# Brake Design HW 1

Pair assignment due Thursday 2/22 at beginning of lecture.

This is the first assignment for the brake design challenge, in which each student will setup a working baseline. The next assignment will be optimization.

1. Complete Working Model 2D Getting Started Tutorial up to Step 8. Turn in print screen of Step 8 that includes trajectory of motion. Handwrite on print out the key parameter values used in your simulation.

2. Calculate extension and retraction force for pneumatic cylinder given:

• Air pressure, P = 300 Kilopascal (this is gauge pressure, which is the typical in industry to specify pneumatic pressures)

• Piston Diameter = 20 mm

• Rod Diameter = 5 mm

3. Setup baseline brake WM2D simulation as follows (see figure below as well):

1. If using Virtual Labs, set pause condition

• World => Pause Control => New Condition => Pause When => Set time (typical value is 5 sec).

2. Set units to metric:

• View => Numbers and Units => SI Degrees

3. Turn grid on

• View => Workspace => gridlines

4. Turn gravity off

• World => Gravity => None

5. Create circle to represent shaft and then set diameter to 20 mm radius

• Create circle and then select it.

• Window => Geometry => Radius 0.01m

6. Use pin joint (green dot on left side panel) to constrain circle to background.

7. Add torque (lower left sidebar) to circle.

8. Create slider to control torque between 0 and 5 Nm.

• Select torque (if hard to select torque by clicking image, then open Windows => Properties. Then select from pull down menu.)

• Measure => Torque

• Select slider => Windows => Properties => adjust min and max.

• NOTE: for most values force, brake pad block to "falls" through the circle. This is because the numerical solver's time step is too large relative to the speeds the objects are moving. The solution is to decrease the time step under "Accuracy" from 20/s to something faster (ie: 1000/s, or something like that.).

9. Plot circle velocity:

• Select Circle => Measure => Velocity => Rotation Graph

10. Display circle position/velocity/acceleration:

• Select Circle => Measure => P-V-A => Rotation

11. Now is a good time to test simulation by clicking run. Click reset when done.

12. Create rectangular brake pad above circle

• Create rectangle 10 mm above circle

• Add vertical keyed slot joint to rectangle so brake pad does not rotate

13. Apply braking force

• Select force of retraction or extension of the cylinder from part 2

• Apply vertical force onto brake pad. Select force => Windows => Properties => Type in value in negative Y direction.

• Run simulation for a torque level of 1 Nm

14. Print results

1. Take screen shot of your simulation and printout

2. Write on printout the final velocity and if the brake pad indeeds stops the break as in its original design. 