only for the section of drive tube that is active. The length of the active section is engineered as a function of the linear seal's ability to seal.
With respect to the former problem, Atmostrack does not expect to become the dearly beloved of rats. (In other words, no, we won't be using leather)
We think an inflatable linear seal will work. An extruded, flexible double tube with a high performance polymer facing (such as Victrex Peek) should do the job.
The pylon connecting the vehicle to the drive tube will be lubricated by an air film and also refrigerated. This will eliminate physical contact between the linear seal facing and the drive pylon and pre-empt any possibility of heat build-up in the pylon. Such heat build-up could damage the linear seal if it was not eliminated in this way.
We believe the linear seal can be extruded as it is installed in the system. This would provide the benefit of a seamless seal and reduce labour and cost.