Great post Shaun! It also gave me a greater appreaciation for the engineer
that decided to call the "Check Engine Light" a MIL... It doens't really
stand for Malfunction Indicator Light... It stands for Mother In Law!! :-)
No wonder your engine is about to choke when it comes to visit... I mean
turns on.
BAAAAHAHAHAHAHAHAHA.....
T.
<<snip>>
<<In my drafting/engineering courses we did some work with finding
the centerof gravity (CG) of vehicles. I'll use "basic" CG logic cause
that's all I ever learned. If any of you engineers out there wanna give
the advanced version, go ahead. Just an eyeball guess, but I would place
the CG of a Dak somewhere near the back of the cab or front of the bed.
With this in mind, think about the weight of the shell. All weight past
the CG of the Dak goes proportionately increasing onto the rear axle until
you reach verticle center
over the axle and then it continues at 100% and slightly increasing with
distance from the axle rearward.
These are force amplification factors. If you opened your tailgate
and put your 80lbs of sand on it, to the rear axle it would actually weigh
a bit more than 80lbs because you drop the springs and shift the CG
rearward forcing the axle to act as a fulcrum, lifting the front of the
truck and proportionately adding weight to the rear.
All this being said, a shell does distribute it's weight more
evenly, so you are correct there. I disagree with your appraisal of 80lbs
of sand over the axle and a 150lb shell being "lighter" because it's weight
is distributed over the box. Since the shell is all past the CG of the
Dak, the minimum weight cancellation is 50% at the very front of the shell
(at CG the weight is split over both axles: thus 50%). This weight
increases dramatically with angle (vector) to axle.
Why use 150lbs? It takes 3 people to comfortably lift the shell on
my truck, it's mostly glass. The installers used a forklift. It's not
light. Again, just rough guessing it, I would say that that shell puts
about 100-130lbs of dead weight directly onto the rear axle
which is more than the 80lbs of sand. You can flush this logic if you
want, but I'm just trying to keep that Newton fellow happy. ^_^
I can't disagree with your 300lb MIL though... but it would have to
be one tough rocker, and driving the Dak would be a bitch with that
constant shifting (rocking) weight load.
Shaun H.
"Just don't rock too far back! It's hard to steer with the front wheels
off the ground!">>
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