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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!mgnetp!ltuxa!ttrdc!levy
From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.auto.tech
Subject: Re: trivia question
Message-ID: <603@ttrdc.UUCP>
Date: Sun, 24-Nov-85 08:58:57 EST
Article-I.D.: ttrdc.603
Posted: Sun Nov 24 08:58:57 1985
Date-Received: Mon, 25-Nov-85 06:54:57 EST
References: <600@drutx.UUCP> <3177@hplabsb.UUCP> <635@bonnie.UUCP>
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 40

In article <635@bonnie.UUCP>, wjh@bonnie.UUCP (Bill Hery) writes:
>> > Why do cars have clutches?
>> >
>> > Because, the engine has to keep running while the car starts from a stop.
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>> Correct!  Gasoline and Diesel engines have zero starting torque.
>
>Not a correct answer to the original question, which asked for the
>reason NOT INCLUDING SHIFTING GEARS.  This solution seems to refer
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>to the need to shift into neutral for starting.
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Oh, does it???  When the auto starts from a standstill (with the
engine running first) the clutch is acting as a lossy coupling as it
is brought greadually into engagement.  The car could stay in first gear,
say, during this startup process; no need to shift at all.  The clutch's
purpose is, in this light, obvious; a way to connect the engine to the
rest of the drivetrain when desired, and to disconnect it when desired,
incidentally providing a (we hope) smooth transition in between inde-
pendent of any gear ratio that might be selected.  It is only because of
the way that gearing is usually implemented that it proves necessary to
disengage the clutch while changing gear ratios.  If your "gearing" is
something like a belt drive on a variable diameter pulley system, then
it becomes unnecessary to disengage the clutch, except when bringing the
car to a stop (or changing directions) without doing likewise with the
engine.  (In this wise, I also protest the original poster's assertion
that it was not for shifting gears.  It IS, if you shift from forward to
reverse and don't have an engine that can do the same!  It would be a mighty
tricky implementation of a gear system to allow THAT without ever disengaging
the engine, short of incorporating a slipping coupling, which could then
be argued to act as a clutch anyway.)
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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