Developing an Auger One Stage Gearbox System - Dissertation Example

Given the gearing ratio of 5.4 to 1, the planetary gearing system was found to be most suitable and was thus used as the prime choice. It was also decided to perform a comparison between a spur planetary and a helical planetary gearbox to find out which one was better. The gear-based calculations were carried out and the number of teeth was found culminating in the perfectly matching gearing ratio. The gear sizes were determined using the overall dimensions of the gearbox as a constraint. The number of planetary gears was chosen as three based on its load sharing and geometrical properties. A lubrication investigation was also carried out in detail to find out a lubricant suitable for the gearbox. The bearing selection was carried out for the gearboxes (both the spur and helical gearboxes) based on their individual requirements. The types of bearings available were investigated at length in order to discern the best possible choice. Materials for the various parts of the gearbox were also considered in detail to discern the best possible choices. This was followed by the evaluation of spur gearbox and helical gearbox design based on cost as the cost was considered as an important factor. The stress analysis of the gearbox components produced satisfactory results which indicated a large operating margin for the gears involved.

The optimal numbers of teeth decided upon were 44 for the ring gear followed by 17 for the planetary gears and 10 for the sun gear. The gears were all scaled relative to each other so that the largest dimensions of the gearbox were not violated. The lubricant was chosen under AGMA 9005-E02 guidelines and it indicated that the lubricant required would be one that lies as close as possible to ISO 1000 grade with a kinematic viscosity of 1632.5 CST at 40oC. Moreover, it was also indicated that a high-pressure additive should also be available in this lubricant to ensure that the large stresses created at the start-up of the gearbox are adequately dealt with. Bearings were investigated and it revealed that the spur gearbox design would require output bearings of 6407 while input bearings of 6009. On the other hand, the helical gearbox design would require output bearings of 7309 BE while input bearings of 7209 BE. The gearing materials were found out best to be AISI 304 while the casing ought to be created from cast iron. Cost comparison shows that spur gearbox is much cheaper especially because of the lower cost of the ring spur gear in comparison to the ring helical gear. Therefore the spur gearbox design was chosen as the optimal configuration for the current problem at hand.

The maximum and minimum stress levels are already pretty clear in this image and other images that I have sent you. The images are always going to be the same as the gearbox under investigation is the same. The yielding strength of the material is 550 MPa and the stress levels are apparent in the picture.

FOS (Factor of Safety) is a measure used to indicate the relative resilience of a component to failure during normal operation. Generally, the FOS is calculated by dividing the material’s own yield stress with the maximum available stress levels. This measure helps to indicate if a component would be able to survive the treatment meted out to it during its normal operation. The FOS for stationary components is generally not more than 1.5 to 2 but for the case of vibratory applications, the FOS is considerably higher especially in the case of heavy equipment such as auger earth drills. The FOS for such cases is generally kept at 4 to 5 or higher. The analysis performed indicated that the minimum FOS was at least 11 which indicated that the design is robust enough for sturdy performance in normal and slightly elevated operating conditions.