lOMoARcPSD|28008182
Sample problems
Education (Bulacan State University)
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BRAKES
1.
On a brake drum, the difference in tension between the tight side and slack side is 5 kN. If the ratio in-band tensions is 3,
determine the tension on the tight side.
2.
In a brake, the tension on the tight side is thrice the slack side. If the coefficient of friction is 0.25, find the angle of contact on the
band.
3. A BRAKE HAS A DIFFERENCE IN BAND TENSION OF 4 KN. THE DRUM
DIAMETER IS 1 METER AND ROTATES AT 300 RPM. DETERMINE THE POWER
NEEDED TO DRIVE THE DRUM.
4. IN A BRAKE, THE TENSION ON THE TIGHT SIDE IS THRICE THE SLACK SIDE.
IF THE COEFFICIENT OF FRICTION IS 0.25, FIND THE ANGLE OF CONTACT OF
THE BAND.
5. A SIMPLE BAND BRAKE HAS A 76 CM DRUM AND IS FITTED WITH A STILL
BAND 2/5 CM THICK LINED WITH A BRAKE LINING HAVING A COEFFICIENT
OF FRICTION OF 0.25. THE ARC OF CONTACT IS 245 DEGREES. THE DRUM IS
ATTACHED TO A 60 CM HOISTING DRUM, THAT SUSTAINS A ROPE LOAD OF
820 KG. FIND THE TENSION AT THE SLACK SIDE.
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6. A STEEL BAND HAS A MAXIMUM TENSILE STRESS OF 55 MPA AND THICK OF
4 MM, IF THE TENSION IN THE TIGHT SIDE IS 6 KN, WHAT WIDTH OF THE
BAND SHOULD BE USED?
7. A BAND BRAKE HAS A STRAIGHT BRAKE ARM OF 1.5 M AND IS PLACED
PERPENDICULAR TO THE DIAMETER BISECTING THE ANGLE OF CONTACT
OF 270 DEGREES WHICH IS 200 MM FROM THE END OF THE SLACK SIDE.
8. THE BAND OF BAND BRAKE HAS 210 DEGREES OF CONTACT WITH ITS OWN
DRUM. IT IS FOUND THAT THE PULL ON THE TIGHT SIDE IS 800 LBS AND THE
PULL ON THE SLACK SIDE IS 285 LBS. DETERMINE THE COEFFICIENT OF
FRICTION.
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9. THE RATIO OF BAND TENSION IN A BAND BRAKE IS 4. IF THE ANGLE OF
CONTACT IS 260 DEGREES, DETERMINE THE COEFFICIENT OF FRICTION.
10. A BAND BRAKE HAS AN ANGLE OF CONTACT OF 280 DEGREES AND IS TO
SUSTAIN A TORQUE OF 10,000INLB. THE BAND BEARS AGAINST A CAST
IRON DRUM 14 IN DIAMETER. THE COEFFICIENT OF FRICTION IS 0.30. FIND
THE DIFFERENCE IN BAND TENSION.
11. A BAND BRAKE IS INSTALLED ON A DRUM ROTATING AT 250 RPM AND A
DIAMETER OF 900 MM. THE ANGLE OF CONTACT IS 1.5Л RAD AND ONE END
OF THE BAND BRAKE IS FASTENED TO A FIXED PIN WHILE THE OTHER END
TO THE BRAKE ARM IS 150 MM FROM THE FIXED PIN. THE COEFFICIENT OF
FRICTION IS 0.25 AND THE STRAIGHT BRAKE ARM IS 1000 MM LONG AND IS
PLACED PERPENDICULAR TO THE DIAMETER BISECTING THE ANGLE OF
CONTACT. DETERMINE THE MINIMUM FORCE IN NEWTONS APPLIED AT THE
END OF THE BRAKE ARM NECESSARY TO STOP THE DRUM IF 60 KW IS
BEING ABSORBED.
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12. A BAND BRAKE IS USED TO FASTEN TO A 900 MM BRAKE DRUM WITH A
TIGHT SIDE 3 TIMES THE SLACK SIDE OF THE FORCE. THE TORQUE
TRANSMITTED IS 2 KN-M AND A STEEL BAND WITH A MAXIMUM TENSILE
STRESS OF 60 MPA AND 3 MM THICK WILL BE USED. WHAT SHOULD BE ITS
WIDTH IN MM?
