EN 2602 Design
Design Task 3
Transmissions, Bearings, Fasteners
Design Part 3: Section 1: Gears
For the first part of the design task it was necessary to design a suitable gear box that will take an input speed of 3000rpm and provide an output speed of 185 10rpm. The best way to approach this task is by a two stage gear box. If it was attempted in one stage, the gear would be excessively large.
Figure 1 - The inside of the gearbox including the gears and shafts. Gear 1 Gear 2 Gear 3 Gear 4 Shaft A Shaft B Shaft C
It is advisable to have a pinion with at least 18 teeth, so for maximum efficiency both pinions have 18 teeth. It was assumed that a gear with 80 teeth in the first stage would provide a suitable reduction in the speed.
Therefore using the standard transmission equation between two gears:
The calculations would have been easier if the number of teeth on the pinion and gear were divisible by each other such as ratio of 18:72. However, this would create uneven wear and resonance, both of which are not desirable in a gearbox.
The gear on the first stage is therefore attached to the pinion on the second stage by a shaft. An appropriate reduction in the speed in the second stage is provided by a ratio of 18:63.
It would have been more desirable to have the value closer to 185rpm; however, due to the requirements of the gearbox such as the face width of the gear teeth, it was necessary to compromise on this value. This combination of ratios and modules were chosen as the most appropriate after trying out 20 different combinations on a spreadsheet. The...