Project overview:

The objective of this project is to design a speed reducing (torque increasing) gearbox for an industrial saw that will be used to cut formed steel tubing. Your design team is required to specify the associated shafts, rolling element bearings, keyways, keys, housing and gears to a level of detail (including CAD drawings) such that the entire system could be manufactured without requiring any additional comment from you.

Specific requirements:

1.     The speed reducing gearbox is powered by an electric motor with the following specifications:

• Basic rated power: 18.0 + X + Y kW (X and Y are the last digits of the team's student numbers)
• Shaft speed (full-load): 1475 rev/min
• The electric motor will provide at most a "light" shock loading
• The motor will run in one direction only, will be started and stopped 4 times per day
• The system should operate 16 hours per day, 5 days per week with a design life of 5 years, i.e. approximately 20,000 hours of operation

2.     The speed reducing gearbox should provide the following:

• The speed reduction ratio should be as close as 10.0 as possible
• Allow for an output which may be subject to "heavy" shock
• Gears are to be manufactured using either Hobs (shaping cutters) or Precision (shaved and ground). The cost of Precision gears is significantly higher than Hob cut gears, therefore this decision should be justified.

3.     Gears

• All gear sets must have a hunting tooth ratio
• The minimum number of teeth on a pinion is 13
• The reliability of the gears should be 99%
• The pitch line velocity must be limited to the design range for the velocity factor of the gear manufacture method (see Fig 15.24, Juvinal & Marshek)
• Pinions can be machined onto shafts if required

4.     Shafts

• All shafts should be designed to Australian Standards
• Shafts must include a shoulder to precisely locate all gears.
• Keyways should be designed to allow connection of the electric motor and industrial saw (note that you must only provide a shaft with standard keyway, motor and saw coupling are not your responsibility)
• Keyways and keys must be designed to allow mounting of all gears

5.     Housing

• The housing must allow assembly of all components
• Feet must be provided to allow bolting to a horizontal surface
• Lubrication of the gears and bearings must be accommodated

6.     Bearings

• Appropriate, sealed, single-row, deep-groove, ball bearings should be specified from a commercial supplier (for example: skf.com, fag.de, nsk.com). The relevant details of the selected bearings should be defined in your report and a copy of the supplier's datasheet provided in the appendix.
• The bearings should provide a reliability of 90%