All that except electricity flows from negative to positive.
Kevin
--- In [email protected], [EMAIL PROTECTED] wrote:
>
> Dennis,
>
> I'm not sure about the earlier model Coupes, but the C-90 in my
Alon is
> grounded via a heavy ground strap from a stud on the engine case to
the lower right
> hand bolt on the engine mount. The purpose of this strap is to
provide a high
> capacity ground from the engine to the airframe.
>
> The negative side of the battery is grounded with a heavy battery
cable to
> the airframe structure near the battery. When you engage the
starter, about 200
> amps flow from the positive side of the battery to the starter.
(These
> starters are capable of drawing over 500 amps per the Continental
engine overhaul
> manual.) The starter is grounded to the engine case. If the engine
case does
> not have a very good, high capacity ground back to the airframe,
that 200 amps
> that went to the starter is going to flow back to the negative side
of the
> battery through the airframe via your throttle cable, tachometer
cable, primer
> line, and any other miscellaneous path that it can find. This is
not good!
> Remember, the engine mount uses rubber isolators, which if in good
condition, not
> only isolate the vibrations, but they also electrically isolate the
engine
> case from the engine mount. All of the other miscellaneous ground
paths from
> the engine case to the airframe are not designed to carry the
starter motor
> current back to the airframe. You definitely need a good ground
conductor between
> the engine case and the airframe.
>
> Attached is a photo showing the ground strap on my engine
installation. This
> strap goes from a stud screwed into the engine case, to the lower
right hand
> engine mount bolt head (between the bolt head and the steel engine
mount).
> Only this strap has the current carrying capacity to return the
starter current
> to the airframe and to the battery. If you don't have such a
ground
> installed, you risk burning up whatever path the starter current
finds.
>
> Of course, check with your licensed A&P mechanic before following
any advice
> given here...
>
>
> Best Regards,
>
> Wayne DelRossi (BSEE, PE, MBA, but no A&P darn it! Gotta do
something about
> that!)
> Alon N5618F
> Hours logged since restoration: 347.5
>
> "Nobody has ever scientifically proven that life is supposed to be
serious."
>
>
>
>
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