🚀 go-pugleaf

> 
> Why do cars have clutches?
> 
	My Camaro has one so I can tach it up to about 5 grand 
to ensure gas is pouring through all four bbls., drop the clutch
and smoke up the rear tires. Ah, nothing like the sound of a
small block Chevy screaming as it sucks in good clean air and
replaces it with the exquisite smell of molten rubber :-)

				Doug

> Why do cars have clutches?
> 
> Because, the engine has to keep running while the car starts from a stop.
> A clutch enables the engine to do this. It is inconceivable to me how an
> engine directly coupled to the wheels could get the car moving from a 
> dead stop without the assistance of a starter, but that would be too
> great a strain on the battery, and wouldn't work as well as with a clutch.
> 
> But then, what do I know?
> 
> Matt Graham
> !ihnp4!drutx!msg

Correct!  Gasoline and Diesel engines have zero starting torque.

In article <321@mhuxl.UUCP> daw1@mhuxl.UUCP (WILLIAMS) writes:
>> 
>> Why do cars have clutches?

Actually the clutch is there so that you can sit on a steep hill
waiting for the light to turn green and not have to bother with
putting on the brake................... 8*( 

Its also a neat place to rest your left foot while driving.

> In article <321@mhuxl.UUCP> daw1@mhuxl.UUCP (WILLIAMS) writes:
> >> Why do cars have clutches?
> Actually the clutch is there so that you can sit on a steep hill
> waiting for the light to turn green and not have to bother with
> putting on the brake............
> 
---> Its also a neat place to rest your left foot while driving. <---

  If you *DO* actually rest your foot on the clutch pedal while
driving, you might as well forget about any life from your
clutch disk and throwout bearing.  It's been proven that resting
your foot on the clutch pedal, even lightly, will cause decreased
clutch and throwout bearing life due to the pressure on them
from the  amplified pressure of your foot on the pedal.
So, if it's a habit, break it, or else, go buy a car with an
automatic!  (Then you'll probably ride the brakes... |-})

Rick.
------------
Rick Bensene
{ihnp4, decvax, allegra, cbosg, ucbvax}!tektronix!tekig4!rickb
Phone: Weekdays (503) 627-3559
       BBS: (503) 254-0458  300/1200 baud, 24 hours a day
US Mail: Tektronix, Inc. - P.O. Box 500, Mail Stop 39-170 - Beaverton,
 Oregon  97077

> > 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.  Can the original
poster respond with the correct answer (assuming that this isn't it)

> Why do cars have clutches?
> 
> Because, the engine has to keep running while the car starts from a stop.
> A clutch enables the engine to do this. It is inconceivable to me how an
> engine directly coupled to the wheels could get the car moving from a 
> dead stop without the assistance of a starter, but that would be too
> great a strain on the battery, and wouldn't work as well as with a clutch.

8 or 10 years ago the clutch cable broke in my father's
1972 Capri.  Solution?  He let the engine warm up quite
a while, and then started the engine with the transmission in
1st gear.  He said it worked fine, but made for a rather
rough ride (as well as lots of nasty looks) until he got out of
downtown Chicago and onto the expressway!

Of course, if you don't know how to shift without the clutch
(it takes lots of practice), the repairs to you
gearbox can cost more than a tow. :')

Jonathan E. Quist
Lachman Associates Inc.
@ AT&T Bell Laboratories
ihnp4!ihwpt!jeq

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        |
 --------------------------------   Path: ..!ihnp4!ttrdc!levy

> > > 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.  Can the original
> poster respond with the correct answer (assuming that this isn't it)

Eh?  Shifting gears is an all or nothing proposition.  You can't gradually
trasfer the load of the engine by shifting from neutral to first no matter
how you do it.  If you do manage, you are wearing your gear like it was the
clutch.  You need the clutch to START the wheels turning since the engine
won't develop any torque when coming from a dead stop.

Once you are moving, you don't need the clutch.  On most manual transmissions
if you shift at the right speed, you will do a very smooth shift even if
you don't touch the clutch.  This doesn't extend to the 18 ton trucks that
I've driven though, too much load on the transmission I guess.

-Ron

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.  Can the original
>poster respond with the correct answer (assuming that this isn't it)

I must disagree with this analysis.  Consider a car with ONLY ONE GEAR
THAT IS ALWAYS ENGAGED.  Even though you cannot shift this beast, you
still would like a clutch for starting the car from standing still.

If this is not a practical enough example, consider a beast that was
seen on the drag racing circuit a few years ago.  It was a fuel dragster
that was equiped with a LENCO two-speed planetary transmission (I might
be wrong about the name "LENCO", but that is not really important).

This transmission was similar to the planetary arrangement found in
an automatic transmission, except that it was manually (as opposed to
hydraulically) operated.  The point is that there was no neutral; the
gears were always engaged, and shifting the thing did not involve the
clutch.  The vehicle was still equiped with a clutch so that it could
sit at the starting line with the engine running.

What it boils down to is that the clutch is really only necessary to
get the car moving from standing still because internal combustion
engines (including diesels) have zero starting torque.  All the other
uses of a clutch can be handled by other means, but there must be
something to disconnect the engine from the wheels so you can stop
the vehicle with the engine running.

In article <603@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes:
>                                                          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,

This can be done by shifting in and out of neutral.  Shifting into neutral
is easy, out of neutral can be done IF the can is moving.  Getting it
out of neutral(into gear) while the engine is running and the car is stopped
is a problem.  It would require meshing a moving gear with a non-moving
gear.  With a cluth, the engine side gear doesn't have to be moving, and
then you'd be meshing two non-moving gears.  Easy.  Otherwise, you'd
have to get the engine down to zero RPM's, and still have it running..  ???
It wouldn't have any torque then, and couldn't move the car.  Slipping the
clutch into engagement lets you start the engine side gear moving while
keeping the engine torque up.  As per someone else's posting.

>                                     It IS, if you shift from forward to
>reverse and don't have an engine that can do the same!

Wrongo.  shift to neutral, brake the car, shift to reverse.  But then,
see my above statement.

I think we're beating this stupid discussion to death..  8-)

==============================================================================
        Steve Wall [Snoopy] @ Rochester Institute of Technology
        USnail: 6675 Crosby Rd, Lockport, NY 14094, USA
        Usenet: ...!ritcv!spw2562                       Unix 4.2 BSD
        BITNET: SPW2562@RITVAXC                         VAX/VMS 4.2
        Voice:  Yell "Hey Steve!"

    Disclaimer:  What I just said may or may not have anything to do
                 with what I was actually thinking...

****                                                                 ****
From the keys of Steve Henning, AT&T Bell Labs, Reading, PA mhuxl!smh

> What it boils down to is that the clutch is really only necessary to
> get the car moving from standing still because internal combustion
> engines (including diesels) have zero starting torque.  

When the hydraulic clutch on my A-H Sprite failed, I found out that
I didn't really need a clutch.  Most cars have an item called a
starter which gives the engine torque at 0 RPM.  In fact I had
enough torque to start the car in 2nd gear every time I came to
a stop sign or red light and couldn't creep through it.  The only
reason I can think of for having a clutch is so you can repair it
rather than the transmission and the starter motor.