Lesson 1/Learning Event 1
The   worm   and   sector   steering   gear   is   very   simple   in   construction.     This
makes it cheap to build and easy to maintain.  A disadvantage is that it has
a lot of friction because of the sliding action between the worm and sector 
FIGURE 5.  WORM AND ROLLER STEERING GEAR.
WORM AND ROLLER STEERING GEAR
The worm and roller steering gear is much like the worm and sector, but the
sliding   friction   is   changed   to   rolling   friction   so   that   less   effort   is
required to turn the steering wheel.  This is made possible by machining the
sector   teeth   on   a   roller.     Friction   is   reduced   even   more   by   mounting   the 
roller on bearings in a saddle at the inner end of the pitman arm shaft. 
The   worm   has   an   hourglass   shape,   smaller   in   the   center   than   at   the   ends.
The   hourglass   shape   makes   the   roller   stay   in   better   contact   with   the   worm
teeth at the ends of the worm.
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