Gauge wire works backwards from screw sizes (#4 screws
are tiny...#12's are large). In wiring, the largest
gauges are zero (0) or what is referred to as a Aught
gauge. The smallest wires (phone cords) use 24 gauge.
No one really knows why they do it like that.
In gauges of wire, the wires in your harness for
lights and things are around 12-14 gauge (10 amp max)
. House-hold wiring is around the 8-19 gauge area (AC
wiring uses more amps for the same or similar voltage
requirement than DC). Your starter sucks high amperage
at a low voltage. And you need ATLEAST a 4 gauge wire.
Most automobiles use 2 gauge starter wires.
Just as an introduction to electrical engineering:
AMPERAGE refers to the VOLUME or the amount of the
electrons passing through a conductive surface.
VOLTAGE refers to the SPEED at which the electrons are
moving. Wattage is a formula to calculate the total
usage of electricity on a circuit. It's value is
Amperage times the voltage. A 100 watt bulb which runs
on your 120 volt home current uses 1.2 amps (100 / 120
= 1.2).
Diameter of the wire (gauge) doesn't affect Voltage
because voltage is not an amount, it's a speed or
rate. But, you do need to consider Diamater when
figuring out Amperage.
Electrical current can be thought of as water moving
through a pipe. So, like in a water pipe - the larger
the pipe, the greater volume of water that can pass
through it, right? So if you try to put more water in
the pipe than it can contain it will burst.
The physics of it are diffent. In electrical terms,
the RESISTANCE is increased, and a tug of war ensues
because the motor is trying to PULL more current than
can fit through the conductor. But the end result is
the same, broken conduit somewhere in the circuit.
This can also cause the motor to loose out on the tug
of war and brake down.
A Lucas starter motor can pull as much as 375 amps for
lock rotation. That's the upper limit of a 6 gauge
wire on DC current. And a sustained burst will test
your wiring quickly. So you might be better off going
with a 4 gauge or 2 gauge just to be super duper safe.
There are also considerations for distance, because as
you increase distance, you lose amps (like a leaky
water pipe), but the motor still requires the rated
amperage to turn a rotation, so you need to put even
MORE amperage through the line to compensate for the
"leak". (I know all the electrical engineering folks
on the list are going to jump on my case for making
analogies to water).
As a general rule the following constitutes safe upper
limits of Amperage draw for conductive circuits. AWG =
Gauge. All are listed at 6 feet of distance.
18 awg = 25 amp max (ampacity)
16 awg = 37 amp
14 awg = 60 amp
12 awg = 95 amp
10 awg = 151 amp
8 awg = 241 amp
6 awg = 390 amp
4 awg = 616 amp
2 awg = 1000 amp
ALSO. Don't forget that the terminations (the eyelets
and posts) must be clean and also rated for high
amperage current. Resistance anywhere in that circuit
spells trouble for your starter.
Sorry if that's been confusing, or if you just didn't
give a crap. You're probably even more confused now.
-Terry
'76 spit 1500
--- richard bonilla <richard@bonilla.com> wrote:
>
> hummm...i will take another look at the
> connections...and upgrade
> my cable to at least a 6 gauge...any reason not to
> jump to the
> next bigger gauge...say 8?...
>
> richard / colorado
>
>
>
>
> ----- Original Message -----
> From: "Vic Whitmore" <vicwhit@home.com>
> To: "Nolan Penney" <npenney@mde.state.md.us>
> Cc: <spitfires@autox.team.net>;
> <richard@bonilla.com>
> Sent: Tuesday, January 16, 2001 9:14 AM
> Subject: Re: 79 spit starter meltdown..?
>
>
> > I have my doubts that the there is a real problem
> here with Spitfire
> starters in
> > general.
> >
> > Could it be that a loose or partially corroded
> terminal (internal or
> external)
> > resulted in an ohmic contact?. With the very high
> current load of starting
> > passing through this small resistance, significant
> heat will build up.
> > Components that would not normally melt with clean
> connections may melt
> even
> > after a short 15 to 30 second cranking. Hence as
> "good" starter can be
> abused at
> > times without any damage but a "poor" starter with
> ohmic connections will
> > self-destruct earlier than expected.
> >
> > Vic Whitmore
> > 76 Spitfire
> > Thornhill, Ontario
> >
> > Nolan Penney wrote:
> > >
> > > 10 seconds on, but how long off? It should be
> 15-30 minutes to allow
> > > a good cooling down. Now of course, none of us
> actually do that.
> > > We crank and crank and crank, hoping that the
> motor will act enough
> > > like a heat sink to allow us to get away with
> it. Often times you can,
> > > sometimes you cannot. Most starter motors will
> allow you to
> > > get away with upwards of a solid minute of
> cranking before
> > > self destructing in a terminal manner. But this
> does not mean
> > > that all starter motors will do this.
> > >
> > > I will say that my Spitfire has tolerated
> upwards of 30 seconds
> > > solid cranking time, with burst after that
> giving nearly a minute
> > > of cranking time. Nothing has melted down in
> the process,
> > > but I do understand I'm breaking down insulation
> in the process
> > > and cutting my motors life short doing this.
> > >
> > > To actually melt the plastic housing the hot
> post sits in, I'd
> > > speculate that you were cranking...shall we say
> enthusiastically
> > > and excessively? :-)
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