It seems reasonable to question why lubrication is so critical—it’s not as if there are huge forces at play in the Echorec memory system—the heads touch the drum lightly with only the merest light pressure, the drum’s rotational speed is relatively slow and the surfaces of the drum and heads are smooth. However, although the heads and drum might appear smooth, polished and mirror-like to the naked eye, they are actually rough and craggy when viewed under a microscope. Tiny peaks called asperities protrude out and scrape against opposing surfaces, causing friction and surface wear. The oil reduces this friction because it acts as a cushion between the microscopic peaks on the head and drum surfaces to prevent them from rapidly wearing each other down. Never doubt, that the drum and head must be kept lubricated with a fine layer oil!
From an initial inspection it can be seen that the Binson oil is a dark orange/brown colour, however the property of colour is totally irrelevant, what is of importance is the oil’s ability to lubricate the drum and heads to reduce frictional wear. The effectiveness of the oil as a lubricant is determined by its viscosity, wetting ability and ability to spread easily over the metal surfaces to which it is applied. Shaking a bottle of Binson oil reveals that it has a relatively low viscosity in comparison to heavy motor oils, which have the consistency of syrup at room temperature. Binson’s original oil appears to have a viscosity somewhere in the region of SAE 10, a grading system developed by the Society of Automotive Engineers, which makes it a light machine oil, something like sewing machine oil.
To confirm that sewing machine oil could be safely used as a substitute without detriment to the machine a quick qualitative test was performed by dropping a droplet of oil onto a clean copper surface. Plate 1 shows that the spreading and wetting of the Binson oil and sewing machine are similar. Out of curiosity the same test was performed with tap water [Plate 2]. Because water has a high surface tension and isn’t attracted to the surface of the metal, it just sits as a droplet rather than spreading out like the oil does.
To summarise, sewing machine oil can be used to lubricate the Echorec memory system and will perform equally well to the original Binson oil formulation. If the heads are tensioned correctly and a fine layer of oil is maintained on the drum surface then the machine will give many decades of trouble-free operation.