-----Original Message-----
From: Keith, Steve <Steve.Keith@compaq.com>
To: 'Richard Notton' <Richard@fv623.demon.co.uk>; Mil Veh Mailing List
<mil-veh@skylee.com>
Date: 13 July 1999 12:17
Subject: RE: [MV] 12V - 24V - 36V
>Many an alternator will definately self energize! If you look at the =
'one
>wire' 6 volt and 12 volt alternators that are offered for sale, they =
have
no
>external excitation.
>
One wire alternators are unheard of over here together with 6V =
versions.
They
might though have external excitation as the one wire presumably goes =
to the
battery and the field could be permanently excited at a very low =
current
probably insufficient to be significant relative to the battery
self-discharge
rate.
They do not have an extra connection. In addition, the alternaotrs I
mentioned, the std GM alternators from the 70-80's will run with a one =
wire
config.
The standard UK mil 24V 90A alternator to cover all applications not =
only
has a
remote regulator but the stator 3=D8 AC output is brought out =
separately and
the
whole machine is not frame grounded, the negative diode connection is a
separate
terminal.
>My local starter/generator shop owner (old geezer) told me that most =
GM
>alternators from the later 70's-80's will run one wire. Before he =
sells one
>(like the one I bought) from him, he tests them to make sure that they =
will
>self energize. The only problem with these alternators is that you =
usually
>need a higher rpm to get them to flash over and start. This can be a
problem
>with older mv's. My M6 Chev Bomb truck has one as do two of my CCKW's. =
On
>the Chevy with the dipper engine, you start the truck, let it warm up =
for a
>minute then put your hands over your ears and push down on the gas =
until
the
>Ammeter shows a charge. What a noise that engine makes...
>
There is certainly a possibility that a tiny amount of residual =
magnetism
might
remain in an alternator and high revs could have it begin to =
self-sustain,
however I've not found any of the common UK ones that will do this.
If you can obtain a US GM alternator with the internal regulator, you =
could
try it.
The dipper Chevy engine is not apparently renown for its robustness
especially
being revved hard, as most alternators are dynamically balanced and =
good for
at
least 10,000 RPM, most domestic ones here are specified to 12,000 RPM, =
it is
worthwhile to arrange for a substantial gear-up in the =
engine/alternator
pulley
ratios. Most of the W.W.II engines do not exceed a nominal 3000 RPM or
thereabouts and may be governed, so 3:1 is not inappropriate.
Richard
(Southampton UK)
=3D=3D=3D
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