Boy is this getting way OT. However, I couldn't resist this one. For 25
years I have been using my clutch to keep the car from rolling backwards
on a hill, and only now do I find out that I needed an automatic
transmission. The truth is that whether you have an automatic or a
standard transmission, to keep a car still on a hill, you need to get
the force that is applied to the wheels to match the force of gravity on
the car. With an automatic transmission, you do this by adjusting the
RPM of the motor as the slippage in the torque converter is fixed. With
a standard transmission, you have two means of controlling the force
applied to the wheels. The first is the gas, and the second is the
clutch. By holding the clutch partway in, you can get it to slip, so
that only a portion of the motors power is transferred to the wheels. To
keep from burning up the clutch, you give the motor just enough gas to
keep it from stalling.

Of course, servos could be put on both the gas and the clutch, along
with a motion, tilt, and stall sensor thus allowing a PIC to perform the
anti-rollback function automatically. Now let's talk about the
techniques needed to implement this scheme.

Hope this helps,
Paul Kolesnikoff


Date:    Mon, 15 Jun 1998 18:08:38 -0700
From:    Mike Hamilton <mikeh9@EARTHLINK.NET>
Subject: Re: Water injection

This only happens with an automatic transmission.  The crankshaft is
connected to what is known as a torque converter.  There is no physical
connection between the crankshaft and the wheels, instead there is a
"liquid" connection.  When the crankshaft hits a certain rpm, it causes
the
liquid to spin.  The energy is transferred through the liquid to the
other
side of the torque converter where the power is transferred to the
wheels.
The car won't move until the gas pedal is pushed far enough to overcome
the
friction and gravity holding the car back.
-----Original Message-----
From: Sean Breheny <shb7@CORNELL.EDU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Monday, June 15, 1998 6:32 PM
Subject: Re: Water injection


>While on the subject of engines and cars, I would like to ask a
slightly
>related OT question that has been bugging me for a long time: How can a
>car sit still on a hill with the engine holding it from rolling
>backwards? The engine, of course, needs to keep its crankshaft turning
in
>order not to stall. However, the wheels are not turning in this case.
>Somehow, the torque is being transferred from the engine to the wheels
>while alowing them to move independently of the crankshaft. How is this
>possible? What component in the drivetrain allows this?
>
>Thanks,
>
>Sean
>

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