1 v and timing belt

ME‐205 : Element of machine dynamics and design

Dr. Muhammad WasifAssistant Professor – I.M.D.

Ph.D. (CAD/CAM – Canada), M.Engg. (Mfg. Engg. – NEDUET), B.E. (Mech. Engg. – NED UET). Member ASME and PEC

Room : 1st on LHS of main corridor, ground floor – IM Building

Machine dynamics : V‐Belts

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Dr. Muhammad Wasif

QualificationsB.E. ‐Mech. Engg. NED UET 2000‐2003M. Engg. ‐Mfg. Engg. NED UET 2005‐2007Ph.D. (CAD/CAM) CU, Canada 2009‐2013

A New Approach to CNC Programming for Accurate Multi‐axis Face‐Milling of Hypoid Gears

ExperianceHinopak Motors Ltd. Prod. Exec. 2004‐2005NED UET (IMD) Lecturer 2006‐2007NED UET (IMD) Director PDC 2006‐2007NED UET (IMD) Asst. Prof. 2007‐2013

2ME‐205, Elements of Machine design and dynamics, conducted by Dr. Muhammad Wasif (Asst. Professor ‐ IMD, NEDUET)

Belt Drives – Review • In power transmissions, use of belts, simplify the machine design

and reduce the cost.

• Is far more economical than buying a motor to run at the speed

required by the driven equipment.

• Due to flexibility, it can absorb a good amount of shock and

vibration.

• It can take care of some degree of misalignment between the

driven and the driver machines and long distance power

transmission.


V‐Belts : Advantages• Transmit greater amount of power with higher velocity ratio.

• Usually made of cotton, ryon or nylon impregnated with rubber.

• A single V‐belts is less efficient than a flat belt due to the wedging actionb/w belt and pulley (high friction), but multiple v‐belts can be used totransmit higher power.

• V‐belts are longer in life due to seamless design (no joint).

• V‐belts are used for short center distance, i.e. compactness.

• V‐belts are manufactured in standard lengths.

• The groove angle of a sheave is made somewhat smaller than the belt‐section angle. This causes the belt to wedge itself into the groove, thus increasing friction.


V‐Belts : Limitations• V‐belts cannot be used with large center distance.

• V‐belt’s pulleys are complicated in design and hence expensive.

• Not suitable for constant speed applications due to creep.

• Less durable than the flat belts.

• Speed limit of v‐belt drives are between 5 to 50m/s due to thedesign of groove in pulley.


=

Table 20.1,20.2 – Page 728, A Textbook of Machine Design by R.S.KHURMI AND J.K.GUPTA


V‐Belts• Pitch length is defined as the circumferential length of the belt

at the pitch width of the belt (width at the neutral axis).

• The value of pitch width remains same for any type of the belt.

(S.I.)

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Applications:

1. Motor pumps (suction pumps)2. Car air conditioner 3. Threshers/Crushing machines4. Lathe machine spindle


V‐Belts• Non standard pitch length and center distances can be

calculated using;

• Relation between T1 and T2 is

2.3 /


Example 20.1 – Page 731, A Textbook of Machine Design by R.S.KHURMI AND J.K.GUPTA


Timing Belts• It is made of rubberizedfabric coated with a nylonfabric, and has steel wirewithin to take the tensionload.

• It has teeth that fit intogrooves cut on theperiphery of the pulleys

• No slip and negligiblestretch.

• Can be used with wide variety of speed.• Higher efficiency (97‐99%)• Five standard types are available according to the applications.


Refernces

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• R.S. Khurmi, G.K. Gupta, 2005, A text book of machine design, New Dehli‐ India, EURASIA PUBLISHING HOUSE.

• R. G. Budynass, J.K. Nisbett, 2005, Shigley’s Mechanical Engineering Deisgn, New York –USA, McGraw Hill.

• R. L. Mott, 2004, Machine Elements in Mechanical Design, USA, Pearson Prentice‐Hall.

• R. L. Norton, 1996, Machine design an integrated approach, NJ USA, Prentice‐Hall.• B. J. Hamrock, B. O. Jacobson, S. R. Schmid, 1999, Fundamental of Machine

Elements, New York –USA, McGraw‐Hill.• U. C. Jinbal, 2010, Machine Design, India, Pearson .• R. O. Parmley, 2005, Machine devices and components, USA, McGraw‐Hill.