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The unknown exact tensile strength of cylindrical cross-section carbon steel and rectangular cross-section carbon steel is a problem faced. The purpose of the research is to obtain the tensile strength of cylindrical cross-section carbon steel and rectangular cross-section carbon steel. The research method is carried out by turning carbon steel specimens to a diameter of 7.92mm, a length of 200mm and milling carbon steel cross-sections with a width of 12mm, a thickness of 4mm, setting the Tarno Grocky tensile testing machine, clamping both ends of the specimen with grips, tensile testing until the specimen breaks, measuring the gauge length after the specimen breaks and is properly cupped again, making stress and strain curves, and analyzing the tensile test results. The test results show that the tensile strength of carbon steel with a cylindrical cross-section is 554 MPa at a strain of 3.86%, the yield strength is 514 MPa at a strain of 3.06% and the tensile strength of carbon steel with a rectangular cross-section is 712 MPa at a strain of 2.45% and the yield strength is 487 MPa at a strain of 0.59%, which implies that both steels are ductilely broken, due to shrinkage. cross-section (necking) which includes ST 60 because the yield strength is more than 360 MPa.

The unknown exact flexural strength of low carbon steel, Randu ribs wood, paving stones, and lightweight bricks is a problem faced. The purpose of this research is to obtain the flexural strength of low carbon steel, Randu ribs, paving stones, and lightweight bricks. The research method is carried out through the preparation of low carbon steel specimens 16mmx200mm, Randu ribs 40mmx60mmx250mm, paving stones 55mmx100mmx200mm, lightweight bricks 95mmx100mmx300mm, Tarno Grocky flexural testing machine settings, flexural testing support distance for low carbon steel 160mm, Randu ribs 220mm, paving stones 170mm, and lightweight bricks 260mm, flexural testing of each material, making flexural stress and deflection curves for low carbon steel, and analyzing flexural test results. The results of the study showed that the flexural strength of low carbon steel was 698 MPa at a deflection of 1.1 mm, the flexural strength of Randu rib wood in an upright position was 40.7 MPa, in a horizontal position was 55.5 MPa, in a normal position of paving stone in an upper position (normal) was 6.64 MPa, in a lower position (upside down) was 6.62 MPa, and in a lightweight brick was 1.28 MPa, which implies that the type of material, the distance between supports and the cross-section of the specimen greatly affect its flexural strength, except for ductile materials for low carbon steel which do not have flexural strength, but have yield strength at a certain deflection.

The problem lies in the inconsistent quality of M10 hexagonal head bolts with a spacing of 1.5 mm, a bolt length of 100 mm and slow production speed for manual production. The purpose of the analysis is to obtain consistent, standard, and productive quality of M10 hexagonal head bolts with a spacing of 1.5 mm, a bolt length of 100 mm. The analysis method includes the selection of AISI 1040 raw materials with a diameter of 10 mm in the form of rolls, the determination of the production process through raw material inspection, diameter reduction from 10 mm to 9.8 mm, the formation of hexagonal heads with a machine, cutting the length of the bolts and the bolt end chamfer, making M10 threads with a range of 1.5 mm with a machine, hardening, 10 m thick Zinc coating, thread profile inspection, sample hardness test, and sample tensile test. The results of mass production with the machine obtained a hexagonal head bolt with a thread size of M10x1.5 mm, a bolt length of 100 mm, a capacity of 500 units/hour in accordance with the ISO 9001:2015 standard with a hardness of 30 HRC and a tensile strength of 830 MPa at a cost of Rp. 1133/bolt and a process duration of 8.3 minutes/bolt which implies that product quality can be more guaranteed to be consistent and uniform.

Waste from used Polypropylene (PP) and High Impact Polystyrene (HIPS) plastic is problematic in its management. The purpose of this research is to obtain the fatigue life of a mixture of used PP and HIPS plastics in its pure plastic. The research method is through the stages of mixing pure PP and 50% volume of used PP, pure HIPS and 50% volume of used HIPS, injection molding of R.R. Moore standard fatigue test specimens for pure PP, pure HIPS, pure PP + used PP, and pure HIPS + used HIPS, checking the straightness and smoothness of the molded specimen surface, fatigue testing with increasing serial loads, analysis of the bending stress curve (S) against fatigue life (N). The results showed that mixing used PP and used HIPS in pure plastic affected the fatigue life at the test speed (n)=2100 rpm for recycled PP was 9.84% shorter than pure PP, and at n=1600 rpm for recycled PP it was 9.32% shorter than pure PP, while at n=2100 rpm for recycled HIPS it was 4.45% shorter than pure HIPS, and at n=1600 rpm for recycled HIPS is 4.77% shorter than pure HIPS, while the fatigue life of pure PP is 1627704 cycles and the fatigue life of pure HIPS is 1291636 cycles or the fatigue life of pure HIPS is 20.65% shorter than pure PP, the implication of which is that the addition of used PP and used HIPS reduces the fatigue life to 9.84% for PP and 4.45% for HIPS.

The problem lies in the difficulty of locking the pulley retainer on automatic motorcycle transmissions without using a special Y-shaped key. The purpose of the study is to obtain a special pulley retainer lock product on automatic motorcycle transmissions that can be adjusted the distance between the two retaining pins through adjusting bolts with easy and effective locking steps. The study method includes the design of the pulley retainer lock component formation, the selection of stainless steel pulley retainer lock materials, the production of pulley retainer lock components through flat and curved forging, turning the handle, forming a Y-shaped lever pair plate, drilling 2 holes at the ends of the lever, drilling the Y-shaped auxiliary tool opening and closing pins, and drilling the Y-shaped auxiliary tool opening distance adjustment bolts, assembling the components that form the pulley retainer lock, and testing the use of the pulley retainer lock. The production results are in the form of a special pulley archery key with a total length of 300 mm, the maximum opening distance on the axis of 2 pens is 110 mm, the length of 2 pen tips is 7 mm with a total pen length of 30 mm, and one diameter is 9 mm with a total pen length of 30 mm, the adjusting bolt for the opening angle of the pulley retaining key measures M6x20 mm, and the diameter of the Y-shaped tool rivet pen used is 6 mm.

