Helix angle the helix angle. The efficiency can be plotted versus the helix angle for a constant friction, as shown in the adjacent diagram. The maximum efficiency is a helix angle between 40 and 45 degrees, however a reasonable efficiency is achieved above 15°. Due to difficulties in forming the thread, helix angle greater than 30° are rarely used. Moreover, above 30° the friction angle becomes smaller than the helix angle and the nut is no longer self-locking and the mechanical advantage disappears. In helical and worm gears, the helix angle denotes the standard pitch circle unless otherwise specified. Application of the
Less-is-better effect Less-is-better effect The less-is-better effect is a type of preference reversal that occurs when the lesser or smaller alternative of a proposition is preferred when evaluated separately, but not evaluated together. The term was first proposed by Christopher Hsee. In a 1998 study, Hsee, a professor at the Graduate School of Business of The University of Chicago, discovered a less-is-better effect in three contexts: "(1) a person giving a $45 scarf (from scarves ranging from $5-$50) as a gift was perceived to be more generous than one giving a $55 coat (from coats ranging from $50-$500); (2) an overfilled ice