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13. A SIMPLE BAND BRAKE HAS A 76 CM DRUM WITH A COEFFICIENT OF
FRICTION OF 0.25 AND AN ARC OF CONTACT OF 245˚. THE DRUM SUSTAINS A
LOAD OF 820 KG AND ROTATES AT 260 RPM. FIND THE POWER ABSORBED
BY THE BAND.
14. DETERMINE THE INTERNAL LOAD EXPRESSED IN LB-FT2 OF A BRAKE THAT
REQUIRES 900 IN-LB OF TORQUE TO STOP A SHAFT OPERATING AT 840 RPM
IN A PERIOD OF 3.5 SECONDS.
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15.
A SIMPLE BAND BRAKE, INSTALLED ON A 500MM BRAKE DRUM, IS USED TO ABSORB A TORQUE OF 250 N-M. IF
THE COEFFICIENT OF FRICTION AND THE CONTACT ANGLE BETWEEN THE BAND AND DRUM ARE 0.2 AND 180º,
RESPECTIVELY, AND THAT THE LENGTH OF THE BRAKE ARM IS TWICE THE DRUM DIAMETER, DETERMINE THE
MINIMUM BRAKING FORCE APPLIED AT THE FREE END OF THE BRAKE ARM.
16.
A CAR IS MOVING AT 96.6KPH WHEN THE BRAKES ARE SUDDENLY LOCKED AND THE CAR BEGINS TO SKID. IF
IT TAKES 2 SECONDS TO SLOW DOWN THE CAR TO 4.83KPH, HOW FAR IN METERS WILL IT HAVE TRAVELED
BEFORE IT CAR COMES TO A HALT?
17. A BAND BRAKE IS TO ABSORB 3.75 KW AT 250 RPM. THE MAXIMUM PRESSURE OF THE LINING AND THE DRUM
IS 830 KPA. THE ANGLE OF THE WRAP IS 206O, THE WIDTH OF THE BAND IS 7.75 CM, AND THE F = 0.15. IF THE
DIAMETER OF THE DRUM IS 20 CM, DETERMINE THE FORCE ON THE RIGHT SIDE OF THE BAND.
18.
A 50 LB MOTOR SHOULD BE AUTOMATICALLY STOPPED BY A BRAKE WHEN POWER IS CUT OFF. THE MOTOR
MUST BE BROUGHT TO REST WITHIN 40 SECONDS AFTER POWER IS CUT OFF. THE LOAD INERTIA INCLUDING
THE BRAKE ROTATING MEMBER WILL BE ABOUT 200 LB-FT 2. HOW MANY REVOLUTIONS WILL THE SHAFT
TURN BEFORE STOPPING IF THE SHAFT TURNS AT 1800 RPM?
19. A SIMPLE BAND BRAKE, INSTALLED ON A 500MM BRAKE DRUM, IS USED TO ABSORB A TORQUE OF 250 N-M.
IF THE COEFFICIENT OF FRICTION AND THE CONTACT ANGLE BETWEEN THE BAND AND DRUM ARE 0.2
AND 180º, RESPECTIVELY, AND THE LENGTH OF THE BRAKE ARM IS TWICE THE DRUM DIAMETER,
DETERMINE THE MINIMUM BRAKING FORCE APPLIED AT THE FREE END OF THE BRAKE ARM.
20. A car is moving at 96.6 kph when the brakes are suddenly locked and the car begins to skid. If it takes 2 seconds to slow down
the car to 4.83 kph, how far in meters will it have traveled before it car comes to a halt?
21.
A car is traveling at 90 kph when the brakes are applied. If it travels a distance of 60 meters before coming to a stop, what is its
acceleration m/s2?
22.
A truck skids to a stop 60 m after the application of the brakes while traveling at 90
km/hr. What is the acceleration in m/sec2?
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23. A 500 mm brake drum has a simple brake that is to absorb a torque of 250 N-m. If the
coefficient of friction and the contact angle between the band and drum are 0.2 and
180º, respectively, and the length of the brake arm is twice the drum diameter,
determine the minimum braking force applied at the free end of the brake arm.
24. An abrupt brake is locked and the car begins to skid when it is traveling at 96.6 kph. If it
takes 2 seconds to slow down the car to 4.83 kph, how far in meters will it have traveled
before it car comes to a stop?
25.
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