The silicone hoseTags : coolant-system
When I think back to when I was first introduced to competitive motorsport - rather more years ago now than I care to remember - I wince now at some the things we used to do. At the time, it was very much a 'make do and mend' attitude, and the amateur weekend designer/racer would often spend more of his time seeking that certain part of the right size or shape to support his backyard vehicle build.
A common part might be, say, a top or bottom radiator hose. If money was not a problem, a motor accessory shop or tame vehicle parts store could be the first port of call, for in those days they would often have bins full of suitable hoses and one could spend hours looking for that exact shape and diameter. When money was tight or even non-existent, the vehicle breaker was the place where, for a few coins, a radiator hose could be acquired which when hacked about would do the job, albeit not altogether perfectly.
In those far-off days little thought was given to the material or its suitability, but we were young then and oblivious to the potential dangers. And, let's face it, it was a wonder that more of us weren't hurt more - I for one remember scalding-hot water spurting out all over me at one time from an inadequate hose.
These days of course we live in enlightened times, and the practices of the past are quite rightly no longer tolerated. As well as that, we now have a choice of a number of companies supplying a full range of pre-formed hoses for various applications and of all shapes and diameters at competitive prices. No longer is there an excuse therefore to make do and mend.
But not only can these hoses be made to fit more or less any application, the superiority of their materials are an added bonus. The most significant of these is silicone rubber, which when reinforced with woven polyester fabric can cater for just about any automotive application you can think of. Silicone rubbers, you see, have a natural resistance to extremes of temperature - as much as 300-plus C under certain conditions and down to -100 C at other times. Furthermore, the elastomer retains a far higher tensile strength and elongation at rupture, as well as better resistance to tearing than any of the other materials frequently found.
But in vehicle engine compartments it is not normally about strength or compression 'set', or indeed even the material's exceptional electrical insulating properties. In the real world the main concern - on top of things like resistance to the latest lubricant formulations or organic acid coolant additive technology, or indeed the effect of various solvents - is its general resistance to catching fire.
In the wider world, silicon elastomers are often used in applications where the risk of fire cannot be ignored. In some industries, if hoses have to used at all then silicon elastomers may be one of those technologies allowed. The reasons for this are very simple - silica-based inorganic compounds are less easy to ignite and the non-flammable silicon forms a protective barrier on exposure to flame. When that flame is removed the substance extinguishes itself and enables the fire to be put out quickly and safely, minimising the risk of a major conflagration.
So they may be readily available in all shapes and sizes and for all automotive applications but most of all, a shiny gloss cellulose finish of blue, red or even yellow will make any engine installation an attractive prospect.
Fig. 1 - A silicon hose makes an attractive engine bay finish
Written by John Coxon