# An Analysis of the Performance of Trolleybus Brushes Developed from Recycled Materials
## 3 Measurements and Results  
The research was carried out for various component mixtures and for commercially available brushes. Electrical, mechanical, and load properties were tested. It should be remarked that the some electrical properties (e.g., current ampacity) were examined using a laboratory stand at direct current value equal to 150 A, which might be considered as a value comparable to those obtained in real-life conditions. Figure 4 presents a photograph of the laboratory stand for testing current ampacity, whereas in Figure 5 the connection scheme of the setup is presented. The system brush-traction electrode is supplied from a 230 V alternating current source via a coil with adjustable inductivity (D) and an assembly box. The main current I\({}_{\text{p}}\) in the examined system as well as auxiliary control current I\({}_{\text{p1}}\) are measured with ammeters. Figure 3: An exemplary ready-made brush. The measurements of electrical resistance were carried out using the bridge method with the Sonel MMR-650 device ([PERSON], Swidnica, Poland). The four-wire (Kelvin) method [27] suited for measurements of small resistances is implemented inside the device. A sketch of the connection scheme to the device is presented in Figure 6. Red wires and clamps pertain to the current part of the measurement circuit. Blue wires and clamps pertain to the voltage part of the measurement circuit. The blackened ovals denote the contact points between the examined brush and the wire. \"TEMP\" denotes a thermopile (a temperature sensor) for monitoring ambient temperature. The measurement range for the device was 1.0000-1.9999 m\(\Omega\), resolution 0.0001 m\(\Omega\), and the fundamental measurement error \(\pm\) (0.25% result of the measurement + 2 digits). Figure 4: A photograph of the laboratory stand for testing current ampacity. Figure 5: The connection scheme of the setup. Figure 6: A sketch presenting the connection of brushes to the Sonel MMR-650 device. The measurement results concerning the resistance of the samples are given in Table 1. The values provided are averaged from ten individual measurements. Description of the samples: 1--graphite + 20% resin + 20% copper, 2--original, commercially available mixture, tradename RH84, 3--graphite +15% resin + 20% copper, 4--another original, commercially available mixture, tradename MY7D, 5--graphite + 20% resin + 20% copper + 30% graphite recyclate, 6--graphite + 20% resin, 7--graphite without resin. Hardness tests were carried out with the HB ball indentation method with the hardness tester HPK 8411 in accordance with PN-EN ISO 2039-1: 2004. During the tests, the ball with diameter \(5\pm 0.025\) mm was used. The succesive load values were 49 N, 132 N, 358 N, and 961 N. The measurements were made at a distance at least 5 mm away from the sample edge, and the distance between successive measurement point was 10 mm. The tests were carried out on samples with smooth, even, mutually parallel and perpendicular surfaces to the direction of the force, without bubbles, scratches, pits, or other visible defects. The tests were carried out at variable temperatures of 80 \({}^{\circ}\)C, 23 \({}^{\circ}\)C, and -32 \({}^{\circ}\)C. The results are shown as graphs in Figures 7-9. Designation of the samples: 1--graphite + 20% resin +20% copper, 2--original, commercially available mixture, tradename RH84, 3--graphite + 15% resin +20% copper, 4--another original, commercially available mixture, tradename MY7D, 5--graphite + 20% resin + 20% copper + 30% graphite recyclate, 7--pure graphite without resin. Commercial brushes made of commercial mixtures reveal considerable hardness (in particular the mixture RH84), but it varies to some extent with temperature variations. For the RH84 mixture an increase in hardness was recorded at lower temperatures, whereas for the MY7D mixture, comparable hardness values were noticed both for the room and for the negative temperatures. The lowest hardness values were recorded for the commercially available mixture MY7D\" and for graphite samples.