For the case study problem, change the power requirement to 40 horsepower. Design the intermediate shaft, including complete specification of the gears, bearings, keys, retaining rings, and shaft.

A mechanical design company wishes to provide off-the-shelf speed reducer (two-stage, compound reverted gear train such as shown in figure below) in various capacities and one speed ratio to sell to a wide variety of target applications. The marketing team has determined a need for one of these speed reducers to satisfy the following customer requirements.

Design Requirements

Power to be delivered: 22 kW

Input speed: 55 rev/s

Output speed: 3-4 rev/s

Targeted for uniformly loaded applications, such as conveyor belts, blowers, and generators

Output shaft and input shaft in-line

Base mounted with 4 bolts

Continuous operation

6-year life, with 8 hours/day, 5 days/wk

Low maintenance

Competitive cost

Nominal operating conditions of industrialized locations

Input and output shafts standard size for typical couplings

The following product specifications provide an appropriate framework for this design task.

Design Specifications

Power to be delivered: 22 kW

Power efficiency :> 99 %

Steady state Input speed: 45 rev/s

Maximum Input speed: 55 rev/s

Steady state output speed: 3-4 rev/s

Usually low shock levels, occasional moderate shock

Input and output shafts extend 6 in outside gearbox

Input and output diameter tolerance: ± 0.030 mm

Input and output shafts in-line: concentricity ± 0.130 mm, alignment ± 0.002 rad

Maximum allowable loads on input shaft: axial, 250 N; transverse, 550 N

Maximum allowable loads on output shaft: axial, 330 N; transverse, 3330 N

Maximum gearbox size: 400 mm ´ 400 mm base, 700 mm height

Base mounted with 4 bolts

Mounting orientation only with base on bottom

100% duty cycle

Maintenance schedule: lubrication check every 3000 hours,; change of lubrication every 8000 hours of operation; gears and bearing life > 15,000 hours; infinite shaft life; gears, bearings, and shafts replaceable

Access to check, drain, and refill lubrication without disassembly or opening of gasket joints.

Manufacturing cost per unit: < $ 500

Production: 15,000 units per year

Operating temperature range: - 15⁰ to 70⁰ C

Sealed against water and dust from typical weather

Noise: < 90 dB from 1 meter