# Daily Archives: October 26, 2020

## What is the basis for the rhythmicity observed in the SCN?

1.Why do you think animals, including humans, would evolve a system in which their testosterone levels would fluctuate with winning and losing in competitive situations?

2. How do shift work, jet lag, and daylight saving time affect our normal circadian rhythms?

3. What is the basis for the rhythmicity observed in the SCN?

4.What can we learn from the EEG recordings taken from different stages of waking and sleep?

5. In what ways should sleep be considered an active, as opposed to a passive, process?

## design suitable bearings to support the load for at least 5E8 cycles at 1 200 rpm using deepgroove ball bearings.

The shaft shown in Figure P11-4 was designed in Problem 10-19. For the data in row (a) of Table P11-1, and the corresponding diameter of shaft found in Problem 10-19, design suitable bearings to support the load for at least 5E8 cycles at 1 200 rpm using deepgroove ball bearings. In addition to the radial loads found in Problem 10-19, the right bearing supports an axial load that is 120% of the concentrated transverse load P. The shaft diameter is 1.153 in, the L10 design life is 500E6 revolutions, and the concentrated transverse load is 1 000 lb. Assume an axial-force factor = 1.2 and a shaft-rotation factor = 1.0. Also assume that the shaft diameter can be reduced at the left bearing where the moment is zero.

## Find the minimum film thickness for a long bearing with the following data: 30-mm dia, 130 mm long, 0.0015 clearance ratio, 1 500 rpm, ISO VG 100 oil at 200°F, and supporting a load of 7 kN.

1.       A paper machine processes rolls of paper having a density of 984 kg/m3. The paper roll is 1.50-m OD X 22-cm ID X 3.23-m long and is on a simply supported, 22-cm OD, steel shaft. The roll turns at 50 rpm. Design suitable hydrodynamically lubricated full-film bronze short bearings of l / d = 0.75 to support the shaft at each end. Specify the viscosity of lubricant needed at 180°F. State all assumptions.

2.       Find the minimum film thickness for a long bearing with the following data: 30-mm dia, 130 mm long, 0.0015 clearance ratio, 1 500 rpm, ISO VG 100 oil at 200°F, and supporting a load of 7 kN.

## Find the minimum film thickness for a bearing with these data: 30-mm dia, 25 mm long, 0.0015 clearance ratio, 1 500 rpm, ON = 30, ISO VG 220 oil at 200°F.

1.       Problem 7-12 estimated the volume of adhesive wear to expect from a steel shaft of 40 mm dia rotating at 250 rpm for 10 years in a plain bronze bushing with a transverse load of 1 000 N for conditions of both poor and good lubrication. If the bushing has l / d = 0.5 and a clearance ratio of 0.001, define the lubricant viscosity in microreyn (μreyn) needed to obtain good lubrication.

2.       Find the minimum film thickness for a bearing with these data: 30-mm dia, 25 mm long, 0.0015 clearance ratio, 1 500 rpm, ON = 30, ISO VG 220 oil at 200°F.

## Specify bearing number, bore, OD, width (all in mm) and the basic dynamic load rating of the bearing.

Figure P11-5 shows a stepped shaft supported by two 6300-series bearings. Two gears with equal and opposite torque are keyed to the shaft as shown. The load on each gear consists of a radial component and a tangential component, which acts at diameter D. The radial component on each gear is 0.466 times the tangential component on that gear. Note that the gear loads are 90 degrees out of phase from gear 1 to gear 2. For the data in the row(s) assigned from Table P11-2, select a suitable bearing (from Figure 11-23 for a 10% failure rate) for bearing 1. Choose the bearing that has the least bore diameter and  meets the load-rating requirement. Specify bearing number, bore, OD, width (all in mm) and the basic dynamic load rating….

## Choose the bearing that has the least bore diameter and meets the load-rating requirement.

Figure P11-5 shows a stepped shaft supported by two 6300-series bearings. Two gears with equal and opposite torque are keyed to the shaft as shown. The load on each gear consists of a radial component and a tangential component, which acts at diameter D. The radial component on each gear is 0.466 times the tangential component on that gear. Note that the gear loads are 90 degrees out of phase from gear 1 to gear 2. For the data in the row(s) assigned from Table P11-2, select a suitable bearing (from Figure 11-23 for a 10% failure rate) for bearing 2. Choose the bearing that has the least bore diameter and meets the load-rating requirement. Specify bearing number, bore, OD, width (all in mm) and the basic dynamic load rating….

## Find the specific film thickness and lubrication condition between the two teeth in contact if lubricated with an ISO VG 1000 oil at 120F.

Problem 7-32 determined the half-dimensions of the contact patch for two steel gears in mesh with a contact force of 1500 lb to be a = 0.0177 in and b = 0.3125 in (half-width of a tooth face). The gears are modeled as two cylinders in contact with radii of 2.500 in (driver) and 5.000 in (driven gear). Find the specific film thickness and lubrication condition between the two teeth in contact if lubricated with an ISO VG 1000 oil at 120F. Assume both teeth have Rq = 4 μin. The tangential velocities of the gear teeth are 55.6 in/sec (driver) and 57.8 in/sec (driven).

## If the spur gearsets in Problems 12-3 and 12-4 are compounded as shown in Figure 12-14 (p. 697), what will the overall train ratio be?

1.       A paper machine processes rolls of paper having a density of 984 kg/m3. The paper roll is 1.50-m outside dia (OD) X 0.22-m inside dia (ID) X 3.23 m long and is on a simply supported, hollow, steel shaft with Sut = 400 MPa. Design a 2.5:1 reduction spur gearset to drive this roll shaft to obtain a minimum dynamic safety factor of 2 for a 10-year life if the shaft OD is 22 cm and the roll turns at 50 rpm with 1.2 hp absorbed.

2.       If the spur gearsets in Problems 12-3 and 12-4 are compounded as shown in Figure 12-14 (p. 697), what will the overall train ratio be?

## Design a two-stage compound spur gear train for an overall ratio of approximately 47:1. Specify tooth numbers for each gear in the train.

1.       Design a two-stage compound spur gear train for an overall ratio of approximately 47:1. Specify tooth numbers for each gear in the train.

2.       Design a three-stage compound spur gear train for an overall ratio of approximately 656:1. Specify tooth numbers for each gear in the train.

3.       An epicyclic spur gear train as shown in Figure 12-16 (p. 700) has a sun gear of 33 teeth and a planet gear of 21 teeth. Find the required number of teeth in the ring gear and determine the ratio between the arm and sun gear if the ring gear is heldstationary. Hint: Consider the arm to rotate at 1 rpm.

## Design a two-stage compound spur-gear train for an overall ratio of approximately 78:1.

1.       Size the second-stage spur gears in Problem 12-27 for a bending safety factor of at least 3.0 and a surface safety factor of at least 1.7 assuming a steady torque, 25° pressure angle, full-depth teeth, Qv = 8, and AISI 4140 steel for all gears.

2.       Size the third-stage spur gears in Problem 12-27 for a bending safety factor of at least 3.0 and a surface safety factor of at least 1.7 assuming a steady torque, 25° pressure angle, full-depth teeth, Qv = 8, and AISI 4140 steel for all gears.

3.       Design a two-stage compound spur-gear train for an overall ratio of approximately 78:1. Specify tooth numbers for each spur gear in the train.