I have been reading with much interest the discussion on alternator
conversions and have learned much. Thanks to all of you for your
contributions. The post by Mike Eck spurred me to comment. Very interesting
info Mike. Thanks.
Missed discussion on finding a correct width pulley for the wide XK belt.
Phil Planck - 677139
Mike, the ammeter in this case is a to and from device with a center
zero…it reads current from the battery (to power accessories such as
ign, lights,and electric motors…It is not however in the cranking
circuit…(too much corrent for its approx #10 guage internal loop around
the pointer magnet…The alternator will since it’s on the accessory
side of the circuit, show the current delivered to the battery…If the
battery doesnt need input to top it off so to speak, then the output of
the generator or alternator will operate all the equipment …providing
that the equipment load doesn’t exceed the output capability of the gen
or alt…
Unfortunately the alts and gens do not operate at a constant speed
(varying engine revs) so there are periods where their output is
fortified by the battery …the ammeter will show this as a
discharge…as rpm and alt/gen increases both the load and the battery
will be served…as the battery comes back to “top off” the ammeter will
show zero even though the alt/gen may be delivering up to its rated
capacity to operate the load from the cars many devices…Since the
cranking process requires heavy current…the battery replenishment
period after starting is always more prolonged or pronounced than the
more usual energy drains during driving…
Although a resistor across the ammeter will affect its appearant current
carrying properties and deflection keep in mind that the internal loop is
a piece of about #10 wire less than 4 inches long…to double its
ability to carry current an additional shunt of #10 wire about 4 inches
long would have to be put across the terminals…trying to measure the
resistance of the wire is fruitless with normal meters…as few of them
can discern between a dead short and this short piece of wire…
Keep in mind however that there are a few ammeters that use a more
complex movement consisting of 2 coils mounted at about 90 degrees wound
with fine wire…These movements are bypass meters in that the needle
itself will deflect on milliamps of current…They therefore have a
shunt across the terminals to pass the currents required by the
vehicle…many of these shunts look like strips of heavy brass shim
stock with 2 holes for the terminals …they are generally about 1/2 in
wide and .020 thick… some appear like a hourglass as they are
trimmed and calibrated for certain current flows allowing for precise
adjustments to the movement…
more later (if you want)…Rick
You guys are going to have me baffled. If there is 10 ga. wire going to the
ammeter, 10 ga. wire through the ammeter, and 10 ga. wire coming out of the
ammeter, how is there going to be any change in resistance, other than the
natural resistance of the extra 10 ga. piece of wire needed to form the
loop?
If that was the case, all I would really need to do, if I wanted to go to
the trouble, would be to measure the exact length of the wire to and from
the ammeter, and add to that the length of wire in the ammeter itself –
approx 4".
Then I’d just need to cut a piece of wire exactly that length, and that
would be my second wire from alternator to battery terminal on the starter
solenoid. I could make it a little bit longer to compensate for any
additional resistance at the ammeter terminals, but that would be about it.
Assuming that I even need to do that at all, since most of the current is
running through the ammeter anyway with the 1 ohm resistor across the
terminals, and the needle is still not rising above the 25 amp mark.
“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – www.cableone.net/jcca----- Original Message -----
From: holland-rick@juno.com
To: xk@jag-lovers.org
Sent: Monday, December 27, 1999 11:11 PM
Subject: Re: [xk] Alternator Conversion
Mark,
My inclination would be to either eliminate the second wire or parallel the
existing wire. If you find from experience that the Ammeter becomes
overloaded then a shunt may be necessary. But I don’t think it will. Just
because your alternator is capable of putting out 55 Amps doesn’t mean it
ever will send that much to the battery.
Mike Eck-----Original Message-----
From: Mark Stephenson marks@starlink.com
To: xk@jag-lovers.org xk@jag-lovers.org
Date: Monday, December 27, 1999 2:15 AM
Subject: Re: [xk] Alternator Conversion
Excellent! Should I dispense with the second wire?
BTW, thanks for your excellent explanation of alternators vs. generators.
It
was enlightening.Mark
----- Original Message -----
From: “Michael Eck” <@Michael_Eck1>
To: xk@jag-lovers.org
Sent: Sunday, December 26, 1999 9:13 AM
Subject: Re: [xk] Alternator ConversionMark,
Remember that the Ammeter reads the current from the alternator to the
battery, and not from the alternator to the lights, wipers, horns, radio,
etc. So the load makes no difference to the Ammeter reading; it is only
affected by the state of charge of the battery.25 Amps is an adequate charge rate for a somewhat discharged battery.
