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Gaskets 2
Sealing substances are divided into liquids and solids. If the solid seal (gasket), made e.g., from paper, cork or also rubber, is no longer available as a spare part, it can mostly be cut out from a standard sheet by hand.
Asbestos is definitely taboo.
If two metallic surfaces lie plane to each other, only a liquid joining compound is possible. As an example, we'll take the divided gearbox housings or those of the crankshafts in boxer engines. In these cases, a solid
gasket is not possible, because it would influence the tight seating of the bearings.
Indeed, in most cases a sealing compound of some sort has to be used, because plane surfaces only appear to be perfectly flat. Under a microscope one can see what appears to be a landscape of craters and hills,
and this presents no obstacles for liquid substances like oil. Sometimes there are even miniscule blowholes in cast light-metals, the tiny openings can't be seen but oil still leaks through, the hotter the oil, the sooner it
will leak out.
Heat could be a fitting key-word when choosing a sealing compound, one must take the permissible temperature into consideration. Furthermore, in the event of any further repairs, it is important to know whether the
sealing compounds will harden out or not. Of course, another important point is, how long will it take for the compound to dry out or to harden. The materials on offer for the motor vehicle field are generally applicable for
all the respective liquids like oil and also for coolant-additives.
Apart from the filling of surface cavities, the compounds also have another asset, which may be even more important. This is all about the expansion coefficients of the various materials used, e.g., in the engine. A
sheet-metal covering on a heat intensive component made of aluminium, requires an elastic sealing compound. Hereby, the shearing-strength of the compound is important.
Silicone is sometimes frowned upon by builders, because it is often used by laymen to hide a botch-up or, for the same reason, to justify its use. Indeed, this can be seen as an advantage for silicone. Which other
material can guarantee such an adherence to perfectly smooth and flat surfaces? Of course, before the treatment, the surfaces must be clean and free of any grease or oil. If one is planning to spray-paint the
component, it must of course, be completely free of silicone.
This is why panel-beaters and car body workers prefer to avoid this filler. Indeed, there are also substitute materials, which are almost as elastic and are still paintable. Of course, the paint must also be able to cope
with any shifting that may occur without it being damaged. In the meantime, it would appear, on condition that the correct product has been used, that nearly anything is possible: Temperatures like those found in the
cylinder head, the supplementing of solid gaskets and the sealing and simultaneous screw-locking ability. 12/14
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