>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 12 May 2006 05:49
>To: Microcontroller discussion list - Public.
>Subject: RE: [ee] Basic physics... Bicycle regenerative braking forces
>
>
>
>
>> Nice formula! Doesn't the force increase proportional to the 
>square of 
>> speed? I think if you double speed, the force goes up four 
>times, AND 
>> you cover twice as much distance in the same period of time, so the 
>> energy per unit time is 8 times (force times distance).
>>
>> In any case, the formula and typical numbers are interesting! It 
>> really looks like the vast majority of the losses are 
>aerodynamic. How 
>> much improvement can we get by using "perfect tires?"
>>
>> Harold
>
>As Russell noted one formula is a derivative of the other. 
>Speed costs money, how fast do you want to go? has a whole new 
>life when you look at it this way. To get a good picture of 
>what is doing what you really need to look at the contribution 
>to the whole. Its usually the little things that add up to 
>create large drag numbers. Some you can fix some you can't. 
>For instance the belly pan of a car is a pretty miserable 
>place for drag. All sorts of lumps, bumps, pipes drive shafts 
>etc. You could cut down the drag of any car by 35-45% just by 
>fitting a smooth belly pan. Car makers won't do it as no one 
>looks under there. About the only half descent one is the 
>lowly VW Beatle the original one. Pusher engine so nothing 
>under. The only car I was ever in that could get stuck on speed bumps.

Quite a few cars do have smooth undersides, or at least smooth panels to cover over the lumpy bits.  My MR2 has numerous plastic panels held on by a frustrating amount of M6 bolts so the whole underside of the car is pretty flat.  Even boring family saloons now have a plastic cover that fits underneath the engine bay which is where a good deal of turbulence occurs.

Regards

Mike


=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist