<story><title>Why car wheels are so flat these days</title><url>https://www.theautopian.com/heres-why-car-wheels-are-so-flat-these-days-and-no-its-not-just-aerodynamics-and-styling/</url></story><parent_chain><item><author>ben_w</author><text>I don&amp;#x27;t claim any physical engineering skills, but don&amp;#x27;t you need a mechanical (non electrical) system for parking breaks?</text></item><item><author>londons_explore</author><text>One day, I believe car design regulations will be amended to allow fully electric braking (ie. no hydraulics, drums, rotors, or pads).   At that point, the motor can be moved into the wheel (unsprung mass = bad, but weight savings from not needing an axle or gearbox will outweigh this).  Suspension and steering design is then far easier, because there is no axle to need to keep straight.&lt;p&gt;Braking redundancy will be achieved by having motors&amp;#x2F;brakes on all four wheels, and within each motor 3 independant phase coils with independant controllers, such that there are effectively 12 brakes on a car.   Normally the controllers work together for smooth braking, traction control, software differential, etc.  But even after 3+ failures braking performance should still be satisfactory for an emergency stop.&lt;p&gt;Obviously braking energy needs to go somewhere.  In the happy case, it&amp;#x27;s regen&amp;#x27;ed into a battery.  If the battery can&amp;#x27;t accept it, it gets dumped into dump resistors.  If the dump resistors fail, it gets dumped into motor coils (of which there are 12 remember).  Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags.&lt;p&gt;So the whole system (except the pedal itself) is 12 way redundant.</text></item></parent_chain><comment><author>jasode</author><text>&lt;i&gt;&amp;gt;, but don&amp;#x27;t you need a mechanical (non electrical) system for parking breaks?&lt;/i&gt;&lt;p&gt;To some of the replies... I think some clarification needed because the wording caused folks to think of something else such as &lt;i&gt;electronically _controlled_&lt;/i&gt; physical brake pads:  &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Electronic_parking_brake&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Electronic_parking_brake&lt;/a&gt;&lt;p&gt;I think the gp was trying to ask about feasibility of &lt;i&gt;electric _powered_ magnetic field resistance braking&lt;/i&gt; ... similar to an exercise bike ... which would require &lt;i&gt;constant electrical power source&lt;/i&gt;.  (Similar to :  &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.google.com&amp;#x2F;search?q=magnetic+resistant+braking+of+exercise+bike&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.google.com&amp;#x2F;search?q=magnetic+resistant+braking+o...&lt;/a&gt;)&lt;p&gt;Magnetic field resistance brakes is practical for regenerative braking but not safe for parking brakes on an incline if the batteries run out of juice.  The context is the gp&amp;#x27;s premise of no physical friction brake components via &lt;i&gt;&amp;quot;(ie. no hydraulics, drums, rotors, or pads).&amp;quot;&lt;/i&gt;</text></comment>
<story><title>Why car wheels are so flat these days</title><url>https://www.theautopian.com/heres-why-car-wheels-are-so-flat-these-days-and-no-its-not-just-aerodynamics-and-styling/</url></story><parent_chain><item><author>ben_w</author><text>I don&amp;#x27;t claim any physical engineering skills, but don&amp;#x27;t you need a mechanical (non electrical) system for parking breaks?</text></item><item><author>londons_explore</author><text>One day, I believe car design regulations will be amended to allow fully electric braking (ie. no hydraulics, drums, rotors, or pads).   At that point, the motor can be moved into the wheel (unsprung mass = bad, but weight savings from not needing an axle or gearbox will outweigh this).  Suspension and steering design is then far easier, because there is no axle to need to keep straight.&lt;p&gt;Braking redundancy will be achieved by having motors&amp;#x2F;brakes on all four wheels, and within each motor 3 independant phase coils with independant controllers, such that there are effectively 12 brakes on a car.   Normally the controllers work together for smooth braking, traction control, software differential, etc.  But even after 3+ failures braking performance should still be satisfactory for an emergency stop.&lt;p&gt;Obviously braking energy needs to go somewhere.  In the happy case, it&amp;#x27;s regen&amp;#x27;ed into a battery.  If the battery can&amp;#x27;t accept it, it gets dumped into dump resistors.  If the dump resistors fail, it gets dumped into motor coils (of which there are 12 remember).  Obviously the motor coils will heat up very fast, so this is probably a one-use-only failsafe, like airbags.&lt;p&gt;So the whole system (except the pedal itself) is 12 way redundant.</text></item></parent_chain><comment><author>2III7</author><text>You don&amp;#x27;t, many modern cars have electronic parking brakes with small electric motors mounted on the rear calipers which push the brake pads against the discs when activated.</text></comment>