USE OF CARBON MATERIALS TO MAKE INSERTS FOR THE SLIDING CONTACTS OF TROLLEY BUSES

no greater than 0.05%, moisture content does not exceed 1.0%, and ash content is no higher than 1.0%. The binder is powdered phenol-formaldehyde resin SPF-011A (TU 6-05751768-35–94, weight content of urotropin 6–9%, fl uidity 20–65 sec). The resin is fi rst reduced in a vibratory mill, with the residue on a No. 01K screen being less than 2%. The electrolytic copper powder of grade PMS-1 which is used in composition No. 3 has a bulk density of 1.25–2.00 g/cm 3 . Petroleum coke of grade KNG (ash content no greater than 0.5%, weight content of sulfur no higher than 1%) is used as an additive in compositions Nos. 4 and 5. Powdered zinc stearate (Zn content no more than 4 wt.%, acid number 75–90) is used in composition No. 5 to serve as a lubricant between the particles of graphite and the binder. To form products, powder compositions were obtained by homogenizing graphite with resin in a vibratory mill. The bulk density of the prepared mixture was 0.6–0.7 g/cm 3 [1]. New designs and methods of obtaining inserts for the sliding contacts of trolley buses. Contact inserts made of carbon-based materials have been used for trolley buses in Russia since the middle of the Twentieth Century. At the Moscow Trolley-Bus Repair Plant, inserts are obtained by the so-called standard technology which entails hot-pressing a mixture of electrographitized coke, phenol formaldehyde resin, and urotropin in dies [2]. Experience with the use of these inserts has revealed numerous defi ciencies in their design and the method used to make them. The standard design of the inserts does not provide adequate wear resistance, while use of the above-indicated components to form them makes the inserts’ resistivity high – 65–148 μΩ·m [2]. To resolve these problems, scientists at the South Ural State University (YuUrGU) and personnel at the Chelyabinsk company Grafi toplast ** – which makes electrical equipment out of carbon-based materials – have come up with an improved, more wear-resistant design of insert. An industrial technology that can be employed to make the insert (Fig. 1) has been successfully used at Grafi toplast since 2004. The design of the new insert and the specifi c manufacturing technology (TU 3497-001-56404425–2002) were developed by Samodurova [3]. * ENERGOPROM Company Group, www.energoprom.ru. ** Grafi toplast Company, www.graphitoplast.ru.