Variable Cam Stuff

[Raymond C Drouillard]

On Wed, 01 Jul 1998 23:57:29 -0400 Frederic Breitwieser
<frederic.breitwieser at xephic.dynip.com> writes:
>>I was thinking of using something similar to the centrepital advance
>>flyweights that are used on a mechanical distributer.  The biggest 
>fly in
>>the ointment would be the large load that is on a camshaft.
>
>Howdy Ray.  I'm thinking aloud here, so don't take this as a fact.
>
>If you use centrifigual force to change the rotation of an object, you
>adjust its acceleration capability drastically.  Rotate a 10lb bowling
ball
>upon an axis, then rotate a 2' wide 10lb dumbell, and you'll see what I
>mean.  The dumbell takes more effort to accelerate rotation (and more
>braking power to stop).

That's a good point.  The extra weight will tend to make it a bit harder
for the engine to accellerate.  Also, there will be a greater load on the
timing chain when the engine speed is increasing.

>
>That aside, if you have weights on your camshaft that can extend in and
out
>towards the centerline of the rotational point of the camshaft, and you
>have equal weight all around, you won't load the camshaft bearings much,
if
>at all (other than what gravity does).  As the weights extend, they'd be
>balanced by their sister weight 180 degrees out of phase.

I wasn't worried about increasing the load on the cam bearings.  I was
thinking about the fact that the centripital advance system that is used
in a distributer is extremely sensitive to the load.  In a distributer,
all it is driving is the rotor and the relucter or points cam.  If you
bolted something like that onto either of the timing chain sprockets, you
would be driving the entire valve train, distributer, and oil pump.  You
could probablly compensate, however.  Also, you would want to retard the
cam when the weights fly out.  Since the drag on the cam would cause it
to want to retard all bye itself, you would need to use springs to
counter that tendency at low speeds, but make them weak enough so that
the fly weights would retard the system at high speeds.  It sounds like
it would be very sensitive to the friction of the valve train.  Change to
a synthetic oil and it wouldn't retard as much at high speeds.  Maybe
that's why nobody has done it that way.

>
>Just a thought.
>
>
>Frederic Breitwieser
>Bridgeport, CT 06606
>

More thoughts...

Ray Drouillard

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