The problem with previous studies was the use of polyester resin as a matrix in kacang goat hair fiber composites, whereas in the latest study, epoxy resin was used, which has not been widely used. The aim was to obtain the tensile strength of composites that could be used as an alternative material for fan blades. The research method used was experimental with composite fabrication using the hand lay-up method, varying fiber lengths of 10 mm, 20 mm, and 30 mm, and varying immersion times in a 5% NaOH solution for 25, 50, 75, and 100 minutes. Tensile strength testing was carried out using the ASTM D638 standard with a total of 36 specimens. The test results showed that specimens with a fiber length of 30 mm and a soaking time of 50 minutes produced the highest tensile strength of 28.69 MPa, while the lowest tensile strength of 15.38 MPa was obtained in specimens with a fiber length of 10 mm and a soaking time of 100 minutes. This indicates that the highest tensile strength value is 46.37% greater than the lowest value, so the combination of a fiber length of 30 mm and a soaking time of 50 minutes is determined to be the optimal parameter in this study.

A decline in performance in automatic motorcycles that have been used for a long time is a common problem caused by wear and tear on the Continuously Variable Transmission (CVT) system. This condition results in a reduction in the clamping force of the V-belt on the pulley, causing slippage and a decrease in transmission capacity. Based on the manufacturer's specifications, the torque is 8.32 Nm at 5500 rpm, while the test results show a torque of 7.41 Nm at 6500 rpm, a decrease of 10.9%. The study aims to analyze the effect of variations in pulley angle and surface roughness on the torque value of a 108 cm³ automatic motorcycle as a method to restore transmission performance without replacing the main components. The pulley angles tested were 14°, 13.8°, and 13.5°, while the surface roughness was varied based on the turning process with cutting inserts having nose radii of 0.2 mm, 0.4 mm, and 0.8 mm. The testing was conducted using a dynamometer at an engine speed range of 6000 – 9000 rpm. The results showed that the combination of a 13.8° pulley angle with a 0.2 mm cutting insert nose radius produced a torque of 7.41 Nm at 6500 rpm, an increase of 8.2% compared to the standard 14.5° configuration, which only produced 6.85 Nm. Modifying the pulley angle and surface roughness was proven to increase the V-belt clamping force, thereby improving transmission performance.  

Many used ABS plastic wastes have problems in their management. The aim of this research is to obtain a prediction of the fatigue life of a mixture of ABS plastic and used ABS as an injection molding product. The research method is carried out through the stages of mixing used ABS with a volume of 10%, 20%, and 30% in ABS grade A and grade B; making fatigue test specimen molds according to R. R. Moore standards, injection molding of a mixture of used ABS and ABS grade A and grade B, checking the straightness and smoothness of the specimen surface, fatigue testing with increasing serial loads, analysis and making a graph of bending stress (S) against fatigue life (N) (S-N Curve). The results of the study showed that the addition of used ABS had an effect on the fatigue life of both grade A and grade B of ABS, where the fatigue life of grade A of ABS increased with the addition of the volume percentage from 0% -30% of used ABS with the highest value at the addition of 30%, namely 43698.9 cycles, while in grade B of ABS, the fatigue life decreased with the increase in volume from 0% -30% with the highest fatigue life in grade B of ABS plastic without a mixture or 0%, namely 41377.5 cycles, the implication of which is that the addition of 0% -30% of used ABS in grade A can increase the fatigue life, but grade B of ABS actually decreases its fatigue life.

The purpose of this study was to determine the effect of pulley angle variations of 13.5ᵒ and 14ᵒ and roller weight variations of 12 g, 14 g, and 16 g on the torque of a 150 cm3 automatic motorcycle. The method with a quantitative approach the method used is the experimental method. For the sample of this research is a type of pulley and 3 types of rollers with different slopes and weights where the angle varies to test the 150 cm3 matic motorcycle torque used. From the results of this study results in a value where the Fcount value is greater than the Ftable means that the null hypothesis (H02) is rejected and the alternative hypothesis (H22) is accepted or the mass of the roller has an influence on torque, the Fcount value is greater than the Ftable means that the hypothesis (H01) is rejected and the alternative hypothesis (H11) is accepted or the mass of the roller has an influence on torque, and that the interaction between pulley angle and roller mass does not affect, and the Ftable value is lower than the Fcount value that the hypothesis (H03) is accepted and the alternative hypothesis (H33) is rejected, roller mass affects torque.

Leaf springs are one of the suspension systems that are still widely used in various modes of transport such as cars and trucks. The spring functions to support the load and reduce vibration from operational activities. This study aims to analyse the bending strength and hardness of steel leaf springs of trucks and cars resulting from tempering heat treatment. The three point bending method was used as the flexural strength testing method and the Rockwell C Hardness method testing was used for hardness testing with leaf springs in raw, tempered 460°C, and tempered 510°C conditions. From the results of the study, the highest average bending strength value of 3733,55 MPa was obtained and an average roughness value of 31,8 HR was obtained for the 510°C tempered truck leaf springs. This also applies to the 510°C tempered car leaf springs, where the average bending strength value obtained is 3392,65 MPa and the average hardness value obtained is 29,5 HR. Thus, it is recommended that tempering heat treatment that can be applied to truck and car leaf springs be carried out at 510°C to increase the bending strength and ductility of the leaf springs.