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66 www. bus- ex. com June 09

Karma Gerken Nordiska F ew things in the modern world function without electric motors in some part of the process. By the same token, electric motors are nothing without the tiny bits of graphite known as carbon brushes. Of course there are standard motors where brushes are sold in their millions, but concentrate on medium to large machines, as does the Swedish firm Karma Gerken Nordiska from Vällingby on the outskirts of Stockholm, and the business assumes a truly niche perspective. " Our customers are at the heavy end of the spectrum," explains managing director Mick Ayres. " We work with power stations, steel mills and the like. The number of these machines is counted in tens or hundreds only. Sometimes we can be supplying just a couple of brushes, although occasionally we do get larger volumes, say for locomotives that have hundreds of similar motors on the rolling stock." Carbon graphite, as used in brushes, is a surprisingly difficult material to make considering that it's made from common or garden ingredients such as coke, pitch and petroleum. In the whole world there are only a handful of companies that have the formula for its production, yet between them they make about 1000 different variations through the addition of varying quantities of copper or silver which enhance its conductivity. Graphite's job is to pass electricity to the rotor, and it is a good conductor. Although there are plenty of other conductive materials, nothing has been found that is as hard wearing or creates less emissions of dust at the same price. Karma buys graphite in 120x50x10cm blocks. Small June 09 www. bus- ex. com 67 Revvingup When the owner of this Swedish graphite brush manufacturer expressed his wish to retire, new leadership emerged to take it forward, as Alan Swaby learns