Much
more than that will generally have undesired effects, such as boiling the
electrolyte and warping the plates.I think you should proclaim the transplant a success!
Mike Eck
-----Original Message-----
From: Mark Stephenson marks@starlink.comMike,
I agree, but even when the battery was somewhat discharged, as when I
first
started it after sitting for two weeks, testing headlights, dash lights,
and
other circuits, it still didn’t feed more than about 25 amps. The needle
would actually fly up and bounce off the peg, then stabilize at about 25
amps.snip
Mark…As Mike Eck iterated…the output of the alternator is indeed
higher than that of the original generator…however your load has not
changed (the stuff in the car that must be operated by
electricity)…other than a higher initial charge rate due to cranking
motor drain, the car won’t (can’t) use any more power than it did
before…the reason that the after cranking current flow into the
battery is higher now is simply that the alternator can provide
it…will a few seconds to a minute or two of higher current cause any
trouble or damage??? I doubt it…“pinning” the ammeter pointer is a
normal occurrence , however it usually pegs to the discharge side during
a short circuit before the fuse pops…do you need to parallel the
ammeter circuit to half it’s deflection??? No it’s a waste of time and
some of the minor current draws will not move the pointer enough to
see…eg: when the coil is carrying current (ign sw on and points
closed)…Will the existing wiring and harness take the extra charging
current??? Most probably yes…best way to gauge this is to feel the
feed wires to and from the ammeter looking for excessive heat…It
would make sense to clean and redress all the wire connect and terminal
points in the circuit too…its at these junctions where I found circuit
resistances higher and heat buildup most evident…Lastly…many
alternators can provide substantial outputs without the need for a
battery to externally excite (magnetize) the rotor…these like a
generator rely on residual magnetism in the unit to start the process
going…many of these are called “one wire alternators” because that’s
all that you need to hook into the system… and yes you can push start
vehicles with these even if they have flat batteries…
Rick Holland 677342
On May 14, Ron Radar asked about converting an XK 150 from
generator to alternator. I explained the factors that
influenced my choice, and in response to follow-up inquiries
about how the conversion was accomplished, I offer this.
We’re using a 100 amp Ford alternator in place of the 30 amp
Lucas generator. While it has higher output, it is smaller.
The original generator bracket is on the engine, but only
the front hole is used to mount the alternator.� The rear
hole will be used to secure a grommet for the combination of
wiring that will carry the higher out put.
In addition to the No. 10 generator wire in the wiring
harness, we’re using a No. 8, (MIL-W-22759/41-8�ETFE
Insulated, �nickel coated copper conductors,�133 strands of
29AWG), which, added to the No. 10, will provide the cross
sectional� equivalent�of a No.6 wire�(a wire cross section
area of 13.3 mm2).� Assuming 65 amps output at 14.2 volts at
the alternator,�and a run of 10.75 feet, it will have an
output of over 13.5 volts at the battery/ starter.
A related issue involves the alternator pulley. While Rob
was able to align it with the other pulleys, the Ford pulley
has a different groove width for the belt. We decided to
change the pulley on the alternator, and at the same time,
address another issue:� the engine pulley on a Ford is
smaller than the engine pulley on the Jag, so to keep the
alternator speed about the same, the diameter of the
alternator pulley should be increased.� Rob was able to find
a 2 7/8’’ Jag pulley to replace the 2 3/8’’ pulley that came
with the alternator.
Rob cleaned up and bead blasted� a 2 7/8 inch Jag pulley.
The required modification was to reduce the boss on the back
of the Jag pulley (to align with the engine pulley) and
enlarge the hole to fit the shaft of the Ford alternator.
Rob installed a new wiring harness, with sightly revised
routing, that goes through the trapezoidal support (I
believe the Jaguar description is ‘‘front inner wing
support’’). The yellow No. 10 generator output wire in the
wiring harness will be combined with the mil spec No. 8 to
take the alternator output back to the battery. While the
Ford alternator is a single wire setup, the casting has a
rubber plug where the other two wires were located on some
models. Removing the plug disclosed that one of the
connections could still serve to power an ‘‘idiot light’’.
Thus, the green/yellow wire in the harness that originally
energized the generator will be connected to the ‘‘idiot’’
light socket in the alternator and power the ignition light
on the instrument panel.
Regards,
Monte
1960 DHC
S838594
http://www.jag-lovers.org/v.htm?1242435535--
p8099
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