Pneumatic “lever” machine

by Pip de Pulford, Simone Forgia, Claudio Santoro

Pneumatic “lever” machine - drawing by Michael van Loozen

Drawing of the pneumatic "lever" group by Michael van Loozen

When it comes to espresso machines, the world of enthusiasts is often divided into two categories; there are those who prefer pump machines for their ease of use requiring only the switching of a button to start extraction, and those who prefer lever machines for their mechanical reliability. The latter category is further divided into those who prefer direct levers for real-time pressure control and those who prefer spring levers for greater repeatability between shots. So far, however, it has not been possible to have all these features in one machine but this is what the owner of Hyper Hyper Coffee in Nowra, Australia, has tried to develop.

It all started when Pip de Pulford decided to leave his glass-painting workshop to start a new adventure with coffee roasting. His mother nostalgically told him that no one could make coffee like the Italian baristas did in the 1960s; it tasted different from today's modern coffees, the cafés and the cups smelled like wet coats. Pip then started researching and found that the machines they used in those years were probably lever machines and the smell and dampness that had remained so impressed in his mother's mind was presumably from the coal gas that was burning and heating the cups. Pip then began to create blends with a percentage of Robusta and roasted them until they had a slightly oily "full city" colour. He also bought a Faema President produced in 1962, changed the plug on its arrival and has never used any other machine since.

Hyper Hyper now has a total of 6 Faema Presidents on his establishment; 4 with 2 groups, 1 with 3 groups and 1 with 1 group, all produced between 1962-1965 and "churning out" over 270 kg of coffee per week reminiscent of that sold in the old Italian coffee shops. To support this extensive use and preserve the physical health of his collaborators, the lever system of these machines was replaced by a mechanism specially designed by Pip that uses pneumatic pressure instead of manual effort, while remaining completely analogue. To do this, the spring inside the grouphead was removed and a unit with a second piston inside (connected to the main piston in the grouphead) was placed in the part where there was originally the fulcrum linking the lever arm and the piston. Two tubes, one above and one below the secondary piston, carry the pressurised air required to operate the system. The air passing through the tubes is loaded by a compressor set at approximately 5 bars that is placed externally in another room. When you want to lower the piston and apply the pressure for extraction, the air is loaded into the pipe above the secondary piston and causes the whole shaft with the two pistons to push down. When, on the other hand, at the beginning or end of the extraction the piston needs to be lifted, then air is pumped along the tube underneath the secondary piston. The excess air on the opposite side of the piston is discharged through a system of valves from the pipe that is not actively used.

Pneumatic unit developed by Pip

Pneumatic unit developed by Pip

What makes this system fascinating is that the pressure exerted on the water is transmitted by the air, and the latter, being compressible, acts as a buffer, cushioning the impact. In addition, due to its inherent design, the pressure is not applied in a linear manner similar to a traditional pump machine, but follows the same declining pressure profile typical of the lever system. This is because as the piston in the grouphead moves downwards, the void space above it increases and therefore an ever-increasing inflow of air would be required to keep the pressure constant. If, however, the airflow generated by the compressor is kept stable, the piston continues to be pushed downwards but the pressure decreases over time. The speed and pressure with which the volume of air is loaded can therefore be regulated through the force of the compressor and by varying the diameter of the tubes.

The first prototype of this pneumatic unit was made for Pip by an excavator mechanic, who was already familiar with this type of air pistons being commonly used in heavy machinery. To calibrate it, the unit was mounted on one of the two groups of a Faema President, adjusting the air delivery until it was equivalent to that of the original lever system next to it. For convenience and speed of use, the compressor is activated by a little switch located where the lever mechanism was previously connected but a version that can be installed inside the aluminium casing and activated by the original President lever has also been created. It is also interesting to note that since this is a unit mounted externally to the actual grouphead, the machine can be restored to its original state at any time.

Pneumatic unit installed inside the aluminium casing and activated by the original lever

Pneumatic unit installed inside the aluminium casing and activated by the original lever

The story has it that Achille Gaggia came up with the idea of the first lever system while observing the engine of an American army Jeep. Based on this inspiration, he created a grouphead with a piston capable of applying enough pressure to bring to life the espresso as we know it today. Who knows if this other idea coming from the world of excavators might in fact represent the evolution or even be the next revolution in this sector. Will a vehicle once again enlighten the minds of the most visionary coffee connoisseurs?