MIT2_007s09_lec12

MIT2_007s09_lec12 - MIT OpenCourseWare http:/ocw.mit.edu...

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MIT OpenCourseWare http://ocw.mit.edu 2.007 Design and Manufacturing I Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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2.007 –Design and Manufacturing I Gears: T erminology, Geometry, Gear Trains, Strength Presented by Dan Frey on 17 MAR 2009 Images from Wikimedia Commons, http://commons.wikimedia.org
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Today’s Agenda • Distribute homework #3 •G e a r s – Applications – Types – Terminology / nomenclature – Congugate action – Involute curve – Analysis & design
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Applications of Gears Sobel, Dava, Longitude Images removed due to copyright restrictions. Please see http://mossmotors.com/Graphics/Products/Schematics/SPM-027.gif http://www.nmm.ac.uk/collections/displayRepro.cfm?reproID=A6263
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Spur Gears • Transmit motion between parallel shafts • Teeth are parallel to the axis of rotation • This is the simplest kind of gear we’ll consider and most of today is dedicated to them
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Gear Terminology Source: Fig. 1.1 in “Gears.” Design and Application of Small Standardized components Data Book 757 . Stock Drive Products, 1983. Accessed September 18, 2009. Courtesy of Stock Drive Products/Sterling Instrument. Diametral pitch (teeth per inch) # of teeth on a gear with a 1 inch pitch diameter Easily confused
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Other Types of Gears Helical Bevel Rack Worm Courtesy OSHA. Images from Wikimedia Commons, http://commons.wikimedia.org Image courtesy of perlmonger on Flickr.
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Early Gears Roman watermills at Barbegal 300AD Application for powering textile machinery 18 th century Drawings of waterwheels and gears removed due to copyright restrictions.
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Conjugate Action ω Α A B ω Β Let’s say ω A is a known. How can we determine ω B ? Let’s say ω A is a constant with time. Can we synthesize a shape of body B so that ω B is also constant with time?
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Pitch Point ω Α A B ω Β What is the pitch point? What is the line of action? What are the relationships among these?
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Sliding and Rolling ω Α A B ω Β What is the relationship to the pitch circles? When one body is driving another, do the surfaces slide, roll, or both? How could you determine this?
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Rack Cutting • A way to get the relative motion you want • Pick one shape as you wish • Enforce the motion you want • Cut away everything that interferes Gear blank rotates in this direction Rack cutter reciprocates in a direction perpendicular to this page Figure by MIT OpenCourseWare.
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Involute Profile • How it is constructed –Demo • Properties – Conjugate action – Allows design of whole sets of compatible gears – Conjugate action not sensitive to center distance variations
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Shigley and Mischke This geometry is not an involute. More Gear
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This note was uploaded on 02/23/2012 for the course MECHANICAL 2.007 taught by Professor Fry during the Spring '11 term at MIT.

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MIT2_007s09_lec12 - MIT OpenCourseWare http:/ocw.mit.edu...

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